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Old 11-27-2010, 12:23 AM   #1
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Default ECM location?

1. On a 1995 Olds regency elite, where the heck is the ECM?
2. Can ECMs go faulty but still let the car run without throwing aa code? I know this sounds goofy, but here'* why I'm asking.

I had the car scanned because the engine is running really slow (630 rpm instead of the normal 750) when warmed up. It'* a 3800 series II non supercharged. There was no codes found, no history of codes. The engine runs relatively smooth, but it'* really slow. I guess one thing I can't complain about is it uses slighly less fuel. Only thng is sometimes it gives me the impression it'* going to quit when it is under load - even with the IAC cutting in.

I've read on the web that ECMs in the early to mid 90'* GM cars may be faulty. If the ECM was faulty, wouldn't it just kill the car? Or would it rear it'* ugly head in this manner. I can get a reman unit for 185.00, but I don't want to spend that money unless I have to.

Also had a mechanic friend suggest that because the car is high mileage (300,000) it could very well be worn out injectors causing the problem. I've never heard of that before. And replacing the injectors (not rocket science) would cost about 370.00 also. Don't get me wrong. I will spend the money to fix it if I know a guaranteed answer.

Anyone got any ideas that would be helpful? 1 last comment, this car is VERY WELL MAINTAINED. I call it my second money pit. But I'm getting to the point of having to decide whether to keep it or sell it.
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Old 11-27-2010, 10:41 AM   #2
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Just a guess, but I think it'* under the glove box. And yes, they can go bad.
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Old 11-27-2010, 12:36 PM   #3
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I know the AC programmer is under the glove box, because I had to replace it this year. Replaced the light control module 2 years ago (that'* a major PITA for such a small module - especially when you have the rear heating option on the car) Actually when you look at what'* under the dash, there'* a whole lot of wierd 'brainbox' stuff crammed in there all over the place. Problem is knowing which one is the right one. I don't have any issues pulling the dash apart, I've done it before.

When you say the ECM can go bad, do you know whether the symptoms I've described would be consistent with the 'failure' or 'degrading' of the unit?

Do you have the service manual for Bonne, Park Ave and Ninety Eight? The only one I've seen on the web is yikes expensive and comes in 3 big volumes.
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Old 11-27-2010, 12:58 PM   #4
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I have a 95 Old cutlass, it has 2 computers! The one for the eng controls has 3 plugs the other is anti-lock brakes. I had to remove the anti-lock puter first. They just snap into place (no screws)

I went to libary and got alldata info and printed it out!
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Old 11-27-2010, 01:07 PM   #5
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I know the 94-95 computers can be flaky and do strange things. That'* about the best way I can describe it.
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Old 11-27-2010, 03:39 PM   #6
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Originally Posted by D Ryan View Post
I have a 95 Old cutlass, it has 2 computers! The one for the eng controls has 3 plugs the other is anti-lock brakes. I had to remove the anti-lock puter first. They just snap into place (no screws)

I went to libary and got alldata info and printed it out!
So this is the anti-lock Mr. Puter? The ones I've seen for ECM on the web have the 3 plugs you describe (with a bizillion wires) but I still don't know where it is. Where was it on your 95 Cutlass? What kind of problems did your ECM cause that you had to replace it? The 95 Cutlass has a 3.1 right?
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Old 11-27-2010, 04:36 PM   #7
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The computers are stacked, my anti-lock has 2 plugs and alot of heavy guage wires, the ECM is directly behind (glove box) it and has 3 plugs and a gillzilion smaller wires. I had the computers out to do some measuring. Car not running right!

I havent heard about the 94-95 being a problem child. Could use more info about that. Is there a work around?
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Old 11-27-2010, 04:56 PM   #8
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.... Car not running right!
What symptoms do you mean by 'non running right? I'm curious to know if you've got the same problem I do.

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I havent heard about the 94-95 being a problem child. Could use more info about that. Is there a work around?
Generally speaking you are right. The 94/95 aren't really problem cars. Mine has a 3800 Series II which IMO (and arguable to some) is one of the best engines GM has built in a long while. I'm not seeing the engine itself as the problem. It'* more the management of the way the engine is programmed to run. According the GM, there is no way to adjust the idle speed; it'* controlled through the ECM. Drilling out the TB to get to the idle speed screw would likely cause more problems than it solves.

The problem I'm experiencing has been a gradual degrade on the engine idle. It started about 2 years ago and has been ongoing. I don't know that there'* a 'work around' way to deal with this. I can't put a finger on why, but I'm really thinking that the ECM programming circuits are the problem. I really need some sound advice on whether the ECM is the cause.

Also, I don't know whether the ECM is plug and play for my car. I have a lot of options including digital cluster and monitoring systems on this car. Does the ECM have to be programmed to the VIN (I've heard of this) or are the ECM'* generic so that the connections on the connectors create the monitored pathways?
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Old 11-27-2010, 05:33 PM   #9
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My 95 has a idel air control when I cleaned it, and the throttle body the RPMS came up! You should start a new thred about this problem.

I havent started a thred about my problem but will some. I'm new here!
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Old 11-27-2010, 05:43 PM   #10
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My 95 has a idel air control when I cleaned it, and the throttle body the RPMS came up! You should start a new thred about this problem.

I havent started a thred about my problem but will some. I'm new here!
Glad to hear your problem was IAC. It'* actually a cheap replacement part too. It should have thrown a code on the dash.

If you cleaned the IAC and reinstalled it you might want to reset it. The GM procedure to reestablish IAC parameters is:
1. turn the key to full on without starting the car for 20 seconds.
2. turn the key to full off for 10 seconds.
3. Start the car. Your idle should be back to normal.

I've cleaned mine, tested resistance (turned out perfect), r&r the TB and TB Plate, cleaned the IAC pintle cavity till it gleamed, cleaned the MAF, replaced the coolant sensor, replaced vacuum lines and boots, new alt, new battery, new plugs & wires to name a few things. You're right though, it could be worth starting a new thread to get some of the new age techno gearheads involved.
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