FI Rough Idle. #4 Misfire

[spiderva]

I have a FI Spider, that has recently started having a rough idle. I pulled the plug wires, and the idle didn't change when I pulled the wire for the #4 cylinder. The #4 injector cable shows voltage when the engine is running, and I did see a spark when I pulled the #4 plug. I went to pull the spark plug, and there was some oil pooled on top. I removed the spark plug, cleaned off the oil, and replaced it, but still had the misfire. Next step is to run a compression test.

Any thoughts on the culprit of this misfire?

[narfire]

Try running it in the dark. See if there is a short in the plug lead and its arking to the head. (I had that issue) I found the hood liner was sagging too much and rubbed the lead a bit thin. Everything in the rotor cap in good shape?
have you pulled the injector lead while running? I know #4 is a bit of a pain but a long screwdriver can pop it off and on from the top.
Just be careful with the hot wires to the starter...no rings on eh.

[So Cal Mark]

use a stethoscope and listen to the 4 injector. It should have a noticeable "click" when the engine is running

[spiderva]

Before my initial post, I replaced my rotor and the #4 plug wire. As suggested, I ran the car in the dark, and did not see any arc'ing. I also tried listening to the injectors, and heard a clicking, but not sure if it was the injector or the valves.

I believe the source of the oil is the valve cover. When I removed the exhaust valve cover, I could smell fuel around the #4 valve. Hopefully I will have the time tomorrow to run a compression test.

[rlux4]

You could check the condition of the #4 spark plug. Pull it, put the wire back on and lay it with the threads grounded on the engine. Crank the car and see if you have a good spark. If you haven't pulled it before you'll need a swivel to get it out without breaking it. Here's a chart to diagnose spark plug conditions:
http://www.verrill.com/moto/sellingguid ... rchart.htm
Ron

[spiderva]

You could check the condition of the #4 spark plug. Pull it, put the wire back on and lay it with the threads grounded on the engine. Crank the car and see if you have a good spark. If you haven't pulled it before you'll need a swivel to get it out without breaking it. Here's a chart to diagnose spark plug conditions:
http://www.verrill.com/moto/sellingguid ... rchart.htm
Ron

I did this, and get spark from the #4 plug.

I could not find my compression tester over the weekend, but did have a chance to check valve clearance with a cold engine. #4 exhaust had a gap larger than my .80mm feeler gauge. The valve adjustment tool would not fit around this valve, but I was able to use a flat head screw driver and pop the shim out. I replaced it with a shim .35mm thicker, and the gap was still larger than my .80mm feeler gauge. I've ordered some thicker shims that I will hopefully have by next weekend. I checked my other valves (intake & exhaust), and they were within spec. Kind of strange that this valve was so far off. But, it would explain the misfire.

[narfire]

Thinking aloud here... but wonder why the clearance would be so much greater on the one valve as compared to all others. Was there a PO that mucked about with it you think? The cam lobe itself show any wear?

[So Cal Mark]

huge clearances indicate a bent valve

[spiderva]

I pulled the cam off, and the valve springs on the #4 exhaust are broken. I bought one of those overhead valve spring compressors, but it slips off when I try to compress the spring. I would rather not pull the head, to replace the spring.

Any suggestions on how to compress the spring? I will need to get the spring on compressed enough to get the two collets on.

[majicwrench]

Lower the piston in the cylinder and then feed a bunch of rope into hole. Move piston up. Now valve is held in place.
Not sure how much clearance on our engines, but you can compress spring in vise, then use baling wire, wire ties etc to hold it compressed. Drop spring over valve and remove whatever is holding spring.
Good luck!