Problem on the 'limp' home yesterday.

[Lou Merrell]

So, tomorrow should start with a compression check on bank 2?
And if that checks ok, bank 2 converter?
So, hopefully I'll just be replacing fuel pump (unless new mpfi and pressure regulator fixes fuel pressure issue), fuel filter, mpfi upgrade, and cats.
On the bright side, it's not winter yet.

 

[stutaeng]

So, tomorrow should start with a compression check on bank 2?
And if that checks ok, bank 2 converter?
So, hopefully I'll just be replacing fuel pump (unless new mpfi and pressure regulator fixes fuel pressure issue), fuel filter, mpfi upgrade, and cats.
On the bright side, it's not winter yet.

Wait, why are you replacing the fuel pump?

And why do you suspect the catalytic converter? Oh, because of the misfires? Isn't there a code for catalytic converter performance on this generation of trucks?

 

[Lou Merrell]

I'll only replace the fuel pump if the new regulator and fuel filter doesn't fix my low pressure idle currently at 46 psi.
The only O2 codes I have are 0154 and 0157, both on bank 2.

 

[stutaeng]

The way I see the guys doing more advanced diagnostics on YT videos is taking care of the lean/rich/misfire as a priority, and that usually "fixes" the O2 codes.

Since your O2 sensor codes are the same bank as your misfire/lean bank, they are probably ok. What that really means is they are actually working!

You can do an easy test on the O2 though: spray some carb cleaner on the intake and watch them for a response. If that passes, they are "probably" ok, at least until you figure out the more critical issue.

Your static fuel pressure is good, so I doubt your pump is the problem. Idle pressure being low is most likely FPR.

 

[RichLo]

-24* ignition timing... ouch!

That could be your misfire. The distributor could have come loose somehow and rotated?

 

[Jeepwalker]

I didn't catch what year tk this was.. ?

I'll go back to what happened on my truck a few years ago. It was running good, then it wasn't. Then it got worse. It almost ran like there was water in the fuel. LOL. Turns out, the star-shaped reluctor in the distributor had broken from rust that had developed on the distributor shaft ..and 'expanded' and broke it. It was not spinning freely, but one or two of the 'spikes' had broken off as I reacall. Plus the reluctor itself was powderly and weak. Also, a couple triangle points on the pick-up coil were badly corroded and worn (corroded) back to a nub. I guess maybe I didn't have a vented cap or the vent was plugge?? When I pulled the distributor apart the pieces fell into my hands ...Its amazing the truck ran at all. Also, those two tiny wires in the picture are known to corrode and break (or badly fray).

There's probably a way to test the signal (check Y/T). The way to inspect is to pull the distributor and remove the gear, so you can pull the shaft out to inspect the parts (beneath the lower plate). A guy can buy quality parts new. I would have rebuilt mine, but, by luck, I found a good like-new distributor on ebay for like $25, a guy wanted out of his shop, and, yeah, ran great after that. Not as bad of a job as it sounds. No guarantees that's your issue, but worth a look if nothing else pans out.

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[Jeepwalker]

So, tomorrow should start with a compression check on bank 2?

Whenever I have something like this crop up, or am working on, it's always a good idea to take a step back and hit all the basics (like you've pretty much done), which includes a compression test (on all cylinders). Plus you get a chance to look at the plugs.

And:
Quadruple-check body and engine grounds
Vacuum (yours probably isn't running well enough right now, to get a good read)
Fuel pressure and delivery (which you've done).
Sensors, wiring, fuses, etc

 

[Lou Merrell]

'96 K1500
New dizzy, wires, plugs in January of this year.
Compression numbers in January were 165-185 on all cylinders.
On my way out now to check again.
Just woke up and having coffee/3rd shift.
Wish me luck.

 

[stutaeng]

An injector balance test is what what I would do next, given that everything else looks good and is pretty new-ish. Injector(s) are probably dead or failing intermittently.

You can't "see" them, but if they act up, kinda hard to diagnose them.

 

[Lou Merrell]

Ok, compression is perfect on bank 2 (FYI, passenger side of engine).
175-185 psi.
Almost had a heart attack on #8!
Note to self: don't leave the compression tester laying on it's relief valve against the inner fender.
Is there a way to perform an injector balance test without a pro scanner?