1991 3000GT SL spits and sputters

buster1959
5

Asked by buster1959 Aug 09, 2013 at 09:10 PM about the 1991 Mitsubishi 3000GT 2 Dr SL Hatchback

Question type: Maintenance & Repair

I have a 1991 3000GT SL and just had a tune up (new plugs and wires), new engine computer and new transmission computer. new ignition coils.
car ran great for awhile, then it would spit and sputter and die... I let it sit for about 5 minutes and it would run good for a couple of miles and spit and sputter all over again. can you help me?

28 Answers

Daniel Foster
3,485

did you make sure to get the plugs back in the correct order also make sure you didn't unplug the maf, if there is a check engine light get it scanned

Daniel Foster
3,485

also wanted to say to make sure you got every single plug plugged back in

1 out of 1 people think this is helpful.
LAVO
25

If we assume that the PCM is correctly programed, I am concerned that it sounds like an issue with your timing. So I am tempted to point a finger to the Cam or Crank Position Sensor. Good luck.

1 out of 1 people think this is helpful.
buster1959
5

all these things were done by a Mitsubishi service garage. the car ran great at first, then started acting up. Mitsubishi said timing was nuts on.

dandyoun
58,695

Did you use quality platinum spark plugs? That is a must with these cars. Did you check the spark plug gap before installing them? This is a must. There is no such thing as gap already set on new plugs. What octane fuel are you running? Must use the highest octane possible 91+. Or it will not perform properly. 10:1 compression. You must use quality high octane fuel. When you put your upper intake back on did you torque it properly? Check all electrical connections to upper intake. Does it only die when slowing to a stop like at a stop light or does it do it at any speed? Hope this helps.

dandyoun
58,695

Oh ok. So it's a crap shoot as to what kind of parts they used or what they did to it. How many miles is on it?

Daniel Foster
3,485

well I would be returning the car for them to fix what they screwed up

dandyoun
58,695

Sorry if is sounded ugly about what a dealer might have done or done to your car. It just seems that now days all they know how to do is plug it into their computer and wait for it to give them the answer. And with your car that's not going to work. Again I apologize.

Daniel Foster
3,485

are you absolutely sure they used the correct ECU ? the numbers have to match, and can not be from a TT on a DOHC and vice versa, also what was wrong with your old ECU ? did it work and if so plug that one in and see how it runs

Daniel Foster
3,485

dandyoun I just wanted to rule out the octane, my stealth DOHC always ran fine on any gas I threw in it,, granted it would run best on 91 or better, but should not make it run this badly, most that ever happened to me is I lost a couple mpg and it didn't have quite the same pep but not all that bad either though

dandyoun
58,695

Ok well just a thought. Cause my 3000gt will idle real weird almost to the point of going dead and will stumble badly on take off if I not running quality high octane gas. This will mainly happen after it has warmed to operating temps. The higher octane level helps prevent the fuel from being ignited prior to the piston making it all the way to the top of its stroke. These cars are ment to run quality high octane fuel. Running anything else while trying to dignose engine performance issues would be counter productive.

dandyoun
58,695

But I do agree with you about the ecu. Drive safe.

buster1959
5

the car runs great till it heats up, then starts to spit and sputter. called mits garage and they said it's something else but I need to bring it back in so they can check... the car shifts great now, just the spitting and sputtering when it heats up.

buster1959
5

I heard that the idle air control valve might be bad or needs cleaning, or fuel filter or pump needs changing. I always put high octane gas in this car so I don't think it's the gas... could it be water in the gas tank or line?

Daniel Foster
3,485

yeh sounds like the iacv to me (idle air control valve)

buster1959
5

just had a cam/crank sensor put in (that's what the Mitsubishi shop in Erie, pa said)... but the car still spits and stutters and shuts down when it heats up. I was sitting in the car for about 10 minutes with the radio on and when I went to start the car it wouldn't start. the last time it did this I had the AC on... any suggestions? HELP

Daniel Foster
3,485

im confused,, I thought ya said that you had the shop do a tune up (new plugs and wires), new engine computer and new transmission computer. new ignition coils.,,,, are you saying that you took it back and that they put in a new cam/crank sensor ?? if so then that obviously wasn't the problem,,, did you ever check your IACV like I suggested ?? also are you getting any check engine lights ??

buster1959
5

check engine light only comes on when the car starts to act up, then go's off...I'm going to check the idle air control valve myself next, I'm getting mad at the Mitsubishi garage. they keep telling me whats wrong, tell them to fix it, and take my money, then they say it's something else. but can't seem to find the problem.

buster1959
5

I just check the idle air control valve myself, looks pretty clean.. put it all back together and took the car for a run. the car ran great till I started to get on it, took off good at first. then after a couple of fast take offs the car started to spit and sputter again. (engine light came on). can anyone help me? hate like hell to have to take back to the Mitsubishi garage. seems there just ripping me off.

Daniel Foster
3,485

well that IACV could be clean and still be bad,,, follow this link and be sure or make it easy and just get a new one and see if it helps if not return it but that link shows how to test it

1 out of 1 people think this is helpful.
Daniel Foster
3,485

also make sure to clean out that whole recess that the IACV plugs into as that can be gunked up and can have a negative affect as well

buster1959
5

what link... I don't see any link, please send me the link so I can check it out. thanks.

Daniel Foster
3,485

my bad I didn't paste the link here ya go it dropped this time lol http://www.stealth316.com/2-isc-iac.htm

dandyoun
58,695

Drive it at night till it starts to act up. Then pull over pop the hood have some one rev it up while you look at the coil packs and plug wires. Do this in pitch black darkness with no lights shining on motor. Look for spark jump. If its the problem it will stand out like a sore thumb. You will see blue spark jumping from either one of the coils or a plug wire or two. If you see it replace effected parts.

buster1959
5

I have a friend who thinks it's not the "idle air control valve" but the "coolant temp. sensor"... any comments?

dandyoun
58,695

Is your temp gauge holding steady at about a quarter to a half of the gauge without any major fluctuations after it warms up? If so I would not think that was it. Have you tried looking for the spark jump at night yet?

buster1959
5

I've had the car scanned 4 or 5 times now and each time they tell me what the problem is they fix that, charge me for it and something else comes up... a scan cost me a $100.00 each time. I'm going to do the spark jump thing next... thanks

Daniel Foster
3,485

scan it yourself and post the codes lol its free at autozone advance auto and many other places like that, if they gave you the codes from the other scans what were they and what did they fix or do after they got those codes ? but we really need current codes though so drive it to the parts store and get it scanned again please,, also did you ever look into the ECU being good or bad ? (I need to reread this thread I guess)

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