I can't remember but is it fuel injected or is it throttle body injected? If it's FI then I'd go after the coil pack for cyl #8. Did you pull the plug? is it wet, white, black?? Do you have individual coil packs (one on each cylinder) or do you have the 4 coils mounted with 2 plug wires each?) If it's the 4 coils, then swap the number 8 wire at the coil with the one next to it. If the misfire changes to the new cylinder then you know it's that one coil causing problems.
Faulty fuel injector.
SOURCE: 1999 chevy suburban misfire
could be one of several things
1) run a compression check, if it low on that cyl then you have a blown head gasket or burnt valve
2) could be the enjector
SOURCE: Check engine light
A multi misfire may mean that one or more of the following has happened:
Faulty spark plug or wires, Faulty coil (pack), Faulty oxygen sensor(s), Faulty fuel injector(s), Stuck/blocked EGR valve / passages, Faulty camshaft position sensor, Defective computer.
The engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wire, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the the problems were faulty fuel injectors.
Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open.
Good luck and hope this information helps, keep me posted, be glad to help you get the truck running 100% again. Not sure if your running a K&N air filter, and if you are there may be a flim of oil on the MAF sensor that is making you run lean. You may want to spray down the MAF sensor with a can of MAF cleaner.
SOURCE: #8 misfire
With the truck running, spray some water with a spray bottle on the wires and cap, also spray the coil. See if you can make it misfire by doing this. It may help to have a helper in the truck with it idling in gear. You may hav egotten a bad wire or plug, too. I find these run pretty decent with the Champions like they came with.
SOURCE: just got 2002 chevy cavalier ls check engine light
RECHECK#2 SPARKPLUG, PULL IT OUT AND INSPECT THE GAP TO MAKE SURE IT'S NOT BENT SHUT, IF PLUG IS OK MAKE SURE WIRE BOOT IS ON SECURELY, IF THATS OK THEN SUSPECT A FAULT COIL.
SOURCE: 1999 Grand Am 3400 v6 misfire.
I was asking about the pushrods because I had this problem with one of these engines that had a bent push-rod. I robbed a push-rod out of an older 3100 and it was just a fraction of an inch longer which bottomed out the lifter. I figured it out by removing the valve cover and loosing the rockers when it was running and it smoothed out. I'm guessing you checked for vacuum leaks already. How about injection pulse on the number 6 cylinder when running. Another thing you could check is running compression. You said you checked compression but did you just check cranking compression or did you check running compression too.
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we also changed #8 injector, checked compression it was good,checked rotor and distributor cap
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