cylinder 1 misfire *solved (bent valve)

[2002 Crew]

Over the past year I have had to replace quite a few things on this 4.3. It has 155,000 miles on it now. I was a professional mechanic for many years so I do the work myself. The distribtor went out so I put a new distributor, cap, and rotor. Ended up with a defective cap and had to replace it again. I did plugs and wires at that time. Then the fuel injection spyder had to be replaced about 11 months ago so I did that and a new fuel filter at the same time. Not to mention the new fuel pump and sending unit assembly that had been done the year before. Well now I have a misfire on the number 1 cylinder. It is only really noticable at idle. I was at the shop I used to work at and my buddy there suggested switching the #1 injector with one of the others and see if the misfire moved with the switch. Well I did it and the misfire stayed on #1. The only thing I can think of is a burned valve maybe. Compression is around 150lbs. Any suggestions would be great.

[HenryJ]

Did you install the upgrade spider assembly?
Does it change when you disconnect the #1 wire while the engine is running?

Never assume new means good. Cap -rotor- plugs- wires- etc are still suspect.

[2002 Crew]

Yes I did install the new upgrade spider assembly and there is not a great deal of difference with the plug wire off. It is a little more ruff but not a lot. I put a 3rd cap an today just to make sure and that was not a fix. Thinking of pulling the valve cover to check the valve springs. If I have to pull the engine and rebuild I will but I'd rather not since I've been out of work for two years and I'm broke.

[HenryJ]

I'd check the compression on all cylinders first. I have not heard of valve train issues in these engines. A broken valve spring should make a knock.

Try swapping plugs and wires to see if you can get it to migrate. You might also try spraying some carb cleaner around to see it it might be a gasket leak?
Are you losing any coolant?

[2002 Crew]

I rana compression test and the gauge would not hold the reading steady for me because the release valve was leaking. But while it was cranking all cylinders were around the 150lbs. I pulled the head anyway and the amount of carbon was crazy. I know this wouldn't cause the misfire so I'l move on. I was shining the drop light on the valves and noticed a small amount of light actually passing through the intake valve to the inside of the intake port. The valve dosen't look burned but there is an obvious leak if light is passing through from the cylinder side into the port. Maybe a bent valve? What do you think?

[HenryJ]

Worth pulling it and rolling it on glass to see if it wobbles. That will give a chance to check the seat. Carbon on the seat would indicate a significant leak.

[2002 Crew]

Pulled the valve and it was bent on the face not the stem. It's all back together except for a new thermostat housing. We'll see if this does it or not.

[2002 Crew]

The valve fixed it, runs good now with no detectable misfire.

[F9K9]