1984FIREBIRD

Well i have a 5.3 that had a huge loss of power all of a sudden and then died on me on the road, Turned truck back on and was hesitating to take off and would shake bad under load and kinda at idle and was misfiring cylinders 5,6,7,8. I knew i had bad knock sensors so i replaced then today and truck works overall better but still has a the p0300 random misfire and still hesitates to take off and what not and now misfires cylinders 6,7,8. When i unplug coil or injectors on those cylinders, the engine acts the same, but if i disconnect any other coil from another cylinder it will want to die. Engine has a noise at idle and it gets faster as i rev it. I was thinking lifters or burned valve. any help or where else to look is appreciated Thank you

gagliano7

I would check to see if the coils are good.

Old Geezer

iTrader: (3)

There's a diagnostic/tune forum, for threads like this......

Darth_V8r

iTrader: (4)

I suggest compression checks to rule out mechanical causes. If 6,7,8 are low shoot some oil in and recheck to see if they come up. If they do, points to rings. If they don't, points to valves.

If you have the kit, leak down test would be even more better.

Also pull the plugs and look at them. A lot of available information from the condition of the spark plugs.

1984FIREBIRD

Plugs have a good burn to them, havent done a compression test, i have the kit and will do it today. Those 3 misfiring cylinder exhaust manifold ports are just as hot as the others and there is spark because i got shocked from them (long story). This old man from a machine shop told me to do the dollar bill test on the exhaust and if it gets sucked in consistently then it would be a burned exhaust valve

Burken01

iTrader: (88)

Was the power loss sudden? Like was it working just fine and then the issues showed up?

Or has any work been done to it right before these issues popped up?

1984FIREBIRD

I replaced the radiator like an hour before this happened. And yes it was sudden, like i was going 65 and the truck fell flat on its face and it didnt have any throttle response so I turned it off in neautral and came to a stop and it took like 20 seconds of cranking to turn it back on and it ran fine for like 4 miles, then i fueled up and it started doing it again and it never went away then.

Horsepwraddict

iTrader: (12)

check the grounds on the front and back of the block. the ground straps are common for corroding/breaking/bad connections causing similar problems

Darth_V8r

iTrader: (4)

burnt exhaust valve will show on a compression test as low compression that won't recover if you squirt oil in the cylinder.