'02 Carrera: High Idle/poor part throttle performance/CEL codes..
02-08-2019, 05:42 PM
#1
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Thread Starter
'02 Carrera: High Idle/poor part throttle performance/CEL codes..
I have posted before on this issue, but here's the latest hoping that any of our members might have some guidance/advice:
Mine is an '02 Carrera with 51,000 miles. It ran wonderfully for my first year of ownership. Out of nowhere, I recorded P0507, P1128 & P1130 codes. The idle was high and part throttle performance completely suffered. My first move was to replace the MAF sensor, which did not improve matters.
Brought it to the local dealer for assessment, and the diagnosis was the air/oil separator accounting for a vacuum leak. $900 later, the car was claimed to be far better and no CEL. Well, one day later I have a CEL and the part throttle performance is anemic...almost wheezy. Once you apply full throttle, it performs as expected, but you can't drive around full-throttle (at least most of the time). It also seems to be drinking fuel at an alarming rate. During the AOS replacement, the throttle body was cleaned by the technician and the service manager suggested that if things were not completely right with the car, it's likely that the throttle body needs to be replaced. It sure sounds like 'plug and play' repairs hoping something works.
Recall that when the AOS is replaced, much of the top-end of the engine is removed to provide access, so I would expect that intake leaks should be eliminated via the work process.
I purposely let the dealer replace the AOS (which I could have done myself) hoping that their diagnosis was based on previous like cases. I could have saved myself $700.
Looking for any input on next steps. The codes I'm getting now are the P0507 (idle control @ stop) and a 5525 (failed data exchange from the DME). I imagine that replacing the throttle body is the next step (dealer parts are $500 vs. $185 on the open market for the Bosch part)?
Thanks in advance,
Bob
Mine is an '02 Carrera with 51,000 miles. It ran wonderfully for my first year of ownership. Out of nowhere, I recorded P0507, P1128 & P1130 codes. The idle was high and part throttle performance completely suffered. My first move was to replace the MAF sensor, which did not improve matters.
Brought it to the local dealer for assessment, and the diagnosis was the air/oil separator accounting for a vacuum leak. $900 later, the car was claimed to be far better and no CEL. Well, one day later I have a CEL and the part throttle performance is anemic...almost wheezy. Once you apply full throttle, it performs as expected, but you can't drive around full-throttle (at least most of the time). It also seems to be drinking fuel at an alarming rate. During the AOS replacement, the throttle body was cleaned by the technician and the service manager suggested that if things were not completely right with the car, it's likely that the throttle body needs to be replaced. It sure sounds like 'plug and play' repairs hoping something works.
Recall that when the AOS is replaced, much of the top-end of the engine is removed to provide access, so I would expect that intake leaks should be eliminated via the work process.
I purposely let the dealer replace the AOS (which I could have done myself) hoping that their diagnosis was based on previous like cases. I could have saved myself $700.
Looking for any input on next steps. The codes I'm getting now are the P0507 (idle control @ stop) and a 5525 (failed data exchange from the DME). I imagine that replacing the throttle body is the next step (dealer parts are $500 vs. $185 on the open market for the Bosch part)?
Thanks in advance,
Bob
Last edited by gcthree; 02-27-2019 at 11:58 PM.
02-08-2019, 05:57 PM
#2
Try taking the oil fill cap off and making sure the o-ring has a good, clean seal. Might be getting air in the system from a poor seal there.
02-08-2019, 06:57 PM
#3
Rennlist Member
Sounds like you have an intermittent issue. Seems as though the car passed the self tests after the AOS replacement and TB cleaning, then an issue came back a day later, as an intermittent issue. Intermittent issues are usually electrical in nature as opposed to physical/mechanical but not always.
I have seen the plastic vacuum reservoir under the intake that serves as reserve vacuum for the various change-over valves leak on an intermittent basis. The leak caused by a crack at the bottom seam can intermittently seal its self as vacuum pressures and temperature change it propensity to leak.
Intermittent issues are very hard to diagnose because test results can not be believed as 100% plausible.
All that said, your symptoms does seem to indicate a vacuum leak, but I would recommend a Porsche specialist to diagnose this again, preferably the one who did the previous attempt, as he is most familiar with this cars issue and has done previous tests.
I have seen the plastic vacuum reservoir under the intake that serves as reserve vacuum for the various change-over valves leak on an intermittent basis. The leak caused by a crack at the bottom seam can intermittently seal its self as vacuum pressures and temperature change it propensity to leak.
Intermittent issues are very hard to diagnose because test results can not be believed as 100% plausible.
All that said, your symptoms does seem to indicate a vacuum leak, but I would recommend a Porsche specialist to diagnose this again, preferably the one who did the previous attempt, as he is most familiar with this cars issue and has done previous tests.
02-08-2019, 07:26 PM
#4
You can try e-gas re-calibration first (free) then ask a shop to do an intake air leak test. From your description it got to be a gross leak that's easy to find (if the root cause is air leak). Then replace the or swap in a known good throttle body.
BTW, I can't find any documentation of code P5525, are you sure that's the right code?
BTW, I can't find any documentation of code P5525, are you sure that's the right code?
02-08-2019, 10:30 PM
#5
02-08-2019, 10:40 PM
#6
Rennlist Member
Thread Starter
Code on my Foxwell was simply 5525 and not P5525. Appears to be a communication issue between the car and the scanner.
I will bring it back to the dealer for further diagnosis, which is why I had the AOS replaced by them in the first place should it not cure the issue. My car has run well since I bought it, but I always felt that the part throttle performance was never what I expected as it was decidedly 'choppy' and pronounced, which I chalked-up to the VarioCam activation. Perhaps it was the onset of a vacuum issue.
Giving thought to trying the propane test to see if I can locate a leak before bringing it in for further service.
I will bring it back to the dealer for further diagnosis, which is why I had the AOS replaced by them in the first place should it not cure the issue. My car has run well since I bought it, but I always felt that the part throttle performance was never what I expected as it was decidedly 'choppy' and pronounced, which I chalked-up to the VarioCam activation. Perhaps it was the onset of a vacuum issue.
Giving thought to trying the propane test to see if I can locate a leak before bringing it in for further service.
02-08-2019, 10:44 PM
#7
Visually inspect your oil filler neck. They tend to crack and cause the issues you're experiencing. I've replaced mine ones so far and I'm much more careful with it now.
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02-09-2019, 09:14 AM
#8
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I agree with everyone...you have a massive vacuum leak somewhere on the engine. Like said, carefully check your oil filler pipe for cracks. You may have to smoke test the vacuum system and crankcase. Also, since so much top end stuff has to be removed to replace the AOS, carefully check the intake plenums and rubber joints, make sure they are aligned properly on both sides and the clamps are tight. Your DME is confused because too much air is getting into the engine after the MAF sensor, thus it is enriching the fuel mix to compensate. Also, after checking everything and hopefully finding the leak, disconnect the negative lead of the battery for 15 minutes to reset the adaptations in the DME, perform an e-gas calibration and then drive for at least 30 minutes and one complete heat/cool cycle. Good luck!
02-09-2019, 06:53 PM
#9
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Thread Starter
First, thank you to all posters with your thoughts and input. Really helpful!
To date:
- I've replaced the oil fill tube shortly after taking ownership of the car as it was identified as a potential issue at the PPI.
- The dealer (Euroclassics in Richmond, Va) just replaced the AOS this week, and in the process removed much of the intake tract in the car to access it. I must assume that all intake tracts are sealed upon their reinstallation.
I agree with DBJoe that there is too much air entering after the MAF, accounting for the high idle and I suspect the high fuel consumption. Smoke test is the next logical step before I begin 'plug-n-play' replacing everything.
Bob
To date:
- I've replaced the oil fill tube shortly after taking ownership of the car as it was identified as a potential issue at the PPI.
- The dealer (Euroclassics in Richmond, Va) just replaced the AOS this week, and in the process removed much of the intake tract in the car to access it. I must assume that all intake tracts are sealed upon their reinstallation.
I agree with DBJoe that there is too much air entering after the MAF, accounting for the high idle and I suspect the high fuel consumption. Smoke test is the next logical step before I begin 'plug-n-play' replacing everything.
Bob
02-09-2019, 10:38 PM
#10
Rennlist Member
Might be a good idea to smoke test when the car us up to temp. Good luck!
02-10-2019, 10:30 PM
#11
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Thread Starter
Ahsai:
I did the e-gas recalibration after disconnecting the battery and after some initial idle hunting and rough running, it all came right. Idle is now 700rpm and the throttle run-up is silk. Haven't had a chance to road test it, but in the garage it is a different beast. Thanks for the recommendation!
Fingers crossed!
Bob
I did the e-gas recalibration after disconnecting the battery and after some initial idle hunting and rough running, it all came right. Idle is now 700rpm and the throttle run-up is silk. Haven't had a chance to road test it, but in the garage it is a different beast. Thanks for the recommendation!
Fingers crossed!
Bob
02-10-2019, 10:40 PM
#12
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Thread Starter
For the record, the e-gas recalibration process is:
- disconnect the battery and leave it disconnected for a few minutes
- reconnect the battery
- turn the ignition on for 60 seconds but do not start the car or touch the gas pedal.
- switch the ignition off for a minimum of 10 seconds
- start the car and allow the DME to relearn; I let it idle for a good 10 minutes.
Bob
- disconnect the battery and leave it disconnected for a few minutes
- reconnect the battery
- turn the ignition on for 60 seconds but do not start the car or touch the gas pedal.
- switch the ignition off for a minimum of 10 seconds
- start the car and allow the DME to relearn; I let it idle for a good 10 minutes.
Bob
02-14-2019, 10:48 PM
#14
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Thread Starter
It wasn't... The idle now sits at 1,200 to 1,300 rpm. Off-idle performance seems encouraging, but there's a noticeable flat spot from 2,400 through 3,400 rpm. Once full(er) throttle is applied, it runs strong and pulls hard. On throttle chop in low gears, the car 'snatches' and bucks. It's far better than before, and unless this is how a 996 runs normally (I have no reference point), it's not right. The dealer suggested (when they replaced the AOS and cleaned the throttle body) that it could be the throttle body, which seems plausible...I guess? Does any of these observations align with a troubled throttle body?