I have a vacuum gauge in my cockpit. My engine normally idles at 21" of vac, cruises at 15", and accelerates at 8-10" with a moderate foot.

While driving tonight, I somehow lost a cylinder or something. The car now has a really jumpy idle. The vac gauge jumps from 11-14" really rapidly. The idle RPM used to be 1000, now it's 800. It almost sounds like a cammed car.

Low RPM accelerations are REALLY choppy. At high rpm, it's harder to notice that something it wrong. It only pulls about 2" on a moderate acceleration. It cruises at 10" of vac now.

What the heck broke? I originally thought that I burned a plug wire on my new headers or something, but all my plug wires look fine. I'll pull them off tommorrow and do a resistance test I guess.

What other common LT1 pitfalls are there?

 

sounds like a wire or 2 to me. especially since you said NEW headers. you'll probably find a burn in them.

if you read this tonight just go out in the dark with it running and look under the hood and see if you can see any arcing.

 

I did not see any visual arcing last night, but I think I found the problem this morning.

I just invented a new and retarded way of testing which cylinder isn't firing. I let the engine heat up for 30 seconds, and then touched each of the header primary tubes. If it burned my finger, that cylinder was firing. If I could hold my finger on it without crying out in pain, that cyl was dead.

That method kept me from having to pull plug wires on all 8 cyls. I discovered that #3 isn't firing, so I pulled the plug. It had a little oil on it. I expect that is normal since it wasn't firing, and not burning the piston ring oil off.

I started the car with the #3 plug and wire not installed, and watched for a spark. There was none.

I'm hoping that I just have a bad plug or wire. I hear people complain about opti's all the time though. Would the opti ever fail in such a manner to only have one cyl stop firing, while the rest were fine?

 

No if ithe optispark was going out most likely it would be a ramndom cylinder misfire. Just pull the #3 wire and replace it.

 

well....

I replaced the plug and wire of the bad cyl. I tested the plug/wire combo to make sure they fired. It still ran the same. I pulled the valve covers and watched the engine run. Both valves are opening appropriatley, and there are no broken valvesprings. I pulled the fuel injector harness, and the exhaust lost the odor of unburned fuel. I pulled the spark plug out and let if run with an open spark hole. Fuel mist came out of the open hole.

It has air, it has fuel, it has spark. I don't know what the hell is wrong with it. I admit defeat. I'm taking it to a shop tommorrow.

 

How about a compression test/leak down test maybe? Maybe you blew a ring? For ****s and giggles you might try a bottle of fuel injector cleaner, maybe it's not atomizing correctly?

Good luck with that..

 

My compression tester is at my wifes house, 200 miles away. I would do a comp. test, but i don't have my tool with me..... And to be perfectly honest, if I blew a ring while driving conservativley home from the mall, I don't want to know about it. This is my daily driver, I don't want to dig into the engine that deep.

 

Just so you know that's not a completely retarded way of testing if a cylinder is firing, the Indy and Nascar guys do that to... Well they use a digital temperature guage, and get to keep the sensation in their fingers, but you know.. lol