How is the idle controlled on a 2003+ (3.8L) Gen3 Monty?

[fernandez32112]

idle die

SO after taking the car to the dealer and being told by the mitsu mechanic that he had no idea what was causing the problem and offering to change the throttle body art a cost of $900, i decided to tackle it my self. I connected my autolink computer to the car to read the live data. the live data told me that the engine rpm was low 550-700 with the a/c on or off while in drive.. the throttle position sensor was reading 2.4 at idle and eratic between 2.5 and 7.1 just before the the car would turn off(in drive, ac on full). I DISCONNECTED THE MASS AIR FLOW SENSOR and read the live data again. Here is what happened:

With the car in idle, in drive and ac full speed
1. the car did not turn off
2. the check engine light turned on-MAF codes only
3. the throttle position sensor read steady at 4.5
4. the engine rpm steady at 875

I repeated this 6 times, 3 times with the MAF connected and 3 times with the MAF disconnected. The result were the same- bad with the MAF connected and good with the MAF disconnected.

I was hoping you would do the same test on your car to see if your results are similair to mine. Im convinced the MAF is bad. I'd like to know your thoughts

 

[nckwltn]

My 03 will die with AC on if I've disconnected the battery recently. Usually driving around for a couple of days, sitting at stoplights in neutral, manually keeping revs up so engine won't die.

I think it lasts long enough for the computer to compensate and then I don't have any issues.

Would love to fix the problem though.

 

[fernandez32112]

After all the test as per my previous post I changed my MAF with a new unit and have driven the car for a week now. The engine idle problem is gone. I live in Miami and I run my a/c at full 70% of the time. After changing the MAF the car is running like new. No stalling just smooth driving. I'm curious to know if any of you have tested the MAF? Please Post!. there many people out there experiencing this same problem with this car. If the MAF is the common problem then we may have the solution to the problem.

 

[haolepinoy]

After all the test as per my previous post I changed my MAF with a new unit and have driven the car for a week now. The engine idle problem is gone. I live in Miami and I run my a/c at full 70% of the time. After changing the MAF the car is running like new. No stalling just smooth driving. I'm curious to know if any of you have tested the MAF? Please Post!. there many people out there experiencing this same problem with this car. If the MAF is the common problem then we may have the solution to the problem.

Man, I'm glad to hear that Fernandez! How much did the MAF cost you? I see it listed online at around $425 (OEM part # MD336482).

I've also seen that cleaning them using CRC MAF Cleaner can ruin them since they are the Karman Vortex style. Wonder if that's happened to mine. I'm trying to find a testing procedure in the FSM to test the unit...

 

[haolepinoy]

I did a little checking around. The MAF Sensor is part # 336482, and it is the same part # for the Montero Sport with the 3.5L engines (99-04). I bring this up because if your area is like mine there are ZERO Gen 3 Monteros in local pick and pull yards, but a good number of Montero Sports. Junkyard pricing is way below the $400 bucks it would cost for a new one of these. I may give the local yard a visit and pick one up to try.

Still haven't found a place in the FSM for testing the MAF sensor though. I try not to be the guy that throws parts at something. I'll post when I find a page reference.

 

[haolepinoy]

FSM Testing Procedures for Volume Air Flow Sensor

Here's what I've found (from the 2003 Montero Factory Service Manual):

The Volume Air Flow Sensor is what the FSM calls the Mass Air Flow Sensor.

13Aa-17: Intake Air Temperature Sensor Check
The Intake Air Temperature Sensor is the small resistor inside the Volume Air Flow Sensor (honeycomb pipe after the air box with the black rectangle on top with wire sticking out).

13Ac-44: DTC P0111 - Intake Air Temperature Circuit Range/Performance Problem

13Ac-50: DTC P0112 - Intake Air Temperature Circuit Low Input

13Ac-54: DTC P0113 - Intake Air Temperature Circuit High Input

 

[haolepinoy]

SO after taking the car to the dealer and being told by the mitsu mechanic that he had no idea what was causing the problem and offering to change the throttle body art a cost of $900, i decided to tackle it my self. I connected my autolink computer to the car to read the live data. the live data told me that the engine rpm was low 550-700 with the a/c on or off while in drive.. the throttle position sensor was reading 2.4 at idle and eratic between 2.5 and 7.1 just before the the car would turn off(in drive, ac on full). I DISCONNECTED THE MASS AIR FLOW SENSOR and read the live data again. Here is what happened:

With the car in idle, in drive and ac full speed
1. the car did not turn off
2. the check engine light turned on-MAF codes only
3. the throttle position sensor read steady at 4.5
4. the engine rpm steady at 875

I repeated this 6 times, 3 times with the MAF connected and 3 times with the MAF disconnected. The result were the same- bad with the MAF connected and good with the MAF disconnected.

I was hoping you would do the same test on your car to see if your results are similair to mine. Im convinced the MAF is bad. I'd like to know your thoughts

Sorry I didn't pay much attention to this sooner. I've been busy and the Montero's A/C hiccup has been on the back burner. I'll try to give this a shot one evening this week as...well, if time allows (busy week, again). Thanks for coming at this from another angle. I'll try the FSM resistance tests as well and post results. Maybe this will give me an excuse to go to the junkyard this weekend (one of my favorite hobbies).

 

[fernandez32112]

Reading the The throttle position sensor is key. You can do that with any code reader that has live data. The MAF signal open and closes the Throttle body accordingly but a bad MAF is sending an incorrect signal and is most likely closing the throttle body too much. The throttle body sensor should be reading 3.5-4.5 at idle. You might find that yours, like mine is reading below 3 which is the reason for the low idle and stalling issues.

 

[fernandez32112]

I would like to have someone else do what I did to confirm my diagnosis and solution. BTQ I purchased the new MAF complete body and sensors on ebay $77.00

 

[Montero Van]

Hi fernandez32112 and haolepinoy,

I just joined and I am looking forward to the all of the information. I just found this thread and I am having the exact same problem with my 2003 Montero (Not Sport). I have had the car since 2004 and it has 135K. Car has always been a champ, but this stalling and low idle is becoming a real issue. I was hoping to hear if the MAF solved the issue for you a few months down the road.

I am in Orange County, CA

Thanks,

Van

 

[haolepinoy]

Hi fernandez32112 and haolepinoy,

I just joined and I am looking forward to the all of the information. I just found this thread and I am having the exact same problem with my 2003 Montero (Not Sport). I have had the car since 2004 and it has 135K. Car has always been a champ, but this stalling and low idle is becoming a real issue. I was hoping to hear if the MAF solved the issue for you a few months down the road.

I am in Orange County, CA

Thanks,

Van

Hi Van. Replacing the MAF Sensor solved Fernandez' issue.

I haven't had the time to deal with it...just learned to cope. I did pick up a junkyard maf sensor...but it turned out to be the wrong one (for a 3.0L Montero Sport rather than a 3.5L...the 3.5L Montero Sport and 3.5/3.8L Montero MAF sensors are the same). Haven't had time to go back to pick up another one to try. Don't have a code reader either to read live data, so it'd just be a shot in the dark for me. This issue is on a long list of petty annoyances, but not near the top right now unfortunately. I've got a bad oil leak from the passenger cam seal that I've got to address before anything else...and being the job that it is I'll likely be addressing a lot of other potential factors as well (I'm going to replace the alternator while things are apart...it get's bathed in oil, and that's surely causing some of my issues).

I'd try to check the MAF with the FSM procedures listed above, and if you've got a code reader that will read the live data, give that a shot too. If not, get a plug in volt meter and keep your eyes on it when idling if you've got a lot of electrical load on...that's what I do in the mean time. It gets me by.

 

[Offroadmuch]

I will be installing my new MAF next week. I will report if it cures my low idle...

 

[Salonika]

Has anyone thought of just trying to clean the MAF vs. replacing it? I didn't see anyone giving that a try first. I know the sensor can get dirty over time and that can cause the sensor to misreport air volume = rough idle.

 

[Offroadmuch]

Has anyone thought of just trying to clean the MAF vs. replacing it? I didn't see anyone giving that a try first. I know the sensor can get dirty over time and that can cause the sensor to misreport air volume = rough idle.

Pictured here is the (inside view) top of the airbox with the MAF still attached due to the mounting bolts spinning as the plastic cracks. Therefore I might try to just clean. To all reading PLEASE BE ADVISED THAT THERE IS MAF CLEANING FLUID. I say this because some may use brake or carb cleaner. MAF cleaner is supposed to "more gentle" for lack of better terminology. I may try this and scrap the replacement if it is going to destroy my air box assembly. I will update with what happens.

 

[KyleT]

I cleaned my Maf, reset the ecu taking the batt off and it seems to have fixed my issue of low idle and dying.


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