Cold 2-3K RPM partial throttle stutter
11-03-2011, 07:07 PM
#1
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Cold 2-3K RPM partial throttle stutter
It seems others have a similar problem, but I think mine is a bit different.
When the car is cold, either in the morning leaving for work, or leaving work to go home, whether it's 30F outside or 70F, my stock B5 S4 6M Avant stutters under partial throttle acceleration between 2K and 3K RPM. It does this only once. It's about a 1/4 mile from my driveway to the next road which at which I stop, and then repeat the same acceleration. It does not do this during the 2nd round.
It's usually in 1st gear but if I shift early, then 2nd. But then no more stuttering after the initial one, until starting over with a cold engine.
I've had the same problem for some time now and I'm starting to get annoyed. I first replaced my spark plugs - same thing. Replaced the air filter element, changed oil, e.g. routine maintenance - problem persists. Recently I replaced the diverter valves, and throttle body boot (the TBB was actually still good) and a vacuum line that looked awful to one of the DVs. No dice. Stuttering continues.
I have no check engine light, no EPC light, and like I said before, after that one stutter, the car runs fine. Any ideas? My idle seems to be fine too, so I'm not so sure it's a MAF. It's the Hitachi one too which is supposedly less prone to failure than the Bosch unit.
I'm not ready to spend sever $100 on O2 sensors and a new MAF sensor unless I can nail down what is causing the issue.
Another thing I noticed is that after replacing my DVs, I no longer hear the typical boost purge on throttle lift during shifting. Is that normal for the 710N?
When the car is cold, either in the morning leaving for work, or leaving work to go home, whether it's 30F outside or 70F, my stock B5 S4 6M Avant stutters under partial throttle acceleration between 2K and 3K RPM. It does this only once. It's about a 1/4 mile from my driveway to the next road which at which I stop, and then repeat the same acceleration. It does not do this during the 2nd round.
It's usually in 1st gear but if I shift early, then 2nd. But then no more stuttering after the initial one, until starting over with a cold engine.
I've had the same problem for some time now and I'm starting to get annoyed. I first replaced my spark plugs - same thing. Replaced the air filter element, changed oil, e.g. routine maintenance - problem persists. Recently I replaced the diverter valves, and throttle body boot (the TBB was actually still good) and a vacuum line that looked awful to one of the DVs. No dice. Stuttering continues.
I have no check engine light, no EPC light, and like I said before, after that one stutter, the car runs fine. Any ideas? My idle seems to be fine too, so I'm not so sure it's a MAF. It's the Hitachi one too which is supposedly less prone to failure than the Bosch unit.
I'm not ready to spend sever $100 on O2 sensors and a new MAF sensor unless I can nail down what is causing the issue.
Another thing I noticed is that after replacing my DVs, I no longer hear the typical boost purge on throttle lift during shifting. Is that normal for the 710N?
Last edited by GomerPyle; 11-03-2011 at 07:13 PM.
11-14-2011, 05:19 AM
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Not yet. I have a MAF and fuel filter being delivered today. I probably won't have it out on the road for a couple days though since I need to to some body work too.
11-14-2011, 03:41 PM
#4
It seems others have a similar problem, but I think mine is a bit different.
When the car is cold, either in the morning leaving for work, or leaving work to go home, whether it's 30F outside or 70F, my stock B5 S4 6M Avant stutters under partial throttle acceleration between 2K and 3K RPM. It does this only once. It's about a 1/4 mile from my driveway to the next road which at which I stop, and then repeat the same acceleration. It does not do this during the 2nd round.
It's usually in 1st gear but if I shift early, then 2nd. But then no more stuttering after the initial one, until starting over with a cold engine.
I've had the same problem for some time now and I'm starting to get annoyed. I first replaced my spark plugs - same thing. Replaced the air filter element, changed oil, e.g. routine maintenance - problem persists. Recently I replaced the diverter valves, and throttle body boot (the TBB was actually still good) and a vacuum line that looked awful to one of the DVs. No dice. Stuttering continues.
I have no check engine light, no EPC light, and like I said before, after that one stutter, the car runs fine. Any ideas? My idle seems to be fine too, so I'm not so sure it's a MAF. It's the Hitachi one too which is supposedly less prone to failure than the Bosch unit.
I'm not ready to spend sever $100 on O2 sensors and a new MAF sensor unless I can nail down what is causing the issue.
Another thing I noticed is that after replacing my DVs, I no longer hear the typical boost purge on throttle lift during shifting. Is that normal for the 710N?
When the car is cold, either in the morning leaving for work, or leaving work to go home, whether it's 30F outside or 70F, my stock B5 S4 6M Avant stutters under partial throttle acceleration between 2K and 3K RPM. It does this only once. It's about a 1/4 mile from my driveway to the next road which at which I stop, and then repeat the same acceleration. It does not do this during the 2nd round.
It's usually in 1st gear but if I shift early, then 2nd. But then no more stuttering after the initial one, until starting over with a cold engine.
I've had the same problem for some time now and I'm starting to get annoyed. I first replaced my spark plugs - same thing. Replaced the air filter element, changed oil, e.g. routine maintenance - problem persists. Recently I replaced the diverter valves, and throttle body boot (the TBB was actually still good) and a vacuum line that looked awful to one of the DVs. No dice. Stuttering continues.
I have no check engine light, no EPC light, and like I said before, after that one stutter, the car runs fine. Any ideas? My idle seems to be fine too, so I'm not so sure it's a MAF. It's the Hitachi one too which is supposedly less prone to failure than the Bosch unit.
I'm not ready to spend sever $100 on O2 sensors and a new MAF sensor unless I can nail down what is causing the issue.
Another thing I noticed is that after replacing my DVs, I no longer hear the typical boost purge on throttle lift during shifting. Is that normal for the 710N?
11-14-2011, 06:05 PM
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11-15-2011, 12:48 PM
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If it is only happening when it's cold you might just have a minor air leak. when the car warms a little the rubber hoses get pliable and seal better. you can build or buy an intake pressure tester. search in the forums for intake pressure tester or you can buy from awe-tuning. http://www.awe-tuning.com/media/pdf/...ure_tester.pdf
The fuel filter isn't the problem and I highly doubt the MAF. The other thing that is happening when its cold for the fist minute or so is the (SAI) secondary air injection is running which forces air into the exhaust to help heat up the cat's and o2 sensors quicker. could just be that air pump isn't shut off yet. I would suspect an intake leak or vacuum leak before anything else. even the vacuum is less likely due to it would probably be a constant issue.
The fuel filter isn't the problem and I highly doubt the MAF. The other thing that is happening when its cold for the fist minute or so is the (SAI) secondary air injection is running which forces air into the exhaust to help heat up the cat's and o2 sensors quicker. could just be that air pump isn't shut off yet. I would suspect an intake leak or vacuum leak before anything else. even the vacuum is less likely due to it would probably be a constant issue.
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11-16-2011, 07:41 PM
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If it is only happening when it's cold you might just have a minor air leak. when the car warms a little the rubber hoses get pliable and seal better. you can build or buy an intake pressure tester. search in the forums for intake pressure tester or you can buy from awe-tuning. http://www.awe-tuning.com/media/pdf/...ure_tester.pdf
The fuel filter isn't the problem and I highly doubt the MAF. The other thing that is happening when its cold for the fist minute or so is the (SAI) secondary air injection is running which forces air into the exhaust to help heat up the cat's and o2 sensors quicker. could just be that air pump isn't shut off yet. I would suspect an intake leak or vacuum leak before anything else. even the vacuum is less likely due to it would probably be a constant issue.
The fuel filter isn't the problem and I highly doubt the MAF. The other thing that is happening when its cold for the fist minute or so is the (SAI) secondary air injection is running which forces air into the exhaust to help heat up the cat's and o2 sensors quicker. could just be that air pump isn't shut off yet. I would suspect an intake leak or vacuum leak before anything else. even the vacuum is less likely due to it would probably be a constant issue.
11-17-2011, 05:12 PM
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