Resolved 1G MPI relay clicking, car bogs, check engine lights briefly

[trevor425]

Right as my car gets into boost (4psi or more), the MPI relay starts going crazy (clicking), the car falls on its face like fuel cut, and the check engine light illuminates only while the relay clicks. Once i let out of the throttle the light goes out. Sometimes it keeps clicking for a few moments before returning to normal.

I cannot read the codes with TMO logger!

The car drives fine while cruising, any more the 50% throttle and it happens again.

If anyone has had these symptoms please help me out, I've searched and searched and it all points to the ECU.

There are no boost leaks BTW

 

[trevor425]

The caps were starting to seap, but wasn't the caps causing the issue, replaced them and the board looks fine.

Any idea's anybody? This has me stumped so far.

 

[1995gsx20g]

im leaning towards a short or a bad ground.

how are your motor mounts?
battery tied down?

is it only while in boost? if you are in gear low rpm and stomp on the gas so the car bucks does it happen?

 

[steve]

Check the voltage when the car is running.

 

[trevor425]

It happens as soon as the turbo spools/engine is under heavy load. I can drive the car like a granny and it runs perfectly fine as long as I stay out of boost. I'll check the grounds again.

Voltage is right around 14.5 volts at the battery, I haven't had time to check it at the MPI relay pins. I just installed a alternator from a Galant, and upgraded the fuel pump to a Walbro 255. I swapped the stock pump back in just to see if it was the cause, but the same symptoms arise.

When the car is completely cold, it will run normal, but within 5 mins of the electronics warming up it starts to happen. I've disconnected the SAFC, no dice. I'm starting to wonder if the MAFT crapped out on me, but at the same time thinking it has to be something with the recent mods.

Anyways thanks for the input so far guys, any is appreciated right now.

 

[steve]

If your voltage is good then I'd check the ECU again. See if somebody can run in in their car, don't put another ECU in yours until yours has been checked to make sure you don't have any issue that might blow a driver.

I see a lot of ECUs, and some of the damage cause by leakage can require measuring the traces or inspection under magnification to see.

 

[trevor425]

Well I pulled the ECU again, went and got a magnifing glass and can see nothing wrong, no trace of leakage. The caps were barely moist and the board was dry, still has all the cosmolene type coating intact around the caps.

I'm guessing a micro chip has failed perhaps? Or could i have corrupted my EPROM chip by pulling the maps off with my chip programmer? I haven't tried to burn a chip yet, so i don't think this is the cause.

Can I bypass the ECU's relay control function all together and run the MPI relay off of a switch to trouble shoot that it is in fact a faulty ECU, or can doing that have some catastrophic side effects?

 

[steve]

So you socketed your ECU yourself?

 

[trevor425]

Yes, I did that a month or so back and it works fine. I reused the stock EPROM, just installed a socket for future use once I'm confident with hex editing.

I have replaced IC chips in big screens and fixed quite a few amplifiers before, I'm pretty confident with desoldering and soldering. I went ahead and replaced the caps again with some from radio shack units just for shlts and giggles, but its still acting the same way.

I tested the voltage to the relay and its getting the 14volts to it while idleing. I cleaned the crap outta the positive side battery terminal and all the leads that feed the ignition, radiator fan and MPI circuits.

I cant find the MPI diagram, I just had it a few days ago.

Another question, if the car were loosing spark under load (have seen this many times at work) could it trigger the ECU to stop feeding the MPI circuit and cause the clicking and bog? I have seen many other mitsu cars were the igniter box fails. but it usually will just kill a couple of cylinders (one coil pack will not fire). I'm stumped as to how the car can run fine, but when the boost kicks in the relays start cycling.

I noticed two chips on the ECU board that have circles filled with a type of thermal goo, its clear not like heat sink paste, more like dielectric grease covering a smaller square chip, have these been know to fail? One of them kinda stunk like rotten eggs. I remember reading this is a sign that the ECU is about to fail, as with the MPI clicking and the car bogging. The only other dsmer I know has a blown engine and his ECU is a 90 non EPROM.

I'm guessing I have to bite the bullet and find a new ECU?

Also noticed the stock boost gauge spikes to 14+psi when the car throws its fits. I'm gonna throw another GM MAF I have laying around to see if it might be bad.

 

[steve]

i noticed two chips on the ecu board that have circles filled with a type of thermal goo, its clear not like heat sink paste, more like dielectric grease covering a smaller square chip, have these been know to fail? one of them kinda stunk like rotten eggs. i remember reading this is a sign that the ecu is about to fail, as with the mpi clicking and the car bogging.

The "goo" is potting to protect the IC under it.
It may have sucked up the smell from the caps leaking.

 

[trevor425]

The "goo" is potting to protect the IC under it.
It may have sucked up the smell from the caps leaking.

So do you think the ECU could be ok, and this is a harness or ground issue? I know its impossible to diagnose my turd via message forums. If this potting were contaminated from the leakage and contacted by accident from skin, would it cause an issue? You seam to be very knowledgeable on these particular units, and have been very helpful.

All the newer Mitsubishi's 2000 and up have excellent PCM's. I personally in my 5 years as a Mitsubishi tech have never replaced one (and have seen a few other techs mis-diagnose PCM's when its a just a wiring issue ). But these DSM's and older Montero are another story.

Our dealership rarely gets any 1g DSM's in for service (or 2g's either), so I can't try my ECU in another car, unless there is any one around the Kansas City area that's willing to lend a hand.

 

[steve]

so do you think the ecu could be ok, and this is a harness or ground issue. i know its impossible to diagnose my turd via message forums. if this potting were contaminated from the leakage and contacted by accident from skin, would it cause an issue? you seam to be very knowledgeable on these particular units, and have been very helpful.

Are you still unable to connect with your logger? How about with the MUT at work?

There aren't too many options for the symptoms you've described and most point at the ECU crashing.

Of the two potted ICs, IC111 is for various power regulation, watchdog, and reset and IC112 is the circuit for the knock sensor.

 

[trevor425]

I can run my TMO logger, and the MUT II but they both won't show any codes.

As I said the light only comes on while the car is bogging. TMO just kinda flat lines all the data I'm monitoring when it happens.

Pretty sure I'm going to have to fork out for a new ECU then, suxs cause I have zero funds for anything but bills.

Oh well, thanks for the input steve, don't happen to have any ECU's for sale do ya?

 

[steve]

I don't have any EPROM ECUs right this second.
Send me some clear pictures of yours and I can see if it's repairable. Click on my name to send me email.

 

[trevor425]

ill get some photos to you later tonight. not sure if my camera will be clear enough, but ill try none the less.

 

[steve]

The trick is to use plenty of light while not getting glare off the coating. The typical on camera flash is the worst for this.

 

[GooeyGus]

I would also triple check your socket soldering joints, and also make sure the chip is making good contact with the socket.

I have an ECU here that was socketed by a vendor that shall remain nameless, it ran perfect until I swapped the chip out, then it had some random issues with clicking and stalling. I re-did all the joints and made sure the pins of the EPROM had good contact and it was fine after that. I still use this as my back-up ECU.

I sent my main ECU to steve for repair about 6 months ago and it has been flawless ever since.

 

[redyute1]

Been battling similar symptoms with my ECU for quite a while now, sometimes it would work for weeks flawless and then the clicking starts then the car shuts down and won't start unless I take off the battery terminal for a few seconds. The socket was done by ECMTuning. I drove down there twice with it they tested it and said it was a good ECU.

Man I'll tell you it is just depressing, for some reason I feel like the problem is in the ECU but I will have to get me an other one.

 

[trevor425]

The trick is to use plenty of light while not getting glare off the coating. The typical on camera flash is the worst for this.

Yea, I'm trying my best, but limited to a 2.0meg phone cam.

I would also triple check your socket soldering joints, and also make sure the chip is making good contact with the socket.

I have an ECU here that was socketed by a vendor that shall remain nameless, it ran perfect until I swapped the chip out, then it had some random issues with clicking and stalling. I re-did all the joints and made sure the pins of the EPROM had good contact and it was fine after that. I still use this as my back-up ECU.

I sent my main ECU to steve for repair about 6 months ago and it has been flawless ever since.

See, this is what I'm thinking may be the problem. It acts like its heat related, a little expansion of a joint or pin and an intermittent loss or weak flow of current under extreme loads.

I can shut the car off for a few minutes and bam its wraping out like a raped ape again (minus the shlt tune) but within a few minutes its back to the stutter/clicking. I'm thinking from popping the chip in and out recently may have caused it.

I'll go through the joints again, and try and straighten up the pins on the chip. I ordered a ZIF socket and some of the SST 27SF512 chips last week so I can hopefully get a damn tune going, ditch the SAFC, and hopefully nip this crap in the butt! Thanks for all the input guys.

Oh and i got my Shark 7in touch screen in today (very nice for the price!) so I can start my carpc/ integrated logger and eventually an auto prom.

I'll load the best pics i can get for ya steve.

Well I resoldered all the joints. Cleaned and straighten all the pins, and checked every trace in the board. The car is still acting up. I'm stumped.

If it is the ECU, I'm thinking of just going with the EVO 8 instead of another EPROM.

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[steve]

I can't really see anything from those pictures. Please make sure the solder flows to the top side of the board when doing the caps so that both top and bottom are soldered.

 

[trevor425]

I can't really see anything from those pictures. Please make sure the solder flows to the top side of the board when doing the caps so that both top and bottom are soldered.

hhmm, now that i may have overlooked. ill check that and fix it if necessary at lunch. i leave my soldering equipment at home. thanks again steve, i shoulda just sent this thing to you to start with!

update.

yep, solder is fully penetrated to the top of the board. bummer was hoping i flubbed that up and found the fix. but sure enough no dice. this has got to be something stupid im missing. i cant seam to chaulk this to coincidently being an ecu failure after a fuel pump and alt swap. im going to rewire the pump tonight to get it done with, at least then i can try bypassing the ecu's relay control circuit, but im not in to rigging stuff so i really need to fix it right.

thanks for the insight guys, hope i can resolve this soon.

 

[trevor425]

oh forgot to confirm the fix, turned out the eprom chip was the problem. weather or not it was from being corrupted or just a contact issue, it was the cause.

 

[steve]

Good to know.