Vortec 4.3L/V-6 misfire Cont.

"JQuigs1977" was finished. Lookin at the Haynes manual, I guess I need to look more in

Was compression at least 150 psi in all 6 cylinders? Did the compression vary between any of the cylinders by more than 20 psi?

If your answer is yes and then no, you're mechanically sound.

What do the plugs look like on the side that is missing? Lean, rich, normal?

Was the misfiring side the cooler or the hotter of the two catalytics?

You can ohm out the injectors to see if they're electrically FUBARED, but if they're mechanically stuck open/closed due to varnish and deposits the ohm test won't tell you squat.

Also, if this is a CPI engine, the injector assembley (looks like a spider, inside the intake) has a tendency to grenade, but that usually causes the entire engine to run rich, not just one side.

Do you have ANY DTC's other than the multiple misfire code?

Doc

The compression was about 180 PSI in all 6 cylinders and didn't vary at all, pretty much right on the money all 6 times.

The plugs were all black, I am guessing that is rich. #4 cylinder plug had what looked looked like liquid streaks on the porcelon part like when you wash your car and don't rinse it off. I don't know if that is normal, but looked odd to me.

Also when I was checking the catalitic converter, I figured I would take out the up stream o2 sensors to see what it sounded like, it sounded like it was misfiring on both sides but it also could have been the echo in the garage, so you could be right about the fuel meter body.

Oh forgot, I had autozone read the codes and they said it was the only code showing up(P0300), but they really don't seem to know a whole lot there, so I am about to lay down the 100 bucks and go to Hudiburg Chevy and have them read it, so hopefully they can pin point this if I can't figure this out this weekend, but in the mean time, all the help I can get is greatly appreciated, since I am not the richest military man out there.

"JQuigs1977" all, pretty much right on the money all 6 times.

If all of the plugs are black it's running rich on both banks. Sounds like the CPI injector body has kicked the bucket. Does the exhaust reek like fuel? Any black smoke out the tailpipe? Were the plugs wet with fuel? Terrible gas mileage?

Doc

The exhaust is pretty stong, like you would smell on an older pre-injector model vehicle and was getting pretty crappy gas mileage. I changed the o2 sensors (one had a burnt wire on it) and when I took them out to listen for misfires, they were already sooty and I had only ran the engine probably a total of 10 min prior to taking them out but didn't really notice any black exhaust.

Quigs

"JQuigs1977" notice any black exhaust.

Gotta be the injector assembley and/or fuel pressure regulator. I've only ripped a few CPI units apart before and my memory is a little fuzzy. There are a few on here who are more knowledgeable than I with this system who will chime in and fill in my blanks. If memory serves, you can pop off the upper intake plenum and see the spider assembley. If the CPI unit has failed, as soon as you remove that upper plenum you'll see and smell gas everywhere.

Doc

Awesome! I'll try tear into that first thing in the morning and see if that fixes it. I'll keep you posted. hopefully I find something wrong there. I really appreciate your help.

"JQuigs1977" that fixes it. I'll keep you posted. hopefully I find something wrong

It won't fix anything, if the injector assembley is shot you'll need the repair kit, I think it's called the "injector nut kit." They might try to sell you the whole spider assembley to the tune of $400 or so, but IIRC the nut kit is about $50.

If you start a new thread eith CPI injector nut kit in the subject line there is one fella on here who has done this recently, can't remember his name though..............

Doc

Can I buy the nut kit at like autozone or there particular store I should buy it at?

"JQuigs1977"

Yes, it is a 2001 Silverado. A buddy and I took the thing apart and didn't really find much. There were no really clean spots in the manifold and everything seemed to be intact. One question though. On the connector side of the injector, there is a what looks like an appoxy drop in the middle covering a little hole. Is that supposed to be there. On 3 of the injectors, they are missing. We also tested the injectors with a 9 volt battery and they were all clicking so I am pretty sure they are all working. Maybe this is just a low fuel pressure problem?

I must have missed the original thread on his question(s). From Doc's replies thought it was a CPI motor.

In article , "JQuigs1977" really find much. There were no really clean spots in the manifold and

Everything you've been told so far has been based upon a mistaken belief that your 4.3 had CPI injection.

Don't know, I never paid much attention to the top of the injector.

Means nothing, there is a poppet valve at the end of the injector tube where it clips into the intake runner, a stuck poppet is very common and you will hear the injector 'click' even though the poppet is stuck.

That should have been your first check.

I did check it at the pressure test port outside of the manifold and was ok, I am just saying bad fuel pressure regulator on the actual fuel meter body? Could that be causing bad pressure problems?

In article , "JQuigs1977"

There is a pretty rich condition goin on. Brand new plugs are pitch black already, and the exhaust if super strong, so it is running pretty rich, but would that be causing the misfire condition also?

In article , "JQuigs1977"

How can you tell if it is ruptured? I didn't notice any really clean areas in the intake manifold area. Are there any other signs of it rupturing? Can it just malfunction internally causing uncontrolled flow. I tried to blow through it and it seemed pretty intact. Couldn't get any air to flow through it. If that's not it, what else can cause the rich condition? I have changed the o2 sensors (physical damage reason) already.