GEN1 LWB 3.0L Troubleshooting random shutdown - SOLVED

[chadzeilenga]

I’m down to one issue.

I have a misfire at idle. Getting weak/no spark to the #2 cyl. When I pull wire from cap there is no spark. I put a spark tester on end at idle the spark light is very faint but then fine at higher RPM.

Going to swap wires to check wire and change out the distributor cap. Beyond this, is there anything upstream that would cause a weak spark on one cyl?


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[chadzeilenga]

I swapped a wire and installed a different cap and an still not getting good spark to plug at idle. I have video of spark tester at idle I’ll upload


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[chadzeilenga]

I checked the plug, wire, cap/rotor and misfire didn’t go away until I swapped out the distributor.
I set the timing and it drove around great. Smooth acceleration etc. I stopped for an errand, restarted and it is back to the random stumble when accelerating. I still have no CEL.

My fuel pressure measured 52psi with vac line unplugged from FPR and 42psi with vac line installed. Factory spec is 38psi with line on, is it possible that the 4psi over is causing me to stumble when warmed up?

I think it might be time for a DRB troubleshooting.


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[MarkGramlich]

And one of these.

 

[chadzeilenga]

I had some time tonight so I pulled the injectors to check. All measured 14.2-14.3 ohms. I did a poor mans cleaning on them by cycling some carb cleaner through. Spray pattern looked good on a paper towel and was a nice mist. Flushed out the fuel rail and installed a new set of seals on each.

I noticed that there was a lot of grime on the gasket surface of the lower intake, so maybe the gasket was letting some air in when warm? Will install a new one to be sure that isn’t the issue.

Also have some 4mm high temp silicone vacuum hose on order to make sure all of that is in good order.


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[Salonika]

Does the stumble always happen in the same RPM range?

 

[chadzeilenga]

It doesn’t stumble at all at idle, but seems to intermittently come in >2000 RPM. I can duplicate it with vehicle stationary and increasing RPM as well as while driving.

Doesn’t happen all the time, and will start out intermittent on acceleration and then will become more consistent as vehicle warms up.


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[chadzeilenga]

SOLVED!!!

Well I have in and took it to a local shop. On a test drive it died and they were able to identify no spark. Worked through system and everything checked out.

I dropped off the distributor engine came with and they swapped and issue gone, so it looks like the distributor was bad.

The strange thing is the bad distributor was from my original engine which had no electrical issues until now. Been running great since. They also charged up AC and that is working great now too.

Is it possible to rebuild the bad distributor as a spare?


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[CaseyR]

SOLVED!!!

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Chad - are you still in the clear with the kill/no-start condition? As you know, I've been fighting a similar/same problem for the past few months and I finally gave in and brought mine to a shop a couple weeks ago. I just got the call, and they traced my issue back to the distributor as well. I'm hoping we'll both be in the clear now, but not allowing myself to completely get my hopes up yet...

 

[chadzeilenga]

Hey Casey,
Yea, I have 300mi on the distributor swap and it has been trouble free. The shop took mine for a test drive and it died in middle of road. The techs diagnosed no spark and then started working problem backwards from there. A new distributor was ~$500, so I was glad I had a spare. The thing i can't figure out is that I'm running the distributor that was originally installed in the engine, but either way I'm glad it's fixed. Probably runs better now that I've gone through everything else (IACV, EGR, MAF, TPS, Injectors, FPR, Fuel Filter, VAC Lines) ha ha!

 

[CaseyR]

Glad to hear you're having a good run. I went ahead with distributor replacement (pricey as you mention), so I'm hoping this is the end of my saga as well. More headache and $$ than I expected, but I certainly learned a lot about the truck while troubleshooting it!

 

[chadzeilenga]

Yea, I need to address some of the smaller items like turn signals and neutral safety switch that are acting up and it will be nice to have some time to do that.

 

['round n' back again]

oso is right on the mark.
the transistor switch it proper name escapes me now. that fires the coil, I believe it's part number j1701 or such, will give u that very problem.
they seldom die but mine did in a snow squall in reno 600 miles from home then again it really died in anza borrego out of cell range, in a canyon, wit my tools 65 miles away.
brilliant stupidity.
but the little bugger will cause u that issue.
BE SURE IT'S WELL GROUNDED.