Mechanics

MITSUBISHI ECLIPSE ENGINE PROBLEM

2001 Mitsubishi Eclipse • 70,000 miles

Blue /black wire from PCM not suppling ground. For some thirty start /runs, 600miles, start up was rough, on warm up only, O2 rear sensor engine light code. Then rough even when start up warm, for five miles. Then made appointment with shop, ran perfect to shop, no roughness, 76°f. They replaced rear spark plugs, retorqued head, outter bolts loose, as always with aluminum engines, expansion co effient of aluminum verses steel head blots. Gaskets, reassembled, ran five minutes, then died fast. Everything works ok except ground return blue/black, between distributor and PCM. Had solenoid failure, poor connection inside relay box, so pushed resistor down metal slots, it works fine. Saw mechanic leave ignition on long time?Burned out 10 amp fuse on driver's dash. Box, ignition?He also connected the battery cables, after being disconnected from batery say twenty minutes prior. Removed and replaced white, long box, engine compartment driver's side? Note diagnostic computer would not connect while I stood by with my IPOD 4G phone ! So with that said I hope to give help to others and perhaps some help for this problem. Took car back from shop, paid for spark plug change, I am capable, built 2 cycle race engines as #1guy in LA mid 60s, 3horse per cubic inch, back then District 37 AMA!Humbled by oddities, Jeff
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Jeff A.
October 30, 2012.




Just found out signal wire is shorted to ground, the transistor in pcm is, I believe is a PNP type, right? Jeff

Tiny
Jeff A.
Oct 30, 2012.
Just found out wire is shorted to ground, in between PCM and engine, jeff

Tiny
Jeff A.
Oct 30, 2012.
The immobilizer has to be programmed if the PCM is replaced. So you have found the cause of the problem? Did resolving the short clear the problem? Sometimes intermittent shorting do not cause any damages, depending on the wire that is shorting.

I did not check the wire you are refering to as I gather you ahd resolved the problem.

KHLow2008
Oct 31, 2012.
Dealt with other issues. To test function of transistor, blu/blk wire goes to Base cotrol of transistor, so it is an NPN transistor, N is circuit ground, P is plus voltage @4-5v dc, N is other half of ground circuit, so it is positive low amp.005amp or so. Point is to test Base control signal from pcm, techs say use smallet amp low voltage to trigger the trans to connect N& N to make ground work, so I bought a multimeter that has holes for the two different transistors to test. Gain. NPN and the other that connect a positive circuit PNP.I will use this as it is available and better than causing burn out with analoge multimeter. The solid thin wires from a tv set is the right size to use in this sitation, will keep you updated as I get to it. Engine performance schematics tell which transistor type, if Base wire goes, comes from positive, then it is an Negitve collector positive BASE signal, Negitive Emmiter destination, find this online for more.I can replace a bad transistor for about thirty cents, then check trans driver control with transistor out, change it for a buck, I keep you posted as lives sometimes hang on a bit of correct knowledge. In a pinch, I gut a suitable computer board, check the specs of the part online, find replacement equals, remove from computer board, install in PCM, after foolowing online testing of "new" replacement part. So hang on to some pc boards, they may save ones as in a pinch. Lets have fun overcoming stuff as a community, humbly Jeff

Tiny
Jeff A.
Oct 31, 2012.
Thanks for the update. Most people would stop when the PCM has a fault and you are more advanced into that. Personally I don't do repairs, just some soldering or capacitors changes are all I am capable of.

KHLow2008
Oct 31, 2012.
Well I learned the hard way, no money, no new parts, that is the reality. So instead off being entertained all the time, I learn to handle some tough situations and survive without depending on the conviences we take for granted, I am a desert bike racer, getting stuck is not an option If you know about capcitors and resistors and fuses, you will be ok, plenty of good spares around. Really easy, just read.I am the kinda guy that comes through when the experts get stuck, I keep it simple. The wire ends will be soldered to make plugs to circut and meter from under dash to distributor. Looking for continuity, then to test gain of transistor. Good carma to help each other.J

Tiny
Jeff A.
Nov 1, 2012.
So I finally got into it, surprises, keep it simple, again. Following the shop, them following a big parts shop advisor, step by step ended with short to ground in distributor blk/blu power transistor drive signal failure.I saw him testing the crank position sensor as the engine was cranked, looked good. Then computers. And other stuff. Watch out for nearby cell phones as testing is done, ok. The schematics for the blu/blk wire fronm distributor was tested, the Base, signal destination, transistor, as a diode. Shared ground, in, diagram, and positive lead to Base gave a.769, so it is ok, no need to go in cab, just disconnect distributor plug, blu/blk, positive, ground to ground, real quick. Then the crank sensor, now it reads 14megs, thats the trouble after all that testing in the shop. There is voltage going to the senor coil when key is on for testing.I did not want to risk testing for amps, it is enough to cause failure, remember this. Turn key on for as short (pun) a time as possible, I dont care what anybody has to say to the contrary, I dont need to support a parts motive if you get my drift(PUNishing arent I. Stay simple minded around computerised methodology buddy, Signed stayin sane inspite of it all, LOL, have a cold one for me, Jeff Andrews, kona, hawaii

Tiny
Jeff A.
Nov 1, 2012.
Also, had the mechanic re torque the rear bank head bolts to + 5lbs from standard, as thermal expansion of aluminum verses steel causes loosening, he rapped each bolt with a small hammer before tightening. This will be followed by me doing the front head. Not much, the+5lbs, but the outter four were loose!So I saved the hassle of a rebuild, probably another 10 thousand mies from now. Another tip. Of concern is over tightening, but depending on the blocks allo, no problem doing this. See the aluminum expands much more than the head bolts do, and it is a slow motion hammering of the bolt, heating and cooling. If the bolts were aluminum, then no problem, car is now stable for many more miles of dependable service.A few tricks that earned me a good reputation in the racing circuit. And a good nite to you America!J.
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Tiny
Jeff A.
Nov 2, 2012.
Actually Mitsubishi engines are recommended to be retorqued after initial driving but seems this is not sufficient to prevent the head bolts from getting loose. I have ancountered numerous cases of oil leaks from the head gasket and this is the only manufacturer I know of that has this problem.

KHLow2008
Nov 2, 2012.
Hi, how do gaskets compare, and what does the tightening, man or machine. With high expansion aloys the bolt thread pitch angle is important. Maybe the bolt maker designer is lock in on iron blocks. Or some compound is used on the bolts to get an accurate ft lbs. Nothing wrong, that I am aware of, with useing aircraft locking washers, real thin ones, also check actual thread involvement, contacts, may be also two slightly different pitch angles. Quality control has dropped the ball big time. Is there any commonality, serial numbers, plant assembly, shift of men, , years of trouble, all these will help narrow down the source, and maybe some support, if approached like Teddy Rosevelt showed, real persuasive patriot. What I like is the mental training that comes from this honest thoughtful occupation. This is what it takes to make it, then apply the approach to ever more important tasks, before you know it, education brings the confidence for dreams to come true. It has been an honor to participate, humbly Jeff

Tiny
Jeff A.
Nov 3, 2012.

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