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350matt, Engineer
Category: Mitsubishi
Satisfied Customers: 20396
Experience:  Mechanical Engineer BEng Hons 22 years experience in car engine industry, 10 years in formula 1
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I have a 2002 Montero sport 3.5 xls. It has an idle problem

Customer Question

I have a 2002 Montero sport 3.5 xls. It has an idle problem and loses power when itshe warm and has an odor
JA: Is the power loss consistent, or does it fluctuate?
Customer: Consistent
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: Took it to a shop and they put in idle senior and a coil
JA: Anything else you think the mechanic should know?
Customer: It runs and has power until it warms up then has trouble idle and loses power.
Submitted: 2 months ago.
Category: Mitsubishi
Expert:  350matt replied 2 months ago.


This could be an airleak after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and can lean the engine out and can also allow the engine to rev up when not desired causing rough running.

As its a mechanical fault it tends not to turn on the fault light and you can sometimes hear a 'hissing' noise with the engine running.

Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.

The best way to locate a leak is to have the engine running and warm and then spray lighter gas /propane around each joint in turn. If the engine rev's up you've found your leak.

Now you might think that spraying lighter gas around a hot engine isn’t wise, however the flash /ignition point of gas is about 400°C so you need a naked flame or spark to set it off and I’ve used this method for many years without incident.

Work your way through each possible joint one at a time and you should find it. I use a slightly flattened piece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.

It’s also worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a poorly pump will all result in insufficient fuel being delivered to the engine

Might also be worth checking the wiring and connector to the airflow meter for any signs of corrosion or damage. you can do a quick fault find if you unplug the meter and run the engine without it.

if the engine condition is the same then chances are the meter or the connection to it is faulty

It’s also worth cleaning the MAF sensor wires, as they can get coated with dirt over time which then offsets the reading

Use some contact cleaner or brake cleaner to spray onto the wires to remove the dirt – on no account touch the wires with anything as they are very fragile

Expert:  350matt replied 2 months ago.


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