99 chevy express engine code cylinder 4 misfire

Asked by Apr 29, 2016 at 11:39 PM

Question type: General

My 99 chevy express engine light is on the code is
cylinder 4,  i replaced injector did tune up but no
luck the light come on after 5 minutes after i reset i
check engine compression  and has 90 psi, next
cylinder has 120psi,   whats engine compression t

8 Answers


check the spark at the coil pack....check the power connection to the coil pack....weak spark...an electrical problem...not a mechanical problem...I think~


Your compression is too low, need 120 lbs to fire properly, 90 lbs too low thus causing the miss-fire. Those engines compression should be up at 155 lbs. The engine is worn out.

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Thanks for answer, yeah i think my engine compression is to low i replaced injectors spark is ok, spark plugs are new, the only think is bad compression because has good spark good plugs, i think the problem is the valves because the cylinder before and after has good compression what you guys think

Im little confuse because my scanner when i use OBDII gives me cylinder #4 misfire but if i use GM program gives P0300 but again cyl 4 has 90lbs oh well i guess need to figure up haw to fix it


Ya, still po300 is a random misfire, there are more cylinders ready to give out. po304 still a misfire indicating #4. Pretty much the same reasons why when these codes come up. Both say low cylinder compression for one of the causes.


How many miles on it? There is a way to determine if low compression is because of the rings or the valves.

Has 160,000 Miles i know this kind of engines goes over 200k im surprise this one has low compression, how can i see if the problem is a rings or valves


You squirt oil into the cylinder, check compression, if compression does not rise, then it is the valves. If it rises then it is in the rings. But if it is in the valves with that many miles on it, doing a valve job would raise the compression and 9 times out of 10 it would then pull oil up past the rings, thus making it into an oil burner.

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