2001 Pontiac Grand Prix Recently repaired Transmission

BUCHEZ

MEMBER
2001 PONTIAC GRAND PRIX
6 CYL
FWD
AUTOMATIC
108,000 MILES

Recently I had a transmission breakdown. I took it to a local shop and had them repair/replace the transmission. When I got the car back I noticed at higher RPM's, +3000, the car would start sputtering, I would get pretty intense vibration and I would have a loss of power. The car never made this vibration previously. If the car is in neutral and I rev the engine I do not get the same vibrations. Just a clean smooth running engine. During these vibrations my check engine light would flash for a about 10 - 20 seconds. Thanks to the wonderful internet I looked this up and apparently it means that there is detonation or misfirign happening and to much gas is getting into the CAT! I've brought it back to the repair place 2 times now. The first time they replace the Torque Converter and a sensor, and this time they said they replace some of the clutches but found no issues with the transmission. I feel like im getting the run around here. The person i've been dealing with says that it might be the bearings in the supercharger. I don't think bearings go bad over night and if they were bad, I think I would have felt it before. When I was quoted a price, It was for a rebuilt transmission with all new internals and a remand Torque converter. The car shifts fine, Idles fine and rides fine.
2 months prior this happening I did replace plugs and wires. The car ran fine all 2 months. I don't know if the transmission can cause the engine to be misfiring, I want to give this place the benefit of the doubt, but too many past experiences tell me otherwise.
Can you maybe shed some light on the issue im having?

1 Reply

FACTORYJACK

MECHANIC
4,159 POSTS

You are correct on the flashing check engine light, it indicates catalyst damaging misfire. There needs to be some misfire diagnostics run to determine if it is confined to a single cylinder. It being a 2001, you should be able to view cylinder misfire info with a scan tool. After determining the specifics on it when it is missing, it can be evaluated even further. It could have a corroded coil terminal, cracked plug and corresponding carbon tracking on the wire. Misfires under load are usually indicative of a secondary ignition type fault. Worn supercharger bearings, I would speculate, would give you noise, and not necessarily misfire. Another possibility is an exhaust that is becoming restricted, this could give you some shifting problems and some misfires. Try firmly placing your foot on the brake, and loading it up hard with it in drive, see if it misfires then. A word of caution though, don't do this for an extended amount of time or you could overheat the torque converter.