jkeaton

94 3.8L V6: Drove to work today, no problems. Got in to leave this afternoon, started up and immediately knew I was missing a couple of cylinders. Opened the hood, made sure all the plug wires were tight, etc. Everything good. Drove home on what seemed like 4 cylinders, smoking, no power, etc. First thing checked, started it and pulled each plug wire off the coil one at a time. #1 and #2 no change in idle plenty of spark from coil pack to wire and also to the plug (tested it with a plug tester), so I do know the plugs are firing, but I have raw fuel pouring out the tailpipe. and two cylinders not firing even though I have spark. Could a valve be bad? Find it hard to believe I would lose 2 valves at once. Car has right at 195,000 miles. Put in a new ignition coil but did not fix the problem. Has been running flawlessly. It does have the cats removed if that would have any bearing. Any ideas?

petrock

If gas is coming out the tail pipe then you either have no spark, no air or no compression.

The juice may be getting to the plugs, but the plug may not be producing spark. I'd remove the offending plugs and check them out. If they look OK (not gummed up or no cracked porcelain etc) then I'd swap them with two plugs from the other side of the motor and see if it helps or if the misfire changes sides. If it does have an effect then the problem is the plugs.

If not, then (with the cyl 1 @ 2 plugs still out) manually rotate the motor so that the inlet valve for cyl 1 is open and shoot some shop-air into the throttle body and listen for air coming out of the cyl 1 spark plug whole. Then rotate the motor so the inlet valve for cyl 2 is open and shoot shop-air down the throttle body and listen for air coming out the cyl 2 spark plug whole. If you don't hear air coming out in either case, then the intake manifold is clogged.

If not, then rent a compression tester from your local autoparts store and run a compression test on all cylinders. The value isn't important. What matters is that they are all within the same relative range (give or take a couple 5 PSI or so). There are a bunch of video's online on how to do a compression test.

I'm willing to bet the problem is lack of compression (open valve) not letting the air fuel mixture get to the correct level for combustion. Good luck...

jkeaton

Thanks. I do have spark. Checked that. I am going to run a compression check this weekend. I was also thinking maybe a head gasket. what about a cam position sensor? where is it anyway?

petrock

Doubt its the cam position sensor. You would get multiple misfires on both sides of the motor, not two cylinders on the same side. Good luck...

NeoTokyo

The CPS controls the fuel injection too, you would be igniting that fuel but you would be backfiring like crazy through both ends, not a good thing.

Like you said this does sound more like a head gasket problem.

Running a compression check is one of the next steps.

Do you have any coolant coming out? Lower coolant levels?

You can also get a combustion gas tester from Autozone to check for gasses in your rad fluid.

At 200k miles on a singleport, blown headgaskets were in your near future.