2001 68k miles hks hi power exhaust, test pipe, aem cai, vafc II. The vafc II is set to stock for now since I need to save up for some dyno time. The car came with it and an air/fuel gauge. For some reason while I am in low rpms especially on a bumpy road the gauge drops to lean and the car bogs like it wants to die. Other times I can be driving along around 3to4k and and it will drop to lean for a sec and I can feel the car shutter for just a sec then go back to normal. I did have misfires in all 4 cylinders and random misfires. The light stayed off for months then just came back on.

I replaced the plugs and all my gaskets pertaining to the valve cover and spark plug seals. What should be my next step. Valve adjustment, map whack, new fuel pump and filter....?

What usually causes a car to run lean like this. I know I can feel a drop in power. Please offer any advice. Any questions please ask.

Thanks in advance.

 

MAP and O2 sensor are probably the two prime things. Fuel pressure is secondary but, still something to watch.

I'd probably disconnect the VAFC and A/F gauge. Get it back to a stock baseline and see if the problem goes away.

 

I'm going to guess that the wiring connections on your VAFC are not solid. Bumpy roads and even air temps can affect such connections.

 

Yep, I was leaning that way too. That's the problem with taking over someone elses project car, you never know if they did good work or crappy.

 

We thought it was a crappy wiring job because one of the wires was loose. When you pushed on the wires the idle got stronger all of a sudden. We re did that part of the wiring and thought the problem was fixed. This was probably 5 months or more ago. Now maybe something else came loose. I will double check the wiring. I wouldn't mind just selling the thing but I don't want to have to mess with all the wiring involved.

If it is the O2 sensor or MAP would it throw a code? How expensive is it to fix those?

Yeah the dealer I bought the car from said it was adult owned owned and everything was professional installed and cared for. Now it makes me wonder.

 

P.S. is there a way to disable the VAFC and A/F gauge with out rewiring everything back to stock?

 

ECU wiring was infiltrated to install the VAFC. You must remove it entirely or solidfy all the connections. "Disabling" it won't do much if the connections are bad. That means that the "normal" ECU signal continuity is also bad. The a/f gauge is likely a "T" tap. If the tap has severed the ECU wire, your engine could be running very badly. You would have to not only remove the a/f gauge wiring, but to make sure the wire it tapped into is brought back to original condition.

 

Viper that is what im worried about. If I find someone with some major electronic and car know-how should I be okay putting the wires back to stock??

Is it possible to leave the A/F gauge and remove the VAFC to get results. I never would of thought the A/F? gauge could be screwing with the car. You know your stuff so that is why I am asking. I will do what you think is best.

Thanks

 

[QUOTE=Kenpo_S2000,Jul 30 2006, 10:00 AM]I know I can feel a drop in power.

 

[QUOTE=Kenpo_S2000,Jul 31 2006, 12:51 AM] Viper that is what im worried about.