86 951 Driver

I am having a problem when I start my car in the morning it sounds like it is running on 3 cylinders. It only does it when it is really cold outside. Today I started it up and it had a really bad fuel smell. Once it was warmed up it was ok. I don't know what the problem is. I have read a lot about this. I'm going to go check my plugs now and see if I can get it to do the same thing right now and start unplugging wires to see what cylinder it is. If you have any advice it would be greatly appreciated.

Peckster

Bad head gasket. Do a search to find out all you'll need to know.

86 951 Driver

With a bad head gasket wouldn't it be burning coolant of have milkshake. Because I have neither of those symptoms.

86 951 Driver

I just looked at my car. The spark plugs have a little white powder coating on them. Also I saw something that resembles a fpr but bigger under the intake manifold. p/n is 0 208 140 501. I also saw a plug that resembles an injector plug not plugged into anything. What is that for. Any help is appreciated.

Peckster

Coolant loss might not be noticeable yet, milkshake only happens in certain circumstances.

Like I say, read the archives for details my friend. Chances are you have a bad head gasket.

unsigned

would this problem be the same in the summer? I'm a reasonable new 944 owner, and my car does run rough while its cold, here inteh cold of winter. During the summer it was fine though. Wouldn't a bad head gasket run rough while its cold no matter the time of year?

nine-44

Tammy's 85.5 does that with a bit of fuel smoke out the exhaust, usually only below 15-20 degrees and not always. Mine has done it once. I was thinking possibly fuel line freeze up? They only do it for about 15 seconds after starting and then clear up. No coolant loss, mixing etc.

Granite 944

I didn't try looking up that number, but what you describe here sounds like the cold idle valve under the manifold. And if its not plugged in, yeah, it will run pretty nasty when really cold. Plug it back in and see. There should be a metal clip keeper on it just like the injector wire plugs have, if not there, it will continue to come off. Just guessing here, good luck.

PeteL

There has been alot of discussion about cold starts and running rough. In another thread, someone suggested the head temp sensor. It didn't make sense to me at first, because if cold, the DME is using "canned" info to keep the car running until the sensors kick in. That being said, what is the failure mode of a bad sensor? If it fails in the "hot" condition, then it is telling DME that all is well and the car is at temp, which would probably lead to too much fuel being sent to the engine, leading to rough running, smoky starts no?
The part under the intake is the Idle Stabilizer Valve. It meters air during cold start. It is supposed to open up while cold, allowing more air into the engine, then as the car warms it closes. On older cars, it is called the auxilliary air valve, does the same thing, but unlike the ISV it is done when the car is warm. The ISV is more active and affects idle to varying degrees when the engine is warm in response to other demands (Air conditioning etc) on the engine.

Tony K

My first guess is the digital idle stabilizer (cold idle stabilizer). That fails more often than the head gasket, and it's a lot easier to test/replace before going on to a big undertaking..

tomc_85.5_944

Head gasket seems a bit farfetched, as many people have posted up about this problem, myself included, and I know there are not that many out there with blown headgaskets. My idle problem is directly related to the ISV, but the losing a cylinder thing is still evading me, although it does not happen in warm weather.

On my old 87, when I blew a headgasket I did have rough running upon startup, but it was accompanied with a whole lot of smoky vapor.

hosrom_951

Look at the exhaust for signs of white smoke on cold start-up for more indication for blown HG.

Porsche-O-Phile

Couldn't it also be a bad idle stabilizer?

86 951 Driver

That part that I had the number for is plugged in. But there is another plug that resembles and injector plug and it just laying there. How could I check the cold idle stabilizer or whatever it is called underneath the manifold. What else should I check?

dgz924s

The only connector in that area other than the ISV connector would be the engine temp sensor. Little blue colored sensor located below the AFM and in the block. That connector is very close to a injector plug. Also one near the throttle body and below it on the block as well. The 2 are somewhat close to one another. Have a look for a sensor w/o a connection to it. The ISV plug is somewhat larger than an injector plug so this is most likely not to the ISV. Is the plug tan in color or black?