1992 Chevy Lumina 3.1L, runs rough and transmission acts up

BILLFRANK85

MEMBER
1992 CHEVROLET LUMINA
6 CYL
FWD
AUTOMATIC
101,000 MILES

I recently puchased this vechile for a back-and-forth between work car. It has right over 100,000 miles, and it ran great when I bought it. Now that it's getting cold, some of these problems are starting to show their ugly face. When I first start it, it tends to idle high (1000-2000 RPM) while in park. When in any drive gear or reverse, it drops down to normal but idles very rough. When I begin moving, the sound of the car changes dramatically. The engine/exhaust sounds a lot lower and deeper than normal, and the car loses quite a bit of its power. Once I finally get up to normal highway speeds, upon entering final gear (or overdrive, I'm not sure which), t feels like the transaxle is starting to vibrate and I have to let go of the gas and then push it back down for it to stop vibrating, but then it goes back into doing the vibrating after a few seconds. So, while I'm driving, I have to constantly let off the gas, reapply, let off the gas, etc. Warming the car up does not make any difference. The majority of the time I drive, it does this. It randomly goes away while I'm driving, too. The exhaust and engine will sound like it's supposed to, but then minutes later both sounds change and driving becomes sluggish again. If I come to a stop at a stop light, the car will idle rough and upon take off, if I give it too much gas, the transaxle will shift rather hard. Hope this is enough information!

billfrank85@gmail. Com

1 Reply

RENAUDTN

MECHANIC
636 POSTS

When it comes to diagnosing a possible transmission problem, there's no much a DIyourself-er can do.
If your car has an ATF dipstick, you should start by making sure your level of ATF is right, and also that it is in good condition. When you do that make sure you follow the right procedure to check the level (transmission warm, shift in all gear at idle waiting for a few seconds in each, then come back to park and check level like you would with your oil).

You should check for trouble codes as well; it may help to pinpoint the problem(s).

A rough idle may be due to a vacuum leak, a defective sensor, wrong fuel pressure, possibly a plugged converter, defective PCV hose/valve, defective EGR valve, leaky valve, clogged injectors.

The car idling high when first started may be normal: since it's cold now, the car needs more gas to keep running and not stall (although 2000 rpm would be very high). However, once the engine is warm the car should idle at normal speed.

The loss of power and the exhaust problem make me think that you may want to start by making sure your converter is not plugged.
You could have too much back pressure resulting in some of the symptoms you describe.

A real diagnosic of the transmission will require a trip to the shop. Sorry.

Good luck