With backfiring I feel we have to make sure beyond a shadow of a doubt that you have the plugs wired as indicated in the pic below..

 

Yes sir. Beyond a shadow of a doubt the firing order is correct.
I also plugged the crossover tube hole in the back of that head. It's allot quieter now but that's about it.
I started it, let it idle for a couple minutes then got on the gas and it just pops through the intake.
Ran KOEO codes and got 312. Insufficient egr flow. Well I know I've got a disconnected vac line for the egr but it doesn't change how it runs. It has this problem when it was hooked up. I had it off because I am going to replace it.

 

312???
Did you mean 512?

 

The ECM is bad. Nearly 100% certain. Stop wasting your time looking at all this other silly **** and go buy a new ECM and put in it.

These trucks are notorious for that. I've had to put an ECM in almost every one of these trucks that I ever owned at some point.

 

No it was 312. And I looked it up and it said insufficient EGR flow.

 

I was kinda thinking that but wasn't sure. Could I have installed the TPS wrong?
Thank you

 

312 has nothing to do with the EGR flow.
DTC 312 indicates that secondary air is misdirected and is only a KOER code.

Possible causes:
-- Vacuum hoses leaking, blocked or kinked.
-- AIRB/AIRD valve, AIR pump inoperative.
-- AIRB/AIRD solenoid(s) damaged, blocked.

 

The whole air injection system is disconnected from what I gather so any code related to it can be dismissed IMO.

 

You have a MAF meter on a '93? Do you mean the MAP sensor perhaps.. little black thing mounted up on the firewall?

It is starting to sound like you probably have a bad PCM all right, the electrolytic caps degrade and eventually short out and explode which can cause damage to other components. These caps have a typical useful life of about 20yrs give or take so it's not an uncommon problem in trucks of this age. The manufacturer certainly never expected these vehicles to still be operational 25yrs later.

 

Yeah the air injection system is removed completely. I will replace it when I can get more time and money.
OK is there a way to test the computer or can I remove it and open it up for physical signs of inoperability?
Thank you!

 

Yes remove it and look for obvious damage inside, be sure to disconnect the battery first and also inspect the pins in the connector to see if any are bent or pushed back. Also take down the box code info on the PCM connector or take a picture of it so you can search for another if this one turns out the be in bad shape.

 

Ok so I removed the PCM. The connector looked it good shape although Ill still clean it up and grease it up prior to installing the NEW computer.
Yes, that's right. I opened it up and at first I didn't see anything obvious and I got discouraged and then I glanced at the electrolytic capacitor (one of the 27micro farad, 24 v ones) looked like it had leaked? The stamped paths on the circuit board were irreparably damaged and so, that most certainly was an issue in the engine running!!!
Is this something that happens? What is weird Is that the PCM says Remanufactured Original Equipment on it. Who know when it was installed. no dates or anything on it.

My question about getting a replacement. What numbers on it do I pay attention to? I see some fairly obvious raised alpha-numeric that looked like it could be a part number but I also saw, very faintly another, barely stamped in there that looked like it could also count.

I saw one on ebay and the guy said it would work with my truck as long as the truck, year, engine and transmission would match, it was fine. Is that the case? Or do I need to search for specific part number?

Thank you guys for the great help! For the first time in two months on this truck I am finally feeling encouraged

 

You can post the calibration number off the drivers B pillar and maybe we can tell you the PCM Computer that came with the truck.

Example the calibration number in the photo below is "4-54E-R10":


/

 

OK copy that I'll check that out tonight when I get off work
Thank you sir

 

Ok that number is 2-64E-R11 and this is the part # I found for it F2TZ-12A650-CC. is that correct? Thanks guys