16 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHIdle Air Control Valve ...or...?
Leading reported evidence
Clean i was hoping
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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Read evidence and context
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Performed · outcome unconfirmed · Original poster
I was hoping to drive this weekend so once it was cleaned I reinstalled.
Leading evidence: 'Clean i was hoping' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, the most frequently mentioned possible cause is 'solution' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Clean i was hoping' (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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Suspected cause · Original poster
When I saw how cruddy it was, I thought cleaning it was the solution.
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Suggestion
Also if the idle speed is above 760 RPM with ISC "disconnected", you have a vacuum leak....
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Suggestion
There are lots of videos on how to make smoke machines and do the simple tests...Vacuum leaks are the most common cause of running issues on m96 engines...
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Suggestion
There are lots of videos on how to make smoke machines and do the simple tests...Vacuum leaks are the most common cause of running issues on m96 engines...
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16 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
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1 acknowledgements have no verified action link; they do not establish a repair result.
Had a P1514 & P1554 code after my hammering of the car at the Porsche Experience Center, so I pulled the Idle Air Control Valve, grabbed a bottle of brake clean and went to town. It was pretty filthy and was looking quite nice when decided to reinstall. I thought I would be good to go for a celebratory canyon run tomorrow but the car has other ideas. Took a video, but the same two codes are present.
What do you guys think this is? IAC or something else?
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No I didn’t get a chance to before I reinstalled it.
When I saw how cruddy it was, I thought cleaning it was the solution. I was hoping to drive this weekend so once it was cleaned I reinstalled. I’ll pull it again and test it. I searched prior and I think the middle pin was the ground, and the outer ones were designated for opening and closing. That sound correct?
ps did the video show up and work for you guys?
What does it do if you disconnect the ISC? It should idle slower than normal but steady and smooth with ISC disconnected...
The ISC is supposed to idle up the RPM just a little, to 760 RPM , and a little more if the A/C is on..
I would install the Durametric and watch the ISC duty cycle and also the TPS voltage....the TPS should be at about .9v and should not move at all unless the throttle is moved....
Also if the idle speed is above 760 RPM with ISC "disconnected", you have a vacuum leak....
I think you have a vacuum leak, I would do a smoke test on the intake to find the leak.
Also it is possible the TPS ( throttle position sensor) is faulty even though no code is present....The TPS has a range of ~.9v to 4.5v and anything in-between that range is believable to the DME to be correct....At idle it should be .9v and steady, full throttle 4.5v and should be a very smooth and progressive rise in voltage as the throttle is opened...IF at idle and the voltage is jittering from .9v to 1.1v the DME will think you are moving the throttle pedal and activate/deactivate the ISC .. The ISC should only be activated at ~ .9v
Another thing I like to do on 99C2's to troubleshoot vacuum leaks, is to make sure the throttle is on the mechanical stop screw, then disssconnect the ISC, the engine should idle at about 600RPM o a little less with ISC disconnected and the butterfly is clean and on the mechanical stop...( the ISC raises and controls the idle speed as needed due to load from accessories and/or A/C) ...The ISC cannot " lower" idle speed, it only "raises" idle speed, so IF the idle speed is "above" 600RPM with ISC disconnected and butterfly on the mechanical stop, there has to be air leaking in aft the throttle body...
Not sure if this is TMI, but a simple smoke test can find vacuum leaks. There are lots of videos on how to make smoke machines and do the simple tests...Vacuum leaks are the most common cause of running issues on m96 engines...
Correct me if I�m wrong but I don�t see an option on the Durametric that displays TPS voltage on a �99. I know that 99�s can be peculiar in what is able to be monitored; not sure if that�s related.
You can just backprobe the TPS at the sensor...I haven't had my Durametric out in a while but I know PIWIS will display TPS voltage...
Glad they found it AND it is in a very easy to find/ix location !!
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