'749 dim check engine light

[4153dodges]

My ecm is intermittent, it will run perfectly fine for a few minutes, then suddenly go bonkers, dumping a ton of fuel in missing alot, the check engine light starts flashing on randomly and once the engine finally dies it goes dim. Sometimes it comes back on its own, sometimes shaking the ecm gets it going again, probably coincidence. Anybody have any ideas? I have been tearing my hair out trying to trace any fatigued wires with no results.
Thanks,
Josh

[buddrow]

Sounds like the prom may be making contact intermittently. What ecm are you running? Have you made the swap to the 27sf512 chip and socket?


Buddrow

[RobertISaar]

PROM/MEMCAL/ECM or if you're really lucky, an intermittent connection near the ECM's harness connectors.

[4153dodges]

Its a 1227749 ecm out of a 90' sunbird turbo, using 27sf512 chips. It seems to start working if I push on the whole carrier, not sure what the heck could be the problem after thourily cleaning it multiple times and checking for cracked joints under a microscope

[joegreen]

Sometimes solder just needs to be reflowed.

[Six_Shooter]

Have you tried another ECM? Sometimes the best troubleshooting method is substitution.

[4153dodges]

I would, but I don't have another laying around

[Scrufdog]

I would say bad ecm. Around those years gm used a cheap clear coat on the circuit boards that would get micro cracks in it and separate traces and solder joints.

[4153dodges]

That would make sense, the clear coat is flaking apart, plus I can sometimes get It to work by pushing on the chip carrier. Can it be cleaned and reflowed? I dont have a good source for amother ecm right this moment...

[EagleMark]

Didn't look to hard in Buy and Sell section?

[4153dodges]

Honestly I didn't even realize we had one! Lets see if I can afford an ecm then!

[billygraves]

I have a GM Reman ECM for the 2.0L Turbo Sunbird if you are interested. It has the updated part number to fix problems they had. I bought this ECM for a project car I had and ended up selling it. I have the ECM with a MEM-CAL if you are interested. Make me an offer. It's in the buy and sell. I never even used it. Cheaper with shipping than gmpartsdirect.com where I bought it. Aftermarket ECM's I've seen have a host of problems after a short period.

[4153dodges]

Thanks for the offer billy, but we found the problem. After soaking the whole board in a solution to take off the conformal coating, we found about 6 broken solder joints on one chip! A little re-soldering had it back up and running great, even talks to the ALDL cable now! Thanks for all the help guys,
Josh

[Scrufdog]

what did you use to remove the coating? Sounds like something I could use for automotive work and modding xboxes.

Glad you fixed it up

[RobertISaar]

i'm also curious..... removing that stuff manually takes a lot of time.

[4153dodges]

I have no idea what it is called, my uses the stuff at work to dissolve potting material. He just calls it solvent, the can didn't even say the name!

[billygraves]

I have no idea what it is called, my uses the stuff at work to dissolve potting material. He just calls it solvent, the can didn't even say the name!

I understand why you clean off the clear jell coating over the ECM Board and over the top of Ignition modules under a cover. Robert Saar and all - The Lab technicians told me the clear coating leads to cancer and is absorbed into your bloodstream. No joke.

[RobertISaar]

ugh.... is that while coming into contact with it while it is already cured or if it has been mixed with solvent to apply/remove it?

it doesn't sound too good either way.

[billygraves]

ugh.... is that while coming into contact with it while it is already cured or if it has been mixed with solvent to apply/remove it?

it doesn't sound too good either way.
It is when it's on the board. I would think it would be worse when a solvent is active. I believe the molecules would be able to transfer into your skin faster and a larger number, as the solvent opens your pores providing a transfer. As the solevent evaporates, it could carry it? After I learned this I don't disturb it. Another very nice and very smart person contracted some bad cancer and all of the lab techs blamed the smoke off the soldering gun. Soon after a large vent system was installed to draw out ALL the solder smoke. I would have never thought of pine tar smoke like this. Never questioned if the smoke had lead in it.
I don't mean to bring bad news but a small precaution could really help someone. The nice person really suffered and still came to work for a while.