Engine Misfire Mystery. Please Help.

[awalts]

I drive a '98 Tahoe 2DR 4WD with the 350 Vortec.

For a few weeks I've had the check engine light on. Code reader says it's a cylinder 4 misfire. Truck shakes pretty good when idling, and smooths out when over about 1200 rpm.

So far I've changed the spark plug, spark plug wire, distributor cap, and the rotor under the cap, and it's still misfiring. I also ran a compression check and it came back at 150 psi which is well within spec.

Failing to find the problem, I took it to a Chevy dealer. They couldn't find anything wrong either. Their suggestion to me was to do a tune-up, hence the new distributor cap and rotor (only part of a tune-up I hadn't already done).

Has anyone else had this problem? Anyone have an idea what I should try next?

 

[SunlitComet]

who's parts were used. #'s?

 

[sbubbaklein]

how about the injector, bad spray pattern, clogged up.

 

[1999hoe]

I had an issue i replaced everything turns out the original cap n rotor were bad i used an new accell cap n rotor still nothing changed spider injector and a bunch of miscelaneous sensors still nothing though injectors were l3aking so worth the replacement soooo i changed cap again using an ac delco after reading someone had an issue with there accel cap on there truck and wah lah she ran like a top and has ever since

 

[chevync]

Also check the gear at the end of your distributor, I had a 4.3 that had a wore out gear and I was getting a misfire code.

 

[1999hoe]

Also check the gear at the end of your distributor, I had a 4.3 that had a wore out gear and I was getting a misfire code.

Yep my first 99 did that then stripped itself