Good results, normally if damage you will instantly will get more than normal blow by, that's how mine started. And again for some stupid reason or another is cylinder 5 and 7.

 

While trying to get the engine heated up for the compression test, I had a lot of opportunities to put the multimeter on the IDM connector, both when the engine was running fine and when it was stuttering.

Basically, when the engine was running fine, I'd ohm the harness and everything was within spec. I'd let it run until it stuttered. Then I'd ohm the harness and several circuits would be higher than spec. If I let it run for a while after it stuttered, several circuits would be way higher than spec. It was a different "several" each time it seemed.


Running Fine:After a single misfire:
(note, the ohms were rising while i was checking them)Running Fine again:After letting is misfire for a several minutes:
I'm not sure what to check next. I guess i can try to get the multimeter on the plugs on the UVCH gasket... the but valve cover side is male, so that will present a challenge. Mine has the two 5 pin plugs and not the 9 pin plug. I'm guessing it is like this:

G I C I G

And I need to check I to C and it should be in the same range as if I checked it from the IDM connector: 2.8 to 3.6 ohms.

That would tell me which wiring harness is damaged, I think?

Let me know if I'm on the right track and thanks much for the help so far!

 

Yeah those numbers look good that's a releif. I haven't done mine yet and my turbo blades looked almost as bad as yours. However, it passes the oil cap test fine and seems to run great so I'm not too worried.


As for your issue, I'll chime in with some advice.

This is not a very common thing to happen but it happened to me and the issue seemed identical.

My injectors were so worn out that it was putting a strain on the IDM. The IDM cut out a bank of cylinders several times while driving randomly before fully giving up on me a few days later. I then purchased another IDM (before realizing my injectors were worn) and drove on that for two weeks. That IDM straight up failed on me without warning in a parking lot after trying to start.

After checking the armature clearance of my injectors, I realized they were out of specs. I sent my injectors off to Jim at Rosewood to be fully rebuilt to stage 1s, bought another used IDM and have had zero issues like that since which I had them changed out about 6 months ago.

Just another idea if your IPR and other things check out! I'd probably try and do an armature clearance check on the injectors as well just to be safe! I believe if you can't get a 0.002 inch feeler gauge under them, then they are worn out! It's either a 0.002 or 0.003, something along those lines I'm sure there is some documentation somewhere.

 

Hmm you guys posted while I was writing up my post!

After reading what you just checked, it makes me think more that your probably may be similar to what mine was.

My IDM wiring ohmed out good when not running so all the wiring seemed fine. I could see your injectors being worn causing a higher resistance on the wires to the IDM. The IDM can apparently shut down a bank of cylinders if it determines there is an issue with one or all of them.

However with me, my injectors shut down two of my IDMs permanently. MY First IDM tried to warn me but I kept going! I still have it sitting on top of my dresser..

 

Had some problems with today's tests checking ohms at the IDM connector -and- at the gasket plug. First two times the truck started stuttering, I did not get high ohms at the IDM or the gasket plugs. They were -higher-, but not out of spec.

On the third test, I got the same results at the IDM as I was getting yesterday and found that some of the gasket plugs were showing ohms out of spec. This test also showed the ohms rising while I was checking them.

#1#2#3#4#5#6#7#8I'm going to repeat this test at least once before I conclude for sure that the problem is under the valve cover.

If I do decide that the problem is under the valve cover, what is the next step? Test the harness itself? Check injectors like Bubba says? Order new under valve cover harnesses? The plugs, at least, were snug when i had the valve covers off.

Remember, this truck only has 110k on it and has been properly maintained -- i was hoping injectors would go another 90k miles before causing me annoyance.

 

Do you have any burnt pins on your harness connectors?

 

Is the truck running when you do this test?

 

There are no burnt pins, but the ones on the passenger side were dirtier -- may have had some oil in them.

Tests are run with the motor off. Batteries and IDM are disconnected.

With the motor running on that last test documented above, I found that I could disconnect the two front valve cover pigtails and there was no effect on how the motor was running. That would suggest that the #1, #2, #3, and #4 were not firing. I was surprised to find, after turning the motor off to check the ohms, that it was the -other- cylinders with high resistance.

 

I'm bolting down the valve covers now and going to look more carefully at fuel.

I put a new UVCH. It looked identical to the one in there, except it said "Made in China" instead of "Made in Mexico". It improved the resistance tests, but the engine still went into its misfiring mode. I think that UVCH Ohms rise with heat, and I was never really far enough out of spec to cause the misfiring. I'm going to skip the armature gap measurement and come back to it if all else fails. I think the 110k injectors are probably good. (I don't have the right torx bit, feeler gauge, and I don't trust my harbor freight torque wrench).

I'm going to take the fuel bowl out to get at the IPR easily, and that will give me room to look more carefully at some of the hidden parts of the wiring harness.

 

were the injectors spurting oil when running?


UVCH OHMs can rise with heat

 

Yup. All the injectors spit a little bit of oil at idle and a little bit more at high idle. Seemed pretty even.

I got a fuel pressure gauge hooked up yesterday and ran the engine for 90 minutes without seeing reproducing the symptom. I'm accustomed to seeing it after five or ten minutes of the engine running (does not correlate with EOT).

Still planning to dig some more this week and hopefully replace the turbo impeller this weekend.

 

Found that wiring under the bowl to have no loom on it, and wires had fused together, especially the IPR wiring. Ended up buying a molex connector and rewired it with a similar delphi plug. At the same time, I rewired a new IPR connector and packed it with dialectic. Something to think of while you have the bowl off.

Were you UVCH's a one-piece or 2-piece connector deal?

 

My UVCH has the two 5 pin plugs. I found one on eBay from a local seller and we met for the deal. Got both gaskets, four wiring harnesses, 4 pigtails, and fancy butt connectors for seventy bucks cash.

Problems with the wiring harness sound likely. There's a lot of brittle plastic under the hood -- I've had to use a bit of JB Weld to fix some broken plastic brackets already... I'll know before next week if there's any problem, I hope.

 

if you run fine with a fuel pressure gauge not dropping while sitting in driveway and then it dies when moving, it could be a tank issue, wonder if you have trash in the tank and blocking the inlet screen

 

Since I've been diagnosing in earnest since Thursday, the truck hasn't been on the road. I've been able to get it to miss just by letting it idle for 5 to 10 minutes. Before Thursday, it only got undriveable twice. After the first time it "healed itself" for a week. Before those times, I think I've noticed some missing when accelerating on a hot engine -- I was thinking fuel tank at the time.

The only things I've done this last week are

• replaced the CPS (didn't help),
• did the compression test,
• stuck multimeter probes in just about every socket i could find,
• replaced the UVCH,
• cleaned and put dielectric grease in all the plugs.

It still failed one time after that. I put the valve covers back on and then set up the fuel gauge. Then, it ran for 90 minutes just fine until I just turned it off. I've been taking care of other business since then. (truck work is feeling less and less like work lately...).

I reckon there is a problem with the rear fuel tank from previous experience, but I don't think that is the cause here. Dealing with that will be a project for another day, if I can convince myself to drop the fuel tanks at home.

Anyhow, I'm going to get all around the fuel bowl and replace the o-rings on the IPR. I've almost convinced myself I'm certain to find some chafed wires under there.

O yeah, and I ordered the EBPV delete pedestal from RiffRaff in the hopes that turbo re-installation (and subsequent removals) will be a bit easier.