Is there something better than the OEM TBI carb for my '95

[Darrell]

You say it's a TBI issue but you don't say why. You say you have to set the timing way off to get it to run right, by you don't think that's an issue? The TBI is generally extremely reliable. If you know you have a different problem fix that first before you suspect, with no evidence, that there is a TBI problem. There is basically nothing to "dial-in" on a TBI unless you need to tune the PROM, which judging by the parts on your build, you do not.

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I guess what I meant by "can't dial it in" was as a whole assy, my bad. After the initial rebuild it's always been temperamental about starting. I've always had to pump the pedal and hold it down about 3/4 the way to start then continue to pump the pedal several times until it was able to idle itself on it's own. Now remember...this is all at it's suppose to be factory TDC timing.

Every sensor (O2, MAP, IAC, TPS and Air inlet Temp sensor) is brand new and I still can't get an easy start from it. I guess one could be bad.

The TBI, I purchased from someone as a rebuild. I know little about them. I'm getting about 11-12 psi coming into it and I see a nice "round" mist of fuel into each bowl after it's started and idling for a few minutes. But if I crack the throttle hard and fast it chokes itself out, I see little to no fuel dumping in as it spits and sputtering and then it'll pick up.

It seems like it's starving itself of fuel on cold starts and (once it's running) it will fall on it's face if I crack the throttle hard and sudden. Seems though it's not getting the proper fuel when it's suppose to be.

Could the Fuel regulator on the back of the TBI be bad and have anything to do with this ?

AC delco plugs are gap correctly and all show an equal amount of light brownish burn on them..appear excellent

I removed the cat, I don't see that as the problem, though it does blow out black soot onto my concrete driveway. I presume from running to rich too and no cat.

I also just read somewhere about the ECM needing reset after replacing the IAC. If that's true I have not done. I also just noticed that the plastic plug that connects into the IAC is brittle and chipped away from 2 of the 4 prongs. So I have one on order.

also from above questions:

* TDC is set true to the damper
* Has the small diameter HEI dizzy with a new external coil
* Have not put a scan tool to it (don't own one but going to buy one now). Just thought I could fix without..yeah right..lol !
* Don't believe valves are to tight, but will look into as well
* Have unplugged the tan/black wire when timing after normal operating temp.
* Will check the coil, didn't think an MSD would be bad but anything is possible.


I greatly appreciate all suggestions as it gives me things to look into.

 

[Schurkey]

The answer is almost certainly in the scan tool data stream. Remember, a "Code Reader" is not a scan tool.

Still curious about the cranking compression pressure.

Just because the sensors are new, does not mean the information is getting back to the ECM. Failed wire harnesses can be an issue. "New" sensors can be defective. And so can the ECM.

 

[Darrell]

The answer is almost certainly in the scan tool data stream. Remember, a "Code Reader" is not a scan tool.

Still curious about the cranking compression pressure.

Just because the sensors are new, does not mean the information is getting back to the ECM. Failed wire harnesses can be an issue. "New" sensors can be defective. And so can the ECM.

What exactly is this scan tool and recommendation on that and a code reader without me needing to rob a bank..lol

Thanks again all

 

[randomguy]

Have you replaced the IAC?

 

[PlayingWithTBI]

The TBI doesn't have an accelerator pump (the AE TPS PW table does this in your bin file) so, pumping it before starting doesn't do any good. When you turn on the key the fuel pump will run for about 4 seconds. If you cycle the key off/on it'll run another 4 seconds. If that helps starting you have a pump or filter problem.

Did you set up the TBI initially?

http://www.gmcmidwestclassics.org/Web pages/Tuning the TBI.pdf

 

[Schurkey]

What exactly is this scan tool and recommendation on that and a code reader without me needing to rob a bank.

There are dozens of brands, and a hundred different models of scan tools. There are two general categories: Consumer-grade, and Professional-grade.

Consumer-grade scan tools may not communicate with anything except the engine control computer--no ABS, no Body computer, no instrument cluster, etc. Consumer grade scan tools may or may not work with OBD-1 vehicles. IF (big IF) they're OBD-1 compatible, you will need vehicle adapter cables for each style of connector in your "fleet"; and there's about two dozen styles altogether. The popular ones would be three kinds for GM, two or three for Ford, a couple for Chryler, etc. Every car brand has at least one of their proprietary connector style.

A used professional-grade tool is typically more functional than the cheapie consumer-grade tools; and will likely come with an assortment of adapters. Professional-grade scan tools will interface with ABS, Traction Control, Body Computer, etc. along with the engine-control computer.

I have an ancient Snap-On MTG-2500. The thing is getting to be old enough to buy cigarettes. Still, it's done a fine job for me on all the vehicles I've connected to it. (I have software new enough to scan vehicles as new as 2006) There are other brands and models---Snap-On has the Solus, OTC sells Genysis, for example. They're all over eBay.

Code-readers are junk. You won't have access to the data stream--and that's the most-important part.

When you turn on the key the fuel pump will run for about 4 seconds. If you cycle the key off/on it'll run another 4 seconds.

Two seconds according to the service manual for my '88.

 

[Darrell]

Lots of great info guys for me to start with....Really appreciate every piece of suggestions/advise. We're in 2 days of rain and all's holding..Grrrr !

 

[ryeguy2006a]

Out of the box suggestion, but have you thought of switching to one of the self-learning EFI solutions out there? That would likely be much easier to get going than using a carb.

 

[PlayingWithTBI]

Two seconds according to the service manual for my '88.

You're probably right - I count fast, LOL.

 

[Darrell]

Out of the box suggestion, but have you thought of switching to one of the self-learning EFI solutions out there? That would likely be much easier to get going than using a carb.

Could you educate me on that system and set-up?

Would that be one of those Fitech's ?