BIGDATOWN

I have this misfire problem ONLY on cyl #6 And ONLY at idle. Any and all ideas would be very helpful in things to try.

Car is a 2001 Camaro z28 A4 with 170k miles

godlyxdan

iTrader: (1)

need more info.
Any Mods done?
Has it recently been sitting for a while?
Take a Known good plug and coil from a different cylinder and plug it into #6, if the miss moves with the coil then you know what the problem is

1ltcap

what he said. also, check ALL basics.

BIGDATOWN

It has been doing it since I bought it and then it was bone stock! It now has lid, filter, bo white tb, longtubes, ory, and a converter.

I tried the moving of the coil, wire and plug. No dice. But like I said, it only does this at idle and as far as I know the car didnt do alot of sitting.

1ltcap

why would you purchase a car with a misfire, and then modify it before finding out what the cause of the misfire is?

get an infrared thermometer, and check the exhaust temp of that cylinder. that'll give you some clue.
use a long screwdriver, and place the tip of it on that injector, then put your ear on the handle, and listen for a good solid clicking noise. compare that to the sound of one on a good cylinder.
hook a vacuum gauge to manifold vacuum, and watch it. is it steady? bouncing?

crainholio

iTrader: (2)

Like 1ltcap said, the injector is your next diagnostic step...I'd swap it with another cylinder and see if the problem follows it.

SVTconfused

if swapping the injector doesnt fix it... im leaning towards a bent valve/ bad seat...

my 2000 z28 had this exact problem on #6

BIGDATOWN

My next step will be swapping the injector with another cylinder and seeing if the misfire moves. I will update with the results.

BIGDATOWN

Moving injector didnt change anything. I am going to run a compression test and if it comes back ok I will pull the valve cover next.

jgb989989

I have the same problem on my car. I changed plugs, wires, coil, injectors. even pulled the valve cover after running a compression test. All checked out good. I found a bunch of oil in number 2 coil were it plugs into the harness. Maybe its just me but it feels like it when away after I cleaned the coil and moved it to another location.

1ltcap

do you have a noid light? if not, go to pepboys, and you can buy one for a couple bucks.

disconnect the injector, and put the noid light in the harness, then start the car. it should be flashing. if it's not, that injector driver's not firing the injector for some reason.

99YENKO

Post a pic of the plug..

BIGDATOWN

Cyl#2 235 PSI
Cyl#4 224 PSI
Cyl#6 140 PSI

Plugs looked perfect. MAYBE a lil lean

crainholio

iTrader: (2)

#6 has a problem.

If you want to diagnose further and have a compressor, you can use a leakdown tester to determine whether the leak is at the valve(s) or the rings.

Otherwise it's time to pull the cylinder head.

BIGDATOWN

Basically just knowing if its valves or rings is where I want to be right now. We plan to pressurize the cylinder and see if we can tell where the air is going. My vote right now is a broken ring. We are going to pull the valve cover tonight also and make sure the valvetrain is all ok.

BIGDATOWN

Alright, We pressurized the cylinder and leak is at the exhaust valve. It is 1 of 3 things, carbon build up, bent valve or burnt valve. Seafoam is next! I will post back later with more results.

1ltcap

when you pressurized the cylinder, did you make sure both valves were closed? by either loosening the rockers, or making sure that both lifters were ont he base circle of the cam?

BIGDATOWN

We made sure we were on the base circle.

1ltcap

i don't know how i missed this post. unless there's something very different about these engines, 224, and 235 are too high.
cranking compression on everything i've ever worked on should be between 140 and 175. running compression is generally about half of cranking compression.

BIGDATOWN

Yes the number sounds high, but it could also be the cam degree that makes the cranking compression higher. This compression number is perfectly fine for these motors.