chevelleman

Guys I need some help. 94 z-28 automatic, it just started to surge/slip one or the other. It only does it under a load-say going up a slight incline or hill and only around 40-45 mph. If I hammer it, it shifts fine and runs normal. I had the transmission rebuilt recently. I took it to them and they hooked it up to a computer and said the throttle position sensor was fine, the converter was locking up fine and the transmission seemed to be fine. They thought either spark or fuel. I dont want to start throwing money into it that does not fix the problem. Any ideas guys or anything to check. Thanks Travis

Guest47904

MAF or EGR possibly.

Does the car seem to lunge forward and the RPM's vary when it does it?

chevelleman

the rpms vary slightly and sort of lunges/misses.

Craddock

I'd say something like plugs and wires or egr. I'm leaning toward plugs and wires cause my car does this exactly like yours, but when I changed out the plugs and wires it didn't do this at all for a couple of weeks. Does it pop if you rev the engine up around 4K and let it drop? Not driving just like you're showing off.

chevelleman

I dont think it pops, I changed the plugs and wires a while back. I guess it could be thoes still. Any way to check the EGR? Guys any other options that you can think of?

Guest47904

Is it possible the problem is occurring at the point at which it shifts from 3rd to overdrive? And perhaps it keeps going back and forth between gears? Why don't you go to your favorite place in town that gives you an incline at the speed you said and put it down into 3rd instead of OD and see if the problem subsides.

You could also scan it to be sure if there are no transmission codes or also to see exactly what the tranny is doing real time.

One way to check the operation of the EGR is at idle, with a hose connected to the EGR valve. Apply a vacuum (suck on the other end of the hose) to see if the idle deteriorates when you suck on it. Then let suction off and see if the idle comes back. Now leave the hose from the EGR solenoid off of the EGR but cap it with something like a golf tee. Now take it for a ride with the exact same conditions as when the problem occurs.

Craddock

If you're in the same situation as I am, and from what you describe you are, then the egr is probably messing up your plugs cause that what it's doing to mine. My car did this before the transmission rebuild also, so it's not the transmission for my car.

Leave your car in park and rev it up, and see if it goes down smooth or pops. If it pops it's probably something wrong with your plugs, but don't expect them to be the fix. I bet your egr is messing up your plugs.

chevelleman

Thanks Guys I really appreciate the help. I saw the EGR block off plates anything bad about putting these on and not a new EGR?

z95lt1

i had the same problem i did plugs, wires, coil and it went bye bye.

Craddock

The computer will put up an error message if you just block off the egr instead of fixing it. The egr is supposed to help out with gas mileage a little bit too when it works.

Guest47904

It will not get a code on a 94 as long as he leaves the solenoid hooked up.

But why would you replace it if it's so easy to test to see if it is the problem?

Have you tested the 3rd gear over-ride like I suggested?

sbca96

My 93 Z28 did that shortly after replacing the coil with an Accel, I spent a lot
of money seaching for the problem since I "knew" it couldnt be my new coil! I
swapped it out for the 25 dollar Wells coil from Autozone and its been fine for
the last 80k miles. Mine did it on slight grades, and it also would stumble and
almost die if I tried to mash it from a dead stop.

Tom