MOBE

Yesterday on my way home from work, my '99 t/a started acting "funny". Basically, when I start moving, from a stop, the car sort of does this stutter/hesitation thing. It idles fine, and when I put my foot in it, it seems fine. But, when I'm at criusing speed it just feels like its not all there, and it just plain feels wierd. What are the possibilities?

When it first happened, I thought it was the clutch slipping, not wanting to enguage. But like I said, when I floor it, it hauls ***. Then I started thinking bad plugs, but its not throwing any codes and really doesn't seem like its misfiring. Plug wires are brand new. Could it be bad O2s?

The car really felt like it was running great the last few days, and all the sudden, this.

Any ideas?

TIA

jmX

Hey MOBE, just heard your voice mail from last night.

It could be O2's. Try resetting the PCM and see how it drives after that. That should clear the long term fuel trims that the car has learned over time. Maybe it'll drive good for a litle while again?

Also, just recently my IAT sensor wire broke inside the insulation (dunno why!) and the IAT would read -30 degrees randomly...when it did that the car would load up with fuel and would really hesitate. It'd probably be good to autotap this stuff. I think I'm selling my autotap next week

MOBE

Thanks Jon. I'll look into it when I get home. Any other possibilities to look into?

SpeedDemon

Jon is on the right track. Most likely the problem with your car is the o2's. The reason for this is at part throttle, the car is in Closed loop, which means it is relying on the O2 sensors for direction. Once you go open loop, the car really quits reading the O2 sensors and relys on what is programmed in the car.

Good luck and if you have any questions, feel free to call.
Thanks,

Nagash01WS6

Why do cars always break when they feel like they are running really good?

MOBE

Ok. I reset the PCM and its still doing the same thing.

I also checked the IAT sensor and wires. They appear to be in good order.

Now what?

What are the tell tail signs of a bad lifter or rocker?

jmX

You need to autotap it and log the fuel trims, IAT, tps, MAF, timing, kr, and o2's. That'd probably be the next step. Or you could pop the valve covers off and maybe inspect the springs and rockers, although I'd think it wouldnt run well at WOT if one of those had been damaged.

MOBE

Well...

Its not a rocker arm. I guess the next thing I need to do is autotap it. I think someone may have mentioned that before? :p

MOBE

After auto-tapping it yesterday, it appears to be multiple missfires especially on #4. I changed out the spark plugs this afternoon, but that did not help. I was going to swap around the coil packs to see if one is bad, but of course, it started to rain.

Z-Rated

I know this is a dumb question, but did you change plug wires too?
And when you say especially on #4 do you mean this cylinder does it more? Or that other cylinders are missing too?

MOBE

Plug wires are MSDs about 5 or 6 weeks old. Yeah, the #4 seems to really be missing bad. The others randomly missed a little bit.

I went and auto-tapped it earlier (after i changed the plugs) and when I went WOT, it back-fired bad.

I forgot to mention that when I pulled the plugs, the #4 was black, and the others were "normal" looking, with the exception of a few of them having whit spots. Probably from running lean. Those plugs were over a year old.

MOBE

Swapped some coils around, and that didn't help either.