Bad MAP Sensor

[jmorri15]

Im have a GVR4 running Speed Density with a HKS VPC and all of a sudden i started having a weird problem with my car smoking after i get off the boost. I replaced my O2 sesnsor. did a compression test 150,160,160,150. checked for boost leaks. It only ever does after i boost and then get off the gas(to shift or just to slow down) So i think ive finally figured out what is causing the smoke. I think my map sensor isnt responding quickly enough and its keeping my car super rich for a few seconds. well anyways id like some input if anyone else has ever seen a problem like this. well here are the videos.
Youtube
Youtube 2
the whole time its smoking it af gauge is reading really rich.

 

Given the color of the smoke I would say it's the oil seals in your turbo. I just replaced a 16g that was doing the same thing.

 

[jmorri15]

only problem with that is that there is no smoke any other time. not high boost, not idle, not high rpm, only when pressure is changing rapidly from high to low. would bad seals smoke all the time? thats what my friends 14b was doing.

 

Mine literally did the same thing. I would get on it, build some pressure, lift, then a second later a big poof of smoke. No smoke at idle, no smoke at 20 psi, no smoke while cruising, only when I lifted after a good amount of positive pressure.

I would also add that if it were a A/F problem the smoke would be black. Get under the car and take a look near your oil drain on the turbo. I had some burnt oil on the clamp that holds the turbine housing to the center housing. See if there's any signs of oil in that area.

 

[jmorri15]

hmmm ill have to look at it tomorrow. the reason i think it is fuel not oil is because my af gauge stays pegged in the rich for anywhere from 1sec to 20 and the smoke goes away as soon as the af drops back into the lean side. thinking about it would an af gauge see burning oil as burning fuel? cause that could be why.

 

Are you using a real wideband? If so, what is your A/F ratio?

 

[thecman02]

Forgive me if I'm wrong, but burning oil would make it read rich.

 

[jmorri15]

its not a true wideband, so i dont have a number or a good solid reading i just know when it stays pegged at one end or the other

 

A/F gauges and O2 sensors measure unburnt oxygen, not hydrocarbons (gasoline/oil.) I guess burning oil could make it read rich if it were consuming some of the extra O2 in the exhaust stream. Less O2 in exhaust means richer, more O2 means leaner.

But, I'm not that edumacated, so I'll let someone else confirm. /ubbthreads/images/graemlins/grin.gif