Wanted to finish this, got it fixed. Turns out the ecm was bad. Replaced it. Got communication with the ecm back and fixed my transmission's limp mode issue. The timing was also off. Disconnected the wire and it was at 16 degrees. Brought it back down to the recommended 4 degrees and it took care of the rest. Runs smooth now.
I actually have a timing light on order, was next on my list of things to check. The whole ecm is some what confusing. I've found the correct ecm but the prom I can't seem to source. This particular truck has a 4l80e and 4.10 gears. Not sure how much it that makes a difference though.
I have gone through and checked all wiring and fuses. Checked the battery and alternator. Went back and checked for vacuum leaks. Replaced the tps, iac, map and o2 sensors. Checked the egr valve. The truck now takes a little bit of throttle on startup for about 30sec when cold then runs and drives fine. Still seems to be burning fuel though. Still cannot get any info from the ecm with either the paperclip or a scanner. I am wanting to replace it just to rule it out but am not sure if it would be the actual ecm or the prom chip. Any ideas?
That's the plan I think. Going to pull the ECU and look for visible signs of damage. The not being able to pull codes bothers me. I've also now lost the AC and my gauge cluster is being goofy so something electrical is going on.
Went ahead and replaced the sensor, checked the wiring, replaced a couple of grounding straps that where broken and replaced the gasket on the tbi. No change. Still takes fuel to keep it idling. It's also running really rich, dumping fuel out the back.
I have just picked up a '92 Suburban 2500 with the 7.4. Got it cheap knowing it need a little work. Body has around 200k but the motor is a newer crate engine. When you start the truck and will not idle with out adding fuel. Once you get it going it will idle but idle rough. When it warms up it will run fine for the most part, has a slight miss coming off throttle. I'm assuming a vacuum leak. When they did the engine swap it looks like they carried over all of the previous engines accessories so I'm going to start replacing things one at a time. To get a place to start I tried jumping the A and B pins to see what codes were stored. No matter what I tried I could not get the light to flash, it just stays light all the time. When you first turn the truck on there is no flash, just comes on and stays on. Tried unhooking the battery for an hour or so to reset it but as soon as I turned the ignition on the light was still there. First time playing with these older trucks, just looking for some tips before I tear into it.
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