5.0 Gremlin : (

[CMPRacing302]

Was hoping some of you would have some ideas for me. This has been driving me crazy...

I've got a gremlin that's hard to describe. Maybe a stumble/hesitation... Basically, when I goose the throttle he gets up to about 4000 rpm and then can't seem to get past it. But when I increase RPM gradually there's no problem.

I've done all sorts of diagnostics and tried different things, but nothing has seemed to affect it.
Trouble codes - 82, 85, 33, 44, 94
He's a racecar, so I'm ignoring 82, 44, and 94. Might hook the charcoal canister back up for fun (85), and will clean the EGR and hopefully the 33 will go away.

I've got a big cam, aluminum heads, bigger intake & exhaust, bigger MAF & injectors to match, etc, etc. But the thing is, I had changed nothing and he was running great before this started. The only thing I did was move. Something must have broken or went bad.

Any ideas would be much appreciated.
Thanks,
maryanne

 

[jrichker]

Possible TFI or ignition coil problem.

The TFI module mounted on the distributor is usually the culprit for a high speed miss on a warm engine. If the problem does not occur when the engine is cold, the TFI module is definitely suspect. You may need a special socket to remove the TFI module, but most auto parts stores will have one for $5-$7.

View attachment 251515

See Automotive Tools Specialty | Auto Mechanic & Technician Diagnostic, Testing Equipment | Thexton

 

[LiquidGT]

It sounds like you have the same problem I had awhile ago, except I couldnt get past 3k and it wouldnt idle right when warm... it was the TFI modlule.

FYI the Autozone Duralast brand 7/32" - 1/4" drive deepwell socket fits nicely in the TFI module hole. If you replace it be sure you get the white thermal paste to slather on the back of the module; it should come with the new module.

 

[CMPRacing302]

thanks

I already tried swapping out the distributor, TFI module and all, but with a "known good" used one. Maybe both have a bad TFI module?

He idles beautifully now since I've been working on him and would sit and run by himself til he ran out of gas if I let him. Since I always warm him up, I'll see what he does cold...

 

[CMPRacing302]

ok the problem still happens when he's cold. Does this rule out the TFI module? Man, it would be nice if that was it...

 

[jrichker]

Where did you come from and how is the elevation (affects air density) humidty, and temperature different?
Google your local airport for the elevation, check the local Weather Channel for the rest.

 

[CMPRacing302]

Being a drag racer, I can assure you that I read weather forecasts as how many feet above sea level. That being said, I can tell you that there are zero differences from the old house to this one. I live in the flat midwest and only moved 20 mins away.

I know TFI modules are not that expensive, but I'm in a pinch. Is there a way to test them?

Thanks again for your help

 

[CMPRacing302]

oh, BTW- I did already suspect and replace the ignition coil a while back.

 

[LiquidGT]

They do have a tester at the parts stores, but from experience it doesn't work. I personally ran the TFI tester about 20-30 times and got it nice and hot... it passed every time. I still suspected the module so I went to the junkyard and got one, after that I could finally roast the tires; I got a new one right after that.

If you put another one on and it did the exact same thing then I wouldn't think its the module.

Hmmm what about the Pick Up Coil, a bad PIP makes TFI modules go bad.

 

[CMPRacing302]

Hmmm what about the Pick Up Coil, a bad PIP makes TFI modules go bad.

oo, maybe...

and how about this: what if I'm getting good and consistent fuel pressure (which I am), but the volume is not there? Air/fuel would show him leaning out, right? I don't have my gauges installed yet, but a dyno pull showed some leaning out, but all in all was undiagnostic. The thing is, I apparently had a bad O2 sensor at time (found it when I pulled codes the time before last), so maybe that affected the dyno results by making him run fatter?

how does one test a fuel pump for volume output?