TBI problem, Truck won't stay running

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xx94Z71xx

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im actually in the same boat myself. i wana tune my PCM for my new motor. dont run bad as is i just know i can get more. im pretty clueless with the TBI programming myself. its nothing like tuning an old holley....

IIRC a ALDL cable was around $50 to $60 on ebay
 

PlayingWithTBI

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Is this something that I could do myself with the correct tools ?
im actually in the same boat myself.


Scanning and/or data logging is fairly easy. Tuning your bin and flashing a chip for your ECM/PCM takes more equipment and research. I'm guessing Darrell's PCM is a 7427 with a 27C512 chip? You can get a 27SF512 ($5 on ebay just watch out for counterfeit ones), and flash it with a Moates Burn2 and tunerPro RT v5 For earlier ECUs (88-91) like the 7747 you need to UV erase and burn them. A better way to go is solder in a ZIF (Zero Insertion Force) socket and use the 27SF512 (I did that 1st on a 7747). Here's some links to look at.

https://xtronics.com/wiki/GM_ECU_eproms.html

For data logging, you need a laptop and these,

For 88-most 94 get the 12 pin, for some 94s and 95s get the 16 pin
http://aldlcable.com/aldl.asp

TunerPro will data log and modify bins
http://www.tunerpro.net/

You'll need some definition file to work with TP.
http://www.gearhead-efi.com/gearhead-efi/def/

If you want to try a different bin
http://www.gearhead-efi.com/gearhead-efi/bin/

Research how to
http://www.gearhead-efi.com/Fuel-Injection/showthread.php?3256-Tuner-Pro-FAQ-and-Tutorials

To flash your chips and more info (I've had good luck with the Burn2)
http://www.moates.net/gm-19851995-c-64.html

If you want to upgrade your older ECU and learn/flash (I sent in my other 7747 for BobR to convert to the EBL Flash2) Lots of good info here too.
https://www.dynamicefi.com/

It takes some homework but it's fun stuff to learn. Hell if I can do it anyone can. I haven't even released any smoke under the dash yet.
 
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evilunclegrimace

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Im having some troubles with my TBI unit also, everyone says get an ALDL connector cable so that it can be attached to a laptop for a scan rea out, of course then Im lost after that.
I just got it back today from the shop and they chased things somewhat, timing was at 12', Fuel pressure was 11.2pSI, voltage to the engines was good, ETC. I haven't drive it except to come home though so we'll see
Bobby v


Bobby, Are you sure that 12 degrees of timing is correct for your set up? Normal 5.7 ignition timing is 0 degrees with the EST by pass disconnected.
 

Darrell

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PlayingwithTBI I greatly appreciate your time as well as all the others chiming in.

I rebuilt my stock '95 5.7 as I wanted to keep it daily driver friendly. It's pretty much a stock rebuild except a very mild cam (Edelbrock 3702) with the Edelbrock 3704 intake. I'm at "0" degrees TDC too (EST by pass disconnected)

TBI mods was only smoothing down the wall around the fuel ports

Edelbrock cam: .050" tappet lift (intake/exhaust) 194/214
Max lift with stock 1.5:1 rockers is (intake/exhaust) .385/.442

My PCM chip is stock, that I know. I believe the engine upgrades and TBI mods I did were very much acceptable with a stock chip.

Chips: This is what I'm confused on. I saw the 27SF512 chips on ebay as mentioned above for about 2/$12. What are these chips and what are the ones I see on TBIchips.com that run anywhere from $225-$295 ? Are they the same or different?

I understand that buying these chips already flashed might be the best way to go for sure versus buying the equipment myself..didn't know it was that involved..lol

Should I at least buy the ALDL cable and software I've seen on ebay for around $60 to get readings?

Also, I just picked up a set of stock ACDelco R44TS plugs which I'll install Friday along with a new fuel pressure regulator (stock).
 

DerekTheGreat

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Since you started playing with the base idle screw, you need a scanner to see what it's base idle is. I use a Snap-On MT2500. Luckily though there are several write ups or pages with the correct information as to what your base idle should be and how to check it. Essentially you need to safely force the IAC motor to close by grounding out some terminals on the ALDL connector. Once it's closed, you unplug the IAC motor and unground those terminals. Connect your scanner, try and start the truck and see what the base idle is. Adjust as recommended. I believe 600rpm is a safe number to try with a 305/350. Then you can flip the key off, reconnect the IAC, start the truck up and see what it does. There is a special procedure to get the computer to relearn the IAC's position, sometimes that is necessary, hasn't been for me. But it sure sounds like you've tried to back off the base idle so much the throttle blades got stuck in the bores. Could be the issue, at least part of it.

Keep in mind the idle itself is electronically controlled & governed by the ECM. So unless you tune it yourself as others have mentioned with a custom chip, it will always try and target that number no matter what you do with the base idle. If anything, you'll only piss the ECM off by adjusting the base idle out of spec, as when you drop that, you're also adjusting the base voltage the ECM sees for the throttle position sensor. Annd if the base idle is too low, when you fire the engine up, especially in cold weather, it'll hunt/surge until it can find a happy spot, if at all. My 454 TBI truck did this because someone else must've thought the idle was too high, which it wasn't per GM engineering.
 

Darrell

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Hey Derek, Thanks for the info on the scanner MT2500. I'll check it out. The throttle blades were sticking due to my error of backing the idle screw out to far..duhhhh!! That's been corrected :)

As far as the IAC (brand new), I just did a basic set-up following some instructions on how to calibrate after jumping the "A" and "B" pin on the ALDL. I have no flashing codes on the cluster panel so I assumed all is good there.

My idle will be sporadic at times and bounce around from a smooth idle at 700 to a high idle near 1500. As well as hard to start initially with what appears to be flooding. My plugs are fouling out and black smoke out my exhaust on initial start only.

I'm starting to believe it could be some chip or ECM confusion.

ECM and chips are new territory to me but I wanna learn. Again I assumed that my upgrades and mods where acceptable with the factory ECM and chip.

I'm spinning my wheels and not sure if I need a new upgrade chip, a new ECM..ect and if so what.

I feel like I'm stuck between wanting to fix myself or finally bite the bullet and take to a shop. My problem is that I'm a fix it right the first time guy (probably like most here), don't trust shops very much and feel that I can fix correctly with some guidance.

Now I'm off to the garage to install front and rear shocks, tie rods, control arms/ball joints and sway bar bushings on my '05 Dodge Ram...lol
 

PlayingWithTBI

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Chips: This is what I'm confused on. I saw the 27SF512 chips on ebay as mentioned above for about 2/$12. What are these chips and what are the ones I see on TBIchips.com that run anywhere from $225-$295 ? Are they the same or different?

The chips on ebay are new blank ones, then you'll need to flash them. Chips from TBIchips or Blackbear are already flashed based on your build. A word of caution, you won't get the best results from your "custom" tune unless you data log and fine tune. You start with your VE (Volumetric Efficiencies) tables to get your AFR ~128 while cruising at different RPMs and MAPs. Then you play with timing, and other stuff.

I started with a chip from TBIchips, after data logging (with help from Davew on gearheadEFI) I reduced my 0-60 and 1/4 mile by another full second. I'm just saying this is my experience. I'm sure others have input/experiences with this too.

Here's some definitions...

http://www.gearhead-efi.com/gm-ecm-pcm-conversion/efi-dictionary.html
 

Darrell

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Sounds like I should start by getting an aldl cable with the software and record the data.

Is this data the volumetric efficiency that you referred to ?

I'm presuming this data logging will then allow me to select the correct chip.
 

Supercharged111

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Your fuel pressure should be 12.5-13, not 11. The difference won't be earth shattering, but it is at least 1 thing that isn't right. Once you have an ALDL cable, try bumping base timing to 4 degrees and monitor for knock if the TBI motors have knock sensors? I think they do. You did add 16 degrees to the intake lobe and likely as much to the exhaust. .385" on the intake sounds stock, you sure that's right? While it isn't much cam, the stocker was pathetic and this could cause an off idle stumble if that's the only real issue you're experiencing.
 

PlayingWithTBI

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Your fuel pressure should be 12.5-13, not 11. The difference won't be earth shattering, but it is at least 1 thing that isn't right.
70Lb/hr @ 13 PSI injectors will be reduced to 64.4Lb/hr

Once you have an ALDL cable, try bumping base timing to 4 degrees and monitor for knock if the TBI motors have knock sensors?
Good advice and TBI motors do have Knock Sensors


Sounds like I should start by getting an aldl cable with the software and record the data.

Is this data the volumetric efficiency that you referred to ?
Yep

I'm presuming this data logging will then allow me to select the correct chip.
If your gonna order a chip from a tuner mentioned above, all you need to do is give them your build and they'll customize the tune and burn a chip for you but, if you have mechanical issues, no chip is going to cure them.
 
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