This Chev.is driving me nuts!!!!!?

Question

I own a 1991 Chev. Caprice with a 5.0 engine. the car has always been taken care of immaculately however, it has developed a problem.the car starts fast and idols smooth until it reaches its full operating temp. then whenever you put a load on the engine the entire ignition system cuts in and out all 8 clinders at once.the miss is random. so far to repair the problem I have replaced the ignition swich, the ignition module, the coil,the cap and rotor, all wires and spark plugs, I even replaced the distributer. all primary and secondondary ignition components have been replaced and the problem persists!.The engine timeing chain has been checked and its A-ok. All wireing harnesses check out good. No trouble codes show up.I have also replaced the T.P.S., the MAP, PVC, and checked the fuel pump changed all filters, checked the injectors all check out good! any ideas out there????

The O-2 sensor was replaced less than a year ago.if the O-2 sensor was out of specks it would through off a code. and I don't think that a O-2 sensor would completely shut off the entire ignition system. yes, the fuel mileage would suffer but the car would run on all 8. the car gets its full rateing fuel milage

The car runs good and does not miss at all when its cold and in closed loop operation. the miss only happens when the car reaches full operating temp.

Answer 1

Well you've checked alot of the things i would go for. So My advice is to try to find a junk computer and see if that fixes your problem. You have a closed loop problem, so it's either sensor input reading causing your problems or computer output readings. I think you've probably got a ground shorted inside the computer and when the vehicle reaches optimal temp. and starts to control engine performance of vehicle sensor input, It sends either wrong info or not enough to keep engine running smoothly.

Answer 2

Check all grounding points. Battery to body, Battery to engine, Engine to body. Another thing I have found on late 80's early 90's chevy's is the way the fuel pump is grounded. The ground is tied to the sender assembly outside the fuel tank. Then the fuel pump is grounded along with the sending unit off the steel line inside the tank. The strap holding the three steel lines together on the outside of the tank will crack causing the intermittent loss of a ground to the fuel pump and a momentary loss of fuel pressure. One of those things I found the hard way in the early 90's. Good Luck.

Answer 3

have the engine coolant temp sensor (s) checked out. sounds like the sensor is feeding the wrong information to the computer.it may be thinking its too hot and what happens is the fuel mix is leaned out too far,thus causing it to stall.it will also sometimes prevent the engine from starting till its cold again because the computer thinks the engine is too hot,so it keeps it off to aloow it too cool,even if there is nothing to warrant it otherwise

Answer 4

I'm not sure how chevy does this, but Subies have two temp sensors. One is for the gauge, the other for the ECU. If the ECU thinks the engine is cold when it is hot, it will be giving it more fuel than it needs, making it run rich.

Answer 5

02 sensor i agree with phil.

Answer 6

oxygen sensor on the exhaust

Answer 7

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