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Old 07-08-2019, 06:38 PM   #1
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Rough idle sometimes stalls

Hello everyone I have a 1998 Porsche Boxster that is running rough and throwing a CEL for general misfire and misfire cylinder 4,5,6 all on bank 2. No other codes are throwing. The car seems to run fine when I am on the gas but as soon as it idles, I can feel it running rough (like itís misfiring) and then occasionally it stalls out when idling. The rpm needle bounces between 600-800 rpm.

This forum is my last shot before I give in and drop it off at a dealership$$$$$


What I have done so far to try to fix the issue:
1. Spark plugs x6 (verified gap is correct)
2. Coil packs x6
3. Verified all coil pack connectors are secure
3. Cleaned the throttle body
4. Replaced the fuel filter
5. Replaced the MAF
6. Unplugged the MAF (recommended on other forums)

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Old 07-08-2019, 07:12 PM   #2
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Quote:
Originally Posted by Syracuse986 View Post
Hello everyone I have a 1998 Porsche Boxster that is running rough and throwing a CEL for general misfire and misfire cylinder 4,5,6 all on bank 2. No other codes are throwing. The car seems to run fine when I am on the gas but as soon as it idles, I can feel it running rough (like itís misfiring) and then occasionally it stalls out when idling. The rpm needle bounces between 600-800 rpm.

This forum is my last shot before I give in and drop it off at a dealership$$$$$


What I have done so far to try to fix the issue:
1. Spark plugs x6 (verified gap is correct)
2. Coil packs x6
3. Verified all coil pack connectors are secure
3. Cleaned the throttle body
4. Replaced the fuel filter
5. Replaced the MAF
6. Unplugged the MAF (recommended on other forums)
They're all on one side of the motor. You've pretty much eliminated spark as the problem. What's left is compression and air/fuel.

Check for vacuum leaks at the plenum on that side. That would effect your mixture.

Can you check your injectors? I don't know if the wiring from all three comes off of one connector, but I would start by checking electrical connections. It's a long shot that all three on one side are bad, but...

Now we get into the internals:

Porsches have "Variocams". I don't know much about them, but that could be a cause. Maybe something's up with that side.

Lastly, have you changed your oil and checked for plastic bits in the filter? If you see bits, it could be your chain guides are gone or going. Or the tensioner on that side is going bad. If either of these is your problem, it could cause slop in the timing chain and throw your valves slightly off time, screwing up your compression. If it gets bad enough you could bend some valves.
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Old 07-09-2019, 11:15 AM   #3
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Location: Woodland Wa
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sounds like it has vacuum leak issues but that would affect all cylinders equally. You could do a vacuum test to rule that out.
My thought is that you have a possible problem related to the cam position sensor on bank 2.
Or as mentioned an issue with the Variocam adjuster on bank 2.

Last edited by blue62; 07-09-2019 at 01:48 PM.
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Old 09-20-2019, 01:42 PM   #4
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Location: Salinas
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My 986 BOXSTER 1997 had a problem very much alike and afetr a lot of work it was a bad fuel injector that was leaking the cause of it. Good luck.

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