Chevy & GMC Vans

I think TPS's are just a variable resistor. If they are, you can unplug it and measure to make sure it isn't open or shorted while pressing the gas pedal.

What abut EGR? Coolant temp sensor? Wish I had more for you guys...this sucks for you!

EGR was replaced & the intake was nice & clean , no carbon build up . The CTS , not sure if it was replaced or not , but if not i have a new one sitting here on my desk .

the TPS , you mean check it with ohms on each end & see if it varies as you press the peddle ?????

I think so Dan.

Well I'm a little stumped, but I would say you have to go back to the basics. You need to put a fuel pressure gauge on it and see if you loosing FP under load. If that's ok, then at this point you really need to get hold of a scanner so you can monitor ECM data under driving conditions. You'll be able to see what the ECM thinks the TPS voltag is. The sensors may be ok, but if you have a wiring problem that won't show up until it's plugged in. Oh yeah how do the plugs look? If you have a weak spark or problem the plugs are going to show signs of it.

I had a similar problem with my Toro when I was sold the wrong fuel pump. Drove me nuts. It would idle fine, but as soon as you put in gear it would stall. I finally put a FP gauge on it and immeadiatley realized there was something wrong with the new pump. Wasted three days and $$$ on it.

Another thought, have you done a compression check? Also is the Cat still on it? You might want to look into that too. A plugged cat will cause power problems too.

Throttle position sensor replaced with NO difference in the way it runs !!!!!

we've had the scanner on it more times than i can count , &everything seems to check out ok . but still throws a code 42 which is electronic spark timing .

i don't know , this thing is cursed .

Put in another dizzy! or go back to your origional post.
It ran with set up you got Lock nothing else.
I had thought about spark advance but have no idea how these engines accomplish it. I just remember old limey 4's and 6's and springs in the dizzy.
Did you check the exhaust? That was a good idea

You need to go back and read that article link on EST. It sounds like your loosing a signal to the ECM. Could be dirty or band crimp on the connector for one of the EST signals.

I would start checking continuity on those connections between the ECM and the appropriate connector. I had one back out on my 91, it was the data wire to the ALDL connector. Sometimes it would work, some times it woulndn't. You could also have some heavy corrosion on a ground or one of th connectors. It may be on the harness side.

all the grounds & connections are in great shape . next thing to do is check continuity on the wires i guess .

exhaust is good , theres no cat to clog up so ......

Check the wire harness that runs from the ECM to the doghouse where it goes through the firewall. Right after that, the wire harness runs on top of the passenger side valve cover. I found there were some burned wires in that loom in a co-workers 93 Astro. His was blowing one of the ECM fuses though and would not even start. We cut and spliced/soldered/heat shrunk all the burned wires and he has had no issues since. If I remember right, there are around 30 - 40 wires in that loom and they all come from the ECM.

Yep I agree, you've pretty much exhuasted all other possibilities. Wish I was close to help. Electrical is one of my strong points. If you can get a wiring manual for it, that would help. I would ring out or check resistance of those circuits. Either that see if you can get a harness from a junk yard.

Keep us posted, you'll get it.

Put in another dizzy! or go back to your origional post.
It ran with set up you got Lock nothing else.
I had thought about spark advance but have no idea how these engines accomplish it. I just remember old limey 4's and 6's and springs in the dizzy.

WTF Jim ????????????????
maybe its me , but i no understand !!! lol

Yeah gonna have to break out the VOM & the continuity tester to see whats going on . man i hate this part , its so damn time consuming .

Have you tried another distributor?

Have you tried another distributor?

no but all the electrics in this one have been replaced & with it running so good in park or nuetral i'm inclined to think the dizzys fine .

Skippy,,,do a real good check on the dist. I'm not up on the later model 4.3 dist. but if it's made like the old HEI's, the base can break from the press fitting and the base will actually turn on the press fitting shaft area. It'll run fine until you give it gas and then it will get so far out of timing it'll start backfiring and you can hardly keep it running. You may have to pull it one more time to check this but you might be able to see it by turning the cap. Make sure the bolt is tight so you aren't turning the entire dist. I spent 2 months trying to run this down a few years back with an HEI,,ran fine untill you gave it more gas and then it would jump timing bad, to the point the headers glowed red.