Hello

- I have an 88 IROC / 305 - automatic trans. - I need to replace the ECM. I've been told the local parts house ones are junk. Anybody have any suggestions ?

Thanks...TIm

 

Really!!,,,....

Why do you think that?

 

If you plan on modifying the car you might want to look at our Bob's Dynamic EFI either the flash or the P4 version the P4 is what I put in my car really happy with it. It does cost more but if you figure the price of burning chips it's cheaper overall

 

I found a genuine GM replacement, new in box, on eBay. Mine (86 TPI) had a cracked circuit board or something - wouldn't communicate with the ALDL and would run (or not) entirely different every time you smacked the case. Probably something to do with sitting in the woods for 11 years. Reman GM from eBay, new in box, cost me $80 IIRC.

GD

 

well, its been running really poorly. I checked for vacuum leaks, and replaced any potential bad hoses. Only code is a MAF - I replaced that. Coolant temp is reading 24 degrees. replaced sensor - its still reading 24 degrees. (mechanical gauge shows 190 ). Checked TPS it is 5.4v.

Took it to my mechanic cause I was out of ideas. He did the same things I did and he says the computer has gone bad.

TP

 

Have you ohm'd the wiring between the CTS and the ECU? Have you tried to bypass the wiring to see if you could get a connection? Take the old CTS and wire it to the ECM directly.

Don't troubleshoot with Visa. Tell us exactly what you have done to prove the ECM is faulty. Mine was so dead I couldn't even talk to it. And I still only replaced it after checking all wiring, power supplies, and grounds, etc. There's always still doubt whenever you call out a bad computer but in my case it actually was failed.

GD

 

What's that? Do these cars (or any other ANTIQUE cars for that matter) have that? Where is it located? is it like under the floor mat or something?

 

Find a late 80's S10 with a toilet bowl injected 2.5L 4cyl. Same computer without the Camaro mark up. Swap the Camaro PROM into the S10 computer, done.

The above assumes there's still an S10 in a junkyard somewhere.

 

If you have enough money, there's good ones out there. No one here will like the price I'm quite sure. Those guys don't come out of their office for pocket change.

GD

 

Thanks for the insights GD, I didn't try most of the things you are mentioning. I'm a 68-72 big block guy so this is all foreign to me. I have no clue what a CTS is, nor a VISA.

I should have posted here before bringing to the mechanic. I'll ask him about the suggestions and see what he says.

In the mean time, I'll call around some wrecking yards and see if anyone has an S10. Budget wise, can't do any of the higher priced suggestions.

 

I found a replacement at Advance Auto Parts for around $100.00.


A caution, the first one was junk, and the car would periodically simply shut down without warning.


I figured out it was the ECM one morning when it was cold outside, and the car was idling in the driveway--my passenger got in, and the car quit running when they shut the door.


The second one has been in my IROC for a little over a year now with no issues.

 

Bob Dynamic can test your old 1 or sell you a new 1. Those boards do crack

 

Well - the mechanic put one in. Not sure of the source, but it's his responsibility. The car seems to start and run, which is a vast improvement, but I still smell gasoline and it doesn't seem to run all that great.

 

Is there any change to the live data? It sounds like there may be an issue still with the CTS if you are smelling fuel and down on power.

GD

 

Hmm - I haven't checked codes yet, we have been having torrential rains here is southwest Florida. The CTS is new, but before the computer went flakey I was getting a Mass Air sensor code. I'm also thinking make sure some of the basics are done, like changing plugs, rotor, cap and fuel filter and checking timing.

On the timing, do you all start with total timing and work back to initial? Or does the computer take care of all that. On my Olds, I changed distributer springs, weights, etc to get the timing the way I wanted the curve. Then went to 39 total and worked my way back to the initial. But Im dealing with a very worked 1970 455 - and obviously - no computer. When I get to these computer cars I'm lost.

Also - I'm curious - I was reading different threads but could not find the answer. Do these cars require Premium gas? It doesn't say anything on any stickers, and from the research I have been doing it looks like this engine is 9.3:1 compression ratio, which to me is borderline. For giggles this morning I was going to fill with an ethanol free, but its an 87 Octane.

Thanks everyone for your insight and help. I'm enjoying learning about this car and having fun reading etc.

Timothy

 

The computer does advance and retard and in stock form it expects the distributor to be set at 6 degrees BTDC for base timing.

They do need premium. If you run regular it will generally cause detonation. It did for me anyway. The computer will pull a ton of timing and performance will go down the drain. You *can* do it but my engine didn't sounds happy one bit. Ran ok after it learned a little but scary noises initially and poor performance. Remember this is corvette fuel injection. It is expecting good fuel.

GD

 

They were designed to run on regular gas. Back in the early 90's, we had folks that would run premium losing injectors, as they weren't designed for it, and it ate the windings. I am sure that particular problem isn't a problem any more, but, the factory recommends 87 octane gas....

 

Maybe it's the ethanol content. My LB9 did not like 87. But I do have a modified PROM running 89 code for the cold start, etc. It might have increased timing. Or maybe it's carbon build up in the chamber. Who knows.

GD