Cylinder 6 misfire.. Cant figure it out..

[westman995]

I bought a 97 yukon with a blown motor. Bought a supposedly "GOOD" 350 vortec out of a 97 truck. Well i put it in and get it running and all that. Well it doesnt run on two cylinders, I replaced the complete injector assembly with the one out of the old blown motor and then it runs on all cylinders except number 6, according to the scanner i had it hooked up to.

So after that, i changed the single injector, for the cylinder 6 two times with ones that were working fine on other cylinders. It still doesnt appear to be running on all cylinders. It has compression. It has spark. I pulled the valve cover and all the rockers or whatever appear to be moving the same, as far as i can tell. I changed the cap with the one from the other motor, different plug wire on that cylinder. Nothing seems to fix it.

So i dont remember why, but i had pulled the distributor, before knowing what a ***** it is to get it back running on these motors. Well after alot of guessing and trying, we got it running again. I would imagine that if the distributor was a tooth or two off or something that it wouldnt even run as decent as it does. It runs, starts good, but it doesnt have power as i feel it should and it also shakes/vibrates or whatever and it definitly still has a miss.. I dont know what else to think or try.. Anyone got anymore ideas?

 

[GMC Yukon]

Do a compression ceck on that cylinder... and the rest. That will tell you if its dead or not.... Did you change the cap? the vortec cap really suck. Check the wires also

 

[SunlitComet]

I don't suppose that when you had the plenum off you plugged the runners and forgot to get it out or perhaps a injector wire came loose?

 

[westman995]

I don't suppose that when you had the plenum off you plugged the runners and forgot to get it out or perhaps a injector wire came loose?

Im not sure what you mean by that? Plugged what "runners"?

And no i dont think any of the injector wires could have came loose? Loose from where? Its just that big plug that goes into all the injectors..

 

[SunlitComet]

I meant stuffing wrags or paper towel down the intake runner ports heading toward the cylinder heads so you don't drop something down there.

Wires coming from the large electrical connector. Are the terminals clean with no corrosion?

Do you have A P1345 code from your scanner? What codes are stored in your PCM active or stored?

 

[westman995]

Oh no i didnt put anything in there, and the problem was there before i even took it apart. All i did was replace the injector and put it right back together.

I guess i didnt look at the connections too well. I could do that i suppose.

I dont have a scanner. I had someone hook it up to it. And everytime we tried it it would say cylinder 6 misfire. He said he cleared the check engine light or whatever and it went off, and went back on before i even left the place.

I have no idea what the codes were. The others were something to do with the 02 sensors or somehing....? But they said that could be popping up due to that misfire. If i had a scanner i could prolly have figured this out by now maybe.

 

[ravingmadman]

Have you swapped plug and plug wires with the opposite side of comparable length? I just replaced my plugs, had a misfire, had spark, and while everything looked good, the ~brand new plug quit working with no markings or other indication that it was bad...

 

[Jaycenk]

You could also check Fule pressure for leak down to make sure the regulator is bad and leaking. test only takes a few min and will quickley eliminate that anyway.

 

[BOSS]

I had a random misfire that was solved by seafoaming the intake, check the threads on how-to. Yours sounds more isolated to the injector/cable/plug to me

B

 

[1slohoe]

Do a compression check before you keep throwing parts at it..