Hot Air ECM Wasted??????

[84T-typeMike]

We had 2 hot air cars side by side.1 has NO issues really of any kind.Runs good,NO SES light,all sensors respond as they should.2nd car runs but like crap!Nothing checks out!Every sensor reading is erratic,IAC will NOT respond to adjustments.MAF reads 000,TPS voltage is either working as it should,next minute it reads 000????We swapped everything out to known good parts except the ECM.A good MAF on my car 7 gps @ idle reads 0 on his car.A good TPS on my car was same as his,either had voltage or nothing next minute.IAC would do crazy things too.1 minute you would think your adjustments were lowering the number,then it would jump and stay a constant 150 and then it would go crazy.OTC reading would look like this 150,150,23,57,250,222,01,253,27,59,etc.Except engine RPM didn't change.Put Known good IAC in and same thing!Swapped chips,SAME crap!My thoughts were this.Kind of un-likely that the engine harness would short out intermittently at every sensor lead.My GUESS was the ECM.BUT it is just that! A Guess!Anybody care to give their thoughts on what might be causing this!

 

[StaticErosion]

It could also be the connection, but if you have a car with a good ecm that you are already transferring parts over from, why not give the ECM a try?

If that doesn't do it, you might want to look at your charging system to see if its too low/high, or has spikes and all that wonderful electrical stuff.

 

[84T-typeMike]

Well,I didn't want to risk my ECM as I drove 250 miles to help this guy.It was a little far to gamble my ECM.The parts we swapped were all my spares that I have put on to check them and just took them back off.I drove up,gave him about a 6 hour lesson on TR's and then drove home.Not that I am really qualified,Or really know my sh-t.But I have come a long way.Do you think a half fried ECM would do things like this or is the ECM an either it's good or bad kind of thing???ALL I can say for sure at this time is there was ALOT of things that didn't jive.Not even close.When you put a good MAF on and it reads 0 and never changes with the throttle,YEP I'm lost on that one.It didn't even set codes with the stuff not functioning.Scan tool said open loop,never went to closed loop.I have a kick ass book that tells me exactly how to diagnose any code but when it never sets any now what??These are the type of things that make me feel it might be the ECM.ANYONE?????????

 

[SLOW_85]

From the hot-air sticky above...
http://www.engraver1.com/help/ecm.gif
You can check the ecm.
Could be corrosion on the pins.Might have gotten moisture in the ecm.
I would check out the ground wires,also the ecm power feed wire.

 

[StaticErosion]

I'll toss in a second on the ground wires. I had a ground problem that was causing all sorts of problems once.

 

[84T-typeMike]

Thanks for the input guy's,Looked at the link Slow 85 left,Need a little more info???If I were to check one of those ECM terminals,Key ON engine OFF, is that with the ECM plugs plugged into the ECM????Is there metal you can see at each wire down in the plug or do you have to probe each wire through the insulation to get your readings????The schematic say's voltages may vary due to ALT. problems.What would determine if the ECM is bad???Is there an acceptable range for the voltage at each terminal or would I be looking for a terminal that reads 0 voltage when it should have 5 volts for example???I guess a little common sense would go a long way here!I can see it might be hard to really answer these questions but a few pointers on what to be on the lookout for would be a big help.Now that I'm HOME, damn I wish I would have swapped the ECM!!!

 

[SLOW_85]

You can check it plugged in from the back side.
Just stick the test lead in and make contact.
You can also unplug the connector from the ecm.
Should be a pin in each slot.
Might want to unplug the connectors and look for corrosion on the pins,terminals.
All this will show whether you are getting signals to the ecm for the different sensors.
With the key on,engine off numbers should be close depending on the battery charge.
With the engine running a bad alternator may lower the voltage.
The numbers should be close to the chart.
If they check good I'd say the ecm was bad.(sensor signals reaching the ecm but no output).HTH