Hi I am new to these forums. I have a 1998 v6 3800 series II camaro with 89,000 milesand I think it has a bad misfire problem. This might be an intermintent misfire but im not sure. I have tried many things to fix it and i cant figure it out. Some times especially when it has sat for at least 20 minutes and is still very hot it will hesitate to start( about 5 seconds), but if i give it gas it will usually fire right up. I think that the misfire happens less when it is cool, also when it is running at higher rpm's(i think but i might just not feel it as much). Iknowwith a mechanic and he cant even figure it out.

-I have put new spak plug wires on about 6 months ago
-New Plugs 6 months ago ( another new # 5 plug today) gapped to .060
-I have used a scanning tool what is always says it P0305B for misfire in cyl. 5 or sometimes P0300B for misfire.[:@]
-I kind of tested the coils by taking wires off and turning key. They all arked across the coil. Which is supposedly right.
-I used a light tester thing which connectedbetween spark plug and plug wire. It flashed, which is right.
-I have put a screwdriver up next to theinjector and i can hear it click, which is right.
-I just tested the compression and it read about 75 psi.[]??
-I also compared ohm reading of fuel injector #5 to others and that was the same. So thats fine.
-When i used the scan tool it did a readiness test and it said that the O2 sensor was not ready, as well as other things i cant remember. But i dont think that would affect an Isolated misfire.[]??
-I have done a ohm reading on the spark plug wire and it was close to others.
-I just put a bottle of injector cleaner in tonight. ( i also did this about 6 months ago, i dont think it did much).

IF ANY KIND PERSON COULD TELL ME WHAT MIGHT BE WRONG I WOULD GREATLY, GREATLY APRECIATE IT.

THANKYOU very much FOR YOUR TIME

 

Sounds like for one think check and/or replace the faulty O2 sensor(s)...

 

Be sure the wire for #5 is not shorting. Mine was rubbing the exhaust manifold. They should be routed BEHIND the engine and back up underneath the manifolds. Take off plug wire 5 and give it a thorough inspection.

 

The P0300 code indicates yuo are getting random misfires. This usually indictes that the ignition module under the coil pack is going bad. Also the 0.060" gap sounds excessive to me and could be the cause of misfire, especially if there are problems with the plug wire or the wires are not routed correctly. Close down the gap to 0.040 & see what happens.

 

Exactly. See, with mine, I'd have a P0300 stored. After using a Snap On MT2500 scan tool and monitoring misfire data, I saw that number 5 was the cylinder with the random problem. Sure enough, the plug wire was routed incorrectly and the manifold had scorched the coating. The spark was being shorted to the block, so BE SURE this is not the case. My plug wires were AC Delcos and had not even been on for 4 full months. Either way, it's vital you examine each plug wire carefully and be sure they're routed according to factory specifications. It doesn't take much for roughly 40,000 volts to jump through even the slightest crack or carbon track in a thin plug wire.

 

Hi thankyou for the quick replies. I have double checked that wire, It looked just fine. I also watched it, while running, for a while to see if anywhere i could see a spark by the wire and i DID NOT see anything like that. The wire is routed correctly. I tested it with a multimeter( resistance OHMS) and it was pretty much the same as the other wires.
As for the gap, 0.060",I went by my manual ( which is for a 1999 camaro) my camaro is a 1998. But i will try it at .040, z28 pete.

Also for the O2 sensor i will look for one but, I dont understand how that could effecta singlecylinder.

what should my compression be? ive tested it with 2 different gauges, one said 75psi, the other about 55psi. But thats a rough guess to what i remember.


Thankyou very much
Hrankarl

 

Oh ya it also backfires when i hit the gas hard. If it backfires, does that mean that the spark plug is actually working or just igniting from something else? I beleive the spark plug is working, i just dont know about the fuel injector being clogged or a valve broken or bent, or compression being off.

I have been running on 93 octane. Is this bad for the 3.8L 3800 series?

Im tired of this problem[:@]


THANKS SO MUCH

 

Hmm, under 3800 specs in the Haynes manual it lists cylinder compression pressure at 100psi minimum, with a 30% deviation from the highest reading between cylinders.

That sounds a little high. An O2 sensor shouldn't effect a single cylinder.

 

hmm
where did you get that specification from for the compression? whats haynes manual?
What does the compression ratio mean? because all ive ever seen and it is like 9:4:1 or something like that. or 9-9.4:1

And if my compression is off what can cause that?

What are you sayingsounds high? compression or octane.

I really appreciate you help

 

Haynes:
http://www.haynes.com/


Or Chilton's (better with a CD available:
http://www.chiltonsonline.com/