86 951 Driver

Okay so a few times now I have seen oil smoke out of my tailpipe. It usually doesn't last more than a second or two then goes away. My car used to not smoke at all. I recently fixed the exhaust by putting in a gutted cat. My old cat was jerry rigged and was hitting the body under load making a horrible sound.

So basically the only thing I have done since the turbo was rebuilt/replaced(9 months ago Lindsey Rebuild) was put in a gutted cat. I have only seen the car do this 5 times so far. Doesn't smoke at idle 99% of the time. Was the cat convertor covering up an issue?

edit: It seems to happen if I am slowing down to a stop with the car still in gear. Then when I am stopped smoke starts to come out. Once I start driving it goes away. Doesn't smoke under boost, and the smoke only lasts a little bit.

Car is all stock 1986 944 Turbo. I just recently changed the Radiator Fan Switch and at the same time switched over to Brad Penn Racing Oil 10w-40

Ronin-951

Need to do a sniff test, could be rich with a bad O2 sensor ... Cat would have covered that.

Black51

He said it's oil smoke.

Zermatt951 just went through this and it (so far) turned out to be a bad turbo. So possibly turbo rebuild time. Or you could just have a cam tower gasket leak. Try snooping around with a flashlight to find any evidence of oil leaks in these areas to start with.

EDIT: And even though you just had yours rebuilt 9 months ago, zermatt951's new turbo was apparently gonzo right out of the box, so I wouldn't rule that out.

86 951 Driver

I was thinking the same thing about the turbo, especially since we got them from the same place. How would I check for that?

Someone said that it might be valve guides/seals.

zerMATT951

My freshly rebuilt 26-6 didn't smoke for the first day or two (under 100 miles), but when it started, it smoked at every red light... and pretty bad. I was embarrassed to be in the car. It would smoke/haze a little at boost too, but I also had too much fuel, so it was oil & fuel smoke coming out together. The turbo finally imploded (shaft broke) after a week or two... had lots of smoke then .

While trying to chase down the problem, I did add a PCV-type setup that helped the idle smoke a lot... it was probably 80-90% better, but still some smoke. I was apparently drawing more oil out of the turbo at idle with additional vacuum, but I'm guessing the seal(s) was shot and I couldn't overcome that with 20 in Hg of vacuum.

I know you've read through my thread on this topic and asked some questions there already. I'm not sure if I can offer any additional insight since my issue ended up being a bad turbo. Yours may not be.

I should also point out that I replaced the hard & crusty old turbo oil drain vacuum vent line elbow with a new LR silicone hose when I swapped the turbo. I'm sure there were vacuum issues because of that old elbow, but it's impossible to say whether or not that had anything to do with my smoke.

Clown

I also had major smoke at idle that would not go away after a few seconds. It was always there at any stop light. Funny thing is that when I had the cat on for emission testing for a couple weeks the smoke was not there and apparently was being burned off by the cat. After emissions I took it back off and the smoke was back as good as new. So yes a cat will help burn off the smoke. If you do a search you will see my old thread on smoke at idle but only without cat or something like that. Also there is a recent thread that Zermatt started a few weeks ago about smoke at idle and how to test.

Sounds to me thought that you have a different problem if the smoke goes away after a few seconds at idle. I had my turbo rebuilt and replaced the O2 sensor as well and no more constant smoke at idle. I have however been noticeing lately that there is some smoke at idle when I first start the car but after it warms up a bit there is no more smoke. I think I need an oil catch can in my car and am looking into that now.

86 951 Driver

I should mention I didn't replace that elbow for the AOS container. I did replace all the vacuum lines before my turbo was rebuilt and replaced by my mechanic. The car runs great. It pulls great. I haven't noticed it smoking all the time.

Did both of your cars smoke all the time? I am starting to think that I am having a slightly different issue. I might try and change the O2 sensor.

Clown

Yes my car smoked every time at idle was not sporadic and was always lots of smoke. The only way to get it to go away was to hit the throttle for several seconds at a light. I would try replacing the O2 sensor.

zerMATT951

Mine was also every time at idle when warm. It wouldn't smoke much, if at all, for the first minute or two when cold, but when it started, it wouldn't stop. Once the car was warm, it smoked... pretty bad... every time... until the turbo blew.

86 951 Driver

So I have been checking it over the past few days and guess what no smoke. Oh well. Maybe it was just a fluke. I do smell a difference in the exhaust, but that could just be the car changing to closed loop or something.

Black51

Something is still wrong. The only flukes that happen with these cars are bad ones...

By the way, have you checked your turbo for shaft play?

86 951 Driver

I haven't, but even before the rebuild it didn't have much at all.

Black51

Well I wonder if you've got a crankcase pressure issue. Read this thread:

https://rennlist.com/forums/944-turb...e-at-idle.html

86 951 Driver

I have read some threads. When I held a bag over the oil filler it was sucking the bag in.

zerMATT951

Are you running a MAF, or a stock AFM w/j-boot?