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Generation 3 Pajero NM - NP Models 2000 - 2006

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  #1  
Old 13-02-20
Having Fun Having Fun is offline
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Default 3.8 petrol intermittantly stalls at idle when warmed up.

OK, so we've had the chirping noise & replaced the accumulator, then we had the dreaded flashing centre diff light & replaced the bits that needed replacing, then we had the crazing readings on the temp gauge on the dash & fixed that too (those last two completely ruined two holidays!).

Now the jolly thing has started to stall if left in D at red traffic lights for too long! Then it will only start after an embarrassingly long time with the hazard lights flashing & everyone else trying to negotiate around it.

No dramas if I'm driving, I'd put it in P & watch the idle speed, then kick it in the guts if the idle speed got too low, but hey, I'm not the one driving it to work in the traffic everyday & my wife forgets to move the stick from D to P at the lights, then tears!

I'm completely over this car, it's not what I wanted, or expected. But I have to deal with it, so;

1. It drives like a dream while in traffic, until it is stopped at traffic lights & has to wait with every other car at the lights for a while. No missing, no rough idling, great power, no excessive fuel use. Then it stalls & refuses to re-start for several minutes.
2. The air filter was replaced last August & is still snow white.
3. The idle speed is IMO too low. It sits on 550-600RPM when warmed up.
4. The spark plugs are due for a change, but it starts great from cold, no rough running at all.
5. The Alternator & battery are showing as fine.
6. Fuel filter??? Like I say, no other issues any other time, except sitting idling at traffic lights for 4-5mins.

7. MAF or throttle body??? Surely there would be other symptoms if they are involved?
8. Exhaust; my experience with blocked exhaust tells me that if it is the problem, it would be hard to start & run like a sack of the proverbial? It isn't & it doesn't.
9. Injectors?
10. Fuel pump?


Thanks for reading, like I said, I'm over it. We're swapping cars in the meanwhile, my wife gets my work Ute & the NP gets to tow my work trailer around.
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  #2  
Old 14-02-20
Roofchop Roofchop is offline
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Mine had low idle.


Changed the temperature sensor for the ECU, fixed! (there are two sensors, one for ECU one for gauge)


On the 3.5 they are next to each other.


To determine which is which, with the engine warm, and off (ign on), unplug one and see if the gauge falls to cold.


If it does the ecu one is the other. if it stays "warm" then you just unplugged the ECU sensor!


When the sensor is bad, the ECU will set the fueling incorrectly.


$30ish fix
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Last edited by Roofchop; 16-02-20 at 09:04 AM.
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Old 14-02-20
Having Fun Having Fun is offline
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Quote:
Originally Posted by Roofchop View Post
Mine had low idle.


Changed the temperature sensor for the ECU, fixed! (there are two sensors, one for ECU one for gauge)


On the 3.5 they are next tom each other.


To determine which is which, with the engine warm, and off (ign on), unplug one and see if the gauge falls to cold.


If it does the ecu one is the other. if it stays "warm" then you just unplugged the ECU sensor!


When the sensor is bad, the ECU will set the fueling incorrectly.


$30ish fix

Thank you for the suggestion Roofchop, I'll give it a try!
I've already replaced the sensor that feeds the temp gauge & like the 3.5, the ECU one is right alongside of it - it makes sense that it could be stuffed, as the temp sensor for the gauge had almost completely de-laminated.
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Old 14-02-20
Having Fun Having Fun is offline
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Well, I bought an ECU coolant temp sensor - I'll put it in in the morning, when the car is stone cold.


I hope that it works, as my wife is gibbering something about throwing a towel over the headlights so it can't see, then shooting it lol.
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  #5  
Old 14-02-20
El_Freddo El_Freddo is offline
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Quote:
Originally Posted by Having Fun View Post
I hope that it works, as my wife is gibbering something about throwing a towel over the headlights so it can't see, then shooting it lol.
Itíll still survive.

It could be a fuel pump issue too. The fuel pump is under the most load when at idle.

Does it stall and not start when youíve got a full tank of fuel? I reckon itíd be less likely - more fuel around it to keep the pump cool. Low tank and no liquid fuel around it to keep the pump cool. It stops, engine stops. Pump doesnít work until itís cooled down.

Makes sense to me. Not an easy task to remedy/investigate.

How many km on this Paj?

Cheers

Bennie
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Old 14-02-20
Having Fun Having Fun is offline
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Quote:
Originally Posted by El_Freddo View Post
Itíll still survive.

It could be a fuel pump issue too. The fuel pump is under the most load when at idle.

Does it stall and not start when youíve got a full tank of fuel? I reckon itíd be less likely - more fuel around it to keep the pump cool. Low tank and no liquid fuel around it to keep the pump cool. It stops, engine stops. Pump doesnít work until itís cooled down.

Makes sense to me. Not an easy task to remedy/investigate.

How many km on this Paj?

Cheers

Bennie

We think alike Bennie! It happened on Tuesday & the tank was around quarter full when it happened, so I asked my wife to fill it & hoped that would change things. It did it again Thursday when she was driving it with a full tank of juice - mate did I cop it over that! My fault apparently! (there were tears involved!)

Absolutely agree that it makes no sense & is extremely hard to pin point!

The car has 191K on it. Full dealer service history when we bought it (at 114K) & no signs it had ever been off road before we bought it (it has now though)

I've driven it around town a fair bit now & I have NO dramas with it whatsoever. But I DO put it in P when I'm stopped at a red light for a while as a precaution.

The idle jumps up to about 700RPM in Park, from 550-600 in Drive.

I'll put this ECU coolant temp sensor in tomorrow & see how it goes I guess!
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Old 14-02-20
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nj swb nj swb is offline
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Crank angle sensor?

If it's deteriorating as it gets hot the output signal may be reaching the point where the ECU no longer recognises it. Once the ECU no longer sees pulses from the crank angle sensor it thinks the engine has stopped, and stops firing injectors and spark. Until the sensor cools down, there are no pulses to tell the ECU that the engine is cranking, so no fuel or spark to restart.

Once the sensor cools down its output recovers sufficiently for the ECU to recognise the pulses, and normal operation resumes.

Sitting at the lights in N with the revs up is reducing load on the engine (heat output) and increasing airflow from the fan over (the region of) the sensor - so the sensor doesn't get too hot, and everything continues to work.

The crank angle sensor either works or it doesn't. No missing, or spluttering - just run or stop.
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Old 14-02-20
Having Fun Having Fun is offline
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Quote:
Originally Posted by nj swb View Post
Crank angle sensor?

If it's deteriorating as it gets hot the output signal may be reaching the point where the ECU no longer recognises it. Once the ECU no longer sees pulses from the crank angle sensor it thinks the engine has stopped, and stops firing injectors and spark. Until the sensor cools down, there are no pulses to tell the ECU that the engine is cranking, so no fuel or spark to restart.

Once the sensor cools down its output recovers sufficiently for the ECU to recognise the pulses, and normal operation resumes.

Sitting at the lights in N with the revs up is reducing load on the engine (heat output) and increasing airflow from the fan over (the region of) the sensor - so the sensor doesn't get too hot, and everything continues to work.

The crank angle sensor either works or it doesn't. No missing, or spluttering - just run or stop.

You could be onto something. I'll try the ECU coolant temp sensor in the morning & if no joy, I'll try a crank angle sensor.


Thanks!
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  #9  
Old 15-02-20
Having Fun Having Fun is offline
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Well changing the ECU coolant temp sensor seems to have done the job (I have literally everything crossed lol)


I took it for a spin after I swapped them over & once warmed up, I did manage to get it to stall in D after idling on a side street for about 3-4mins. But it started straight up, first turn of the key afterwards.


So, took it home, unhooked the battery for 30mins, then did a relearn on it. Took it for another spin & tried very hard to get it to stall, A/C on & off, Sports mode, full auto, PRND all left idling for extended periods, no stalls!


Thank you to those who responded, especially Roofchop!
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Old 15-02-20
disco stu disco stu is online now
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Great news hope it's sorted permanently
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