I think I lost a cyl while driving.

[Malice]

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?

[Z28pr0jekt]

check your plugs while you're at it..

but this could very well go back to your valve adjustments... what guide did you follow in order to properly set the lash on your valves?

[Malice]

check your plugs while you're at it..

but this could very well go back to your valve adjustments... what guide did you follow in order to properly set the lash on your valves?

I basically used method 3 on shoebox's website. I can't imagine this being related to valvetrain, because I got the valvetrain to be whisper quiet, and then drove 50 trouble free miles.

All of a sudden, at a stoplight, the idle just dropped from 1000rpm and 21" down to 800rpm and 11-14".

[Malice]

Well, 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?

[KissMyWhtSS]

hope it works out for you. :sweatdrop:

[VendettaV8]

Well, 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?

check to make sure that the plug is connected on the opti side, Ive seen plugs installed and the peice inside that goes on the opti isnt connected where as the boot makes it look like its on.:peace2:

[Fastbird]

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

Just to be clear, you did ground that plug out when checking for spark right?

[phantomzer0]

Well, 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?
My brother in law had a z28, and after he put the headers on, the opti went AWOL. One cylinder shut off completely, just like what you are going through. He took it to a shop and they replaced the opti and all the plugs/wires and it fixed right up.

[Malice]

My brother in law had a z28, and after he put the headers on, the opti went AWOL. One cylinder shut off completely, just like what you are going through. He took it to a shop and they replaced the opti and all the plugs/wires and it fixed right up.



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.

[VendettaV8]

+1 for opti then!

[1994Z28Lt1]

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.

i would also try a compression and leakdown test on your #3 cylinder before you admit defeat and take it to a shop to be bent over

you have fuel/air, you have spark, but do you have compression?

[bricez28]

Well, 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.



awesome

[Fixxer99TA]

awesome

Awsome, Amazing.... I could think of a few :D