gm trucks/vans and their ecu

So I have a new to me 96 chevy van with 5.7 motor. I knew the previous owner. It had some drivability issues prior to my purchase. I mutual friend did the work. It would develop a missfire. The ultimate fix ended up being a change in ecu. A used ecu cleared up the problem. When they swapped out the old ecu, the one in the van had writing on it like it was from a junk yard as well.

Fast forward to today, about 3000 miles later. Gas was near empty and I filled it up. Starts to stumble, CEL comes on. I have a short drive, and I get a blinky CEL. Wonderful. So now I'm stewing over it at my desk. It is entirely possible I have bad gas. I let the tank get as low as it's ever gotten while I've owned it. Might have even stirred up some stuff at the bottom of the tank. Van had sat for a while previous to my ownership. I won't be able to get an obd2 gauge on it until this evening.

So do get the ball rolling, are the ecu's problematic in this era of gm truck/van? If I find a replacement ecu cures the current problem, do I chalk it up to bad luck? Is there a possibility that wacky wiring elsewhere is causing damage to ecu's in this vehicle.

I am fairly certain a friend has a beater tahoe, that we might be able to swap ecu's to see what happens if trading ecu's makes the problem follow the ecu.

Any chance you might have a broken wire in the loom that is causing this sort of problem? Happened to me with a '95 GMC truck.

With a gm vehicle and those symtpoms, I would think it is the fuel pump. Those fuel pumps DO NOT like any sort of interuption of flow. They will burn up pretty quick.

Other than that, I assume this is a TBi vehicle. If so, I think they only use the TPS, MAP, CTS, IAT and O2 sensors to run well. That is all we used on our TBI converted malibu.

The different year systems used different fuel pressures. I am not sure if the ECU(s) are the same or not.

Rob R.

Boxhead tim, anything is possible.

wvumtnbkr, fuel pump could be a real possibility. I takes a long time to start on occasion like it has lost it's prime. I imagine could be a contributing factor.

Po102 Mass air something or other. + Random missfire code.

scan tool was showing voltage at the sensor.

I was able to confirm the mass air flow sensor gets voltage, and has a good ground. I found online a way to test the hz to see if it was functioning properly, sadly my multimeter doesn't do hz. I pulled out the ecu and reseated all the connections. Didn't appear to help. One connector has a hacked wire, which makes the hair on the back of my neck stand up, wondering if another wire could be bad. Wiggle all wires at the connectors did not change anything.

online research indicates the po102 code generally leads to MAF sensor replacement, or the wire between the maf and ecu proves bad, or the ecu proves to be bad. Think I'll be doing some junkyard diving to find a maf and ecu to see if those change anything. The MAF was used in a lot of gm vehicles so that should be easy enough to find, however I suspect the ecu. If the ecu is bad, is there something that could be killing these?

Try dielectric grease on the connectors.

Looks like I can get a ecu programmed with the correct setting from ebay for about $60 shipped. So I'm going to take the lazy way out and do that first. I don't think I could get one at my junkyard for less than it, especially factoring in time and gas.

Did you check continuity of the wires between the MAF and ECU?

Also, I know that on Gen3 GM engines unpugging the MAF will force the fuel strategy into speed density. If that clears up the trouble it indicates a bad MAF. I'm not sure if this tip works on the earlier stuff.

I did not check continuity to the ecu, I don't know the pin outs. I'll have to find that out. Got my replacement ecu. Did not appear to help. I did try to uplug the maf and it did not appear to help.

This time around It has not tripped the CEL.

Random misfire code suggests an ignition module, has that ever been checked or replaced?

Ignition module has been replaced. Cap, plugs(plug wires deemed good).

When I unplugged the maf after installing the new ecu, the cel came on. It has turned the light off, after plugging it back in. I bought some MAF sensor cleaner. I'm going to try that next. I'm sort of hoping it was bad gas, I'm letting it idle while eating lunch, to see if it can burn through. I may pick up some dry gas this afternoon to see if that does anything as it is a cheap option. Also found online somewhere that the ground to the back of the passenger side of the motor can be problematic. Going to check that.