2001 GM 3.4L V6 Cyl 1 Missfire

[Colt45ws]

It is back. It is still on cylinder 1 as well. To reiterate what I have done so far; Last time I tried to figure out what was the problem, I tested compression, which was excellent. 170-175+psi on all cylinders. I also put it back together with some tactful component swapping. I put the spark plug from #1 in the #6 hole and swapped the 1-4 and 2-5 coil packs. One thing I didnt swap is the spark plug wire itself. These are new, but I may do some swapping of those as well. Have to find one that is about the same length.
I thought this was only a cold start problem but I drove it once and after sitting for about 45 minutes to an hour I started it up with a very bad miss. Cleared up after about 30-60 seconds then ran smooth as butter.
Any suggestions?

 

[Colt45ws]

I tested the injector coil and ignition secondary coil resistance. All were well within specifications.
I have decided to replace the fuel filter, as it does not look like it has been done and it has nearly 100kmi on it.

 

[eljefino]

Had this on my 97 van and it was a leaky injector. Didn't want to try cleaning or fixing that part and got another off ebay. Perfect since. Clue was it flooding when starting and had to floor the gas... and that it ran more tolerably on the highway.

 

[Colt45ws]

I may have to get a fuel pressure tester and check leak down.

 

[Nyquist]

Do some electrical tests on that injector when it's cold and warm.

 

[Colt45ws]

I tested the resistance of the injectors. They are all within spec and very close to each other.. .1-.2 Ohm difference between the highest and lowest injector.

 

[JTK]

Originally Posted By: Onmo'Eegusee
I tested the resistance of the injectors. They are all within spec and very close to each other.. .1-.2 Ohm difference between the highest and lowest injector.


The code indicates cyl #1 only? You need to direct your efforts only to that cylinder then. Like said, swap that injector, coil, etc. I forget how the EGR is ported on these engines, but I've seen where EGR jetting gets so plugged with carbon that more will blast to one intake runner more than the others causing that particular cylinder to misfire.

Joel

 

[Colt45ws]

Swapping the injector would require me to remove the upper intake and a whole lot of supporting [censored]. I already swapped the ignition coil. Im going to change the fuel filter and run some fuel system cleaner through it. I have serious doubts it will do anything, but I have to try.
Out of curiosity, I went out and used my knife to press the schrader valve open on the fuel rail. Got nothing. It had been off about six hours. I turned the key a few times to pressurize the rail and was rewarded with a nice spurt. A leaking injector is my working theory right now. It fits well. When I pulled the plug a couple weeks ago I had intentionally replicated the situations it misfires and shut it off before it finished. I pulled the plug and it was wet.

 

[ArrestMeRedZ]

I think you have it figured out. As you mentioned, it's just going to be a PITA to get the upper manifold off and change out the injector.

 

[Colt45ws]

I hope I dont. Like I said Im going to try a chemical treatment first and go from there. I doubt it will do anything, but [censored]!
At least I do not have to open the coolant system...OH WAIT, yes I do. *Face palm*
Well, if I end up having to change the injector, it will give me the opportunity to replace the heater hoses, one of which is starting to show signs of leakage. Couldnt replace them when I did the gaskets because I couldnt figure out which ones I needed to order! Then when I tried to source them locally they had to special order and were two days out! I was on a deadline.

 

[mechtech2]

Do you have a vacuum pressure regulator on the fuel rail?
It also could be puked.

If you yank a plug right after it runs poorly, you should see any problems. It's too late after it clears itself up.

 

[Colt45ws]

Yeah, it has a vacuum regulator. It is fine. I checked it.

Filter was dirty. Not plugged but dirty. It probably has absolutely nothing to do with this, just PM. I poured in some gumout cleaner. We shall see. $75 for an injector!

 

[Nyquist]

Originally Posted By: Onmo'Eegusee
I hope I dont. Like I said Im going to try a chemical treatment first and go from there. I doubt it will do anything, but [censored]!
At least I do not have to open the coolant system...OH WAIT, yes I do. *Face palm*

It's been a long time since I've seen one of these apart, but I don't think any fluids run through the upper intake. I don't think you will even see fluid (except for gas) since that all runs through the lower intake which is not touched.

 

[Colt45ws]

The upper intake is heated around the throttle body area.

 

[eljefino]

When I did my 97 3.4 van I was able to twist or remove the TB enough to get at my injector. I just had the upper intake or plenum or whatever they call it hanging a few inches up. Might have held it with bungees from the hood or something interesting like that.

The fun part, actually, is lining up the EGR "stove pipe" back with the valve and intake.

My good used injector was $9.99 shipped.

 

[benjamming]

What usually fails on an injector? Are they repairable?

 

[TexasHonda]

If you're losing any coolant, you may have a head gasket leak. I had same symptoms on 94 Accord EX; missing badly for 0-2 minutes after a warm startup. I figured out which cylinder was missing, and pulled plug after stopping warm engine (water on plug).

good luck

 

[Colt45ws]

Compression tests good, 175psi +/- 5psi on all cylinders.