I rebuilt the motor about 4 months. It only seems to do it when it is cold. Its only at part throttle. WOT no problem. The car is trying to go but its like it is holding back. I have tried adjusting timing, no good, adjusted fuel pressure up to 48 and the next morning no problem at all it was gone, but that afternoon after work it started again. Someone told me to check a ground wire running from the ECM to the Ignition switch does that sound right to anyone. I cannot figure it out.
Later, Gary

 

L98,

It sounds like you might be a bit lean, which can also be a cause of backfire. Adjusting the FP up a bit was a reasonable step, but you also need to check for the possibility of vacuum leaks, excessive idle air, CTS function, and MAP funtion. The SD schemes rely heavily on the lookup tables for open loop fuel and spark, so if you've modified the engine you may need some custom programming.

What is the TPS voltage? AFAIK, a '90 is not adjustable, and even if it isn't, there is a minimum/maximum spec.

Not to belabor the point, but why would you go to WOT with a cold engine? Don't you like your car?

 

Thanks Vader, The TPS is .9 because i had to adjust the TB blades open to make the car idle. The voltage goes all the way up to 5 volts smoothly with no jumps. And Yes i do like my car but it pisses me off when it does that **** so i just hit the gas to make it go. What does the CTS function mean?

 

CTS = Coolant Temperature Sensor. If the CTS is reading too high, the mixture will tend to be lean. You can check the resistancee of the sensor and compare it to the table at a know temperature:

[img]http://216.121.161.76/files/CTSMAT.gif[/img}

The TPS is probably O.K. From what I can recall of the fixed types, anything less than 1.0VDC at startup is acceptable, and the ECM will assume that as the idle position.

Not a flame about the cold acceleration, but just a reminder that harder acceleration with cold oil can cause a lot more wear than when the engine is warmed.

 

No I understood it was not good but I just get mad at it. Do they have tables for comparison, I have the ECM program and can check everything but dont have anything to compare to be able to see whats wrong?
Thanks