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About Octane4evr

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    Contributing Member

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  • From
    Seattle, WA, USA
  • Porsche Club
    PCA (Porsche Club of America)
  • Present cars
    2003 C4S X51, 2006 325i, 2015 Q5, 1965 Mustang 5 speed - 415HP, 420ft-lb, 1997 Tacoma, 2003 Suburban
  • Future cars
    2011-2013 BMW M3 Coupe
  1. You might want to throw a water pump and surge tank in while you're in there and a new belt and tensioner for good measure. My 2003 C4S had a very heavy clutch pedal when I bought it a year ago at 80k. Turned out that the helper spring, slave cylinder and hose were bad as well. Don't know about the grinding on downshift, I've not had that issue. Keep the maintenance/wear parts up to snuff and you'll really enjoy this car. Best of luck!
  2. If the seals for the crankcase are leaking would I see oil leaks? This engine uses almost no oil, about one quart per 6000 miles.
  3. Drove with the MAF unplugged all the way home ~45 minutes. No noticeable difference in idle after the drive. The comment from Porschetech3 on the crankcase vacuum being too low has me wondering about the seals you mentioned or anything else that would cause reduced vacuum in the crankcase. Other than the seals you mentioned, should I check anything else when I have it on the lift for the oil change? Also, my independent Porsche shop expressed a concern about lifters sticking causing this issue. Any thoughts on that?
  4. I did clean the MAF with CRC's product designed for that purpose, no change. I'll pull the plug on the MAF and see what happens. Any issue in driving it for a long distance without the MAF connected or should this just be a short test? I did feel the rough idle when the data shows the variation. I'm due an oil change, planning that for next week. I'll check the Variocam+ and intake valve lift solenoid seals. In reading on this in other threads there was some success others have had by changing the IMS and cam chain tensioners. Any thoughts on doing this preemptively? Porschetech3, I tested this with a home made manometer, see the picture attached for the principle I used to create it, mine's just a length of clear tubing on a piece of plywood but inches of water is inches of water. I've heard all kinds of things about the AOS and faults with it but I can't seem to find a diagram showing where it is and where all the various hoses are and how to access. Any help would be appreciated. I'm going to get my local shop to do a leak down test, hopefully next week. Thanks for all the help!
  5. Thanks for the great info and advice. I've attached two log files, one for a full trip home of over an hour and one of a couple of minutes of idle after the drive. The rough running values for several of the cylinders are higher than you're seeing on yours. This time it's not #2 though. I have a call into my shop, I recall they did a compression check when they did the plugs and coils. Not sure about a leak down. I'll post that info when I get it. Idle after 1 hr drive.xlsx Full trip.xlsx
  6. FIRING ORDER!!! Now I understand why the column order was wacky - Thanks! I did swap the column order, not just the labels. It took me a few minutes to get the Durametric set up so the car was warm when I started logging the data. I'll create a log file on the way home tonight and add coolant temp to the list and post the results. I see the same thing on cylinder 2 but I wasn't sure what the acceptable range actually is. I'm not sure how a leak down test is accomplished, is that something a shop would need to do?
  7. Here's an updated file with the data as numbers instead of text so it can be plotted.2017_11_11_15_41_50_UW_TRIP - Data.xls
  8. Over the past couple of weeks I've checked the cam deviation values when the engine is fully warm, they change only slightly one varies from 1.63 to 1.75 degrees and the other from 0.00 to 0.03. They are steady at whatever value they have for that trip throughout the RPM range. The plugs and coils are only about 4000 miles old. The symptoms were present before they were changed. There are no misfires logged on any cylinder during idle or at cruise. I've attached a log file of a recent trip logging everything I could think of and Ahsai's suggestions. The other thing I checked was the crankcase vacuum at idle. It is 2.5 inches of water. I also found another thread where Ahsai and JFP helped discover that the problem that a 986 owner was having was the MAF. JFP has already suggested this might be and MAF problem. I'm willing to change it out depending on your confidence level after seeing the data. Is there any way to check for a stuck lifter? Thanks for all the help!!! 2017_11_11_15_41_50_UW_TRIP_KEEGAN.xls
  9. On the topic of going to coilovers... Has anyone used the BC Racing BR Series Coilovers? Seem like a bargain for getting all the adjustment you need to get the right ride height.
  10. Cleaned and did the TB/Idle reset. No effect on the problem. No Idle control valve on the 2003 engine. Checked around for a vacuum leak. Moved around the Oil Tube to see if there was a leak, no change in engine performance. This time when pulling the oil cap off the engine RPM dropped and got very rough, I may not have had it fully warm last time. I've attached the Durametric screen showing cam deviation, two separate tests. They aren't the same on both sides, not sure what they should be though. When I activate the "valve lift control banks 1 and 2" (There are two of them listed with the same name) the engine shuts off immediately.
  11. It really does feel like a vacuum leak. I'm more familiar with small block V-8's and this is a lot like it feels when the carb isn't fully sealed to the intake manifold or there's some other vacuum leak. I'll clean the TB, I'm not sure the 2003 has an Idle Control Valve, as you suggest and check for disconnected tubes/cracks in the oil filler. Thanks for the help.
  12. So, I finally got a Durametric so I can test the MAF. I plotted MAV and Idle speed in the image below. As you can see, the curves lay right over the top of each other, as you'd expect. What I don't know is if this variation is normal. I cleaned the MAF with CRC's specialty cleaner. No effect. I pulled the oil cap off with engine idling, slight increase in engine RPM, no increase in the shudder feel. Any ideas?
  13. I have a 2003 C4S with the X51 package that I purchased last November. I use the car as my daily driver so I've put about 11k on it since purchasing. The engine has always run a bit rough, like an old V8 with a bigger cam than stock. Kind of a smooth - shudder - shudder - smooth cadence. The motor pulls hard but I feel the shudder even free rev-ing the engine and trying to hold a steady RPM. At idle, when it's doing the shudder thing, the RPM's jump imperceptibly on the tach but I can see them bounce through the OBD reader. The plugs and coils have been replaced for other reasons and I've used Liqui-Moly injector and valve cleaner several times with no effect. There are no codes in the ECU, no misfire or cam or injector codes at all. My local Indy repair shop thinks it may be the vario-cam not fully disengaging. Oil's been changed twice in my ownership but I've not used any lubrication modifier or anything like Sea-Foam to mess with the oil. Any ideas? The vario-cam thing seems likely but before I spend that kind of time or cash I'd like to be sure.
  14. I have a similar issue with the passenger door. Seems to only happen when it's hot (Seattle hot, over 70). The window does not move at all and the red light is continually on for the door lock switch on the dash. Seems weird that it's only when it's warm. Window goes up and down. I've re-trained the window stops but it doesn't help. I'm thinking it's the door lock actuator. Ideas? Toddmac12, where did you get the good used part for $60?
  15. FYI, a P12 Nitrile O-Ring works great!

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