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Bad ECM?


mra32

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1991 Lumina with the 3.1

 

So my car started acting ridiculously. It will take forever to start and i really have to get on the throttle to get it to start when it normaly takes 2 or 3 cranks (I dont think its ever taken more than that).

 

Once it starts, its a wild ride, sometimes the rpms drop so low that the engine is shaking back and forth violently and at other times the idle is pretty high. Sometimes it will stall and other times the high idle will allow you to cruise at 40 mph without any assistance from the throttle or cruise control.

 

On accelleration, the bucking rivals a carnival ride.

 

The weird thing is that it occasionally acts normal. But then will go back into the fits.

 

I checked the codes and it flashed 53 (i'm fairly certain. the car flashes 12 three times then all the codes three times then 12 again, right?)

53 is supposed to be the ECM reads a voltage of 17.1 or higher for 2 seconds. This makes no sense in this situation and may point to a bad ECM. Any other ideas?

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Get your car scanned at autozone or something and see more detail on what sets code 53... Since its getting more voltage than its supposed to, then there is a sensor gone bad most likely...

 

Also, its getting 17 some volts... Nothing should ever be getting more than 14 or so volts... Sounds to me like your alternator is the problem... There is a resistor that controls how much voltage your alternator gets and that seems to not be working, making it so you are overcharging your battery and sending to much voltage to all the components.

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Get your car scanned at autozone or something and see more detail on what sets code 53... Since its getting more voltage than its supposed to, then there is a sensor gone bad most likely...

 

Also, its getting 17 some volts... Nothing should ever be getting more than 14 or so volts... Sounds to me like your alternator is the problem... There is a resistor that controls how much voltage your alternator gets and that seems to not be working, making it so you are overcharging your battery and sending to much voltage to all the components.

 

I don't think AZ can help with the scan tools they have.

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Where are you located? Autozone scanned my 93 when it had a high idle (around 2200)...

 

Come to think of it, my car acted the same way when I had a vacuum leak... It caused the car to go up to around 40 without even touching the gas pedal... Follow all of your vacuum lines and make sure thats not the problem

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Check your IAC as well - mine completely shit itself one day and would spin all the way in and out whenever it wanted to. I had to do a neutral drop into gear twice from 2500rpm...then after awhile it spun all the way back in and barely idled (missed like crazy)..

 

If the ECM is getting too much voltage something is probably pissed off and causing the wierd driving issues. I'd say you may want to keep an extra ECM on hand in case this one shits itself after getting high voltage through it.

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Where are you located? Autozone scanned my 93 when it had a high idle (around 2200)...

 

Come to think of it, my car acted the same way when I had a vacuum leak... It caused the car to go up to around 40 without even touching the gas pedal... Follow all of your vacuum lines and make sure thats not the problem

 

I would think that the intermittent issues rule out a vacuum leak.

 

The check engine light is also on the whole time its acting weird and goes away when it is fine.

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It was intermittent with my car also... but mine was the 3.4... It wouldnt hurt to check all of the lines... The one coming from the intake was loose on mine... When I plugged it back it it never happened again.

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I checked the codes and it flashed 53 (i'm fairly certain. the car flashes 12 three times then all the codes three times then 12 again, right?)

53 is supposed to be the ECM reads a voltage of 17.1 or higher for 2 seconds. This makes no sense in this situation and may point to a bad ECM. Any other ideas?

 

Yes, you are right on how you checked the codes. With code 53, I'd be looking at either the alternator or the ECM. Either the ECM is getting an overvoltage, or it thinks it is. Whichever is the case, that would wreak havoc on the system. In any system that references certain voltages (like these cars do), a voltage outside the needed range could effectivly cause the ECM to get bad info, and make bad adjustments, causing the car to act really strange.

 

I'd check the voltage on the system with an analog volt meter when the car is acting up. I suggest analog since it usually responds faster to voltage spikes than digital meters do. If it shows a problem, then the regulator in the alterator is probably shot, and the alt needs replacement. If the ECM is screaming about high voltage when there isn't any, then it has lost its mind and needs to be replaced.

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OK thanks for the replies, I'm gonna check the IAC and the vacuum lines and if that doesnt lead to the solution, I'll check the voltage. I only have a digital multimeter (i've never seen an analog one in person, but that would be a cool tool to have). What two points should I check the voltage?

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If the voltage is over 17 volts for more than 2 seconds, a digital meter should see that, so it might be OK. Id either check the voltage at the 12V terminal on the alt, or on the pin that feeds the ECM, that way you'd know for sure exactly what voltage it was getting.

 

An analog voltmeter is just the older style that uses a needle rather than a digital display.

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OK. New code: 23

 

23: Manifold air temperature sensor signal showed an air temperature of -31� F for 10 seconds after engine had been running for 4 minutes.

 

 

Well it is pretty cold out, might point to vacuum leak?

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cleaned the IAC and took it out for a spin. When it was running like it should, it ran better, but my car also only had one little spat where it threw a fit.

 

The issue is the worst when it stalls at stop signs and when I get it started again, it bucks its way across the intersection.

 

On another note, should the plunger dealie on the IAC be able to be depressed by hand? Mine couldnt do that, but I figure its normal since its hooked up to a motor.

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OK it just doesn't start at all anymore. It just rained, so possibly faulty coils? I'm definitely getting fuel. I dont have a gauge for fuel pressure but its certainly enough, but i dunno if its too much?

 

There would have to be a massive vacuum leak for it not to start, right? And it wouldn't make sense anyway since I have to mash the throttle to get it started when its acting up.

 

What are the symptoms of bad coils?

 

And since i'm immobilized, who wants to sell me a known good computer?

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I'm guessing my alternator shouldnt be buzzing when the key is in the on position?

 

So i guess the alternator went and took the computer with it. Fabulous.

 

My alt has always buzzed with the key on, when it was original, and after it was Remanned.

 

I'm thinkin your ECM died. Do you get code 12 when you jump the terminals?

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yeah, i got code 12 (3x) then code 23 & 53 (both 3x) and then code 12 again.

 

Would code 12 mean anything? Cos I'm pretty sure thats just the default diagnostic mode code, right?

 

Correct!

 

If you need an Alt. cheap, I have one off my TGP still. It was a reman withi prolly less than a year on it.

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yeah, i got code 12 (3x) then code 23 & 53 (both 3x) and then code 12 again.

 

Would code 12 mean anything? Cos I'm pretty sure thats just the default diagnostic mode code, right?

 

Correct!

 

If you need an Alt. cheap, I have one off my TGP still. It was a reman withi prolly less than a year on it.

 

PM a shipped price to me, but I need this out quick.

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yeah, i got code 12 (3x) then code 23 & 53 (both 3x) and then code 12 again.

 

Would code 12 mean anything? Cos I'm pretty sure thats just the default diagnostic mode code, right?

 

Correct!

 

If you need an Alt. cheap, I have one off my TGP still. It was a reman withi prolly less than a year on it.

 

PM a shipped price to me, but I need this out quick.

 

PM sent. Im avaiable to ship tomorrow afternoon and Saturday afternoon

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Here's the interchange on the ECM.

 

CORVETTE 90-91 Elec Cont Module (ECM); base

 

CUTLASS 88-89 Elec Cont Module (ECM); 6-173 (2.8L)

 

CUTLASS 89-92 Elec Cont Module (ECM); 6-191 (3.1L)

 

CUTLASS 93 Elec Cont Module (ECM); 6-191 (3.1L), VIN (8th digit) "T", TH125

 

GRAND PRIX 88-89 Elec Cont Module (ECM)

 

GRAND PRIX 90-92 Elec Cont Module (ECM); 6-191 (3.1L)

 

GRAND PRIX 93 Elec Cont Module (ECM); 6-191 (3.1L), TH125

 

LUMINA CAR 90 Elec Cont Module (ECM)

 

LUMINA CAR 91-92 Elec Cont Module (ECM); 4-151 (2.5L)

 

LUMINA CAR 91-92 Elec Cont Module (ECM); 6-191 (3.1L), gasoline

 

LUMINA CAR 93 Elec Cont Module (ECM); 6-191 (3.1L), gasoline, TH125

 

REGAL 88-89 Elec Cont Module (ECM)

 

REGAL 90-92 Elec Cont Module (ECM); 6-191 (3.1L)

 

 

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Nice job Jay, something tells me I will need that list, as he may have me grab a JY ecm for him.. I duuno yet

 

Where do you get your interchange info from?? You have a Hollander Interchange program of some sorts??

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