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I didn't swap the prom chip. From what I could tell the 87-88 should be plug and play.
I had to find an LX338, the ac Delco d1996 was the wrong one. Looks the same, but the ICM harness is different.
I can try prom and report back, may be a few days though.
The only thing I am confused about is whether this engine used the cam position sensor in the ignition circuit as well. I've read some posts on other sites that say yes and others no.
again, you completely glossed over prom I mentioned. You can swap ecm all day but if it doesn’t have any calibrations it won’t do much.
also, your ICM then was it converted to the 88 style or was it the early type. Early type is notorious for problems you could have sheared teeth.
your ecm needs to see it’* 3x and 18x signals and without both it won’t work, limp home can be caused by numerous issues. Does your engine have the right interuptor teeth as in balancer. Also is your 12 volt from the ecm present at your ICM
I don't know how to tell if the ICM has been converted.
Is there something to look for?
The interrupt ring has 3 teeth on it. 12 volts from ECM to ICM is good.
The only thing I am confused about is whether this engine used the cam position sensor in the ignition circuit as well. I've read some posts on other sites that say yes and others no.
a diagram for your year should indicate. I would assume a cam sensor is used to get an accurate position on the camshaft to make the everything more accurate but shouldn’t depend on it. I never owned an lg3.
but your ICM is likely the original which is older. You should consider upgrading it if they are in anyway retrofitting capable. Like even the early 90s magnavox is better than that. I could sell my ln3 harness and module amd coil. They work, aren’t old, but have been sitting open to the elements on my engine without a hood for a while so I’d only recommend it if you wanted the bracketed and harness to have some cores or something idk It may not be compatible
anyway, show me your pcm you can use a website link if you domt got pics. I’m reading that there are 3 different ecm between 87 and 91 and I have two computers both the same from 88 and 90 with their respective MEMCAL (prom). I don’t know about the other computers, but they should still have a prom. A new computer willl NOT come with a prom because it’* application specific. You transfer the chips from a cover on the ecm. I have an 88 lesabre prom and a 90 olds 88 prom which are vastly different from yours, andneven each other. Same engine. Ln3.
if yiu have the same computer I can sell you an 88 lesabre computer in working order just needs a chip, my 90 died and it barely ran. Gave codes left and right for sensors.
also, I do recall your engine coolant sensor was able to back feed water through the wire to the ecm under the insulation nverify the coolant sensor wire is good at the computer, the pin should be clean and not corroded. D
Swapped PROM and same result, no distributor and in limp home mode. I purchased an ECM from an 87-88 century 3.8 with part number 1227783. Similar to the one pictured.
I figured the ICM should have fixed it based on this pic. This is what the ICM pins looked like when I took out the old one. I never took the harness off before I received the new ICM.
Installed new ICM before trying a new ECM and still had same result.
I would think crank sensor plug is bad, but I get continuity through the wire from ICM harness to the crank sensor plug.
All connections at the old ECM look good, no corrosion.
That connector in your hand is bad. Did you fix it?
Car will not start without a cam signal. If the engine is running the cam signal can fail and the engine will continue to run.
Last edited by carfixer007; May 26, 2021 at 10:34 PM.
