stumbling,bucking problem

[Tommyg]

My car does this between 1000 and 2250 rpms,its fine above that. It only does this on occassion. On previous posts I've been told to replace the coil pak/module and am about to do so but don't want to start guessing around. I bought a scanmaster and my error codes are good and the maf readings are stable. Should I bite the bullet and spend the money or is there another way to figure this %$#$%% car out? Tommy

 

[nero]

What's the tps and IAC values looking like at idle? (car must be fully warmed up)!!! You need a scantool for this...

Is it part throttle aka "tip-in" stuttering/hiccup thing? I had something similar happening (still tuning when I have time to fix it) you may have the same... tune the IAC and tps and report back!

 

[strikeeagle]

torque converter locked or unlocked?

 

[Tommyg]

I have the scanmaster hooked up and mounted but I don't know much about how to read it. Can someone put it in laymans terms for me? I've been told several times on this board that I should get a new coil pak. I did so today and changed it out--no difference!! My parts guy is kind enough to let me try it and if it didn't work,he will take it back. That will save me $100. I'm just out the time it took me to change it.(nice guy) He thinks it might be a cam or crank sensor. Again, I don't want to keep guessing untill I stumble on the right solution. Thanks, Tommy

 

[BJM]

Does the car do this in gear and in neutral too?

 

[87owner]

I still havnt figured my problem out. Which sounds alot like what you have. It stumbles and misses, but if you boot it past that RPM range it takes off fine. It only happens to me when the car gets hot to like 180 degrees or so. Everyone seesm to think its the ignition contol modules that are the problem. I did mass air, TPS, coil pack, and ICM. And its better but not totally fixed. Couple ppl were saying the after market ICM's cant take the heat and drop voltage like this. But who knows. Still hoping to figure it out and fix it for good someday.

 

[Tommyg]

The car idles fine in neutral and drive. It starts coughing as soon as you accelerate mildly and continues until you get above 2150 rpm. It doesn't matter what the temp. is--cold or hot. It will go fine for 2-3 days and then act up. It's been nasty for the last 3 days now.

 

[BJM]

It idles fine, but what happens if you rev it to the problem RPM in neutral? Does it mess up then as well?

 

[Tommyg]

No,in neutral it is fine. This is a problem only under load. Again,it is only under normal driving conditions. If I punch it enough it goes fine. If I hit it enough to kick in the turbo it goes fine also.

 

[Slowhawk]

This same thing has been happening to me the last few weeks.Replaced the MA with a LS1 model,translater,different chip,ignition coils and module with no helping.Still runs like a$$ at part throttle/closed loop.

Someone must of had this problem before and fixed it I would love to know the fix too.

 

[Sleeper-6]

Once the car is running, try unplugging the cam sensor. The emgine will go into batch fire mode. You should be able to hear a change in the injector noise. Now take it out for a spin, If it's cured it's somethng to do with your cam sensor or it's adjustment. Worth a shot, That's what was causing a nasty stumble in my car just like you're describing.

 

[Tommyg]

Where is the cam sensor located?

 

[Sleeper-6]

You've got mail.......

 

[87owner]

any luck with this issue guys? Mine has been acting up bad lately. I never got around to fixing it when this post was active because it got better on its own for a while. I'm going to try the cam sensor thing.

 

[65vette396]

Unplug the torque converter lockup solenoid from the outside of the tranny. It sounds like the car is locking the converter too early. Good luck, Drew

 

[GN&GTO]

i have had a coolant temp sensor cause symptoms similar tto what everyone here is describing. replaced it and it ran fine.
just my .02.

 

[dgreene]

Been there done this.

I had the same trouble about two years ago with mine.
Changed plugs, wires, coil pack, Ign. module, cam sensor, crank sensor, O2 sensor, fuel filter and also cleaned all the grounds to make sure they were making good connection. Everything looked good on the Direct Scan and had good fuel preasure thru WOT. but it would still bog and spit then go likea bat out of hell.

Turned out to be weak valve springs. They weren't that old either. I would check out everything else first, but if that doesn't get it and the valve springs have more than 40000 on them or are more than 4 years old I would check them too.

 

[87owner]

Originally posted by Sleeper-6
Once the car is running, try unplugging the cam sensor. The emgine will go into batch fire mode. You should be able to hear a change in the injector noise. Now take it out for a spin, If it's cured it's somethng to do with your cam sensor or it's adjustment. Worth a shot, That's what was causing a nasty stumble in my car just like you're describing.

that was it.... thanks

 

[83ttypecooled]

stumble

Hi,
I agree, MAF could be causing this. You say TPS is normal? It would be about .4 v at idle with no glitches in voltage as it goes up in throttle opening, very linear to 4 volts and above. How about crud in the intercooler, or a leak in the intake system? just ideas, one's got to hit...
Dale

 

[83ttypecooled]

Hi,
Can't argue with success! Good luck, let us know what the followup is.