Sounds like a good approach. I was thinking something with the valves/spring.

Got this from another forum think I might check some of it out:

Burned valve
Broken ring
Damaged piston
Flat cam lobe
Bent push-rod
Broken rocker arm stud
Broken Rocker Arm
Bent valve
Broken valve spring
Rocker arm nut fallen off
Blown head gasket
Cracked head
Cracked cylinder

Think I can rule out some because it holds a cylinder compression, what do you think?

Thanks for the fast reply! New to this forum, so far impressed!

Hi-

I am having virtually the same problem with my 2001 Lesabre except on cyl #5. Just this last weekend I had the upper intake manifold gasket, head gasket, #5 intake valve and valve spring replaced --- still getting a hesitation issue. Did everything else you have done, coils, plugs, wires, icm check, fuel injector check... still getting the hesitation problem.

Have you asked anyone about the evap purge solenoid valve? I am thinking of trying that next...

Very frustrating.

2002, The autozone and tests that Dan posted up aren't conclusive by any means. I've had to actually swap the ICM to find one be bad. Do you have anyone local with one ro maybe a salvage yard. That would be my suggestion.

Even though the ICM tested good, I would still be looking at it. Do the other tests first, and buy another ICM last.

Also, bill is correct, the test will tell you if you have a bad ICM, but will not say if you have a good ICM.

Thanks for reiterating focusing on the ICM, I do have access to a 2000 buick lesabre that I can swop out the ICM'* and see if that is the issue.

Today I put some SeaFoam cleaner in the vacuum lines and engine oil. I thought it might be a sticking valve and thought this would help. Didn't smoke like most people, didn't stop the misfire. (Hopefully this wasn't a mistake I'll regret)

I haven't asked anyone about the evap purge solenoid valve. I haven't gotten any engine codes like P0449 "Evap Vent Solenoid Control Circuit Malfunction". But I will look into the Evap Solenoid because I am running out of ideas.

Yes, Very frustrating.

Thanks again for the posts! I will try your suggestions

over45 i wouldnt worry about your evap if your not getting a code, even if it was malfunctioning it wouldnt cause only one specific cyl to misfire.

tks. don't mean to hijack this thead with my issues but it'* essentially the same problem and I'm running out of ideas. my car is not throwing any codes at all now which makes this even the more frustrating.

went to another auto parts store yesterday and the guy said he would try replacing the injector even though it was tested as o.k. also had a story about working on a 3.8L engine with the same problem and it turned out that the magnets in the camshaft position sensor (i think that was the one) had broken off and one had stuck to the block in just the right way so it was semi-working so the computer could still read it but that causing the hesitation. No codes were showing. He said there are 2 sensors on that side of the engine (below the coil packs) and one of them was the culprit.

Who knows. Tks for the replies.

If I missed it somewhere in these posts I apologize, but I don't see any mention of checking the injector on cylinder #3. If you haven't checked it, there are 2 simple tests. The engine must be misfiring when you do this.

First, listen to the injector to see if you can hear the mechanical clicking that indicates it is firing. Listen to the other injectors for a point of reference. Ideally you want to use a mechanic'* stethoscope ($12 to $15), but a wood dowel may work.

If you don't hear the mechanical clicking to indicate the injector is firing, get an automotive 12V bulb that is the type where the wires on the end can be straigtened out and extended from the base of the bulb. Pull the electical connector off the #3 injector and push the bulb wires in to contact the two wires in the injector connector on the wire harness. Start the car and look for the bulb to flash. Increase RPM'* and watch for a corresponding increase in flash frequency.

If you hear the clicking, the injector is probably okay. If you don't hear the clicking but the light flashes, replace the injector. If you don't hear the clicking, and the light does not flash, you have a problem with the injector not getting a signal to fire (ICM, etc.???).

I had a misfire that turned out to be a bad injector. I found it by listening with a mechanics stethoscope, and could not hear the clicking I could hear on the other injectors.

Recap: Misfire on #3

- New spark plug wires
- New spark plug
- Switched ignition coils, misfire stayed on #3
- Pulled the spark plug #3, cranked the engine and it sparked
- Swopped fuel injectors, misfire stayed on #3
- Checked fuel injector connector voltage on #3, was the same as others
- Fuel line not clogged
- Cleaned MAF sensor
- Checked Ignition Control Module, it was fine
- Ran Seafoam in vacuum line and oil to de-carbonate

Update: I swopped the ICM with a working one and it still misfired. I put my ICM on the other Buick and it worked fine. So the ICM is fine.

Also I rechecked the cylinder compression and I think this might be my problem

Cylinder compression:
1- 120psi
2- 155psi
3- 95psi
4- 130psi
5- 175psi
6- 120psi

They all held a compression. When I squirt oil in the cylinders the psi was the same.

Any thoughts?

That'* it. It'* a mechanical problem. You either have a chipped piston, bad rings, or a stuck or burned valve, or broken valve spring. Although a broken valve spring generally does not show up on a compression test.