4g61t.org

1991 Plymouth Colt 200GT
4g15 w/ 3sp Auto

Initial problem: car sat for almost a year, fuel went bad. PO had parked it due to an oil leak.

Symptoms: Engine dies frequently, will not start again for anywhere from 10 mins to 2 days with no spark, Coil ohms within serviceable range (barely).

Testing done: MFI relay tested good, ECU tested good for injectors and coil, ECU visually examined with no corrosion or damage, extensive grounding tests all good, plug wire resistance great.

Work done: new plugs, new cap & rotor, new fuel filter, new extra ground to L side head (at the dipstick retainer), new rear main oil seal (unrelated), all new fuses (OCD related).

The Quirks:
1) every time the engine dies, the ISC unit continuously clicks back and forth until the key is turned off. I am unfirmiliar with the ISC circuitry and unsure if this is normal.

2) the throttle drop delay is almost 2 seconds long after the butterfly closes, idle speed will drop to ~400rpm before rising back up to ~900rpm where I have the hard idle set to at the moment. I'm assuming a dirty or faulty TPS.

3) sporadically, the CEL will flicker while cranking the engine, but will not throw a code. I'm still searching for a ECU circuit systems list but with the lack of fail safe functions in the ECU this boggles me.

4) while cranking, voltage at the MFI relay will drop to ~11v with a fully charged battery, but jumping the key+ directly to the battery appears to make no difference at all.

im not familiar with the 1.5's but it sounds like the ecu is bad.. I know you tested it but best way is to find a known good one and swap it out to see if that cures the problem.



Steve

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Steve 89 colt 2.3 stroker stock top end. evo3@20 psi 13.489@99.30mph 3/10 2012
On drag radials.auto trans.launching @ 5 psi and no traction thru 2nd.

Anyone got a spare to sell? Or a 4g37 parts kit? Severe problem with parts availability here.

Personally I'm leaning towards distributor, either coil or pickup or both, but my wallet is too thin to just throw parts at it, even though it could use it.

Update. Fuel pump works fine, thanks to lilevo.com and a piece of wire I just cleared out as much brown coloured gas as the pump could reach. Tried to drop my tank but the bolts are 22 years old and won't budge. Being 1000 miles away from my shop, this is nowhere close to being a good time for this crap.

ISC clicked the entire time the FP test wire was hooked up, I'm really starting to hate that thing.

I would agree on the ECU, I had one that would run the car but it had a bad miss. New ecu and now its running great.

Update. More testing done.

TPS is giving a read 1.5k ohms low of what the book says it should be, and that's cranked all the way. The way it was set, it wasn't even registering at closed throttle. Added to the list of things I need to replace.

Coolant temp sensor tested as working good.

ISC Position Sensor failed. No continuity (checked while the ISC clicked back and forth). Unplugged for the time being.

Still hoping I can get home in 3 weeks... Can't get an ECU locally at all.

Update. Car seems to die a few seconds after ECU pin 103 (wht/grn) loses power, and will not start again until power comes back.

I managed to restore power once by wiggling the key, again by slamming my knee to the column, but nothing after that.

Does this fit as a major cause?

Can anyone tell me where the wire leads to from the clear connector beside the fuse block so I can avoid ripping my whole dash apart?

103 ECM Supply Volts Permanent RAM Supply
Ignition ON / OFF.


not sure why it would lose power with they key in ON position.. it should have same volts as the battery on or off.. which leads me again to a bad ecu.



here is the link if u need any more ecu pinout info..

http://www.4g61t.org/forum/viewtopic.php?f=27&t=15426


Steve

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Steve 89 colt 2.3 stroker stock top end. evo3@20 psi 13.489@99.30mph 3/10 2012
On drag radials.auto trans.launching @ 5 psi and no traction thru 2nd.

Can't tell how good the ECM is if there's no power to it tho... Haven't tested 102/107 (Red) but having no power to the ECM strikes me as a bad thing. I will test the red ones in the morning but that draws power from the MPI relay (working) so there's not a lot of room for that one to go bad.

I traced the wire back to the fuse panel, continuity is ok there and intermittent voltage. Any chance there's another connection between the f/p and the ignition? Probably going to have to pull the column apart anyways.

Apparently pin 103 is fed from the "Room" fuse. Replaced. Gibsmacked myself. Start over tomorrow and see which, if any, of those symptoms are actually caused by something other than my hatred for door buzzers.

Stupid coincidence.

I need an ECM. Anyone got a spare E2T36672M kicking around? Pm me w/ shipping to Canada v0g1l1 please.

When in doubt, it's always the ecu

Anybody that owns an older Mitsu should have at least 2 extra known good ecu's for their car. I'm sure I could grab the 1.8 dsm stuff at one of the local yards for you but I have no way to test them either other than opening the case up and checking over it.

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93 Mitsubishi Expo LRV 1.8/manual
95 Eagle Summit DL Coupe 1.5/manual
01 Mitsubishi Mirage ES Sedan 1.8/manual

I suggest the 4g15 12V ECU, for starters, as upgrading should only happen when you know the rest of the car is up to snuff. Food for thought.

Sending my ECM out to ECMTuning in the morning, still asking about any extras someone might have though for spare or in case mine is unrepairable.