12 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHRPM slow to fall after throttle blip
Leading reported evidence
Replace 2000 miles ago
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
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0
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1
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Performed · outcome unconfirmed · Original poster
fuel filter changed 2000 miles ago - but worth a look
Leading evidence: 'Replace 2000 miles ago' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, the most frequently mentioned possible cause is 'intake/vacuum leaks' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Check fuel trims trying' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Suggestion
If you have durametric, you can check the fuel trims trying to diagnose it further.
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Suggestion
If cabled, I'd check both the pedal and throttle body for smooth action.
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Suggestion
Either way, check the throttle body to make sure nothing is gummed up or being interfered with...
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12 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
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Have tried a search but can't find anything.
Recent issue - when changing down a gear for example from 3rd to 2nd, and using heel and toe - if I blip the throttle it will increase without delay but will then stay at a relatively high level for several seconds so I will end up in 2nd with the rpm remaining at say 3000 if the clutch is depressed. it will stay there for a few seconds while the clutch is held depressed before returning to idle at 900.
could this be a vacuum leak or AOS starting to fail ? No other issues or smoke etc at start up and the car drives really well other than this rpm issue.
any thoughts appreciated.
Sorry for my ignorance (my '99 C4 is e-gas) - is your car e-gas or cabled? If cabled, I'd check both the pedal and throttle body for smooth action. Either way, check the throttle body to make sure nothing is gummed up or being interfered with...
Thanks guys - car is e-gas and throttle body recently cleaned but that has made no difference.
I have heard that the electronic unit stepper motor on the throttle body sometimes plays up but I would have expected poor response in both directions in that case.
idle hunts at first start when cold but is stable when warm.
After a long drive, idle will sit at 1500 for about 15 seconds when coming to a stop, then reduce to a stable 800.
fuel filter changed 2000 miles ago - but worth a look
Thanks
There is no "IAC"....
The Porsche engineers have decided the throttle plate control parameters, what you are experiencing may well be SOP.
Blip, downshift,....then CLUTCH...
Unforeseeable action...?
You have a problem right there at idle so maybe focus on diagnosing that first. The spec rpm with ac OFF should be 700 +/- 40 rmp. Your 800 is too high if ac was OFF.
Agree it sounds like a vacuum leak. If you have durametric, you can check the fuel trims trying to diagnose it further.
Doh, that's what happens when you have 5 cars.
Was looking under the cowl under my windshield the other day for awhile trying to figure out where the cabin filter element door was on the wife's MDX. Forgot it was in the glovebox. lol
And I always do the left to right key shuffle dance as well quite often too.
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