ecm crashed?

[pwmin]

i know this isnt really a tuning question, but i guess this is where it goes...

so, my car has been having this sputtering problem for a while just off idle till about 2000 RPM or so, so i tested the fuel pressure...good, the ignition system is good (new plugs, wires, coils ohm test good, icm bench tested good), etc. i tested the TPS voltage today and it was below spec in all areas.

so, i replaced it w/ a delco unit and the all hell broke loose. the car wont idle for shit and it bogs down when you give it too much gas. i did an idle relearn (actually about 3 or 4 total) and also replaced the iac and map for the hell of it. same thing. then, i put the old tps back in and same thing. i also got a code 22 (tps) and 34 (map). both are reading 0 volts now and both test charts led me to a bad ecm or wire, so its gotta be the ecm, right? there are a couple other codes, but nothing that serious (23, 35). i also did the tap test for loose solder joints on the prom and no change.

a little more history: i didnt do any tests, but it seemed like in the past when i would unhook the battery for a long time to do some repairs (im talking days to weeks), it would run fine for a while and then start acting up again, recently it has been the worst. the night my belt shredded, after i got a new one on, it was acting up after it had been fine up until that point. it also got better right away after i replaced the wires, but it was still acting up some, just not as bad.

so, do you think bad ecm? i cant think of anything else that would case both the MAP and the TPS to read 0 V. btw, it does have one of those possibly illegal FFP chips made by ben w/ EGR and AIR delete, stock shift points (7K)

[Rhedalert]

Definetly don't rule out the ECM. Swap to the stock chip first, and if there's still a problem. Always good to have a spare ECM for diag, especially yours since they're dirt cheap.

[CNCguy]

It may be how you are checking the voltage. Did you try checking it between wires "A & C" at the sensors?

I checked the diagram for a '92 16149396 ECM and it shows the MAP and TPS as each having separate ECM connections for the +5vt supplies (C12 = TPS +5vt , C7 = MAP +5vt). If yours is the same, I assume there is a single +5vt supply inside the ECM that feeds both +5vt outputs and that it would be an ECM issue since a single bad wire connection would not kill power to both at the same time.

[Superdave]

we had a similar problem the other day in a 3400 swapped Sunbird.. the IAC wouldn't do anything, TPS was reading 1.77% at WOT and we had a host of other issues. Same trouble codes as you are getting.

We checked all the engine grounds and swapped out sensors.. turned out that we did infact have a weak TPS but the problem stayed untill i uploaded another bin to the Ostrich. Looked to be a program error or something.

So in short, try another memcal (the original).

[pwmin]

thanks for the input, guys. there was another chip that came with the car that says "new" on it, so ill give that a go and see what happens.

It may be how you are checking the voltage. Did you try checking it between wires "A & C" at the sensors?

i tested it where alldata said. i also had it hooked up to a Tech II. ill check w/ the snap-on "brick" just to triple check.

I checked the diagram for a '92 16149396 ECM and it shows the MAP and TPS as each having separate ECM connections for the +5vt supplies (C12 = TPS +5vt , C7 = MAP +5vt). If yours is the same, I assume there is a single +5vt supply inside the ECM that feeds both +5vt outputs and that it would be an ECM issue since a single bad wire connection would not kill power to both at the same time.

thats what i figured, i just hadnt looked at the schematics yet to make sure.



i probably wont be able to look at it till the middle of next week since ive got some overnight trips next week and my uncle is here from PA this week, but i hope to at least check those couple of things out soon.

[pwmin]

got a little time and was able to swap out the chips and check w/ the snap-on scanner and same thing. im going to get an ecm and try that. hopefully by next weekend, ill have a good running car.

[pwmin]

well, fuck me. replaced the ecm and still the same shit. its gotta be a wire or something, right?

so, i found and replaced a blown AIR fuse (20 A), which wouldnt cause that, and unplugged and plugged the harness back in the goes over to the MAP, fuel injectors, etc. and car right perfect. went down the road about a 1/2 mile and started acting up again.

im at my wits end w/ this. i dont have a fucking clue whats going on.

so, no power to MAT, IAC, MAP, or TPS, but knock sensor is working correctly. theres got to be a wire that feeds those that is somewhere messed up, but what wire?

[CNCguy]

Did you check that 20A fuse after it started screwing up? Is one of the +5vt wires shorting out and killing the 5vt supply? Only other thing would be a broken or loose ground.

[pwmin]

as i suspected, the fuse didnt change anything (eg. it was ok after it acted up again). its gotta be a shorted wire. pulled the plenum and the injectors all test good. just pulled the harness out and started looking at it.

i found a wire that could possibly have been shorting out. the +5V wire for the TPS had a spot of insulation missing. i just dont see how that alone could be causing all these problems. could it?

[1988GTU]

Is the car running rich, lean, OR is it good in that area?

[pwmin]

when its acting up, it runs really rich. i dont know what a/f exactly, but you can smell the fuel in the exhaust. the 02 sensor was new as of a few months ago, but i had it returned defective JIC and put the new one in. i hate throwing parts at it, but i can return most of them and i get parts for pretty good prices.

i plugged in the IAT/MAT sensor and thats working fine. i was wrong about that. so, the only codes i have now are for running high idle and low V to MAP and TPS

[1988GTU]

So you know for sure the oxygen sensor is functioning right? Also you know the fpr is not blown out? Seems to me as soon as the car goes into closed loop it acts all funny.

[pwmin]

it acts funny in open or closed loop. i am going to hook it up to the Tech II again and do the o2s check.

apparantly, i shorted TPS wire can cause the ECM to go crazy and make the car run terrible, cuz i got that wire covered up and reloomed the harness and its running great now. hopefully, none of the problems show up again. tps and map are within spec now and no codes,