1994 cutlass supreme - vibration in overdrive

[pacmmk1]

i just bought a 1994 cutlass with 86,000 miles. as i was driving it home, i noticed a severe vibration in overdrive going up a hill. the vibration had been there all along, but under load like this, it was very bad. no vibration in neutral, no vibration in 3rd. with your foot on the brake, if you let off just a little to let the car move, you can feel a shake.

am i looking a a major transmission problem? or, could it be the TCC (Torque Clutch Converter), the MAS (Mass Air Sensor), the EGR valve, or, as some have suggested, a complete cleaning of the manifold, as there might be carbon buildup (the previous owners drove the car only 40,000 miles in the last 8 years)

thanks for any suggestions and help!

[pacmmk1]

i got the car back yesterday, and they cleaned a ton of carbon out of the "EGR passagways". the SES had come on, and they said it needed a new EGR valve. i asked them to clean the mainfold first, before replaceing a $280 dollar part. i never would have thought of that, if it hadn't been for checing this site forst. thanks guys!

i didn't notice a severe vibration on the way home, but then again i was only a mile from home. i am taking it to a transmission place tomorrow for diagnosis and service. i will get it up to highway speed for a long period of time. i guess i will know then if the vibration comes back.

[pacmmk1]

ok, so i took the car to a transmission place about 45 miles from home (friend of my wifes family). here is what i noticed. the vibration came back, but only in overdrive. and only below 2000 RPM. above 2 grand, no vibration in overdrive. the vibration was severe under load, like when you have a manual transmission, and you are in the wrong gear. when i started the car, and it was cold, i didn't notice a vibration at low RPM.

stay tuned.

[pacmmk1]

when i mentioned to the trans tech about checking out the torque converter switch, he didn't seem too impressed with my suggestion. so i wasn't too surprised that he couldn't find anything wrong, and said it was an engine problem.

i think the engine runs fine, so how much should i expect to pay to have this part replaced?

[Mrbizness1]

I believe trans shops will want to change the transmission and the convertor together, not just the convertor. Before doing any work perhaps you should have a complete fluid flush which could cure the problem. You could also disconnect the convertor by unplugging it (most GM cars have a electric plug on the side of the convertor) or check the fuse box.

[pacmmk1]

luckily, they thought the transmission was ok. i had them change the fluid & filter, but i am going to take it to a different place, and have them check the torque clutch converter switch. i would do it myself, but i don't have the luxury of time at the moment, so i have to rely on paying somebody else for their expertise.

we will see what happens. i bumped another thread that had a similar condition, so check that out & see if i am on the right track.

[sleber]

Might want to check on the coil packs also. when mine started going out I thought it was the tranny (vibration under load, etc). I changed plugs, wires, pcv valve, cleaned throttle body, clean IAC and a few other things before I gave up and took it to the shop. If someone would have suggested coil packs I might be a few hundred dollars richer now.

[pacmmk1]

i got the car back from a third set of eyes. this time, the whole manifold was cleaned out, not just the "EGR passageways" as the first had done. VIBRATION SOLVED. the TCC was fine.

i do suspect that there is a small little gremlin somwhere else, as the engine does not run entirely smooth. however, compared to what was occuring, i can track this down via the other posts on this site. would NGK versus ACDelco sparkplugs make any difference? just a curiosity question for those out there.

[chiefwahoo]

the problem with the surging is coming from either the plug wires grounding out and cross sparking or most likely it is an injector that is starting to fail, my 94 is doing the same thing right now and I'm looking into injectors now. my cousin is a gm mechanic for many years and has helped me in the past with this car, this is his diognostics and i trust him completely when it comes to the olds engines