Bad spark control module


#1

Ive got a '90 gmc 1500 z-71 with a 5.7 liter and its running rich. When i get on the throttle the check engine light comes on and will sometimes go off on its own. I’ve hookes it up to the computer and it says electronic spark control module (the module under the rotor in the distrubiter) is bad. I have replaced it and it runs good, dosent run rich, had more power for a couple hours, then goes back out again, ive put a few in, all brand new, and nobody can figure out whats causing it to keep going out. Any help i can get from yall would be greatly appreciated


#2

What that module does I think is turn on the current for the appropriate amount of time and at the right time in the crank rotation to the primary of the coil. If the coil were bad, partly shorted out, it could put a load on the transistor that does this job and overheat and quickly burn it out. If there’s a shop manual procedure for measuring the resistance of the coil(s), both primary and secondary side, that’s what I do. If any of the spark plugs or HV wires were shorted out, same thing. But if that were the case, you’d notice it I expect. If your car uses a separate condenser from the module, so when you replaced the module, you didn’t replace the condenser, you might try replacing that too. A bad condenser could cause an electrical glitch that could burn out the same transistor. Does your car have a replaceable distributor cap and rotor? Good idea to replace those two parts too. I always replace both whenever I do a general tune up of my Corolla. Worth a shot. Best of luck.


#3

I’d also consider getting an OEM part and not a cheap aftermarket. The quality really can be different. And make sure that all the connections are tight and in good condition. Some electrical components require a thermally conductive compound to conduct heat from the body of the device away to the mounting–not sure if your module does or not, but it may be worth checking.

It’s possible that whatever electrical connector goes to the module has an intermittent problem either in the connector or wiring nearby, and that when you’re replacing the module, you’re moving the wires around just enough to make it temporarily work–the modules themselves may not really be bad. (I’m not familiar with this module, but have seen this phenomenon with many electrical devices)


#4

The part inside the distributor is the ignition module. You say you have a fault code indicating trouble with electronic spark control module. You’ve been replacing the wrong part. The ESC module is on a bracket on the right side of the engine along with the egr solenoid.

The car will set a code for ESC every time you check or adjust the timing. Are you clearing codes? The code can be caused by checking timing, bad ESC module, bad ECM, wiring problems, etc. This shouldn’t cause the symptoms you describe. I think your problem lies elsewhere.


#5

When i replace that module the truck runs perfect, i put the gel under it when i put the new one on. I’ve been contemplating putting a new distributor in to see if that will help, when i went to the chevy dealer, that’s the part they had listed for the spark control module


#6

There are 2 ignition modules on that engine. The Electronic Spark Timing module

is mounted on the firewall or intake manifold and if you get a code scan and call a dealership they will likely make no effort to confirm what is needed. They will usually just throw the most commonly sold part on the counter. The sale will be non refundable. The module in the distributor is usually referred to as the IGNITION CONTROL MODULE. The one outside the distributor is referred to as the ELECTRONIC SPARK CONTROL MODULE, the there is the computer, the ENGINE CONTROL MODULE… Like @asemaster said, confirm the module

I seem to recall a brown wire with a black stripe connecting the distributor module to the ESC module on early OBD I systems and a code 43 indicating that a problem existed in the timing control. Maybe asemaster has more experience than me on that problem but I have never replaced the timing controller. A bod ground wire from the ignition module to the floor behind the dash or a bad computer have turned out to be the cause for me. A current or previous problem with a leak at the bottom of the windshield would make a failing ground very likely being the cause… And a poor ground can trash the computer and the distributor module.


#7

I just glanced over the OBD I codes and none specify a failed ignition module. Codes 42 and 43 deal with electronic spark timing and could be set by any of the 3 modules or the wiring.


#8

Unplugging the tan/black wire, which is what you do to check or adjust ignition timing, will store a fault code for ESC. I think the esc code may or may not be related to the poor running. Need more information.


#9

Will give you all the info you need, i dunno if it matters or not, but the smog pump has been taken off and dual exhaust has been put on


#10

I need info as to what is happening at the time the trucks runs poorly and dies. I think your ESC code may be a wild goose chase, you say the truck runs better with a new ignition module in the distributor, but the system on your truck has no way of detecting or setting a fault code for an ignition module. The code for the electronic spark control module will be set when you check and
adjust the timing.

Are you able to get any scan data that shows what’s happening when it runs poorly?