Pajero Idle fault

[dvk-kp]

Hi, my 3.5 v6 pajero seems to have developed a fault and I can't figure it out.

Symptom 1 is bad fuel economy, I currently got 250ish Kay's to 2/3s of a tank, probly 50ish litres. It's never been great on gas but it's really bad now. Usually get 5-600 per tank.

Symptom 2 is a strange idle. If I start it warm it will at ~1500ish and sometimes rise to ~2000 over the next 15-30 seconds then drop down to a normal idle. Rev amounts/length of time vary a little but always starts high, climbs a bit more then drops to standard idle most times I start it.

Ive change AFM and didn't seem to change anything. Changed the idle control thing on the bottom of the throttle body but with the replacement it wouldn't idle at all. Pulled the idle control thing apart and noticed it's adjustable when turned... pushes the plunger in and out. Plunger is also "sooty", black build up and doesn't look like it's been sealing.

Sorry for the long post but figure I should explain it properly.

Maybe I should start with an ECU reset? If so how do I do that?

Thanks
Cole

[derk]

running a diagnostic tool across it may save a lot of time trying to guess the fault

[dvk-kp]

Like a plug in one at the auto sparkies?

[Crash bandicoot]

The key is in your comment ....warm engine idle runs erratic then settles down.

Check for vaccum leaks ...spray brake cleaner around the inlet manifold whilst engine is running...if idle picks up it has got an issue....

Start with checking wiring to the o2 sensors aren't damaged

Put an multimeter over the two pin temp senders on engine ohms cold should be high getting lower reading as it gets warmer.

Air flow meter hotwire arms may have build up and can't read air flow correctly...especially if the air box hasn't sealed properly at some stage in its life....


Normally fuel consumption issues

[Crash bandicoot]

FYI the auxalary idle control valve doesn't always close completely....if there are other issues the computer may compensate by not shutting it off at all.

[dvk-kp]

Thanks bud, your on the money.

Had it scanned yesterday and there were no faults. Auto sparky told me how to test the idle stepper motor with a multimeter and that also checked out fine, although he said they can be a common Mitsi problem (he had a box of them under the bench).

Throughly cleaned the throttle body and when I was putting it back together I found a split in the intake hose... definatly could be the leading cause of the problem. Taped it up for now while I track down another mint one. Still done the thing where the idle rises tho but I'll give it a decent drive and see how that goes.

Will check the temp sensor is doing as it should this evening, I have cleaned the AFM so that should be mint.

Also I don't have any O2 sensors in my exhaust. I built a new exhaust and thought the sensor in there was just a cat temp sensor so just didn't put it in. Exhaust has been fitted for 18 months without issue.

Thanks

[Crash bandicoot]

I learnt from a mitsi wise man that the pajeros use the 02 sensor(3 wire) to help govern fuel....if your AFM eve fails turn the truck off. Unplug it and restart it..... the ecu can use th 02 sensor to govern fuel load in the event the AFM fails.... Also note the AFM not only measures air flow...also density and temperature....to do with altitude etc.

[dvk-kp]

Well that's interesting, I just assumed it was cat temp. Will see if I've got one in a factory exhaust somewhere and get that fitted ASAP. Will get rid of the dash light too which will be a bonus.

[NJV6]

There are two exhaust sensors, the cat one and the o2 one. It needs the o2 one as mentioned for fuel mixture.

The cat one isn't reqd, just keep it plugged up but tie the sensor out of the way. If unpluged the dash light will be lit.

[dvk-kp]

Hmmm I didn't notice 2 when I pulled the original exhaust off. Will investigate the parts trucks and see what I can see. How do I tell them apart? Should the o2 sensor be placed in the join of the pipe coming from each bank?

Replacement intake pipe is on its way.

Maybe I'll get more then 550ish kays to about 90 litres gas after the o2 sensor is fitted!!

[NJV6]

The O2 sensor is closest to the engine and is after the 2 into 1.

[Crash bandicoot]

550 is pretty good, im averaging about 400 . lol

there is a 3 wire before the cat and a single wire sensor after the cat...fyi mines a japanese import not a nz new one.

[dvk-kp]

Cheers guys, hopefully get time to sus it out this weekend.

So it's the 3 wire one I'm looking for?

Gees that's thirsty! Yours is a 3 litre isn't it crash? Mines a jap import also.

[Crash bandicoot]

Yep but its got the 3.5 throttle body and diamante multi point injectors and cams so make a bucket load more power good for snatching safaris over sand dunes.

[dvk-kp]

Oh cool! More cheap mods for the old 3.0!

Is that cams and injectors from this shape Diamanté...

https://trademe.co.nz/1160622428

Haha safs need all the help they can get!

[Crash bandicoot]

.

[Crash bandicoot]

Yep but the ralliart vx version. E-f27a was the chassis code anyway the standard magna/ diamante is e-f25a

[dvk-kp]

Cool thanks crash. My brother will be on the look out for his paj.

Anyway I got this sensor off my parts truck but I'm pretty sure it's the cat temp sensor but want to confirm...

It's only got 2 wires

[dvk-kp]

Found the right sensor. Was in a spare Y pipe I had.

Munted the thread getting it out, had bound up real bad, but will get it cleaned up and make a bung at work tomorrow and weld it in.

Is it bad if I got CRC on the sensor trying to remove it?

[Crash bandicoot]

No I had vice scrips on mine . lol

[dvk-kp]

So did I! Great tool!