Brainz006

Ok, since the CTT didn't sell and you're fixing the trans leak, I want to run another idea by you on the stuttering: Could it be the MAP (not MAF) sensor on top of the intake Y pipe? Here's my theory: Everyone knows how sensitive the CTT is to vacuum and boost leaks - could it be that the MAP readings (and related ECM programming) are partly to blame? What if the ECM is programmed to incorporate manifold vacuum/boost readings into fueling and transmission shift modes (including Torque converter lockup and shift timing)? That could explain why we get weird shift issues and even a transmission limp mode error if there's a big enough vacuum/boost leak [Ever tried driving with a disconnected boost hose? Transmission goes into limp mode]. So what would happen is the MAP sensor didn't accurately measure the intake pressure? Honestly, I don't know, but doesn't seem like it would help. So I did a baseline test for you, and the results were somewhat interesting. With my MAP unplugged, my engine runs at a much lower boost/power level. The engine/power was actually really smooth, but weak relative to the normal CTTS tune I'm used to. It does feel like it's boosting a bit, but as the MAP is unplugged, the gauge reads zero so I can't say for sure. The transmission gave some weird, jerky shifts at low speed - - not horrible, but not quite right. And eventually the CEL came on - - I think it took 2 or 3 driving cycles. I cleaned the MAP with some MAF cleaner (both the contacts and the sensor part) and plugged it back in. The CEL went out in a couple/three drive cycles and everything was back to normal (or maybe even slightly smoother, but that may be a placebo effect). Seems like an easy, albeit potentially inconclusive test for you. In your case I'd want to see if the stuttering happened as the car got fully warmed up. If the stuttering goes away (which would be amazing), you may want to try replacing your MAP sensor. That's my thought for the week. Hope that helps. Sent from my Nexus 6 using Tapatalk

Zakowsky: Love the [temporary] solution. It's actually pretty insightful to know what rate you are leaking. Lewis: Sorry to hear your CTT didn't sell, but happy to still have you on the forum. I have another idea on your stuttering issue, but I'll post on that thread. Sent from my Nexus 6 using Tapatalk

If you are trying to save money on the valve body, the TransGo repair kit is your cheapest option. But it is a meticulous repair and is not for the feint of heart. But it does work. Sent from my Nexus 6 using Tapatalk

I used a non-Porsche gasket/filter kit and it seemed fine. No leaks on mine. I used both 3309 and Toyota Type IV. Both were fine, and the latter is cheap and available. If you are getting the 5-4 hammer on downshift, that's the valve body - - you've learned to drive around the conditions that trigger it. Mistimed up shifts in the low gears when cold was an underfilled symptom for me (so was temporary loss of drive, usually when cold). Poor shifting/rough running in the low gears/revs can also be a vacuum (or boost) leak. Good luck. Sent from my Nexus 6 using Tapatalk

I thought the same thing. Looks more orangish-pink than dark red. But may be the photo. Does it smell like coolant? Sent from my iPad using Tapatalk

Was the loose bolt and surrounding area the most wet? Your weep holes look relatively dry versus when my seal went. I'd wipe the whole area clean/dry and drive it some more to see where the ATF appears to be coming from. Regarding shifting issues, when my trans was underfilled, it would have hard/erratic shifts first thing in the morning, presumably because the fluid drained into the pan and/or aerated when it started up. That would cause erratic shifting until the trans fully primed. Once filled to the correct level, that issue went away. One other issue, is that our transmissions are very sensitive to vacuum leaks in the intake. Apparently the Transmission Control Module must look at the MAP sensor (or similar) and it will make the trans shift awkwardly in the low gears. At speed its less an issue. Banging on downshifts is the valve body. Fix your leak and refill the trans first. Good luck. Sent from my Nexus 6 using Tapatalk

That completely sucks - - sorry to hear. Mine went a few years back. I'm all for turning a wrench, but removing the trans is a big boy job requiring a lift and a buddy to help with removal. I paid the transmission shop about $1300 and called it a day. Frustratingly, the repair shop pinched the oring on the trans filter and underfilled it, leading to additional work to sort out why it was shifting oddly. Eventually it got sorted. Sent from my Nexus 6 using Tapatalk

Good luck! Sent from my Nexus 6 using Tapatalk

I would think that 125k km would still be too new for variocam wear - - there's plenty of Cayennes running around with way more miles without this issue. Random anecdote per Ddavidoffs post: My brother had a rock crawler that was giving him fits. It had a Chevy LS engine in it with a Painless Wiring harness. Started fine and ran great when cold, but as it warmed up it would intermittently stutter and lose power. I seemed to remember it throwing a code or doing something that made us suspect a failing crank sensor and O2s - - replaced those and some other bits, still no joy. While testing it one day, we notice that the ECU voltage was dipping when the issues were happening (note that it would also hesitate and stutter at idle when hot, which made troubleshooting easier than your situation). We wondered if maybe the ECU was failing, but wanted to check all the wiring first before throwing more dollars at parts. So as I wiggled all the wires on the various harnesses and suddenly the engine stutter would coincide with the wire wiggle. It turned out there was a bad/weak crimp in a major (positive, I think) lead to the fuse panel that fed the ECU amongst other circuits. And as the amperage heated up the wire crimp, the connection got slightly intermittent - - not enough to cause an obvious electrical issue, but enough to sag the ECU and make it hiccup. New crimp - - No more issues. Lesson: electrical gremlins are a b*tch. We got lucky to find that wire. Consider logging ECU voltage, cleaning ECU harness plug with contact cleaner, checking any suspect connections, and maybe wiggling wires. Sent from my Nexus 6 using Tapatalk

I seem to remember high mileage BMWs suffering such issue with VANOS. You are in a hot part of the world, so a heavier oil could make sense. Remind me: What's your mileage? Sent from my Nexus 6 using Tapatalk

12.6V is quite good, and the new battery should rule out a failing cell. When my 997 battery recently failed, it would charge up to 12.6 (or more), but very quickly lose charge under load. After a few cranks it was sub 12V. Sounds like that's not your issue, although perhaps grounding is. Might be worth confirming voltage at different points on the car just to see - - I'd start with the rear tail lights if you're getting an occasional error. Sent from my Nexus 6 using Tapatalk

What's your resting battery voltage? I could swear my CTT runs better when the battery is fully charged. I do a lot of short trips (work is only 3 miles away), so my battery tends to lose power over time. I know it's time to charge the battery when I get the CD changer error. On my 997, a low battery causes a Check 3rd Brake light error. I use a CTEK charger, and it seems to do a good job bringing the charge back. Sent from my Nexus 6 using Tapatalk

So strange. I have no idea what the issue could be. Your symptoms sound like a vacuum leak - - or are at least remarkably similar to my symptoms with various vacuum leaks. I keep reading and hoping you find a solution, but alas, no joy yet. I'll keep my fingers crossed for you. Sent from my Nexus 6 using Tapatalk

That 02 sure does look suspicious and makes perfect sense for your symptoms (only hot and mid throttle, precisely when the O2s are supposed to be doing their job). Fingers crossed you found the issue. And Yes. The Scanner Danner YouTube vids are highly educational. Completely recommended for learning how to troubleshoot with a scanner. I successfully used that on diagnosing my 997's issues (which as I noted earlier in the thread, I did see a meaningful improvement with new O2s despite low mileage - - I think they got fouled). I'm really hoping this is it. Good luck Sent from my Nexus 6 using Tapatalk

Diagram 1: Jet pump: Yes, I believe it's molded into #4, and is back by the firewall at the back of the manifold -- not sure whether the cylinder is the jet pump or the checkvalve after the jet pump, but same area. One thought: #4 has those weird squeeze fittings on both ends. Make sure both ends of #4 are firmly seated on the respective nipples -- it's easy to not get them fully seated. Good that Pipe 12 is new. Can cross that off the list for now. See Diagram 3, Pipe 5 below. Diagram 2: Yes Tee 25 is notorious for cracking/crumbling. If you've not replaced that, definitely start by replacing it with a brass or aluminum tee. There are two crimped fittings each on the turbo vent lines 18 and 20 at the back of the manifold -- are those the fittings you suspect of leaking? I remember some modest play in mine, but I don't remember thinking they might leak. I have no idea the exact function of 18 and 20, although I suppose they allow the turbo oil catch tank to breathe which keeps the oil flowing freely to the sump. Strange that you cant blow/suck through them, although I suppose maybe you're trying to blow/suck the oil in the drain line too, which could be difficult. Another thought: With the engine running, if you place your palm (or a sheet of paper) over the uncovered oil fill hole on the valve cover, is there good vacuum? Diagram 3: The other corrugated pipe I was thinking of was #5: As best I can tell, it's the main crankcase vacuum line. If you don't have crankcase vacuum per the test above, that line or the AOS would be suspect. That's big vacuum line. Also check the "turbo check valves" that it attaches to -- it's the "3-leg L fitting" that connects to the AOS spigot. I just had another thought: I believe it's possible to install the turbo check valve a couple ways (but there's only one right way -- the leg you can blow into goes to the AOS spigot on the valve cover). I suppose if you rotated the check valve clockwise one position, the valve would accidentally function as a giant intake leak. It's worth confirming that's not the case. Lastly, all the little hoses and connectors from #25 to the purge valve are suspect until proven otherwise. It's those hoses that can rub on the belt pulley under the Y pipe. I suppose a quick test of that plumbing (and the purge valve) would be to temporarily plug #25 at the manifold and see what happens -- similar to the purge valve test. Best wishes. Sent from my iPad using Tapatalk

The jet pump is a venturi pump that's part of the vacuum lines that go to the brake booster. Under closed throttle, vacuum from the back of the motor suctions across the jet pump (which may have an embedded check valve, not sure) and keeps vacuum on the brake booster. Under boost, pressurized air from under the Y pipe flows across the jet pump to impart a venturi vacuum on the brake booster. That way the brakes have vacuum at idle or full throttle. I have no idea what all the little lines do at the back of the intake manifold nor whether there is anything moveable inside (but I don't think so). Seems possible but likely unnecessary on a turbo engine as you don't really need an adjustable intake length to make power - - the turbos have that covered (and is consistent with how Porsche does it on the 997s, i,e, the turbo models have a simpler manifold). That said, there is some sort of strangeness at the back of the manifold including the little jumper line that go from the manifold back to the manifold - - I'd love to know what that's for. Could the big corrugated vacuum lines on the top front of the intake manifold have a crack that makes a resonant sound at different engine speeds? The ones that go to 2-way AOS check valve....? Sent from my Nexus 6 using Tapatalk

Transfer case has a chain in it that reportedly gets stretched over time, but it doesn't make sense that would be your issue. There's also the hi/lo motor that reportedly gets frozen, but from reading, that gives an error light but no drive ability issues. Here's the piping diagram. Let me know if this diagram doesn't come through in high resolution and I'll PM you. Your symptoms sound most like the time my line that goes from the Y pipe to the brake jet pump didn't get fully seated under the Y pipe. That particular line also connects on the back of the manifold, but seems like if you had a crack on the manifold side of the jet pump that you'd get a brake booster error. So seems like from the jet pump to Y pipe would be most suspect. Good luck. Sent from my Nexus 6 using Tapatalk

Mine does not really whine noticeably -- some whirring from the rotating bits, but not much. There's a bit of clicking from the fuel injectors, but it's otherwise pretty quiet -- mostly a fan/blowing noise. My CTT only has ~50k miles, so that might make a difference. Assuming you're already ruled out the AC compressor, alternator, or power steering, by doing different things to increase/decrease the load on those components, I have heard that a useful way to diagnose an engine whine is to remove the serpentine belt and run the engine for a SHORT amount of time to compare the noise with and w/o the belt. No noise without the belt means you know where to look: idler pulleys, alternator, water pump, etc. I've had luck disassembling idler pulleys and repacking them with fresh grease on other cars, which can reduce rotating noise. If your noise is still present with the serp belt removed, then it must be something else (including maybe an intake leak) that's making the noise. Just to state the obvious for posterity, you don't want run your engine without the serpentine belt for very long as it will quickly overheat (as the water pump will not be turning) -- so only test for a minute or so, while cold, to check for whether the sound changes. The more I think about your issues and compare them with things I've experienced and subsequently fixed on my CTT, I think you have an intake leak. Your symptoms most closely match the time the line that snaps onto the bottom of the Y pipe was not plugged in -- my car bucked and stumbled at light throttle and low rpm and felt like it had bad driveline lash -- you couldn't be smooth with the throttle at low speed. I never got any error messages or CELs. It was annoying as hell. And I'm wondering if there is some vacuum tubing behind a check valve (like the purge valve was) that would not otherwise be easily tested by a smoke test. Or maybe the tee or crimped connectors at the back of the manifold that you've mentioned. Or perhaps the leak is in one of the corrugated or black plastic lines under the shrouds at the top of the valve covers or to the brake booster (although a leak on that line will throw a code and make the brake vacuum pump run and get hot -- BTDT). One other idea would be the AOS membrane, but I seem to remember that you checked that, and I hear they whistle or honk or cause voluminous smoke out the tailpipe (I can confirm the latter when I accidentally reassembled my AOS the wrong way after opening it up to examine it). There's a vacuum piping schematic on a sticker on the hood slam panel above the radiator on my car. It takes a bit of time to figure it out because its more a flowchart than a scale diagram, but it's pretty useful for figuring out what the various lines are supposed to be doing. I keep meaning to make a copy of the sticker and color code the lines with a description of where the valves and connecting parts are located, as it would be very helpful for troubleshooting the vacuum system (or keeping track of what vacuum lines you've tested!). There's a lot of places for the Cayenne's vacuum lines to have an issue, especially as the plastic ages an gets brittle. As always, hope something above helps you or someone else. Best of luck. Sent from my iPad using Tapatalk

Do you notice the stutter more on an upward or downward slope? That could indicate low ATF, as it may aerate the fluid and cause weird issues. Mine was most noticeable on the first drive of the day and when driving slowly up hills. Honestly though, other than a bad valve body and under filled trans, the next most common stutter issue I experienced was a vacuum leaks. One was the tee behind the manifold, and the other was the fitting that snaps on to the bottom of the Y pipe - - it wasn't fully seated and created a big leak. And then there was the time my LHS boost pipe from the turbo to IC popped off (because I'd not seated it correctly). In all cases, rough running in the low to mid range, but OK up top (except the boost pipe issue obvs). The boost pipe error throws a PRND trans error, BTW. Good luck. Sent from my Nexus 6 using Tapatalk

Your fuel trims look very good, honestly. Are they that good at all load levels, or just idle? If that good at all load levels, it makes me question whether the problem is air/fuel related. I'd still probably do the O2 sensor, but only to have everything on an equal baseline. Fuel injectors seem unlikely to be bad (and are more expensive to fix, although a few bottles of Techron never hurt). Dirty/clogged injectors usually make for a poor idle, especially when cold, and heat soak/electrical issues would hurt your full throttle, not just mid range. Also, I would expect the ST fuel trims to go crazy if the injectors had a temperamental electrical issue. Is it possible you're having transmission shudder and not engine stutter - - they can feel similar? An underfilled transmission is very easy to do on these cars, especially if you accidentally pinch the trans filter oring - - ask me how I know. And an underfilled trans will do odd things - - it might slip or shudder ever so slightly while driving, particularly at lower speeds and RPMs because the trans will not smoothly apply the torque converter lockup which happens between 1500 and 2500 rpm. I remember the issue being worse when cold, not hot, so that may not be it. How old is the ATF? What brand/type? Mobil 3309/Toyota Type IV is the factory spec, and is what I've used successfully (once the fill level issue got sorted). If you turn off PSM, or manually shift such that RPMs are above 3000rpm when you change gears, does that alleviate your stuttering? I'm otherwise out of ideas for now. But I'm still stumbling upon odd revelations about the Cayenne after almost 5 years of ownership. For example, this weekend I learned that a low battery will reduce the maximum HVAC blower speed and make you think your fan controller is failing. It's happened a bunch of times, but I never realized it was due to low battery voltage after sitting for a week (the battery needs replacing). I write back if I think of anything else. Good luck and best wishes. Sent from my Nexus 6 using Tapatalk

I remember reading your posts whilst you were sorting those issues. I didn't recall reading that it was ultimately solved by replacing the purge valve -- but agree that it now makes sense -- and you're right, a bad purge valve can cause a weird vibration at certain speeds/loads (mine did too, but the hard starting after fuel up was way more obvious). Unfortunately I don't think I'd figured out the importance of the purge valve at that time or I would have suggested it. Glad to hear you got it sorted. To my thinking, the general rough-running troubleshooting should probably go like this: 1) Scan and fix and obvious codes (with a Durametric or quality scanner that can read Porsche codes). 2) OBD2 data log the O2 sensors, long term fuel trims, and short term fuel trims, versus load and RPM. I use the Torque App on my phone with an add-in called "Realtime Charts" -- not super-high logging rates, but still helpful. Cheap, but somewhat time consuming. Can also be tricky to interpret. Can be a good baseline tool -- I keep the logs for comparisons later, including after making parts changes. Watch for LT fuel trims that are +/- more than 10% -- that usually means something is not right. The closer ST and LT trims are to zero the better (note that ST will move around more, whereas LT moves gradually). 3) Purge valve test / block the hose to the intake. Costs nothing. Takes 5 mins plus a test drive. A usual, but often overlooked suspect. 4) Fuel pump fuse test. Just to make sure you're main pump isn't flaky. Costs nothing. Takes 5 mins plus a test drive. 5) Camshaft solenoid test. Lewis's test in this thread were quite good. My sense is that you'd do this only if you were missing low-mid range power, but OK on top. Costs nothing. Takes 5 mins plus a test drive. 6) Smoke/pressure/vacuum test the intake. Can be time consuming and expensive, but is almost certainly worth it. Most of my running issues have been leak related. 7) Coils and Plugs: Check for cracks, measure resistance, and/or replace coils. Change plugs while you're in there, they are relatively cheap. Coils themselves are not cheap or quick, but an eventuality and not too terrible to DIY. 8) Primary O2 sensors: You may be able to see a difference between the responsiveness of the sensors on a OBD2 data log. If you're looking to save money, change the sensor that appears less responsive first. If a new sensor helps (and is confirmed working better by the OBD2 log) consider replacing the other one for good measure. The parts aren't too expensive, but I have heard that one of them is a PITA to get to. Buy only Porsche or BOSCH. 9) MAFs: I'm pretty sure the MAFs would throw an obvious CEL code, hence they would be the last thing I'd throw money at unless I'd done all the above troubleshooting and still had running issues. But if I had done the above trouble shooting and LT Fuel Trims that were way off (+/- 10) in any of the load ranges, then that would be my next guess. Buy only Porsche or BOSCH. Hope that helps someone (and particularly so Lewis, although I think he's already done most of these in this thread, with useful explanations how to do such).

Well bummer -- I had my fingers crossed that you had a defective (new) purge valve. In any case, I'm happy to have contributed to the cause with a quick and simple troubleshoot (and potentially long-term fix) for the purge valve. I've appreciated your efforts to document your trouble shooting -- there's a lot of very useful information in this thread that covers the vast majority of the usual Cayenne suspects, as well as a few rare ones (such as the variocam and how to troubleshoot). A few more thoughts: 1) Definitely do the other wideband O2 -- I didn't realize your issues were part throttle only. At startup and full throttle, the engine runs open loop, so a bad O2 wont impact (or mess up) fueling for those operating conditions. That's my new primary suspect for your issues. 2) Have you tried running with one or both of your MAFs disconnected? I believe it will throw a code, but the ECM should be able to handle it with the MAP sensor -- I've not done this myself recently, but would be happy to test it if needed for comparison. It would be interesting to see if/how that changed your driveability issues. Any improvement would make me suspect one or both MAFs. I got a much better idle and low speed responsiveness when I changed the MAF on my 997 -- it had become oil fouled from the PO's use of an oiled air filter element. MAFs and O2s are the heart of the closed loop system, so once coils and air leaks have been ruled out, those are the next most suspect parts. 3) It's possible that the rubber hoses under the Y-pipe that have the check valves that go to the purge valve can be installed in such a way that they come into contact with the serpentine pulley -- Mine did and wore a hole in the rubber hose -- I've seen at least one other report of this happening on the forums. While I don't expect that this is your issue given the scrutiny that you've given all the hoses/plumbing, it's worth noting for posterity that the section of hose that wore in my case was between the check valve and the purge valve and hence would NOT have shown up on a smoke test. Nor would my trick of plugging the end of the hose help much, as the hole is in the middle of the run. As always, best wishes and good luck. Feels like you're close. It's always the last place you look....

Lewis, I've continued to follow your journey with interest -- you have my sympathies in this frustrating, long-running matter. At the risk of jinxing myself, I wanted to provide an update regarding some of my own recent experiences that may provide some additional areas for exploration. Somewhat like you, I had a stuttering in power that was particularly noticeable (to me) in the middle RPMs under medium to full throttle, but also faintly there even under light throttle on my 06 CTT. One day last year, I started having hot start issues after refueling, which is generally indicative of purge valve issues. So after a few months of this annoyance [having to floor the accelerator to get the engine started after refueling], I decided to check out the purge valve to see what it was actually doing. I found that the purge valve is normally closed, thus keeping the tank vapors from being ingested. In my case, I could apply power to the purge valve with jumper leads, and it would click, suggesting that it was working. Except that as I continued to cycle the valve, it would eventually [heat up and] get stuck open (as confirmed by sucking through it - - yuck). A stuck open purge valve would appear to act either as a vacuum leak and/or extra source of fuel - - but you'd never find it on a smoke test, because there is a check valve in front of the purge valve that keeps intake boost from pressurizing the fuel tank vent system, so you won't see it as a leak by normal means. But when it's open, the purge valve admits unmetered air/fuel to the engine. I think the ECM, in conjunction with good O2s, is probably capable of dealing with this extra air/fuel, at least under steady conditions like idle or cruise or whenever the purge valve would ordinarily be commanded to be open. But one could envision how slow O2s and/or a bad purge valve leak would cause the ECU to hunt for the right A/F mix, particularly under dynamic situations, resulting in rough running or stuttering. So in my case, I did an experiment - - mostly because I was sick of the hard start after fueling up. I put a vinyl/rubber vacuum cap over the intake side of the purge valve nipple, the part that the rubber​ hose slides over. I used a pick to poke a small hole in this cap (~1mm or less) and reassembled the intake hose over the cap onto the purge valve nipple. Result: 1) No more hard starts after refueling 2) No check engine lights (I was worried about not enough vacuum being pulled on the tank and triggering an emissions issue) 3) STUTTERING UNDER ACCELERATION WAS GONE! It runs great and strong! Transmission shifts better/smoother too. Its all linked on these cars. 4) I occasionally get a faint gasoline smell in the cabin, but I think it was actually worse before my hack/test. I suspect I need new fuel filter/pump/tank gaskets. I think this is unrelated, but I wanted to mention it, because I may not be pulling as much vacuum on the tank as the factory designed given that I've restricted the purge valve. I've driven like this now for about 3-4 months and it seems great. I bought a new replacement purge valve, but haven't gotten around to installing it. I don't know if this hack will fix your car - - it may not given that you've reportedly already replaced your purge valve, although I suppose its possible that the replacement has also failed - - but I do think it's a simple test/fix for anyone with possible purge valve issues. A few additional thoughts: 1) The simplest way to test this purge valve theory would be to disconnect the rubber hose from the purge valve and completely plug/cap the rubber intake hose (not the PV) with something. While this may throw a code over time, it would be a quick test of whether the purge valve is the source of your surging. 2) For those looking at this as a permanent fix, I used a small vinyl vacuum cap with small hole in it to restrict the flow. I figured that it would be held in place by the hose/clamp that went around it. It worked, but note that the cap got stuck in the rubber intake hose when I pulled the hose off after a test fit. No biggie, but I needed to thread a screw through the hole in the cap so I could fish it back out of the hose to reinstall it on the purge valve upon reassembly. Hope that makes sense. 3) There are likely other ways of restricting the rubber hose to the purge valve - - whatever you pick, make sure it won't damage your engine if it gets sucked in accidentally. Soft materials like rubber or vinyl are probably best. 4) I didn't experiment with the size of the orifice, but I'd think there's probably a sweet spot. The hole I made with the pick was pretty small, but definitely flowed air/vacuum. Start small. If you get a check engine light, consider enlarging the hole a bit more. Lastly, and unrelated to the above fix, have you replaced the primary O2s? It made a world of difference on my 997, even though the sensors had less than 50k miles on them. Much improved running under all conditions. My guess is that the O2s get slower to respond over time, making any real-time A/F issues much more noticeable. Hope that helps, and best wishes. Sent from my Nexus 6 using Tapatalk

It's stuttering under heavy acceleration / boost? My '06CTT does something similar - - annoying to me, but others might not notice. It's not rough when revving, though (thankfully). I wonder if it's aging MAFs and/or O2s? Laziness or miscalibration of either could cause issues under transient loads.

Seafoam in the intake or gas tank? Use Techron if you are worried about deposits - it does smooth running but won't fix the issues of the magnitude you're having. Did you check that the MAFs were plugged in and search for obvious boost leaks? Have you pulled the codes again to confirm the same ones? The codes you have could be coils, but most people complain of rough idle with coils, and from your description you seem to have rough acceleration. Since you've already fixed one cracked coil (and replaced the plugs) the next step would be to recheck the other coils for obvious cracks and move the #1 and #8 coils to different cylinders and see if the error codes move. And you might consider replacing all the old coils proactively depending on how much you value your time/money. Also double check that your coils are fully plugged in. I seem to recall the connectors being hard to seat fully. One other thought, if it idles fine, but has no power/won't accelerate, maybe there is a fuel pump issue (seems like that would throw more codes, though). I've not had fuel pump issues (knock wood) but its reasonably common on the forums . Search for "Cayenne fuel pump test" as there are two pumps, and pulling a fuse can diagnose their functioning. Good luck.