low rev misfires
 

hi, can anyone help me? ive got a porsche boxster 986, and lately i started having misfires in the engine only in idle. when accelarater is pressed slightly, the misfires disappear, but on idle the engine will sometimes also die. i have the engine check bulb on and sometimes it blinks. ive been to a porsche garage and they are finding it hard locating the problem. they changed the lambda sensors, checked ignition coils, but to no avail. the problem is that the engine is only operating on 3 cylinders in idle position, but when in motion all 6 will fire up. the annoying thing is engine dying in traffic!! any suggestions?

What year is your boxster and how much mileage is on it? Have you had your spark plugs changed yet?

If you can, adjust your throttle cable where it meets the throttle body so it has a "stronger" idle. That way it would be like holding your foot on the gas a little when at a stand still. And maybe keep your car from dieing.

Over the weekend i was at my mechanics shop and he had a 99 996 in that wasn't running correctly under load.

After hooking up the obd scanner to it he found out that the engine was misfiring on 2 cylinders. His diagnosis is that a cam adjuster was bad so the engine was severely out of tune which was causing the misfires.

Whether or not this applies to your situation or a boxster for that matter, a misfiring cylinder is a severe issue and i hope you are not driving the car anymore until it's fixed.

yes ive had them changed. its a 1999 model with 69,000 miles on it

the obd is just saying that its misfiring on 3 cylinders when idle, its not giving any diagnosis. now theyre gonna check the catalytic converters.
at the moment im still using it yes, you think i shouldnt?

good idea, at least i can do that until the problem is fixed!

Have they checked the MAF?

Hi,

Could be MAF, Fuel Filter, or any number of other things including a mechanical timing issue. I would not risk driving the car until it is sorted, you could cause major damage in some instances...

Happy Motoring!... Jim'99

i agree with Jim in regards that it could be a number of things but worse case scenario....

misfiring can cause burnt valves (not good) and if it has to do with a bad cam..that means your valves are not in sync and that could mean the potential for bent valves and a damaged cylinder head...i shudder to think what that might cost.

not wanting to scare you as it may be something minor but as the saying goes...better safe than sorry.

good luck with figuring it out and i hope all turns out well with it.

no i dont beleive they did. could it be that it needs replacing?

fuel filter is new. i dont think they checked the MAF though. does it usually effect the revs when the MAF is dirty or needs replacing?

yeah i agree, though the garage told me that i there doesnt seem to be any risks if i carry on driving, im mot feeling so comfortable driving it, especially when i'm in traffic and the engine shudders and dies!

Kinda funny you used the German "Lambdasonden" for oxygen sensor.

An engine that dies at idle, misfires, and is severely "out of tune", and they can't find the problem - but they think it's okay to drive? I think you need a new Porsche mechanic.

Yes, the MAF could be responsible for these problems - at least in the beginning. Some of what you are experiencing could simply be the after effects of running with a bad MAF.

You can keep driving it - but exactly how many more problems are you interested in fixing?

Unplug the MAF see if it goes away.

hmmm
 

its a MAF problem for sure.

The problem you mentioned, is exactly what i had. I tried to diagnoses it with vacuum leak test, i even took it further to test the Air/fuel ratio, smog check etc. to test the stalling, I tested the Fuel pressure to see if fuel filter is bad or pump is bad, i even had the Coil over plug checked, spark plugs. I cleaned the idler controller, i cleaned the throttle body, tested the ignition module etc. etc.

don't waste your time its MAF, if it isn't then move to the idler contoller to see if its working properly