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Matt
Matt, Engineer
Category: Nissan
Satisfied Customers: 20597
Experience:  BEng hons Mech engineering, worked in auto industry for 22 years on engine, transmission and suspension design
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Frontier XE: 2002 frontier 4cyl,75,000 mi.Runs great til warm

Customer Question

2002 frontier 4cyl,75,000 mi.Runs great til warm then stumbles and dies at idle.Starts up immediately.Have changed idle air control mtr,TPS sensor,cleaned throttle body,new:plugs -rotor -and cap, and air and fuel filters.Shop replaced mass air flow sensor w/$700.00 part and said it made no difference or possibly slightly worse (ran rich!).Talk now about replacing ECU w/reman unit,but not sure if that will take care of problem.
Submitted: 1 year ago.
Category: Nissan
Customer: replied 1 year ago.
Also did idle re-learn program.
Customer: replied 1 year ago.
And tried oxygen sensor replacement w/no results.
Customer: replied 1 year ago.
Removed new mass air flow sensor and reinstalled OEM part.
Expert:  Matt replied 1 year ago.
Hello 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 cleaning out the idle speed control motor / valve as these get clogged up with carbon and some brake cleaner washed through helps free things off. 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 Air leaks are very temperature dependent as gaps can open or close up as things expand with heat, so the weather and engine temperature can effect them.
Customer: replied 1 year ago.
Has brand new idle air control motor and have visually checked every inch vacuum hose for cracking loose fitting or diconnected lines.
Expert:  Matt replied 1 year ago.
Hello OK a visual check is good but I'd really reccommend the method I've mentioned for locating leakseither that or a smoke test
Customer: replied 1 year ago.
I usually use contact cleaner for an air leak test.
Customer: replied 1 year ago.
Airflow meter located in snorkel before air box?Mass air flow sensor bolts on the throttle body and has only electrical connections.
Expert:  Matt replied 1 year ago.
hello thats correct, the MAF meter is part of the air inlet ducting and should be located just after the air filter box
Customer: replied 1 year ago.
You mean just before airbox?
Customer: replied 1 year ago.
Is this also known as intake air sensor?
Customer: replied 1 year ago.
Or intake air temp sensor?
Customer: replied 1 year ago.
I checked for leaks on ALL vacuum connections-Zero.Connectors on air flow device located in air inlet snorkel are clean and tight.Still stalls after idling for a few minutes after warm-up.Will re-start perfectly.Run and die again after extended idle.
Customer: replied 1 year ago.
So far you have provided me with no useful info at all.will be seeking full refund.
Expert:  Matt replied 1 year ago.
Hello OK
This could be a wiring issue as things tend to expand when hot and its possible a poor or partial electrical connection is being pushed apart on one of the major sensors so check the connection plug and wiring to the following;Airflow meterCrank position sensorCam position sensorO2 sensorThrottle position sensor Also worth checking the connections to the fuel pump for the same reason - unplug each in turn and give them a good squirt of switch / contact cleaner - Not WD40 and also unplug and inspect the main power relays and fuses for signs of overheating or corroded terminals - so the ones for the ECU and the fuel pump And also unplug the wiring loom connections in the engine bay one at time and inspect for corroded or recessed pins.

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