I have a 92 z28 camaro. 5.7 TPI. I only drive the car about 3 times a month. I was driving the car and all of a sudden it started running like ****. When I have it in gear and stopped, it feels like I have a small cam in it, car shakes a little more than normal. (Does not change in park or not). 99% sure not tranny. New tranny. As soon as it gets a heavy load on it like in overdrive, the entire car bucks and shakes. Sounds like a bad misfire. When the car idles, I smell fuel. I am hoping it is as simple as bad fuel (water in gas) but I do not know how a car runs with bad fuel to be sure. I changed the sparkplugs, wires, distributor cap & rotor. No change. Sparkplugs looked okay. I have changed the EGR Valve, (but just bought it from Advanced Auto Parts, do I need to get a high quality one from dealer???), blaster coil, vac lines, about 8 months ago. Ever since I bought the car, I have had this annoying problem that after it rains, the car will intermittently shutter while going down the road. After running for about 15 to 30 min, it will clear up and run fine. Now it seems like it is doing it only 50 times worse and will not clear up at all. Could it be a sensor gone wrong and maby even an injector. HOW DO YOU TEST THE INJECTORS???

 

I doubt all the injectors are intermitently failing during wet conditions. It sounds like an electrical problem. Take a test light and clip it to a good ground. Then take a water bottle and spray down the coil and secondary wires. Brush every wire and even around the coil with the test light(pointy part). See if you can get any arcing. Other than that, water may be getting into one of the primary ignition and timing wires. But do that test first so you can eliminate it. Also, check if your coil is getting a full 12v and than excess resistance in the wires isn't messing things up. The next step would be to check the distributer's signal wires. You're saying all the cylinder's start to misfire and not 1 or 2, correct?

 

i think ill hop on this thread instead of making my own. I have the exact same problem. like he said it seems to get even worse when its low rpm and under load but mine will still misfire and kick and buck in the upper rpms too. i can give it full pedal and it will go smooth all the way up but only after it kinda sputters at first around the 1500 rpm range. I have also changed my egr and my tps sensor. I was going to start looking hard at an o2 sensor problem or maybe the map. I dont have any codes so i really dont have a direction to go in. this is driving me nuts though. if im going about 40 mph and the trans goes into overdrive and i start to lean into the pedal without making it disengage overdrive it will start to misfire and then will completely stop firing all together...but the engine seems to still be turning because it still registers an rpm on the tach. its hard to describe but thats what its doing. it seems that if it starts messing up and i take my foot all the way out of it and ease back in it makes it stop or at least not do it as bad
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mine idles just fine though and will rev smoothly when in nuetral. I wouldnt think the trans could do this but im open to anything at this point

 

I can't say for sure but I have heard about the housing on the dist cracking and causing something like that.

This one sounds like wires and plugs to me.

 

start your car in the dark and open the hood and look for sparks along the route for the spark plug wires. my guess is that the wires are arking to the block

 

My Trans Am just started doing this also. The check engine light came on and then went off after about 15 minutes. I was wondering if the plugs were fouling or whether there might be something wrong with the distributor or O2 sensor. I have a code scanner but haven't had the opportunity to take my underdash apart to get to the plug for the scanner. Kinda has a me a little worried because the check engine light is no longer on and it is running like crap.

 

OBDI cars do not have a misfire monitor like all OBDII cars must. There is no Mp_Learn in the software to recognize the crankshaft profile. Start shorting out plugs to do a cylinder balance test. That is assumin proper fuel pressure and volume are reaching the injectors.

 

Easiest way I found to do that is take 2inch piece of vacuum tubing and put them inline between the dizzy cap towers and the plug wires. Then take I test light clamped to ground tha touch the probe the the rubber tubing.

Might not sound right but it works. A method I picked up working on DIS ignitions.

 

Yes, that's one of the best ways. Vacuum tubing is made of carbon which is conductive. The test light produces a great ground to arc from the vacuum tubing. Find out which plug wire doesn't cause a change.