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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

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1 hour ago, Brainz006 said:

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
 

Great theory and I did try this a few times with the same results! 

It smoothes out the power and reduces it with little to no boost it feels. But the key is the hesitation doesn't disappear it's only reduced and this is because the boost is much less in this limp type no boost mode with MAP sensor disconnected. 

This was actually many months ago I experimented with the map sensor. But the conclusion I have is the boost kicking in obviously requires more fuel and that is exactly the point where the lack of fuel delivery from partly blocked injectors with poor spray pattern really show themselves as the stutter hesitation. We will be finding out in a week or two when I get them cleaned. I'm actually alittle bit glad the car didn't sell just so I can close this out in my mind as well as to why the engine hesitates. 

 

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  • 3 months later...

Lewis, what plugs are you running? I realized I installed NGK BKR6EIX plugs when I should have installed the cooler BKR7EIX (now on order). The wrong plug type/temperature might cause a hot stutter and otherwise not be an issue when cold. Apologies if I you already covered it.

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3 minutes ago, Brainz006 said:

Lewis, what plugs are you running? I realized I installed NGK BKR6EIX plugs when I should have installed the cooler BKR7EIX (now on order). The wrong plug type/temperature might cause a hot stutter and otherwise not be an issue when cold. Apologies if I you already covered it.

Sent from my Nexus 6 using Tapatalk
 

The pig is sold but to answer your question I was indeed running Bkr7eix and it made absolutely no difference to the original plugs to be honest and if your not in a very hot climate I doubt the cooler plug will benefit you much either it may get more sooty if you don't do a lot of highway miles.

Unless your modified boost wise that is?

 

Bare in mind even a mild boost increase probably won't show any real issues on a healthy engine. The turbo S vs the turbo still used the same plug I'm pretty sure. 

 

I'm running cooler copper plugs in my stage 2 Audi 3.0t and having bought two set (they are dirt cheap vs iridium or platinum) I swapped them out after 10k km and found them to be very sooty which proves being a cooler plug and having a lot of idle time (waiting around in the heat must leave car running) this plug is not best suited for the car despite having increased boost the plugs are not running hot enough to clean themselves but they may protect the engine a little in the summer peak temperatures here and I won't let them go for too long before changing back to iridium hotter original spec plugs. 

 

More info than you wanted maybe .........lol

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Thanks for the detailed answer. I'm in Houston, so it's fairly hot and my stutter is mostly a summer phenomenon, and then most noticeable when the engine and environment are hot. Given that the heat range 7 is specified, I should definitely not be running a hotter plug in Houston. Will report back for posterity if it makes a difference.



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1 hour ago, Brainz006 said:

Thanks for the detailed answer. I'm in Houston, so it's fairly hot and my stutter is mostly a summer phenomenon, and then most noticeable when the engine and environment are hot. Given that the heat range 7 is specified, I should definitely not be running a hotter plug in Houston. Will report back for posterity if it makes a difference.



Sent from my Nexus 6 using Tapatalk
 

Hot weather misfire always leads me to ignition or sensor. 

Have you ever whipped out the crankshaft position sensor and had a look, measure the resistance and also check how strong the magnet is? Very easy to get to don't even need to remove any covers, just put suspension into highest mode and slide under the passenger side just rear of the front tyre. It's right there on the bell housing. 

Other ideas is electrical connection getting warm and resistance increases, look in the wet fuse box under the relays and fuses at the cables and connectors also the dme. Then think about the engine loom it's sensors and also the fuel pump / coil pack relays! Cheap to replace and very hard to diagnose a intermittent fault with. Good luck. 

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Thanks. I suspect plugs first given wrong spec and as my stutter is pretty mild (not sure a non-enthusiast would notice) and only under full load acceleration in the mid-rpm range. The car runs very well otherwise - - especially after exorcizing a few miscellaneous vacuum leaks which played havoc with shifting and part throttle response in the 1500-2500 rpm range.

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  • 1 month later...

Post script: I replaced the plugs. Some improvement in smoothness, but minor hot stutter was still present. However, whilst changing the plugs, I identified one coil (all revision 8) to have a crack. One new Beru coil later and the stutter appears to be gone. The car is velvety smooth now, although not noticeably faster. It's quite nice. Also note that I never had any starting or idle issues, which many cite as the most obvious signs of failing coils.

Given how sensitive these engines can be to a single intermittent coil, all without throwing codes, I can't help but wonder if Lewis still had a bad coil or two, despite having replaced his with new ones. I guess we'll never know for sure.

Anyway, fingers crossed it's fixed. Any future issues and the other older coils will similarly be replaced.

Hope this helps someone. Best of luck to all.

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One other note: I was running NGK Bkr7eix plugs, not the "6s" as I'd thought. I had some boxes of 6s in the garage that must have been for a former car - - that threw me off per my above post. Anyway, the old Bkr7eix came out, and new ones went in. I remember gapping the old plugs to 0.028, and they measured close to 0.035 upon removal, so I was glad to be replacing them after what was only 15k-20k miles. I regapped the new plugs to about 0.027, a bit tighter than before. All good for now. Cheers.

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11 minutes ago, Brainz006 said:

Post script: I replaced the plugs. Some improvement in smoothness, but minor hot stutter was still present. However, whilst changing the plugs, I identified one coil (all revision 8) to have a crack. One new Beru coil later and the stutter appears to be gone. The car is velvety smooth now, although not noticeably faster. It's quite nice. Also note that I never had any starting or idle issues, which many cite as the most obvious signs of failing coils.

Given how sensitive these engines can be to a single intermittent coil, all without throwing codes, I can't help but wonder if Lewis still had a bad coil or two, despite having replaced his with new ones. I guess we'll never know for sure.

Anyway, fingers crossed it's fixed. Any future issues and the other older coils will similarly be replaced.

Hope this helps someone. Best of luck to all.

Sent from my Nexus 6 using Tapatalk
 

You will know. 

I changed the coils for newest revision 21 when I bought the car, (the coil in their were cracked and it did misfire under load at higher rpm) and after 11 months I replaced them all again. Changed plugs also for beru oem, and two sets of ngk plugs, regapped them twice with no effect on the stutter. 

Didn't make any difference, so coils and or plugs wasn't the issue I'm almost 99.9% sure. 

 

My issue was the injectors, they didn't spray clean or in a decent pattern. I tested them with solvent cleaner spray can and a 12v battery to open them.

I never had them properly cleaned before selling it, anyone test driving couldn't tell the stutter was present unless they was a very keen motorist or mechanic. 

 

Good luck, hope the Fix is permanent. 

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