94 Mighty Max 4g64 SOHC 8-valve in need of help

Kyle Koch · Apr 2, 2019

Hello all,

My name is Kyle and this is my first post here. Before I get to the nitty gritty I would first like to apologize. I am aware that my post would be better suited on the mighty max forums but I have yet to be approved on their forums. I can not post there yet and I am getting desperate. Also if this post is in the wrong place I apologize. I have searched this site for another post with a problem similar to mine but have not found one yet. I am posting here since the posts I have seen show there is a wealth of helpful folks here with a treasure trove of knowledge.

Moving forward...

I have a 1994 Mighty Max with a SOHC 8 Valve 4G64. This is my first Mitsubishi and I am no expert with them or engines in general. As far as I know the motor is original to the truck. I made a video earlier explaining everything I could to the best of my ability. I figured this might be easier than writing a novel haha!

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I tried inserting that as a link but it keeps just inserting the video. My apologies if that is wrong as I know some forums frown on it.

This second, short, video is to show the injector pulses coming from the ECU with the use of NOID lights.

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If I could get any help from you all it would be most appreciated. Any questions or ideas would be met with utmost enthusiasm!

Thanks in advance.

Kyle

pauleyman · Apr 3, 2019

You've done a lot of work. Try a leak down and compression check on those cylinders

pauleyman · Apr 3, 2019

Did you use the same lifters in the sam position?

pauleyman · Apr 3, 2019

Could also look at the injectors themselves. You are getting a signal but that only means they're opening. Remove a plug after cranking. Is it wet? Move the injectors and see if the problem follows to that cylinder. Easy quick check.

ThunderChild · Apr 3, 2019

@pauleyman with the 1, 2, 3 rapid-fire!

From looking at the vids and listening to what you've got going on, I'm thinking something with lifters or a mechanical issue, like compression as pauley said. We're the lifters cleaned and check before reassembly? Iirc the sohc motors have very small hydraulic lash adjusters (lifters) in the rocker arms. It also makes me wonder if the correct valves were used and/or if valve tip height was checked.

You should be able to pull codes from the diagnostic connector with a paper clip or something else to jump the proper pins.

pauleyman · Apr 3, 2019

Given that it was running before he took it apart I want to say it isn't mechanical. I'm curious how long it's at and what condition the fuel tank is in. Injectors may be getting a signal but that doesn't mean they're firing any gas if they're clogged

Kyle Koch · Apr 3, 2019

pauleyman said:
You've done a lot of work. Try a leak down and compression check on those cylinders

I will have to get a compression tester to check. I will say that before the head was machined I could spin the motor over far easier than I can now afterwards.

pauleyman said:
Did you use the same lifters in the sam position?

The lifters are new... Sorry if I did not cover that in the video

pauleyman said:
Could also look at the injectors themselves. You are getting a signal but that only means they're opening. Remove a plug after cranking. Is it wet? Move the injectors and see if the problem follows to that cylinder. Easy quick check.

I have tested multiple configurations of the old and new injectors. The problem never moved.

ThunderChild said:
@pauleyman with the 1, 2, 3 rapid-fire!

From looking at the vids and listening to what you've got going on, I'm thinking something with lifters or a mechanical issue, like compression as pauley said. We're the lifters cleaned and check before reassembly? Iirc the sohc motors have very small hydraulic lash adjusters (lifters) in the rocker arms. It also makes me wonder if the correct valves were used and/or if valve tip height was checked.

You should be able to pull codes from the diagnostic connector with a paper clip or something else to jump the proper pins.

The lifters are new. When spinning the engine over by hand (i know they are not pressurized) all of the valves do open and close.

I will get a compression tester on my next day off and will update with results as soon as I have them.

ThunderChild · Apr 3, 2019

Ok, compression is basically the last thing.
Even if the valves open and close, I'm worried about them seating fully. It would seem odd that any reputable machine shop could get two cylinders wrong, but I've seen oddities.

motomattx · Apr 3, 2019

If the lifters were not bled properly and installed fully extended you could have bent valves upon cranking it over, compression test is paramount at this stage.

ThunderChild · Apr 3, 2019

motomattx said:
If the lifters were not bled properly and installed fully extended you could have bent valves upon cranking it over, compression test is paramount at this stage.

Does this apply to the sohc lash adjusters as well? The last sohc I had apart had way different lifters than our heads, and maybe had a few thousandths of squish when "bled" (they were relaxed when I pulled them).

Granted I haven't pulled apart many sohc heads, and I'm not doubting that you @motomattx , just genuinely curious. It is definitely a good possibility and worth checking since everything else has been effectively ruled out. Compression test should tell the tale.

pauleyman · Apr 4, 2019

Kyle Koch said:
I will have to get a compression tester to check. I will say that before the head was machined I could spin the motor over far easier than I can now afterwards.

The lifters are new... Sorry if I did not cover that in the video

I have tested multiple configurations of the old and new injectors. The problem never moved.

The lifters are new. When spinning the engine over by hand (i know they are not pressurized) all of the valves do open and close.

I will get a compression tester on my next day off and will update with results as soon as I have them.

I know what the Noid light tells you however per my previous suggestion have you pulled the spark plug on those dead cylinders and see if they have any fuel on them? I say this so you definitively rule out spark Fuel and compression one at a time. I would imagine you have spark because you are not on a coil pack system but rather a distributor and you have already gone over all of that. That doesn't rule out Spark but it sounds like you have done enough work that spark is not the problem. You have done some fuel testing but do you actually have fuel? It could be unlikely but what about fuel pressure? How long did this truck sit before you got it? I would imagine you are right on the edge of solving this problem. Have you gone so far as to do a visual check of the computer as well? It is old enough to suspect image. I would imagine A Mighty Max has similar properties as our cars. I'm basically saying I'm not sure I trust the Noid light. The Noid light only told you that you are getting some sort of signal to those injectors but not the quality of signal or if the injector is actually opening. Check for fuel inside those cylinders.

motomattx · Apr 4, 2019

ThunderChild said:
Does this apply to the sohc lash adjusters as well? The last sohc I had apart had way different lifters than our heads, and maybe had a few thousandths of squish when "bled" (they were relaxed when I pulled them).

Granted I haven't pulled apart many sohc heads, and I'm not doubting that you @motomattx , just genuinely curious. It is definitely a good possibility and worth checking since everything else has been effectively ruled out. Compression test should tell the tale.

Yes, I knew that this was a sohc, and bleeding down lifters applies to ALL hydraulic lifters, even the bucket style on my 1.8 Audi/VW engines, they bend valves the same way if they arent bled.

Kyle Koch · Apr 7, 2019

Just a small update. I have not been able to run the compression test yet. Mother nature has not been cooperating on my days off. Also I typically dont get home till sunset most days so I am just biding my time till i can get it done. I have the tester in my truck ready to go, just need clear weather and the time off.

pauleyman said:
I know what the Noid light tells you however per my previous suggestion have you pulled the spark plug on those dead cylinders and see if they have any fuel on them? I say this so you definitively rule out spark Fuel and compression one at a time. I would imagine you have spark because you are not on a coil pack system but rather a distributor and you have already gone over all of that. That doesn't rule out Spark but it sounds like you have done enough work that spark is not the problem. You have done some fuel testing but do you actually have fuel? It could be unlikely but what about fuel pressure? How long did this truck sit before you got it? I would imagine you are right on the edge of solving this problem. Have you gone so far as to do a visual check of the computer as well? It is old enough to suspect image. I would imagine A Mighty Max has similar properties as our cars. I'm basically saying I'm not sure I trust the Noid light. The Noid light only told you that you are getting some sort of signal to those injectors but not the quality of signal or if the injector is actually opening. Check for fuel inside those cylinders.

I pulled the plugs and did not smell fuel on the plugs. This why I focused so much on the injectors as the cause of the problem. I checked both cylinders before and after i replaced the injectors and no smell of fuel.

nismojones · Apr 7, 2019

This is deja-vu to me- had this experience with a same year and engine Summitt. Pull the ECU and look for swollen capacitors on the board. I had the same issues and once I repaired the ECU it was back to normal

pauleyman · Apr 7, 2019

nismojones said:
This is deja-vu to me- had this experience with a same year and engine Summitt. Pull the ECU and look for swollen capacitors on the board. I had the same issues and once I repaired the ECU it was back to normal

I concur. Check ecu.

Kyle Koch · Apr 7, 2019

pauleyman said:
I concur. Check ecu.

We did the ECU check and it was spot on.

Pics in Google drive

https://drive.google.com/drive/folders/179n0EKbGy1Dcxidb8zvcOdh1klOY6v8j?usp=sharing

It should be set so anyone can view with that link. please let me know if it does not work.

motomattx · Apr 7, 2019

Simply pull the intake hose off and spray some ether of flammable carb cleaner into the throttle after you hold it open and then crank it and see if it tries to start, thats a super easy quick check.

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