[Mook]

5.7 Truck has 150,000 miles, today out of the blue, my truck started to misfire and engine light started to blink. I checked it with my scanner, got code 0308 misfire in cylinder #8. I have had the worst luck this last month with all of my cars!!!!! Any idea of what it could be? Tune up less than 6 months old, plugs, wires, cap, rotor. Really don't want to go to the shop! thanks

[Larry P]

Engine light is blinking because of the misfire, no extra alarm there.

Could be a few different things. Ignition even though it's not that old. Fuel Injector leaking or plugged, intake gasket. Its a tough call without looking at it.

Get a vacumn gage on it,( #1 diag tool), lets make sure it's not a mechanical problem.

If you have the tools to check the spark and fuel pressure, we might be able to help diag.

Sorry, I dont have a silver bullet answer.
Larry

[Txbobcat]

Been there and done that. It needs a new cap and rotor and then you will be cured.

[goatnut]

Like txbobcat said replace dist cap the after market caps are junk. Use a AC Delco or GM cap they are the only ones I have found that will last as long as the original did. All of the after market caps we have tried here at the shop come back in a few mounths with misfire codes.

[ged2227]

If there are no knocks or new engine noises, I would go with cap, plugs, wires, etc. I had a #4 misfire code on my 1996 Tahoe with a 'mechanical' sound from the engine. Found #4 pushrod through the lifter, #4 intake pushrod shaped in a Z, both #4 roller lifters in pieces and #1 intake roller lifter in pieces.
Start with the simple fixes and work your way south

[goatnut]

ged227 your parts look pretty well sludged how often do you change your oil ?

[Mook]

I did a tune up in the spring, all AC Delco parts. Today I checked the #8 plug and wire, both were fine. The first dealer wanted $130 to check it out and if I got it repaired the $130 would not be counted toward the repair! I drove 2 miles down the road to King Pontiac, the real nice folks for a dealership, service guy took it right in an had it looked at, all the ignition parts checked out fine, pressure check was good also. I'm told that the CPU that controls the injectors is the culprit and GM has an updated CPU and its $700. I was told that the intake must come off to install the new part! They did give me a free rental!

[Larry P]

Sounds good, glad you had it diag by a good shop. No sense wasting money changing parts.
Only the upper intake needs to be removed, but its probably a good idea to change the lower gasket also. They will be half way there anyway.
You'll get another 150K from it now.

["QUICK-SILVER"]

97? Intake must come off to install the new part?
Sounds like one of the plastic injector lines broke or came off.
Wouldn't hurt to check and see if the oil smells like gas.

[Mook]

Originally Posted by "QUICK-SILVER"

97? Intake must come off to install the new part?
Sounds like one of the plastic injector lines broke or came off.
Wouldn't hurt to check and see if the oil smells like gas.

Well the invoice said fuel pressure fall and or bleed off- replace CFI with updated unit

injector was $608.54.............! $440 labor!!!