I've got a 91 turbo i just bought with 93,000 miles on it. the last owner installed a 3" exhaust, k&n air intake, upgraded blow off valve, and a SAFC 2.

since i got it i changed the spark plugs, TPS, cleaned, inspected and checked the TB, O2 sensor, ICV, and all vacuum lines both at idle and under load.

My problem(s) is that though it is running much better, I've got white smoke on deceleration (BHG maybe), a steady missfire around 4000 RPM until warmed up then it's not nearly as bad, a code 51 when i mash it or when i'm running the A/C then it's a steady 51.

Also if i adjust the SAFC 2 down to 22 on the LO and 14 on the HI i've got no steady missfire (just an occasional missfire and backfire when getting on it) and plenty of power, but it smokes more and stinks plenty when i do that.

What am I missing? I just can't figure it out. I'm thinking maybe timing, it also has a new timing belt so maybe it was timed wrong.

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since i got it i changed the spark plugs, TPS, cleaned, inspected and checked the TB, O2 sensor, ICV, and all vacuum lines both at idle and under load.

Why did you change the TPS?

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I've got white smoke on deceleration (BHG maybe), a steady missfire around 4000 RPM until warmed up then it's not nearly as bad, a code 51 when i mash it or when i'm running the A/C then it's a steady 51.

So you are pulling codes and you step on the pedal and get 51? It is supposed to do that. Don't do it.

Smoke on decel is usually oil being pulled in due to very high vacuum. The source is the problem. It could be fuel, due to a lack of fuel cut, or even the turbo.

Is the misfire under load?

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Also if i adjust the SAFC 2 down to 22 on the LO and 14 on the HI i've got no steady missfire (just an occasional missfire and backfire when getting on it) and plenty of power, but it smokes more and stinks plenty when i do that.

I havent used an SAFC, but I can tell you how the car is supposed to work. If you have more smoke, you are making it richer. I figured lowering a number would scale the AFM, but apparently not. Unless I am not getting all the info.

Did you gap the plugs yourself? NGK or ND, on your nearly stock application is best. What tool did you use and how did you adjust the gap?

i changed the TPS cause of the code 51 and when i checked it the ohms were off.

what do you mean by lack of fuel cut? i don't understand how that is supposed to work. what should i be looking for?

I plan on inpecting the turbo next. right now when the turbo spools it has alot of power. but i understand that if the oil seal is bad it can cause white smoke. i wouldn't be surprised if that is my problem. is there a way to rebuild it and not have to buy a new one or a rebuilt one?

The missfire is under load around 4000 RPM. And it's bad until it warms up. then it's barely noticable but it's still there.

The SAFC i plan to remove. but for now i have the correction set at 0%. which i wasn't able to do before i did the work i did do. it is my understanding that by adjusting it -22% i was cutting the fuel% as well. again confusing that's why it's at 0% now and why i plan to get rid of it

i checked the gap with a gap checker (the circle type not the wire) and i didn't need to adjust it.

Thanks

This message has been edited. Last edited by: robertsws,

51 means the idle contacts are not closed during the diagnostic test. If you step on the pedal, it will trigger 51. Otherwise you just loosen the screws and turn it until 51 is not flashing, or the ohms is good.

Deceleration fuel cut exists to save fuel(emissions) and slow the engine.

You need a richer mixture when cold, it is easier to light. A weak igntion can cause a cold problem, so will an ECT sensor that is short. But you would have a code for that. A worn engine will do that also. A warm engine can hide a lot of problems.

Check to see if you have cold resistance in the ECT circuit. I prefer to do it at the ECU. There is a pin chart in the factory electrical wiring diagram.

Your problems could just be that SAFC, I don't know its workings, other than it scales the airflow meter. That can also be a problem, you need the correct air/fuel ratio, especially when cold, as pointed out.

so i found my smoke problem. i opened the hood after a drive and noticed smoke pouring out from behind the engine, i cleaned the gunk and oil off and ran it again and then checked it. it was my valve cover. turns out the bolts weren't even finger tight. i replaced the gasket anyway and tightned everything down. i also did a compression check and everything checked out. i am in the process of going over the fuel system and the ignition system and timing.

so i adjusted my timing and checked my ignition system. i needed to clean up the contacts on the coil packs but other than that it all checked out. I've got some gurgling in my cooling system but i'm not losing any coolant so i'm off to find a small leak. i think it's at the thermostat housing.