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Matt
Matt, Engineer
Category: Nissan
Satisfied Customers: 20602
Experience:  BEng hons Mech engineering, worked in auto industry for 22 years on engine, transmission and suspension design
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Nissan hardbody 2.5 tdi not idling when cold

Customer Question

nissan hardbody 2.5 tdi not idling when cold
Submitted: 1 year ago.
Category: Nissan
Expert:  Matt replied 1 year ago.

Hello

I'd 1st
check the connections to the EGR valve, if either the vacuum pipe of electrical connection are damaged / corroded then the EGR can be on all time which certainly will hurt performance. Its also possible that its a fault with the EGR valve so its worth removing the valve and cleaning it out with brake cleaner, if it looks particularly clogged then replace it.

Customer: replied 1 year ago.
Hi no luck still the same
Expert:  Matt replied 1 year ago.

Hello

OK the next step is to consider changing the fuel filter as if this partially blocked this will reduce pressure at the main pump and it may have developed an air leak on the fuel supply pipe from the tank to the engine. The engine has no separate lift pump and relies on the built in one in the injection pump. If a leak has developed on the fuel suction pipe then air entering the system will air lock the pump.
Try pumping up the fuel using the hand pump in the engine bay on the filter housing, then crack off / loosen each injector pipe in turn while cranking the engine and getting an assistant to operate the primer. This will expel air from the injection side and the engine should fire up. The problem will be cured by checking the supply pipe along its length for signs of leakage and repairing any you find.

Also worth checking that the glow-plug relay is switching off as they can stick on and leave the glow plugs also on - on some cars this can force it into limp home

Also worth considering a bottle of injector cleaner into the tank as a clogged injector nozzle will reduce power and give poor combustion - the next stage on from this is to remove all the injectors and have them ultrasonically cleaned and flow checked

If the above are all OK then try checking for airleaks after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and leans the engine out causing rough running.As its a mechanical fault it tends not to turn on the fault light and you can sometime 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 around each joint in turn. If the engine rev's up you've found your leak.

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.

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

Expert:  Matt replied 1 year ago.

Hi

do you still need help?

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Customer: replied 1 year ago.
Hi Matt still no luck when you unplug cam or crank sensor vehicle idles
Expert:  Matt replied 1 year ago.

Hi

if the vehicle idles without the cam sensor connected and with the engine cold then I'd replace the sensor with a new part and check out the condition of the wiring to the sensor