Q45 exhaust smoke

[trajan]

I have a 1991 Q45 (219,000 miles!)that I use to commute about 120 miles to work every other day. When I return home I have noticed that the rear of the car is dirty around the exhaust. A friend noticed that the car has some smoke coming from the exhaust. When the car starts in the morning I noticed some smoke coming out the exhaust but when driving on the highway I have not noticed it. Any idea what might be the problem, if any? I love the way that the car runs on the highway!

[911/Q45]

With that many miles on the engine the clearances have opened up and some oil is getting burned. Hence, the smoke and deposits on the rear bumper. It will smoke more on start up because when it's cold the clearances for the rings and valve guides are larger. Fact of life with that worn an engine, no fix for it that is cost effective. Pour in some oil occasionally, run hotter spark plugs to prevent fouling and enjoy your car as long as you can.

[trajan]

Thanks for the info. What about sensors? My engine light is on and Jiffy Lube suggested that i change my Air Filter. Could that be contributing to the smoke?

[DAEDALUS]

Welcome! The check engine light shouldn't be ignored. I think a dirty air filter will increase your emmissions, but not sure if it will increase the amount of smoke. I wouldn't be concerned unless the smoke were really thick or if you were losing a lot of oil or coolant without a leak.Use the search button above to find out how to read the error code for the light that's on. How long has the light been on? Any other problems?

[maxnix]

A clean air filter every 10K-15K will not hurt and is cheap maintenance when it comes from http://www.infinitipartsusa.com .

Have you checked your O2 Sensors? You can check codes generated by the ECU or have a dealer hook a consult. It's a time/ dfort vs. money issue.

[Q45tech]

O2 should be changed every 100-120k, same with PCV valve and all associated hoses clean of the oil residue that passes inside them.

When you get above 200,000 miles the detail level increases as the time between proceedures halves!

The owners manual treats 30k and 60k like they go on forever not the case.............every cleaning proceedure gets more and more often...............I have to clean the thottle body about every 3 months at 241k to maintain a perfect idle.

[Chally]

On the smoke issue at cold startups, make sure it isn't condensation as well.

[trajan]

Thanks for all of the replies. You guys are great! If I get the Throttle Body serviced, will the Oxygen Sensor be replaced with that service?

[AZhitman]

No. TB service really is just a thorough cleaning.

The Q has 2 O2 sensors. Not cheap, so you're better off buying them and having a local mechanic change them out.

[landtodd]

At that mileage (congrats!) valve-stem seals sound likely to me. If so, it's far too expensive to fix relative to the value of the car, so it's something you live with until the car expires of something else. At 200K, you're something like 2/3 through the design life of the motor, depending on maintenance and severity of service.

Valve-stem seals would give you the classic "puff of blue smoke in the morning" kind of thing. You *might* also see it from a chase car when decelerating by downshift rather than by brake. Engine vacuum would pull oil right past the valve guides.

How do the plugs look? The answer might be to go a heat range warmer and keep driving.

[trajan]

I saw the same type of smoke coming out of a late model BMW so that made me feel a better. Actually for the past few days my rear bumper has not been so dirty and I have not noticed the smoke on startup. Could it have been because I used some of that octane booster gasoline additive? I am more concerned about the sound of the engine inside the cabin than anything else. Inside it sounds like a hot rod but outside the engine sound is really quiet.

[Chally]

Quote »Could it have been because I used some of that octane booster gasoline additive?[/quote]

Yes. Could have cleaned some crap from the inside .