lumina "bucks" above 50mph then dies when brakes applied

[ibewhand]

1993 3.1 lumina euro
138k miles

this car cranks and idles fine, has to be driven for 20 to thirty minutes before troubles start. replaced fuel filter, plugs and wires, on thursday. on friday the wife drove car until it died and wouldnt crank, had to leave it in a parking lot overnight. went back this afternoon and the car still wouldnt crank so we pulled it home. once at home i removed the ECM fuse for about 20mins. replaced fuse and the car fired right up! drove it around for about half and hour before it started "bucking" again.

replaced :
ignition module -- last summer
spark plugs--
plug wires--
fuel filter--

ive been searching through this forum for an answer but have not found anything that really describes the trouble .

[maxwedge]

Welcome to AF.Won't crank means what? Won't turn over or turns but will not start. If it turns but will not fire do you have spark when this occurs?,wll it fire if you spray carb cleaner into the intake, all basic diagnostics.

[ibewhand]

sorry wedge, the car would turnover, but wouldnt start. the car will start and run fine now, but after driving around for a half hour it starts to "buck". sometimes when you stop it will die.

the check engine light is not on .

could these be symptoms of a bad crank positioning sensor? or clogged egr?
or could the ecm be going out?

[maxwedge]

Start with checking fuel pressure and spark as I said. 35 psi at the rail.

[Bearwulf]

Minimum 40.5, max 47psi @ the schrader valve, key on engine off, GM specs. When was the last time that the trans was serviced?.

[maxwedge]

Not to be argumentative, but mys specs show 24-40 psi depending on engine load.

[ibewhand]

i have been working out of town and have not had a chance to check the fuel pressure yet. hopefully i can do it this week.

i am the third owner of this car, and i have never had the trans. serviced.

[cadgear]

It actually sounds like the transaxle is locking to the crankshaft, and when he applies brakes it does not release. The bucking, depending on how severe, could simply be the solenoid sticking in a apply-release cycle.

Just a thought.

[ibewhand]

how hard is it to locate and disconnect the TCC?

[Bearwulf]

Originally Posted by cadgear

It actually sounds like the transaxle is locking to the crankshaft, and when he applies brakes it does not release. The bucking, depending on how severe, could simply be the solenoid sticking in a apply-release cycle.

Just a thought.

And not disengaging when brake applied and vehicle slows down, therefore killing engine when car stops. Try shifting into neutral when stopping.
My fuel press. specs came from the GM Chevrolet Service Manual, 1993 Lumina.

[cadgear]

"has to be driven for 20 to thirty minutes before troubles start." sounds like the time for the transaxle to reach normal operating temp, give or take. I'm willing to lean towards the transaxle being an issue, given that fuel is eliminated.

[ibewhand]

i disconnected what i assume is the tcc connector. i drove the car for a few miles and noticed that there was no overdrive. did i disconnect the right one?
the car still bucks, however not the same.

[maxwedge]

All one connector on the 4sp trans, you can only disconnect this for test purposes do not leave it off, bucking is not the same because there is less load on the engine with o/d and tcc disabled. Based on you statement in the original post this is not a trans related issue. Your getting off trac here, a no start or difficult restart is always engine related.

[ibewhand]

ok so lets get back to the basics. I bought a fuel pressure guage.

key on engine off: 40-42psi
key on engine idle: 38 psi

what's next?

[maxwedge]

Possible misfire under load, bad plug, wire, coil are some, dirty injectors, a full scan while the condition occurs then a freeze frame to look at possible misfire counts, also look at tps reading being erratic, no quick answer here.