I have a 1990 Corvette with 150,000 miles that doesn't wanna run correctly. I've changed the spark plugs and plug wires and it cleared up some. I'm gonna change the distributor cap and rotor this afternoon. The car doesn't get driven a whole lot so that may have something to do with it. The main problem is that when it goes into overdrive and locks up the torque converter, it'll stumble and shake as soon as you try to accelerate. Any ideas????

 

700R4 blues is what it's called. The tranny likes to up and down shift at around 45 mph if I remember. This wears out some internals I can't say off the top of my head. You can get an eliminator for the O/D up and down shifting doing this, but it's too late in your case sorry to say. Good luck

 

Can't remember, but does your '90 have an LT1? If it does, there is an updated distributor cap that has a vent built into it. Old style did not and causes problems with moisture and rust buildup in the cap with nowhere to go. If cap does not fix problem, u made need to have a profesional injector clean, 1st, to try that first. If that doesn't fix it, have an injector balance test run to see if one or more have problems. Shouldn't be more than a half pound of pressure drop difference between injectors. [8D]

 

thats exactly what hapend to my 94 LT1. since it sat in the storage for so long rust built up in the optispark. i had to completly replace that and it was running just like new.

 

Thanks for the help. It is a regular TPI small block, not an LT1. The transmission is not hiunting for gears, it's locking in and holding tight so far. I'm thinking it's more along the lines of a fuel injector issue. It feels like just one cylinder is not pulling it's wieght as it should. I just replaced the spark plugs, plug wires, distrubutor cap and rotor to no avail. I've got some Seafoam in the tank and it's doing a good bit better but it's not completley resolved. I'll just keep hitting the bottle and see what happens. I'm also getting a trouble code (#32 EGR) but have since removed the vacuum line from the EGR valve and plugged it. I hooked a vacuum hose to the EGR and pulled it open with mouth suction, held it in place to see if the diaphram was holding and released and listened for it to return to closed. That all sounded good so I suppose that the valve itself is functioning just fine. It's probably just a problem with the EGR switch located at the driver's side rear of the intake manifold but I'm not too concerned with that at the moment. I also checked the fuel pressure regulator diaphram for leakage in the same manner as the EGR valve and it seems to be holding fine as well. I probably just have a fuel injector that's close to being plugged. I'll get it together one of these days and maybe I can get by just using some injector cleaner on it. If not, I'll get some new injectors and have it running smooth again. If ya'll see anything I've missed, post again and share the wisdom please!!!!
Thanks,
Joseph Carson

 

Here's my two cents worth having worked on a few of these. Try taking the EGR valve off the manifold and the connector pipe to see if they are clogged. If they are, you may have to pull the intake manifold and clean the passages. Other things to check are the PVC valve and vacuum lines. With 150K on the engine, you very well may have some vacuum issues. Also, check the EGR switch connections. Hope this helps.

 

Try @ cruise speed, under light acceleration, when the car starts to shake, lightly put your left foot on the brake pedal while keeping your right on the gas. What you are doing is takeing the converter out of lock up by depressing the brake pedal. If it quits the problem, the you have torque converter probs, either the converter, solenoid in valve body. At any rate, need to pull the trans pan to see if there is a any metallic looking fluid, maybe has brass in it. If so you have at least a converter or other major trans problems. The EGR valve won't cause the problem you are experienceing and if you unplug the vacuum line it would cure that anyway. Valve might cause idle problems if sticking open. I would pay any attention to that right now. Good Luck. []

 

Tried your trick MECH but to no avail, I'm pretty sure it's a bad injector since I have 1 black plug on the drivers side of the motor. I'm gonna get around to putting in new injectors, fuel pressure regulator and new plugs ( I always like to change them in sets). I'll post what happens.