hemivett

Could try putting the old distributer cap back on. Maybe you got a bad/cracked one? h

Tom454

Runs great between 1100 and 1900.

Eliminates the cap.

Bfenty

Oddly enough I have a '85 vette that runs like crap in that RPM range, but fine elsewhere. Wondering if we have opposite sides of the same issue.

Tom454

Installed a new HEI module... no difference. Ordered a reman ECM. Always a possibility that the prom is messed up. PO was in there with a pick & shovel. So where/how do I get a factory replacement prom?

Matatk

Ebay is your only chance for a replacement PROM, good luck with that.

Did you do any troubleshooting? ECMs go bad more often than PROMs, but anything is possible. Could be a wiring issue, too.

Tom454

Did a LOT of research. The ECM I have is a reman. So I can't backtrack that item. When I bought the car, there was a HyperTech 127072 "Thermo Chip" in a GM box marked 16070745. So- I am assuming the car has 1) reman 1227165 ECM, 2) 16070745 OEM prom. The broadcast code supposedly is ABTN, prom ID 747, scan ID 7831. This matches the labels on the installed chip. The labels on the reman ECM, EM7165S, imply the ECM is correct. However, I ordered a NEW ECM and I'm waiting for delivery. It can take a little bit too much force to seat the prom and I can see some knuckle dragger jumping up & down on it. I replaced the 160 thermostat with a 195. Running cold or running at 195 makes no difference... the problem persists. HyperTech cannot provide a "factory" prom. I asked them. I think the only thing left to replace will be the MAF sensor. Somebody glued a GPS base onto the lens where the CEL is located. The lens is almost completely obliterated but I can barely see the words "Check Engine Soon".
RE: troubleshooting... I purchased TunerPro 5 and the Moates cables hoping to get the systems "pulse". I downloaded the appropriate files, renamed them (they download with the htm extension) and imported/loaded them into TunerPro following the authors direct guidance (via email). Tried to "acquire" data. Nothing. Gave up on that. $29 OBD1 scanner doesn't work either.

Wiring Issue: Yup. Could be. Clueless where to start. Everything looks good. Was hoping TunerPro would help me with that. At least ballpark it somehow. This has been educational to say the least. The Honeymoon is over. LOL

Tom454

When I brought the car home, it ran okay. Just a little "sloppy".

The running fuel pressure was 43psi.

I just did a follow up check on the "running" fuel pressure... and it is now 35psi.

Key on/engine off, fuel pressure shoots right up to 43psi. But when I start it, the pressure drops to 35.

Here' is what I think happened-
I jacked the front of the car up as high as I could get it to work on it. There was probably some sludge in the tank, and it probably moved around and plugged up the "sock" or filter on the pump in the tank.

So... when the key is turned on, there is enough fuel in the line to pump up to 43, but once the engine starts to run, the pump can't maintain the required volume to render 43psi. Is that feasible?

35psi cause it to flat spot at 1700-1900rpm?

xrav22

I was reading something in the tpi forum that sometimes people will try to adjust the idle with the screw. That cant be done properly , Can you try to do a minimum idle adjust it seems to help mine whenever I do it. Make sure timing is on and that your balancer isn't twisting
http://www.digitalcorvettes.com/foru...ad.php?t=58873

Tom454

The factory idle plug is still intact. The car ran when I brought it home. I did something to it, I just don't know what. It idles okay. When it hits 1700-1900 rpm it misfires and does the shake rattle & roll. It can't be forced above 1900rpm.... simply won't rev any higher.

RF1

Didn't read the whole thread, but have you checked air in/air out?

No chance the air cleaner is blocked?
No chance the cats melted down and blocked the exhaust system?

xrav22

That is what happened to me when I was messing with the timing. I tried to turn the dizzy to advance the timing and took it for a ride and all hell broke loose. I thought I broke it. I sputtered back home to find one of my plug wires fell off and I turned the timing back with the car off and this time disconnected and reconnected the timing advance tan wire hoping to reset itself. It ran great again, check your timing situation.

Tom454

Disconnected and pulled the MAF off for test... airway wide open... no difference.

Cats could very well be a problem.

Replacing the fuel pump today. See how that goes.

RF1

No. That is the vacuum regulator working exactly as it should.

Tom454

New pump.... running pressure about 38 psi.

No change in problem.

Now I'm leaning toward plugged up Cats.

Tom454

Disconnected both exhaust manifolds and stuck a large bolt across the openings between the manifolds and the y-pipe. Exhaust wide open. Still won't rev. Air filter is clean.

Tom454

Okay... now I'm SOL for a while. I received the "NEW" ECM from AMAZON/Stockwise Auto and the box was opened and full of greasy fingerprints. Obviously, somebody bought it, used it to test, and sent it back. That's unacceptable so it will take me a while to sort this out... Stockwise refused to pay the return shipping for a used part that was supposed to be new.