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Generation 3 Pajero NM - NP Models 2000 - 2006

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BrokeAsFix BrokeAsFix is offline
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Default How do I know if itís t̶r̶u̶e̶ ̶l̶o̶v̶e̶ the MAF sensor?

I have read lots of tips on how to clean the MAF sensor and what potential signs of a MAF fail are, but how do I know that I know that I know that I need to replace it?

Given the part costs between $70 (eBay) and $900 (Repco), Iíd like to be sure this is the reason my car is idling rough when the gear is engaged, hesitating when I increase throttle, and splattering unburned fuel from the exhaust.

Iíve cleaned it with MAF spray and no improvement. Iím have a kind to buy an eBay special, even if it doesnít last long, just to get some clarity on the issue.

Last edited by BrokeAsFix; 1 Week Ago at 07:14 PM.
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Having Fun Having Fun is offline
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Which engine are we talking about?
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BrokeAsFix BrokeAsFix is offline
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NM 3.5 petrol (but I imagine the diagnostic process is something which would apply to any MAF sensor).


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Perhaps put your vehicle details in your signature
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The symptoms you describe could also be one or more injectors with bad spray patterns, which could also be a fuel pressure problem. Have you done some testing to rule out these causes? Although a $70 MAF sensor would be a comparatively cheap and simple test.
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paulv1818 paulv1818 is offline
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Could I suggest you check out the ignition system? If its splattering unburnt fuel then in my mind it appears as a symptom of a bad plug or lead. Also check the spark plug well for oil. My old NL used to give me grief from the spark plug tube filling up with oil (from a leaking gasket) causing the plug not to fire. Cheers
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Quote:
Originally Posted by BrokeAsFix View Post
I have read lots of tips on how to clean the MAF sensor and what potential signs of a MAF fail are, but how do I know that I know that I know that I need to replace it?

Given the part costs between $70 (eBay) and $900 (Repco), Iíd like to be sure this is the reason my car is idling rough when the gear is engaged, hesitating when I increase throttle, and splattering unburned fuel from the exhaust.

Iíve cleaned it with MAF spray and no improvement. Iím have a kind to buy an eBay special, even if it doesnít last long, just to get some clarity on the issue.

I agree with Paulv1818 - I'd say that you have worn valve stem seals & the cylinders are filling with oil, fouling the plugs. It'll show symptoms worse at idle.

The various sensors will send info re the misfires to the ECU & the ECU will try to compensate, probably over compensate. Thus the fuel splatter.

I imagine that your O2 sensors are coated in oil & showing failure at the ECU, which exacerbates the problem.

On top of that, every time there is a bad misfire, especially when cruising, there is the possibility that the camshaft angle sensor &/or the crank angle sensor will show failure.

On top of all that, the misfires will not be doing your coil packs any favours!

That is why I asked which engine you have. The above isn't applicable to a diesel & the 3.8 is OBD2 compliant & easier to diagnose than the 3.5.

But like NJ SWB said, a $70 MAF sensor would be a comparatively cheap and simple test.

I'd do it, it can't hurt!
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BrokeAsFix BrokeAsFix is offline
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Default How do I know if itís t̶r̶u̶e̶ ̶l̶o̶v̶e̶ the MAF sensor?

Excellent suggestions.

I can confirm I have new coil packs, leads, and sparks, new valve stem seals (what a job that was!), and my local Mits dealer with a MUT-3 found a misfire on one cylinder but I cleaned that out and the misfire code is gone. Compression on all cylinders is 150psi and doesnít increase dramatically with a wet compression test.


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Last edited by BrokeAsFix; 1 Week Ago at 07:12 PM.
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I have said this before elsewhere, but it still is worth repeating here - when you put the HT leads on, make sure that they cannot sag onto the rocker covers or other brackets. Use all the lead saddles that are there - don't skimp. Run the leads carefully so that they do not touch Earth or each other. Then get the vehicle in a totally dark place, lift the bonnet and run the engine. If there are any HT lead insulation breakdowns, you will see them fairly clearly. If you see none, then you can eliminate the HT leads as a possible cause.

If you do see a breakdown somewhere, all is not lost. Re-mount the leads and also check for air leaks in the manifold. A slight air leak will cause a massive variation in air/fuel ratio at idle, but the leak will be swamped out once the throttle is opened a bit. The oxygen sensor will try to compensate f or the air leak and this could account for the intermittent nature of this problem.
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