: tuning problem need help !

10-20-09, 06:42 PM
I have a 97 cat with 100,00 on it. The car persistently sputters a bit when pulling away after a dead stop. If you go easy on the accelerator it doesn't sputter. The harder you punch it . the worse it is.In older cars we used to say that it had a flat spot in the carburater . I had it scoped and there were no error codes showing. The only unusual thing was that the air fuel ratio was off a bit and it missfired one time during the test.It doesnt sputter when it is cold. I went over the vacuum system with a fine toothed comb it all looks right, but who knows. vacuum leaks are tricky!

Can the MAF sensor be faulty and not show on the scope?

Any input on this would be appreciated. ,

10-20-09, 11:17 PM
that's what happened with mine when the maf sensor went out. it only gets worse. try spraying it down with some mass air flow sensor cleaner and see if that does anything, it may not completely fix your problem but if it helps for even 5min it can tell u if it is the maf sensor. second guess could be something like the cps unit.

10-21-09, 09:26 PM
I cleaned the MAF with contact cleaner . did not do anything, MAF appears to be working, I disconnected it while car was idling . it hesitated then continued to run. Still sputtering while pulling away from a dead stop and running rough now.

10-21-09, 11:51 PM
I have read that MAFs can fail slowly or all at once. Mine quite after it warmed up for 20 min. Not sure "how" they fail slowly.

If your air fuel was off to the rich side it could be a dirty injector. If it is just dropping fuel into the chamber it will not burn properly or completely. Not an easy thing to check unless you pull the injectors and spray each one into the air and watch the pattern. They should spray a foggy mist, with out any solid liquid in the stream.

Find a shop that can pressure clean them on the car, for like a $100.

Or try a few bottles of injector cleaner over a few tanks of gas.

On the other hand it could be the coil pack or wires. Pop the hood at night (as in very dark out side) and lightly spray (mist from a hand bottle) a little water over the plug wires and coil pack and look for any sparks jumping. If you see any at all you have found "a" problem. Most coils fail at higher RPM. But leakage can cause little or no spark to reach the plugs at lower RPM causing bad combustion at idle.

Good luck.