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Erratic Idle Problem


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My 98 RoW 996 was working fine up until a few months ago. One morning, I started the car and it would start fine, but die right away as it could not hold idle. Re started it about 5 times and the same thing happened. I called the local mechanic and he told me to take it out for a spirited drive. I did and at the end of the drive, no problem. The same exact scenario happened about a month ago, but that time, I cleaned out the throttle body and MAF connectors with some carb cleaner. Tons of black soot around the butterfly. Once cleaned, it ran fine. This morning, yeap, once again, no idle. "Nice drive" and now the idle is a tad high (900-950), but at least its holding idle.

Any ideas what is causing this? It has a 3 month old fuel pump and filter. Is it the MAF going bad? Is it some sort of warm up regulator? ICV? :cursing: I don't want to replace everything only to find out I only needed to do something else. Your help is greatly appreciated!

Gus

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My 98 RoW 996 was working fine up until a few months ago. One morning, I started the car and it would start fine, but die right away as it could not hold idle. Re started it about 5 times and the same thing happened. I called the local mechanic and he told me to take it out for a spirited drive. I did and at the end of the drive, no problem. The same exact scenario happened about a month ago, but that time, I cleaned out the throttle body and MAF connectors with some carb cleaner. Tons of black soot around the butterfly. Once cleaned, it ran fine. This morning, yeap, once again, no idle. "Nice drive" and now the idle is a tad high (900-950), but at least its holding idle.

Any ideas what is causing this? It has a 3 month old fuel pump and filter. Is it the MAF going bad? Is it some sort of warm up regulator? ICV? :cursing: I don't want to replace everything only to find out I only needed to do something else. Your help is greatly appreciated!

Gus

Remove the idle control valve from the left side of the throttlebody and clean it real well with carb cleaner. Make sure window pivots smoothly.

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My 98 RoW 996 was working fine up until a few months ago. One morning, I started the car and it would start fine, but die right away as it could not hold idle. Re started it about 5 times and the same thing happened. I called the local mechanic and he told me to take it out for a spirited drive. I did and at the end of the drive, no problem. The same exact scenario happened about a month ago, but that time, I cleaned out the throttle body and MAF connectors with some carb cleaner. Tons of black soot around the butterfly. Once cleaned, it ran fine. This morning, yeap, once again, no idle. "Nice drive" and now the idle is a tad high (900-950), but at least its holding idle.

Any ideas what is causing this? It has a 3 month old fuel pump and filter. Is it the MAF going bad? Is it some sort of warm up regulator? ICV? :cursing: I don't want to replace everything only to find out I only needed to do something else. Your help is greatly appreciated!

Gus

Not sure is this applies to 996's but it does for boxsters... If it is your MAF going bad, you can tell by firs disconnecting your battery, then disconnect the electrical connector to the MAF then reconnect battery and see if the issue comes back. If not, then its the MAF. you wil get a CEL about 20-40 minutes later but the car should run better with the maf disconnected if it infact is malfuntioning

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My 98 RoW 996 was working fine up until a few months ago. One morning, I started the car and it would start fine, but die right away as it could not hold idle. Re started it about 5 times and the same thing happened. I called the local mechanic and he told me to take it out for a spirited drive. I did and at the end of the drive, no problem. The same exact scenario happened about a month ago, but that time, I cleaned out the throttle body and MAF connectors with some carb cleaner. Tons of black soot around the butterfly. Once cleaned, it ran fine. This morning, yeap, once again, no idle. "Nice drive" and now the idle is a tad high (900-950), but at least its holding idle.

Any ideas what is causing this? It has a 3 month old fuel pump and filter. Is it the MAF going bad? Is it some sort of warm up regulator? ICV? :cursing: I don't want to replace everything only to find out I only needed to do something else. Your help is greatly appreciated!

Gus

Remove the idle control valve from the left side of the throttlebody and clean it real well with carb cleaner. Make sure window pivots smoothly.

Just did this with my 99 996C2 and it worked well in stabilizing the idle. As explanation the IAC valve is on the left side of the throttle body as you are facing the rear of the car. On my car, and probably on all of the non E-gas cars, it is held on my two bolts. Disconnect the plug and unbolt it. Be sure to hose out the ports that flow air from one side of the throttle plate into the valve and then out to the other side of the throttle plate. Also rinse the IAC valve thoroughly with MAF cleaner. Let everything dry and reassemble. Be careful when removing the IAC to keep the small gasket between the IAC and the throttle body. I reused mine with no apparent problems.

I would also check and make sure that there are no unmeasured air leaks, i.e. that the oil/air separator bellows is not cracked, that the oil fill cap is on tightly, that there aren't any other vacuum leaks that could be throwing the MAF off.

Also, are you pulling any codes? I know you don't have OBDII requirements but the ECU should still be storing codes. Might try having those pulled and see if they show anything.

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Thank you all for your replies. I had to leave on a business trip this afternoon, so I am away from my car to try and clean out the ICV. My car is not throwing any CEL at all (nor do I want it!). Will report back once I get this taken care of next Monday or Tuesday. Again, thank you very much.

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My 98 RoW 996 was working fine up until a few months ago. One morning, I started the car and it would start fine, but die right away as it could not hold idle. Re started it about 5 times and the same thing happened. I called the local mechanic and he told me to take it out for a spirited drive. I did and at the end of the drive, no problem. The same exact scenario happened about a month ago, but that time, I cleaned out the throttle body and MAF connectors with some carb cleaner. Tons of black soot around the butterfly. Once cleaned, it ran fine. This morning, yeap, once again, no idle. "Nice drive" and now the idle is a tad high (900-950), but at least its holding idle.

Any ideas what is causing this? It has a 3 month old fuel pump and filter. Is it the MAF going bad? Is it some sort of warm up regulator? ICV? :cursing: I don't want to replace everything only to find out I only needed to do something else. Your help is greatly appreciated!

Gus

Idle problems can also be caused by vacuum leaks and by failing / failed O2 sensors. Have the car tested at a Porsche Dealer - the PST2 or PIWIS will find the problem in minutes.

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  • 2 weeks later...

Well, I finally found the time to read the posts on how to remove the ICV and I did so (cleaned it with carb cleaner). Bunch of soot came out. The rear bolt (closest to the interior of the car) was a 3!tch to get to! Since my last post the car has not acted up again and lets hope that the cleaning out of the ICV was the root the the inconsistent idle problems

Goes without saying that :renntech:

Edited by GOB
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  • 3 weeks later...

And here I thought I had dodged a bullet. Well, yesterday afternoon the car would not idle properly (sometimes held rpms in the 400-600 range, if it was a drop from 2K rpms or so, it would just die) so I again took it for a "spirited drive" and what happened after taking it to 7K rpms in second and third was that the rpms now held steady at 1,800! This high idle was present for approximately 5 minutes after the run. I restarted the car and the high idle was still there. Turned it off for about an hour and when restarted, all was fine. Took it to the dealer this morning and they told me that it sounds as if the MAF is going bad, but since no CEL on, that to use it until it does light up. I told them about my ICV cleaning (they were amazed to hear that someone would actually do this by themself) and they told me that the BMW 318is (E36 series) uses the same ICV and costs half as much as what Porsche dealers charge. So, I guess I am back to having an erratic problematic idling car. :censored:

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  • 1 month later...
And here I thought I had dodged a bullet. Well, yesterday afternoon the car would not idle properly (sometimes held rpms in the 400-600 range, if it was a drop from 2K rpms or so, it would just die) so I again took it for a "spirited drive" and what happened after taking it to 7K rpms in second and third was that the rpms now held steady at 1,800! This high idle was present for approximately 5 minutes after the run. I restarted the car and the high idle was still there. Turned it off for about an hour and when restarted, all was fine. Took it to the dealer this morning and they told me that it sounds as if the MAF is going bad, but since no CEL on, that to use it until it does light up. I told them about my ICV cleaning (they were amazed to hear that someone would actually do this by themself) and they told me that the BMW 318is (E36 series) uses the same ICV and costs half as much as what Porsche dealers charge. So, I guess I am back to having an erratic problematic idling car. :censored:

i was experiencing idle problem too ..........until i replaced spark plugs n air filter!!! weird~ :lightbulb:

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GOB, recheck the position of the throttle cable, assuming you are not an egas car. The small plastic flange that the cable passes through on the throttle body is shaped at an angle and may be the cause of your high idle. I had it in upside down at first and it put tension on the cable itself. Flipped it over and all was well with the world.

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See, you guys are going to jinx me :rolleyes: To date, no more problems with the idle. The high idle occurred that one time only, so I doubt that the cable is misplaced (but you never know!). Plugs, wires, and all filters (and numerous other odds and ends) were changed 3K miles ago.

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