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Rough Running 3.9


Mean Green

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Hello all, the saga continues....

As first posted on the "old place" a few weeks ago my newly acquired 3.9 auto Rangie has a couple of running problem. It had stood for best part of 2 years before I bought it, but has since clocked up about 3000 miles.

It hunts wildly at Idle, ranging from almost stalling to idle at 2000 rpm. It drives fine on the open road, pulls well and everything seems to be in order, but when you pull up to a stop - like at a junction- the revs die and it almost stalls (sometimes it does stall). It can be cured by putting it into Neutral, after a few secs the revs recover to about 1500-2000rpm then drop back to normal.

As far as I am aware it is standard except for a K&N and full SS Sport exhaust.

The problem is much worse then the cooling temp sensor is plugged in, so much so it is almost impossible to drive in traffic.

So far I have tried the following....

Full Service (oils, plugs etc)

Replaced HT leads

Replaced Coolant temp Sensor

Flushed all the carp out the fuel tank and cleaned filter on pump

replaced perished vacuum hose

Replaced Road Speed sensor

Swapped Stepper motor for another

Re-attached Dizzy Bobs (they were flapping around not doing much)

Swapped ECU for another

I think this is everything.

I really need more suggestions as I have started the LPG installation but would like it running OK on Petrol before plumbing in the gas.

Help!! pleaaaaassssseeeeee

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Sorry if it's already been suggested over in "the old place", but have you changed the ECU temp sensor? It's the one at the front of the inlet manifold, just to the right.

Yes, at least if you mean the Coolant Temp sensor, located just behind the dizzy.

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Negative to both.

Not re-checked the timing since the dizzy was done. Tonight's job I fear.

And forgot about the fuel pressure. How do I check it again? (damn those LRE folks closing the site when I need to use the search facility!!)

Oh if only it was a Tdi :D:P

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Get out there in the cold & dark :P

The fuel pressure is quite sraight forward if you have the tools. The tools consits of a T piece that will fit in the line at the fuel pressure regulator connection O/S rear next to plenum, with a guage on it range of around 10 bar max. Stephen might have one, I lent mine to someone & never got it back.

I have a very fancy test kit but it's under a whole bunch of stuff & you would need a week to read the instructions. Should be around 2.5 - 3.0 bar and fairly steady, better check RAVE just in case.

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The fuel pressure is quite sraight forward if you have the tools. The tools consits of a T piece that will fit in the line at the fuel pressure regulator connection O/S rear next to plenum, with a guage on it range of around 10 bar max. Stephen might have one, I lent mine to someone & never got it back.

Don't forget to release the fuel pressure before splitting the pipe, otherwise you'll cover yourself in petrol, which ain't generally a good idea!! ;):D

Easy enough to do, pull the fuel pump fuse out and start the engine up, it should only run for a couple of seconds... job done :D

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Get out there in the cold & dark :P

Cold and dark!!

I'll have you know I didn't build a garage with enough lights to be visible from space to work in the dark! (I got a sparky that you and I both know to fit "what he thought I needed" by way of lights!!! - he got a bit carried away!)

Cold... hmm complared to where you are possibly... here it is positively tropical!

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I haven't been on here for a few days and all I can find here now is abuse!!

Niall - no I do not have your pressure thingy (TDis don't need ponsy thingys!).

Greeny - Your garage lighting was carefully calculated and based on a working example - and then reduced when some inconsiderate person (you!) put a damn great roller shutter in the way.

Too many big words - need to lie down now

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I haven't been on here for a few days and all I can find here now is abuse!!

What makes you think that's going to change?

no I do not have your pressure thingy (TDis don't need ponsy thingys!).

Remember that when your Ponsy Fuel Injection Pump cr@ps out :P I wasn't implying you had purloined it, just that you might have something suitable, you certainly have a selection :rolleyes:

need to lie down now

On the job again then :lol:

Drop me a line I need to ask you a few questions.

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IGreeny - Your garage lighting was carefully calculated and based on a working example - and then reduced when some inconsiderate person (you!) put a damn great roller shutter in the way.

Now I am not going to comment about anyone I know trying to fit a 6 foot light into a 5 foot space..... :blink::unsure::lol:

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Mine did this at first, so I replaced the idle valve, this did bugger all except cost me >£60, then I took of the stupid 'sports' exhaust and this improved matters no end, still not right though, so I took off the K&N, put back the original airbox and pipework and hey presto it ran like a dream ever since. I guess the ECU doesnt know what to make of the changes to air inlet air pressure and exhaust back pressure drop with the sports system. Go standard, or at least try it.

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Quote from RPI

"This change in emissions (High CO and HC) is why most mechanics would be incorrect when they advise that your carburetion or ignition is in need of attention, when in fact the problem is more likely to be camshaft wear, along with erratic ignition and cam timing due to the timing chain stretch. "

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Interesting quote from RPI - needs further investigating!

update - swapped AFM for another - no change, although it is not known 100% that this AFM is OK (Simon I might still be up for yours at some time!)

Also tried taking the K&N off and putting the original back on.... yep ... no change!

Next on the list is to pull all the pipes off and check for cracks/holes or perishes! i have already had to change a couple of fuel pipes due to them being perished, so I suppose anything is possible.

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I hope it's neither worn camshafts or stretched timing chain. My baby hasn't even got 64000 miles on the clock. Looking through the oil filler, everything is a light shade of brown, which would normally indicate very little general wear. Plus it has oil changes every couple of thousand miles...

Anyway, have a list of things to try as long as my arm :)

Cheers,

Chris

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