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      03-12-2011, 03:45 PM   #1
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Is my idle valve starting to go? Engine almost stalling on 6MT

Hi gang. Wanted to start a new thread because all idle valve issues I've read here start with erratic idle (and I've been around for a while ), usually involving higher rpm. I made the title specific for future searches.

Just came back from another 800-mile trip, and other than a stupid falcon hitting my hood (fortunately nothing happened to it) and having a flat that forced me not to exceed 80 mph on the way back ('stop & go' tire repair kit worked great), all was well with the exception that in TWO occasions my engine wanted to stall (twice the second time), with the complimentary ugly noise and shaking. This is a 6MT, and it happened after pulling over from the highway for TPMS light and bathroom break (not low in gas). No problem with cold starts at all so far, which is usually the first symptom of a bad idle valve. I've done this run many times before, and only filled up at Chevron stations, with the exception of a few gallons of Texaco, but this was after the 2 incidents. I've always filled up at the stations in question, which are high-volume gas stations (I always fill up with Chevron whenever possible). Oh, and A/C off, so can't blame that.

Any ideas if we're dealing with the idle valve here? I just can't find an explanation of 'bad gas' causing just this issue, and just twice.

My questions are the following:

- Does a regular OBDII scanner would read codes related to the idle valve issue (misfires, IAP sensor, etc)? Remember reading that they don't read Motronic codes, but after checking what ECU we have, it turns out it's a SIEMENS, not Bosch. Is that also considered 'motronic'? I know car has several ECUs, so maybe others are Bosch Motronic. If somebody can enlighten me of the different ones and what they do, it'd be great .

- Has anybody changed the idle valve on their own? How much is it? Might have no choice but letting only local dealer fix it if too expensive (probably the case), but it's a small city, and according to my SA they never heard of idle valve problems, so I know it'd be an uphill battle to get this issue resolved. As most of you know, the stupid car diagnostics rarely points to the idle valve itself. Plus my car would have to throw some codes before I even bother to take the car in.

With so many dealer f**k ups recently, and not trusting only local dealer in town, I'd like opinions from DIYelfers on how to approach the issue if it worsens.

By the way, I tried to inspect the idle valve when car was new, but had to abort the job when I found special clamps on the hoses, since it'd had made it obvious I worked on the car if replaced. Thanks gang.