1990 Montero dies when pressing gas....

[Dartmouthbrian]

I have been working to figure this problem out. Essentially, the Montero runs like crap. It idles kind of rough, but will smooth out and idle fine, but if I touch the gas it dies. On a whim I poured some Seafoam in the oil and that is when it started to idle normal, still dies when I touch the gas.

1990 Montero 5spd Base model

Things I have done..
1. check and tested fuel pump
2. replaced fuel filter
3. tested MAF sensor
4. Cleaned throttle body
5. replaced TPS
6. checked air filter

I am at a loss here... Any experience with this problem?

 

[Toasty]

Not sure i can help with the problem but it sounds like either a bad optical sensor ora MASSIVE vacuum leak after the MAF. Good luck homie

 

[vk_miniatures]

need more info about when this problem started. did it start after you did something to the car or did you recently purchase the vehicle with this problem? have you replaced spark plugs recently? if so, check wires to make sure they are in correct order. also check all vacuum lines.

 

[Dartmouthbrian]

Thanks Toasty & vadimkruts. I purchased the vehicle with this problem. I've worked on many vehicles over the years. I switched from Land Rover to Montero... This feels like a Rover problem LOL

 

[vk_miniatures]

so pretty much you have no history of what kind of work was done to the car. ok double check the spark plug wires to make sure they go to the right cylinders (also check their condition). one time i accidentally put wires in the wrong order on my car and it ran kind of same as you are describing. second check your air filter. I bought a Discovery one time with similar problem ,wouldn't idle properly and died when you press the gas. the owner took it to the shop and no-one was able to figure out what was happening because everything checked out fine. all it was a dirty air filter that was completely clogged by the dirt. things that make an engine run are: compression, fuel-air mixture delivery and spark. try pulling out one spark plug (the ones you can get to without pulling plenum off) after car stalls. do it as fast as possible to see its condition. is it wet? maybe the engine gets flooded with fuel instead. check all this little things first. let me know if anything will help

 

[vk_miniatures]

I'm sorry, just realized that you did in fact checked the air filter. my bad

 

[vanatee2000]

Check the timing too.

 

[normal_dave]

"Stop pressing the gas..." https://www.youtube.com/watch?v=g-4-gLlF0uw

But seriously folks, if you're coming from a Land Rover, this should be a cinch. I'm a little out of my specialty here, but I am old school so let's try a few basics.

With great care for safety, let's get the Monty in a "very dark room", engine running, and look for ignition grounding, near the distributor, spark plug wires, coil, etc. It's amazing what you can find this way, or how fast you can earn a trip to the ER. "Danger Will Robinson", this is how you get gravely wounded. Also carefully inspect the distributor cap for tracking (grey lines) from firing onto the wrong surfaces.

I ran across two more discussions that I liked that dealt with basics, and were common to that era Mitsubishi. So often I go down a rabbit trail chasing symptoms only to forget we need to eliminate the obvious.

You've cleaned the throttle body but let's take a second look at the IAC/ISC motor: (sure hope this applies to your year model)
http://www.4x4wire.com/mitsubishi/tech/throttle_body/

Edit: another IAC discussion
http://www.4x4extremesports.com/index.php?http://www.4x4extremesports.com/mitsubishi_iac.php

While you're at it, trace your spark plug wires against this awesome 3D wiring chart link in this post printed in the Queen's English:
http://www.pocuk.com/forums/viewtopic.php?t=143201&sid=c996fa9fabe71f0f44bbb6275d63ac5d

Pretty sure you don't still have a vacuum advance distributor, but if so, use a Mityvac to see if the diaphragm is holding pressure, and follow Toasty's advice and start the hunt for vacuum leaks. If you don't have a mityvac kit, it's a great tool to add to the collection, and now is as good an excuse as any.

Good Luck! and apologies for the first line comment, (did I say that one out loud?)

 

[Dartmouthbrian]

Hey everyone... Thanks for the comments. Going out now to do some more trouble shooting. Will report back. Normal_Dave loved the first line LOL

 

[Dartmouthbrian]

None of the above... And the mystery continues.

 

[normal_dave]

Bummer.

You mentioned a change when you added seafoam to the oil...makes me curious about the condition of your lifters. Are they holding pressure, etc. If they aren't pumping up properly, then your cams aren't able to do the job of opening the valves far enough to allow proper flow, and that would really put a cramp in your style. Only real way to check them is to remove them. Do you hear any detonation or sound like spark knock when lugging up a hill in drive for example? Are they ticking away at idle and you are just used to it? Not saying you should do this job as a troubleshoot, just something else to think about.

Here's what I think is the best resource for technical info, you'll just have to weed out the diesel discussions. Spend some time searching through posts for info on driveability issues specific to Gen 1, 6G72 motor.
https://www2.pajeroclub.com.au/forum/forumdisplay.php?f=5

 

[Dartmouthbrian]

Hey Normal Dave: I can't drive the truck. One of the main problems is the moment I push the gas pedal it dies.


I was able to get it to idle for 30mins yesterday, but the moment you push the pedal she dies. I am completely baffled at this point. Also, this Montero is manual.

 

[normal_dave]

Based on the information provided, I'm running low on ideas. We all are assuming you've correctly and successfully tested the items you already listed, and recommendations made and read through the Aussie forum without any bright spots. Consider starting from scratch and confirm each of the steps you have taken.

I can't help but wonder about the ignition timing. There is a procedure in the manual that details the correct way to set the timing with a light, and you have to remove the computer's control over the timing advance to get it set right. If the base timing (initial w/o computer advance) isn't right, then it could stumble, sputter and die every time you apply fuel. It could also explain the rough idle, if it is retarded for example, same extreme for too far advanced although it wouldn't explain the stumble. Related to this if your distributor is worn inside, broken advance mechanicals, etc., all your adjustments won't help.

It may be time to seek professional help...a good diagnostic import mechanic in your area, especially since you bought it in this condition, and don't have a baseline experience to return to in terms of performance.

Forgot, also check out 4x4 wire for technical as well.

Best of luck.

 

[Dartmouthbrian]

Normal_Dave: Thanks man, much appreciation for the insight. I'm going to check the timing and IM going to KICK myself if that's it. HAHA I'll report back.

 

[Bottomfeeder]

Very good info here. I can't help but think it may be ECU related. You would need a know working ECU to check tho. Swap computers to see if anything changes.