Question for code 26

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RockPaws

RockPaws

Joined
Jun 28, 2007
Threads
3
Messages
41
Just when I thought it was safe to go back in the 4-by! :doh:

As many of you know I had a code 25/26 a couple weeks back. In the end I found a cracked mini hose and replaced it. Truck runs great, and no CEL until....

Yesterday, CEL returned. Pulled codes. Expected a 25/26 again, but only code 26 now (rich). In the course of the last 25/26 venture I:

replaced 02 sensor
cleaned injectors
replaced dist cap/wires/rotar
replaced sparkys (NGKs)
tested AMF
tested/cleaned throttle body
adjusted TPS
tested cold start injector (s/b 2-4 ohms, I got 4.1)

I realize a code 26 points to poss problems with injector/circuit, fuel line pressure, CSi, O2, coolant temp sensor or a short somewhere between one of the many sensors and the ECM... here's my question.

I pulled the #1 plug and the #6... yes, they're new but if it were running rich wouldn't the plugs have at least a slightly oily sheen to the top threads and/or firing tip? Both plugs looked beautiful. Perfect, in fact. The firing tips just becoming a little (light) ashen, insulator tips clean and white, and the first few threads slightly darkened by heat, but not oily in the least.

If this were your truck with these circumstances, where would you start? Does it sound like a faulty code (like maybe a short causing a false trigger), or does it take awhile for plugs to show signs of rich running?

In the meantime I'll go check the coolant temp sensor. Thanks again for your guidance!
 
it may have been a momentary condition tha caused the light to trigger if it does it again after you clear the codes and it does it again than woory about it
 
It also had Bosch Plats in it for years, and now with the NGKs maybe it has to establish a new normalcy. <?>

IAC I finally got the coolant hose out of the way to barely reach the coolant temp sensor... and yet another type of harness! No two harnesses on this engine are made the same way. I feel like I'm entering the Gates of Mordor every time I look at a harness.
 
...and coolant temp sensor tested normal. (1.7k ohms @ ~90 degrees F).
 
Hey Jerod, great to know! I did happen to disconnect the neg battery terminal to clear the codes because even though I left the EFI fuse out for over ten minutes while cleaning up, it didn't do the trick. (Removing the EFI fuse to clear the codes has never worked for me... we're talking the big round EFI fuse, right? There isn't some secondary EFI fuse is there?)

FWIW I also tested the cold start injection time switch and it tested fine too.

So I took the truck out and the CEL came on after about 7 miles of casual stop n go driving, stayed on a couple miles, and went off again. It stayed off for the remainder of the ride home (only a few more miles).

I think you're on to something here, about the computer needing to reset itself... do I have to have the EFI fuse out at the same time the battery cables are disconnected? Should I disconnect both +/- cables? Or did it reset just from what I did?
 
we have to remember that this is a obd 1 system and the computer doesnt learn anything is just goes off sensor values,no stored information except for trouble codes no datastream nothing.you must be running rich fuel pressure regulater maybe have you checked its operation?vacuum leakssometimes cause a motor to run rich o2 sensor reads the extra o2 and adjusts fuel accordingly
 
The fuel pressure regulator was next, barring easier measures I could try beforehand. But it seems unlikely to me that’s it, as that would indicate that my original code 25/26 problem was triggered by two separate and incidentally simultaneous events: a vacuum leak occurring at the same time the FPR happens to “go bad.”

This feels more like an “affect” of the code 25/26 problem. Maybe the FPR had adjusted to compensate for the vacuum leak (does it do that?) and just needs some miles to readjust to normal operation now that I eliminated the lean condition. <?> I only put about 80 miles on it after replacing the vacuum hose… and the CEL turned off so quickly after it came on yesterday…. Not like before (25/26) where it would stay on.

And I will disconnect +/- and take out the EFI for several minutes. Having worked in the computer industry from 88-95 building boxes and troubleshooting hardware, I know firsthand how funny electronics can be. Sometimes things that shouldn’t make sense end up fixing problems and no one ever knows why. :D

Will let you know what happens... if the problem persists I will look at the FPR though. Hope it doesn't come to that... but I guess the good news would be I could check my injectors and O-rings at the same time.
 
the fpr runs off engine vacuum it doesnt adjust to anything only alters fuel acording to engine load ie high or low vacuum.did you try spraying brake clean around engine while it is running to check for vacuum leaks?
 
No, but I'll do that. I kind of had vac leaks associated with 25/26 (or 25 alone), so after I found the leak and fixed it and code 25/26 disappeared a few days.... then returned as code 26, I interpreted that as having eliminated the vac/lean part of the equation. Wouldn't 25 still be coming up if a vac leak was causing a lean condition that was triggering rich running and this code 26? Or am I giving the ECU too much credit for exactitude? (Not challenging you at all, on the contrary I'm learning!)
 
it is kinda hard to say,it could be that o2 sensor picks up the vacuum leak adjusts fuel mixture overcompensates and then reads the fuel mixture as rich.I will research this some more and see what i come up with.I am kinda leaning toward fpr though.
 
Sprayed Brakleen with engine running to check for any leaks and found none.

Also took a closer look at the fuse box and saw the EFI thing I was pulling was not the fuse... as you all already know, the EFI fuse is the first fuse at top on the left... on the Fuse box lid it has a huge EFI over the round capaciter-looking jobber and that's what I'd been pulling out to try to clear the codes. (I know.) So I took out the real EFI fuse (& the wrong one for the heckuvit)
and disconnected both battery terminals to clear the ECU real good. Connected it all back up and went for a ride.

As usual, the truck ran great. And this time, no CEL.

Looks like I'll take your original advice, JL, and do a wait and see. If it takes awhile for the code to reappear, that might lead me to a different conclusion than if it appears right away again. Or who knows... maybe it won't come back. Coulda been some very small leak, perhaps, that resealed itself. ::Judy Tanuda:: "It could happen!"
 
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