Barney1

Well today for the first time I came off a light, and saw a very rich looking puff of smoke come from the rear. I went through the gears like normal and it seemed fine. At the next light I gave it a blast in second gear and heard a loud backfire around 5,000 rpm. I then checked the last boost on the profect B and it was still just 17psi. I put it in third and rolled into it a bunch more times and it was fine.... no check engine light, can it be bad post cat 02's? It seems to run fine now..Thanks for input

911/Q45

MAF?

Barney1

mmmm...good point. I have a larger MAF in the car. I will remove the element and clean it..Thanks

soltino

"post cat 02's?"

?


tino

Rassel

Did you see the colour of the cloud of smoke?

Barney1

Black....but only once

Rassel

Seems like you burned some oil. Any leakage from the Turbos? Or actually, look at Kevins post (the sticky) in the 993 TT board. Much is explained there.

WHB Porsche

I believe that only the primary (pre-cat) O2 sensors determine mixture/have any role in engine management and the secondary (post-cat) O2 sensors are only used to determine whether the catalytic converters are working or not (so post-cat O2s can throw a CEL but won't have any bearing on the car's operation).

Barney1

Fresh Turbos, Valve covers and gaskets. She's bone dry... Looks to have been rich for a second. I'm going to take out the mass air and give it a clean first.

dbf73

or perhaps momentary boost leak which caused momentary rich condition? check to make sure your boost hoses are tight

Rassel

Hmm.. well that's a good thing.
MAF could set things of as you said of course. And you had no overfill of oil?

IamSMC

Yes, the 993tt runs 2 pre-cat O2 sensors and 2 post-cat O2 sensors.

Barney1

Well cleaned the mass air today and it did have some black color on the elements. I have a Pro- Flow larger mass air in the car, and it comes apart to clean. All hoses were tight. Took it for a ride and it runs fine... I don't know, just a small brain fart I quess. Thanks for all of the input.

911/Q45

Oil would be white smoke.