Gonna try this again. Lost first post.
Damn It! It was a good one.
This is gonna be much shorter.

02 Monty Sport, 3.5L AWD, 150K miles.
Not passing smog, run issues also.
Numerous codes (PO154/ PO155/ PO137/ PO141) These are all 02 sensor related.
The PO invested bunches of money in new 02 sensors, fuel system service/clean etc. To no avail. It runs and drives, but not well.
This truck is in really good shape and definitely not ready for the junk yard.
So it's my turn. I paid $1K.
My repair budget is $1k. Hopefully less is required.
Had a consultation with my local wrench yesterday. I've used this shop before w/ good results.
He reviews the service records and says "probably the computer" .... What!

This is not my first rodeo, so I'm a little sceptical about the computer statement. Realistically it could be the converters or an EGR issue or a Vacuum leak, I don't know.
I don't have the test equipment so it's up to the shop to diagnose.
Any assistance from the Inmates will be greatly appreciated. Thanks for your time and replies. PaydayGabe in Beautiful Boulder City Nv.

 

You are right - lots of codes, but they are all related only to Bank 1 Sensor 1 and Bank 1 Sensor 2. Multiple codes point to the same sensors. It's possible that computer had failed, but I would first try to rule out any damage to the wiring harness. Try to find a FSM for your Sport and go through a step by step diagnostics/checking of the wiring harness for both sensors. You might end up with the cost of a wire splice and electrical tape. Do not replace the sensors, unless you COMPLETELY rule out any malfunction in the harness and a bad computer.
It would be helpful to find a wiring diagram and to see if Bank 1 Sensor 1 and 2 possibly have a common wire going to the computer.

The reason your Montero doesn't drive well is B1S1 (along with the B2S1) is responsible for providing data for PCM to calculate optimal fuel/air mixture. If Sensor 1 doesn't work, vehicle will run in a back up mode.

 

Is it me? Why are my replies not posting?
Every third attempt gets thru. Or directed at Administration.

So while I have you, ,
Took the Monty to the shop for the diagnosis regarding the run/smog issue. The Tech did his thing and determined It was a DEAD cylinder (# 1)
w/ Zero compression.
Apparently the previous owner/hack replaced the timing belt and failed to check for any bent valves. I'm surprised the machine ran at all in its condition.

So, , w 150k miles on the clock, the mechanic said any extensive repairs on this old engine would be a "band-aid" fix.
I concur with his opinion.
So here we are. Disgusted .
The truck is in reasonably good condition except for the engine itself.
I'm thinking of pulling the heads but don't want to open a huge can of worms. Advise and support needed.
Thanks again for your replies. G.

 

If the truck ran, that means there are no super "major" issues there (such as a hole in the cylinder, ceased bearings, etc. With that in mind, your repairs should not bee too expensive. Pull the passenger side head (or both at the same time), replace the bent valves, put it back together and go for a drive.
Honestly, valve job is not very difficult if you have any mechanical experience. 150k miles is pretty low for these engines.

 

Thanks for your reply again Hunter,
The complexity of a valve job is a
non- issue. Been there many times.
The outside temperatures are the main deterrent, plus the carport.
I would potentially do this repair over several months due to the heat and budget. As I intermittently disassemble the top end eventually,, I'll share my findings.
Do you have a good parts source for quality components? Cheers,, G.

 

Depending on what you need, I use all of the following:
Mitsubishipartssourse.com
Mitsubishipsrtswarehouse.com
Partsouq.com
Rockauto.com

 

PayDayGabe, I think it is something with the browser you are using. It's weird - forum thread shows a new post by you, but it is not visible...

 

Thanks for your time. The issue w/ browser I have (Google) Is not working with this forum. Moving on ✌.