Rough running, please help!

Bullet Bob · 12-29-2006, 08:11 PM

My car is running terrible and I need some direction on the troubleshooting. It has a rough idle and is very sluggish if the rpms drop below 2k (starting from a stop etc...). It will cough and sputter until the rpms pick up. At the higher rpms everything seems fine. Also, while letting off the throttle at higher rpms (to shift) something in the engine bay would make a buzzing sound and I believe that it is the component that the vacuum line and breather hose connect to near the oil filler cap. It had come loose from the retaining bracket. Lastly, at idle it appears to be missing and it coughs puffs of white smoke (gas?).

Thus far I have just poked around and checked the various vacuum hoses and they visibly appear to be in good shape. I also disconnected the O2 sensor and it didn't make any difference (engine was warm). I also recently replaced the plugs, plug wires, rotor, cap, fuel filter, and air filter.

On the open road all is great but in stop and go traffic it runs miserably. What could be the culprit?

Thanks,
Bob

Jim Smolka · 12-30-2006, 12:43 AM

Could be a vacuum leak. Check the back of the motor, especially the hoses to the two pressure regulators and the rubber/metal hose for the vacuum boost to the brake booster.

Did it run OK after the tune up?

mhinch · 12-30-2006, 03:28 AM

Bob, had the same symptoms on my car, I removed the air filter lid and discovered that one of the 90° rubber vacuum pipe connectors had been contaminated by oil/petrol and when the 4mm vacuum hose was attached the fitting wasn't as tight as it should be, I replaced the offending part with a spare from my 944 and the car runs alot better now. Replacement part has been ordered from the Forums host. 928-574-717-02-M100.

cheers

Mark

Bullet Bob · 12-30-2006, 09:10 AM

It ran great after the tune up but only for a few weeks. I know the mechanic did not check for vacuum leaks because he noticed the ignition wires were arcing and the plugs were shot so he assumed those were the culprit.

How many vacuum hoses are there? Should I go ahead and replace the whole lot?

Thanks,
Bob

SCWDP911 · SCWDP911's Garage

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SCWDP911 · SCWDP911's Garage

Check to see if your clock and dome light are working. I just had the same problem tonight on the way home from Memphis. I got home (barely) and searched Pelican, and found someone replied to another similar sitch and, low and behold, my 5 amp fuse that has the dome, clock, and Oxy Sensor (nice design Porsche - not!), was blown! The funny thing is right before we get home tonight, my wife said, "I think your clock stopped working". What happened to me tonight is my wife wanted to read something, but my dome light did not come on. Pulled it out while driving to find that the pass side of the keeper had snapped off. I must have shorted it out while driving.

Glad it was something simple. I was starting to get a sinking feeling...

Good luck!

Bullet Bob · 01-19-2007, 09:46 PM

I took it to the mechanic today and the problem was in the distributor. Everything was really gummed up and the advance mechanism wasn't working correctly. Got it cleaned out and all is well.

Thanks,
Bob

88911coupe · 01-21-2007, 06:11 PM

I've been wrestling with a similar situation on my '88 and just got new plugs from our host which seems to help a little and I could definitely see some arcing on my old Berus. It still acceperates sluggishly so I'm replacing the cyl temp sensor which I ordered with the plug wires.
Very frustrating...
Good that you found your problem!