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Discussion Starter #1
Okay here is what I have done. New all AC Delco parts, wires, plugs, rotor, distributor cap, egr, cleaned EGR tubes. Still getting the stumbling, hesitation on the highway. Cat okay. I have only 3 things left to replace, ECM (AC Delco for $75.00) TPS (AC Delco for $83.00) and MAP (AC Delco for $41.00). Anyone taken their 89 Cadillac 4.5 litre into the dealership to see what they had to say about this problem so I can select the ECM, TPS or MAP to replace next? The AC Delco distributor guy says GM was famous for bad ECM's in the 80's and 90's! Anyone else want to take a guess at what should come next? My hands are raw from changing those plugs at the back of the engine. What a job!!!!! HELPPPPP!!
 

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I cured my hesitating on my 86 4.1 deville by advancing the timing slighty, had a terrible flat spot before. sometimes nearly stalling.
 

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on acceleration , on initial take off it would hesitate and then leap forward, but since the timing has been advanced it seems ok.
Also i owned a 69 camaro SS which hasitated and backfired, i replaced the worn camshaft and it cured it.I know they are two different cars , but the mechanics are the same :) These are the problems and cures i have had anyway, goodluck with yours.
 

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Several years ago JD Power did a survey about what was the most reliable 10 year old used car. It turned out to be an 88 4.5 Deville. Somehow "most reliable car" and "famous for ECM failures" does not seen to jive. I recall those PCM's being very reliable despite what the ACDelco rep says. Keep in mind he is trying to sell PCM's.....

You might want to start some diagnosis before replacing any more parts.

How about a compression check to see if all cylinders are hitting the same compression. Do the test with the throttle wide open. A worn camshaft could cause the problem and changing all the ancilliary parts in the world will not correct that.

Find a shop with a multi-cylinder scope to look at the ignition wave forms to see which cylinders are acting up. A cylinder balance test will also do this.

If it only misses under load just load the engine gently against the torque converter (power brake it in gear against the brakes) to load it and cause the miss for diagnosis.
 

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Discussion Starter #6
Took car into Auto Lab today and they pulled the following codes 19, 16,18,15,12,24,27,26,21,23,20,48,77. I am assuming all "E" or 'P'. Also stated "2 hours of further diagnostics required, may be faulty ECM or bad harness" . Should I get a new ECM?
 

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kneesrbad2 said:
Took car into Auto Lab today and they pulled the following codes 19, 16,18,15,12,24,27,26,21,23,20,48,77. I am assuming all "E" or 'P'. Also stated "2 hours of further diagnostics required, may be faulty ECM or bad harness" . Should I get a new ECM?
A lot of codes usually indicates an electrical problem. Try to play with ECM harness. Replacing ECM is not expensive try.
 

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I guess I'd do the simplest things first: check for good connections at all the connectors and clean, tight grounds.
 

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My experiencve with an ECM that throws that many codes is a defective ECM. Put in a known good ECM and see what happens.

Mike
 
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