Ok, I'd like to get some advice please ...

I got this 1990 Mighty Max 2.4L SOHC back in August 2020. I knew it needed moderate work done but anyways, it has an issue with at driving speeds it seems to hiccup or like it is jumping in and out of gear.. which i'm still tryin to track that stuff down but two nights ago on my way home from my daughters' house which is about 30 miles away, it ran fine there and fine almost all the way back home except for the last 10 miles of the way. Now the first of this past week i changed the oil which it is full, last week i replaced the transmission (3spd w/overdrive which sucks btw) fluid, filter and gasket. Also, finally 3 days ago i took it to a friend of the family that owns a muffler shop and had my muffler system worked on. Anyways, as i got about 10 miles from my home all of a sudden my truck had no power, tried to stall a couple times but didnt, wasnt running hot or anything either, it would only do about 45 mph total. When i got it home i parked it then yesterday i tried to crank it.. which it did crank but then stalled, then i cranked it back and it stayed running but still had no power like it had released all its compression... now tonight i changed the plug wires hoping that that would help but nope now it wont crank at all only turn over.. almost like it tries to catch but can't. like its not getting spark or something and i was wondering if this sounds like the timing has jumped or something? it sounds odd when trying to start which is like the sound when its timing is out or something.. I am hoping that its this instead of the head warped or worse.. its far easier to get a timing kit and do the work myself than to have to try and rebuild an entire motor etc.. Any suggestions, advice or pointers would be greatly appreciated! Thank you!!!

Check your timing. Get the crank onto TDC#1 and check the rotor position on the distributor. A sudden full loss of power might mean a blown timing belt. It might not have broken the belt completely - just stripped some teeth off the belt. Luckily the 4G6X engines are forgiving to work on but if you need to replace the belt, replace both the timing and small balance shaft belt at the same time. You'll have to check them both anyway as the small belt can do a lot of damage if it snaps.

double check you put your leads on in the right order

then test the plugs for spark
if they all have a strong spark, put them back in and try starting the engine on some starting fluid
if it starts, it might be a blocked fuel filter, or a dodgy carb float
if it runs or wants to, but bucks then it could be an issue with timing
if it has good spark but wont fire at all then it might be compression

could be a few different things, i have had similar problems which turned out to be a dead coil and weak fuel pump.

if you have access to a compression tester that would be a good start. But you can check the radiator for any milky oil, same with under the oil cap.

First things first. Replace the fuel filter then report back. After that we can look into other problems like a belt going bad. But that's if it has a plastic timing cover. My bet is fuel filter. The filter is behind the cab in front of the tank. It's hard to spot but it's there.

Hi, i already have replaced the fuel filter like 3 days ago, the day b4 it decided to throw me this curve ball..lol. it sounds & acts like it jumped time. It has an ECU, & throttle body, so no carb. Its a SOHC thank god its not a DOHC. like i said this happened all at ince. I just replaced both plugs & wires today, still doing the same nothing changed except it only turns over not cranking. But it sounds funny not as it normally does.

pull the catalytic converter and check that it isn't clogged. When they get hot they'll plug up and stall the engine.

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Originally Posted by Lon Moer

pull the catalytic converter and check that it isn't clogged. When they get hot they'll plug up and stall the engine.

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Try a bottle or two of CATACLEAN from O'Reilly's make sure the gas tank is less than 1/4 full ~ chances are it will fix a dirty catalytic convertor

Hi, if the belt had broke then it would have cut off and not started back up. I have had it started 3 or 4 times since the lost of compression, like i said it would only go about 45 mph, I did find out that there is oil in the water but its like a lava lamp, if you know what i mean, its like its not mixed or anything. The oil is below the water but not mixed up with the water. Also, i found out that number #1 plug has no spark. So, I went ahead and changed all the plug wires specially since i have no idea when they were ever changed. I have only had the truck since last August or Sept. I also, decided to go ahead and get a timing kit and a head gasket set to be on the safe side and everything will be changed out and installed within the next two weeks. However i'm thinking that the coil may be on it's way out which could explain the loss of power and all. Also, my cousin, without my knowledge btw, decided to take off the catalytic converter and replace it with just a pipe, that was a couple days before this all happened so i was thinking it could also be the 02 sensor on the exhaust manifold has gotten false readings and needs to be replaced as well. Remember this is a 1990 mighty max with a 4G64 engine (2.4L) while it has an EFI throttle body etc.. it does not have what we know today as a computer in it controlling things, just alot of sensors.. Also, i must add that i have no idea what the person that sold me the truck has or hasn't done to this poor vehicle lol. I hope that this all helps.

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Originally Posted by geezer101

Check your timing. Get the crank onto TDC#1 and check the rotor position on the distributor. A sudden full loss of power might mean a blown timing belt. It might not have broken the belt completely - just stripped some teeth off the belt. Luckily the 4G6X engines are forgiving to work on but if you need to replace the belt, replace both the timing and small balance shaft belt at the same time. You'll have to check them both anyway as the small belt can do a lot of damage if it snaps.

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A day or two before this all happened my cousin decided to take off the darn thing and welded a straight pipe back on so there is no converter there now. It was running decently before he done that but like i said a couple days later all this happened.

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Originally Posted by xboxrox

Try a bottle or two of CATACLEAN from O'Reilly's make sure the gas tank is less than 1/4 full ~ chances are it will fix a dirty catalytic convertor

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A couple days before the power loss thing happened it was taken off and replaced by a straight pipe so now it doesnt have a converter... i'm wondering if it needs one of those sensor emulators on it now. It ran decently before my hard headed cousin decided to do exactly what he wanted no matter what i had said, took off the converter then a couple days later is when it done this. I hadnt really driven anywhere between the time he done it and the time it limped home. So yeah between some oil in the radiator, #1 not firing and the converter taken off its a wonder if i hadnt gotten stranded in the middle of the night lol. Anyways thank you all for your thoughts on this.

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Originally Posted by Lon Moer

pull the catalytic converter and check that it isn't clogged. When they get hot they'll plug up and stall the engine.

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All of that along with head gasket, timing belt(s), its a SOHC but has two belts lol. and other things will be replaced in the next couple weeks. Thank you and i will let ya'll know whats up as soon as i know. Thank you again!

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Originally Posted by camoit

First things first. Replace the fuel filter then report back. After that we can look into other problems like a belt going bad. But that's if it has a plastic timing cover. My bet is fuel filter. The filter is behind the cab in front of the tank. It's hard to spot but it's there.

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Yes most of all that has been done. #1 cyl has no spark, the converter was removed without me knowing it a couple days before it went crazy.. there is some oil in the radiator so yes the head gasket is being replaced, the timing belt is as well. The fuel filter is being replaced etc.. I will report back as soon as i know what's going on with it.. thank you all

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Originally Posted by tortron

double check you put your leads on in the right order

then test the plugs for spark
if they all have a strong spark, put them back in and try starting the engine on some starting fluid
if it starts, it might be a blocked fuel filter, or a dodgy carb float
if it runs or wants to, but bucks then it could be an issue with timing
if it has good spark but wont fire at all then it might be compression

could be a few different things, i have had similar problems which turned out to be a dead coil and weak fuel pump.

if you have access to a compression tester that would be a good start. But you can check the radiator for any milky oil, same with under the oil cap.

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Im not super familiar with it because ive never had a mitsi engine in my truck - but there should be a jumper plug on the "ecu" that you can reset - after you do all that work

sounds like you're doing the right things. dead #1 spark and oil-in-water are clear symptoms that have to be fixed regardless. i'd echo that doing a compression test would be pretty easy and useful. also, will say (having just done it) that pulling the top timing belt cover to expose the cam sprocket and check the timing belt for slop/damage, is really pretty easy. good luck! look forward to hearng the report back.

Hey everyone, sorry for not getting back sooner...

Here is where i'm at now.... Ok I've changed the head gasket & gotten the motor back together, however, it still will not start. I have made sure that all the timing marks are correct and the distributor is set etc., however it wont crank, just spins over. The plugs & plug wires are new, the rotor is as well. I made sure to put fresh gas in it as well & changed the fuel filter.

When i got the head off the old gasket was blown in 2 places.... between the 1st & 2nd and between the 3rd & 4th. So new head gasket was necessary period. But this non-cranking is driving me nuts. It turns over but just wont catch, I'm fixing to go back out there & test for spark in each cylinder as well as making sure that the injectors are getting signal so that they can squirt the gas etc... But i really need some advice on this, I've worked on autos many years, not the 4G64 or Mitsubishi but on the Toyota 22R and more than i can count of 6 & 8 cylinder American cars like Ford, Chevy & Chrysler, But this is the first time in my 40+ yrs of doing this type of work on motors that i have gotten stumped this badly. If anyone has any tips tricks or advice on these issues please contact me. My motor is for 1990 Mighty Max Microcab, auto trans, 4G64 SOHC with ECM & throttle body. it does have A/C but it isnt hooked up or run.

Any help would be greatly appreciated. It was running & one night i was coming home, when i got off my exist & after doing 55 or 60 mph home, trying to pick up speed, it wouldn't go any faster than around 45 mph. Got it home, it had no power & while would crank, it would shut off if i tried to put it in drive. After 2 times of cranking, then after dying it wouldn't start again. This is why I knew the head gasket, for 1 thing, was in need of changing.
Thanks again and hope that someone can help me with this darn thing :)
SyrsKnight

It sounds like it went into limp home mode (this will explain the sudden loss of power). Check the ECU for error codes. Beyond that - fuel filter (you have replaced it, but the stuff swimming in your fuel tank doesn't know when to quit), ignition coil, ground lead connections in the electrical harness, fuses and fusible links... :shrug:

*what is the actual fuel like too? Only takes one tank of crap fuel to mess up your truck :shakehead: