GM TBI disagnostics. im stumped and need people smarter than me to help.

Truck is a 1995 c1500. 5.7 TBI, recent 4l80e swap using BJDR bin burned onto a memcal using the moates software and prom adapter. Stock everything else with 166k on it.

Since ove pwned the truck (9 months or so) its been dead nuts reliable. Until the 4l60e died.

The 4l80e swap was uneventful. 1000 miles since the swap. While we were in asheville, started acting up. Would kick the check engine light (paperclip trick only showed one long flash), and shift hard. Shifted extremely late 1-2, and it acted like first was slipping (not pulling in first like it normally does. Like converter was a really loose one suddenly). Would go away after a key cycle, and go back to normal. Couldn't figure out a reason for it, or a precursor to the CEL and behavior that seemed to be consistent. I guessed that the TPS was the culprit, and put tunerpro on it. Noted consistent and linear TPS readings from the computer end. So I replaced the connector, as it was pretty crusty looking and no longer had the weather seal on it. This was done after the first instance of the CEL and shifting, before asheville. Happened three times after replacement of the connector.

Yesterday, after fixing the air conditioning, and extended idle times, things got worse/weird. No CEL, second gear only, idle at 2000rpm.i shut it off, hoping the trick that we learned in the mountains would fit it again. very difficult restart. As in, extended crank times, no start. Finally did, and got it home. Hooked up tunerpro, and other than noting IAC order being at 90, and TPS voltage being high, nothing odd in the data and no codes set. Tried unhooking the TPS and no change.

Today, we tried to start it to move it. No start. Noted that there was no prime pulse form the injectors. However, fired right up on ether and revved good. Got it moved, second gear only other than reverse. So I know we have spark, and fuel when its running. Tried swapping ECM with another (reusing my burned chip setup) with same results.

Got no idea here, and don't want to start shotgunning parts at it. Has to be something im not thinking of.

Far as diagnostics go, Im not even sure where to start, as there's no codes or obviously strange data to lead me in any particular direction.

What diagnostics/where to start?

I was curious when you did this that you didn't pull the ECM from the donor truck as a poor boy work around on this trans and piggy back it .....that is how my mind works on this kinda E36M3. Yes  I know what I just described is a cobbled up mess, but until a proper "tuneburnwhodadthoughtit" can take place, it sounds to me that perhaps the ECM (4l603) is now bumfuzzled....sorry no real answers just thinkin' out loud bro......did  you get the donor ECM?   

Weak pump?

In reply to 759NRNG (Forum Partidario) :

Donor was an obd2 truck. No conceivable way to piggyback, really. And im using the code that the factory would have in this truck, wired the way the factory would have done it

 Other than the limp mode/knock filter side of the chip, its a 4l80e truck factory wise. And from my research, the limp mode side didn't change any

In reply to vwcorvette (Forum Supporter) :

I don't think so. Theres no prime pulse whatsoever, but a fantastic spray pattern when running 

Dusterbd13-michael (Forum Supporter) said:

In reply to vwcorvette (Forum Supporter) :

I don't think so. Theres no prime pulse whatsoever, but a fantastic spray pattern when running 

Any chance the burned chip is bad?  Can you write another with the same program and see what happens?

Fuel pump relay?

The old TBI's used a relay to turn the pump on (prime, and operation), but ALSO used an oil pressure switch AS WELL just to get you home I guess, if the relay quit.  There should be a fuel relay pigtail jumper thing in the wiring harness you can send V+ to to turn the pump on externally.

With a faulty relay, you'd get extended crank times and no prime pulse since now you're relying entirely on oil pressure.

In reply to SkinnyG (Forum Supporter) :

This but it doesn't explain the problems when driving, only when cranking, should have plenty of oil pressure when running.

Side note: it appears we are both having weird tbi problems and both of us posted them here and on gmt400

Ill try relay. Swap it with another known good. 

Also, the ignition control module has some control over prime pulse,  so i need to find test procedures for it. But that doesn't explain running issues to me either, as there's no failure mode that I can fathom that would cause that from an ignition side.

Far as the chip: i can burn another. No problem. I can also try a different pcm, as i have another on the shelf but it is an unknown. 

Opti: it comes in threes. So, another gmt400 tbi guy will pop up with issues soon. Sorry whoever that is!

So, swapped pcm with another i had on the shelf Saturday afternoon. No change in behavior, except now has cel after running. Had to ise ether, as no prime pulse. Swapped the known good fuel pump relayfrom the other truck. No change.
Today, git the laptopout and hooked up, spun the key. Fired right up, cel on.

Cel is for tps voltage high. Pegged at 5v according to tunerpro.

Swapped in old ecu, fired right up like normal, cel on for tps voltage.

Went for drive, other than shifting super hard, seem to be back to normal.

My thoughts:
1. Replace tps, see wht happens. Have a spare used laying around.
2. Leave the original reman ecu in place after replacing tps, put some miles on it.
3. Replace ignition control module with new to correct prine pulse, as i think its starting to die.

Y'all's thoughts?

Sounds like a plan.

Do the TPSes on TBI have the manual adjustment that the TPI ones have? Curious.

In reply to GCrites80s :

Not really. You can slot the holes if needed. 

The one in the shelf went on. .4v at idle, 4.4v wide open.

Drives right! Even did a tunerpro log of about five miles, and didn't see anything wonky. But i also don't know what I am really looking at here either. 

Old TPS is trying to say it thinks you should be spending more time at WOT. 

In reply to Robbie (Forum Supporter) :

Needs way more supercharger for that 

Dusterbd13-michael (Forum Supporter) said:

In reply to GCrites80s :

Not really. You can slot the holes if needed. 

The one in the shelf went on. .4v at idle, 4.4v wide open.

Drives right! Even did a tunerpro log of about five miles, and didn't see anything wonky. But i also don't know what I am really looking at here either. 

When you playback the log basically you do what you did and look for wonkyness. Like if TPS voltage increases don't result in an increase in RPM and MPH. Add or subtract displays to get the info you need without too much clutter.

In reply to Dusterbd13-michael (Forum Supporter) :

Might as well stick that blower on top of an LS 

Do yourself a quick favor and go over a few areas:

Grounds: Specifically the back of block to cab and battery to block. 

Ignition cables: Check to see if the coil wire is arcing to the intake. It may never run rough doing it but it will mess with some stuff. 

Connections: All of them. Maybe some electrical grease for contact oxidation. 

Grille and headlamps: Are they new? Blame the guy you got them from 

In reply to QuasiMofo (John Brown) GRM Plush :

One step ahead on the grounds. Ive been cleaning and greasing every one i come across. Doesn't mean i haven't missed aome though. But I DID add extras to block, body, and battery. Seemed prudent. I do need to speed some quality time with contact cleaner and dielectric grease. Thanks for the reminder! 

And coil wire, as well as all of them, are within 5k of new. But will verify, just to be sure. 

Alt is good (bench tested before installing), battery is fine. 

And yeah, the guy that sold me the headlights and grille totally boned me. I mean, look at it!!!

The new, $80 gm ignition control module will be here sometime today. 

New module in. Took a ten minute lunch. also cleaned and grease the handy electrical connections. Hasn't ever fired that quick. Neither has tbe red one.

Heres to hoping its all done!

In reply to Dusterbd13-michael (Forum Supporter) :

Trans shifting properly??   

In reply to Justjim75 :

After the replacement of the tps,  yes!

In reply to Dusterbd13-michael (Forum Supporter) :

Heck yeah!

In reply to Dusterbd13-michael (Forum Supporter) :

I swear, that guy and his shady dealings. Well at least your truck is running 

Can I say WOO HOO SCOREBOARD????