WG 2.7 CRD Rough idle hunting problem

[Yes we bought one]

Hi

I have done a truck load of research now if anyone can shed some light please do. Car done 190000km injectors replaced by previous owner. i have the receipt however number one has tooling marks so may be original.

Car has always started fine and still does however it hunts about 100rpm when cold in the morning. It has occasionally done it warm but only a couple of times. i hold revs between 900 and 1000 for 5 to 10 seconds and everything seems fine. Should the fuel pressure solenoid the one at the back of the rail "close" when the car is off? i can draw fuel through the rail via the return hose with a vacum pump. Should i be able to do this?

There are a number of very cluey people on here so i am hoping someone can shed some light as to what further testing i should do.

Thanks in advance

[markredgum]

I think small air leaks are a common issue with this vehicle.
As the pump is on the engine rather than in the fuel tank it can often suck in a bit of air.

The suggested solution is to check for leaks and replace old o-rings on the various hoses.
Unfortunately, replacing the O-rings often results in snapping off brittle fittings, which then requires replacing the hoses themselves.

Personally, I just live with a bit of hunting from a cold start. On my vehicle it soon goes away once warmed up. I have a small can of start ya bastard in the vehicle - just in case

I sure the more experienced hands will provide more detail on other possible causes.

Cheers

[fester]

Another easy thing to eliminate from the list is the EGR. It can be turned off for a couple of dollars. Read up on it in the 2.7 sticky thread on the front oage. EGR only operates at idle and light throttle.

Get rid of the EGR and check your codes through the odometer and we can follow from there but orings is another cheap thing to eliminate. If you go carefully the fittings aren't too bad.

[Yes we bought one]

Thanks for the replies. I have already electronically bypassed the EGR as about a year ago the solenoid threw a code and limp mode resulted. It has codes 702 703 and 1685 I think I may have created the last one by flicking key too quick to retrieve codes but who knows. Trans seems fine so I am assuming they are not related issues 703 I have not seen before but could have resulted due to recent removal of electric brake module. MIL is off and car runs fine apart from hunting.
Cheers

[bodgie]

Originally Posted by Yes we bought one

Hi
Car has always started fine and still does however it hunts about 100rpm when cold in the morning. It has occasionally done it warm but only a couple of times. i hold revs between 900 and 1000 for 5 to 10 seconds and everything seems fine.

It wouldn't hurt to check the glow plugs, although I wouldn't expect them to introduce hunting just a rough idle.

Try cleaning your MAF as if it is oiled up it may not be operating as effectively when you first start the car.

Originally Posted by Yes we bought one

Should the fuel pressure solenoid the one at the back of the rail "close" when the car is off? i can draw fuel through the rail via the return hose with a vacum pump. Should i be able to do this?

Thanks in advance

This is the fuel pressure regulator and I wouldn't expect it to be closed when the engine is off.

Jason

[Yes we bought one]

Maf has been cleaned along with inlet temp sensor. Do I need to remove the glow plugs to test them? What one calls hunting another calls rough idle. It sounds like an engine with a huge cam in it lumping over. I replaced the o rings in the low pressure lines but still no improvement. May have to look at an injector leak test.
Cheers

[bodgie]

Originally Posted by Yes we bought one

Maf has been cleaned along with inlet temp sensor. Do I need to remove the glow plugs to test them? What one calls hunting another calls rough idle. It sounds like an engine with a huge cam in it lumping over. I replaced the o rings in the low pressure lines but still no improvement. May have to look at an injector leak test.
Cheers

It won't hurt to do an injector leak test. To me hunting is where the idle increases/decreases etc, sounds like you may just have rough idle if it is like an engine with a huge cam.

The glow plugs will create this situation particularly when the ambient temp is low. You can disconnect the plugs and measure the resistance of the glow plug, they should all be pretty close to each other. If one or two are different, chances are they are stuffed and need replacing.

Have you checked the fuel lines for air bubbles, you'll see it if there is a problem.

Jason