Stalls at idle. Gas pedal keeps the engine running - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Hi guys! My 99 2.5 stalls if dont hold down the gas pedal Describing the storyline: 1-car running ok 2-changed oil and oil filter (diy) -> after that, rough idle and stalls after 20-30seconds 3-cleaned throttle body (diy) -> after that, car wont start without pressing gas pedal 4-replaced fuel filter (diy) -> same symptoms as #3 5-replaced idle control valve (diy) -> same symptoms as #3 I can keep the engine running as much as I want holding down the gas pedal. No codes in durametric. Additional info: the car has a coolant leakage (idk if it may affect) What should I check?

Check and clean MAF.

Quotes source post: 634253

you should check & fix this before you do anything else

I agree with both of the above, especially the coolant leak. Before you changed the oil, the car ran without issue? Like no issues whatsoever? And then as soon as you changed the oil you started having issues? If that's the case then I would worry something got buggered up here. What type of oil did you use? What type of filter? Is this the first time you've changed oil on this car? If so, what exactly did you do? I had an old boss who always said "wherever there is an issue, look to where the hands of man have been". Very poetic way of saying that if you've got a problem after doing something, it's most likely you've got a complication from the procedure. Sent from my POCOPHONE F1 using Tapatalk

You didn't tell us if you found anything in the parts you cleaned. My 2.5 had the same issue. Once I cleaned the idle control valve it ran fine. Then it started having the issue again and when I opened it that time the inside of the valve, throttle body and intake has chocolate milkshake in it. Just previously I had a coolant low without a leak. Just got my replacement engine yesterday as the intermix was so bad I'd lose 2 gallons of coolant into the sump in a 5 minute drive.

Quotes source posts: 634255, 634258, 634267, 634273

Coolant leak fixed. It was a hole on a pipe. Disconnecting MAF the car works so much better (starts with no problem and 800rpm idle but still fluctuates a bit). So, I plugged another MAF (from junkyard) but it gives me the same as before. Reading codes (with the second MAF): P0130 oxygen sensor ahead of catalytic converter (cylinders 1-3) P0150 oxygen sensor ahead of catalytic converter (cylinders 4-6) P1117 oxygen sensor heating 1 ahead of catalytic converter P1121 oxygen sensor heating 2 ahead of catalytic converter P1318 misfire, cylinder 6, emission related P1316 misfire, cylinder 4, emission related P1317 misfire, cylinder 5, emission related P1313 misfire, cylinder 1, emission related P0306 misfire, cylinder 6, damaging to catalytic converter P0304 misfire, cylinder 4, damaging to catalytic converter P0305 misfire, cylinder 5, damaging to catalytic converter note: european car so it doesnt have the other o2 sensors (behind) Maybe I was unlucky buying the MAF from junkyard? The misfires are concentrated in bank 2. Could it be an o2 sensor?

Quotes source post: 635220

The first thing you need to do is get a new MAF sensor. I would only use a Bosch MAF sensor these cars don't do well with other brands. Second: Your O2 sensors are not working. I see from the codes that both O2 sensors have the same issues. Could be a wiring issue. Could be that they are both shot. Third: The misfires are not related to O2 sensors. I would look at the coil packs on the plugs. Look for cracks or your sprark plug tubes could be leaking oil causing the plugs to short out.

Ok, this may sound like a stupid question but I feel like we're missing something here - what exactly did you do when you changed the oil and filter? What exactly did you do when you cleaned your TB? Blue is right, it seems like you've cooked a maf sensor as well as your precat o2 sensors. The bigger question here is why? Absolutely nothing done during an oil change should have influenced your intake, fuel, or exhaust system. Cleaning a TB shouldn't effect these things either. Not trying to be critical, there's just no logical chain of events that I can put together here that explains everything. Sent from my POCOPHONE F1 using Tapatalk

Check the alignment on the rubber collars connecting your plenum (throttle body) to the intake manifolds. I bet you have an air leak.

Quotes source post: 635400

I second that. I've had mine off a few times and diligence is necessary when reinstalling them. Good call, Jag.

Also check the seal on the plastic snorkel (inlet) on the throttle body. That is a PITA to put back on properly.

Let's start back up at the top. Says the car will die when let off the throttle. Maf, TB cleaning, plenum ducts, etc will all cause a rough idle (and some of the codes above) but they wont cause the car to stall, just run like crap. Might be best to clear the slate and report what the current issues/symptoms are. It is sounding to me like something isn't connected after all the work that was done in step #1. Double check your connections.