OK guys, my recently purchased 1992 has all-of-a-sudden developed a real bad missing upon acceleration. Happens both from a stop and at speed. Whenever I push on the gas pedal it sounds like not all cylinders are firing(or in correct order), is sluggish and I can even "feel" this through the steering wheel and hear it through the tailpipes. As long as I do not step-on-the-gas, it seems to run OK(maybe a slight hint of a "miss"). My Vette has 88,000, new plugs(autolite 2-platinum), new Packard wires. I'm gussing it's either fuel delivery or ignition related. Ran fine up till two days ago. EGR seems to be working fine(goes in and out when I press the bellows). Would a bad injector be a good starting point? What about bad O2 sensor? Bad coil? And of course, I realize it may well be the infamous Opti starting it's death throes. I have wiped a clean white rag under the water pump several different times and no green liquid at all. Anyone have an opinion to help me start searching for a cure????

 

take 5 minutes and an ohm meter and check the injectors. they should ohm out at 16 +-.5.. if any are below 10 they are shorted and probaby causing your problems, But, it could be something else, the injector test is easy and the stock multecs are failing at a high rate.

 

Check for codes
http://www.corvettebuyers.com/c4vettes/codes.htm

 

No check-engine light, no codes at all.

 

Have you checked voltage at the TPS?

 

If it just started with new wires, i would check them. If they are a cheapr brand they might be arcing causing the misses. My winterbeater is a olds aurora and when the wires go it does this. The stock gm ones always died every 20k especially noticeable in the rain. It's been 35k km and 3 seasons with the Magnecors and still so perfect

Other than that I can only guess optispark. How long ago did you do the wires? might want to check to make sure you have them on right.

 

If the wires were recently installed, make sure they are all seated correctly but, more importantly, make sure that none have gotten burned by being too close to the exhaust. This happened to mine about 6 months ago--a sudden miss that came and went due to the insulation having been partially burned in one spot. Whenever that spot got too close to the manifold, a spark would jump and there would be a miss. I have since replaced the wires with MSD and the mechanic was very careful to route away from the manifold.

Doug

 

Turn off the underhood lights. At night in a dark place, start engine and look at each ignition wire along its length and look for sparks. The spark is supposed to ONLY be at the spark plug gap. If you have damaged or missing plug wire looms, install new ones, they keep the plug wires from touching metal. All plug wires have microscopic pinholes in the insulation and if they touch metal, they can spark through these pinholes. Dress your plug wires so they do not touch metal! Engines that miss do so because the plug did not fire.

 

Randy,

Did you ever resolve this issue? I'm having the exact same problem and it's driving me bonkers trying to figure it out.

Any info you can provide would be great.

Thanks,

Marino

 

Ha! Same problem here. I've been told it might be bad O2 sensor(s), but I'm still doing the research. The engine cuts out bad close to WOT, but is fine otherwise.

 

Old thread, but did you ever figure out what caused this?

 

My 92 C4 was doing the same thing and the shop diagnosed it as a bad injector. They are replacing it tomorrow with a new one.

 

Bad idea. I'd get a set of reman ones as opposed to 1 new one. When you have a worn shoe, you don't just buy a new one do you?

 

Thanks CA1992C4!
Totally appreciated! I had a similar thing happen to my other C4 that I sold years ago, so I actually previously upgraded to a complete set of new style Bosch injectors on this one (from a well-known vendor on this forum...highly recommended!) and still experienced the problem. In my case, I found out last March when I suddenly had to press this car back into daily driver duty after having slept in the back of the garage for years. Naturally, it immediately started running worse and worse. Turned out to be the aging, original optispark distributor. I changed it and wow, not only did it run better immediately, but the less than 100% running issue disappeared and the engine was immediately able to full advantage of the new generation Bosch injectors...wow, the motor came alive!!! Best it has ever run ever! Well over 3,000 miles later in three months, I am still smiling!!!

In the end, it came down to two issues...an aging, injured, original 21 year old optispark distributor and a faulty coolant temperature sensor that worked adequately (read lousy) enough not to trigger a code, but not great (the one in the waterpump, not the other one in the block near the manifold) confusing the PCM/ECM.

I just can't believe the difference...feels like a totally different car with 150 more cubic inches. Live and learn, huh?

 

And I agree with Aklim, better to change them all with remans (or new) from a reputable supplier. Sadly, I also understand where you are coming from as I once had a crazy issue with my previous 1990 C4 and ended up having to pay a shop a ridiculous amount to change two injectors for an amount where I could have easily had all eight on my own. Sadly, they had me between a rock and a hard place at the time, so I had no choice, the price of diagnosis with a broken car, I guess. Cost me two grand for two new injectors installed on a tuned port (included some other minor work) and then the remaining injectors failed six months later so I ended up changing all of them again (apx $200?) on my own anyway.

 

Great ideas - thank you!

I need to get the car running to pass smog so I can get it registered. My friend that gave my son the car said he had the distributer replaced last year, so I am hoping it's not going out again.

If another injector goes out I will replace them all, but right now it's at the shop and the cost to diagnosis what was wrong and the injector and instalation is already around $280. I need to get a manual for it so I can do some of the work myself.

 

Could have gotten all the injectors for a hundered bucks less from FIC. My 94 did this it was the front two o2s. No codes would fart and buck.

 

We just got the car on Saturday and I know very little about them. I joined the Corvette Forum right after that and I'm learning about them as quickly as I can. In the future - I will read what I can about my problems and ask about possible repairs, and hopefully save some money. I'm pretty sure the shop is replacing the injector with the OEM one - but it's good to know there are cheaper ones to be had.

 

I send mine out for cleaning and testing every 3 years since there seems to be buildup. It not only cleans but tests that they are within spec which is why I save my money up from NOT buying those "cleaner in a can", "mechanic in a can", snake oils, mouse milk, whiffle dust, etc and spend it on something quantifiable.

 

I only run top tier gas from Chevron or Shell, I avoid the cheaper mystery gas from the bargin stations. I'm not sure if that really helps, but I've been told Chevron gas has Techron that helps to keep the injectors clean.