Rev's surging? Diesel.

[joshy]

Gday,

Ive got a Zd30 navara and it seems to have developed some sort of wierd rpm surge. Almost as if you were running out of fuel. Doesnt do it so much on idle, but if i hit the heat switch or driving along it is fluctuating 100-250rpm. Its got a lift pump and surges with or without the pump running. And does it wether the motor has just been started up or running for a few hours.
Any ideas would be great.
Cheers.

[V.W.Dave]

Is it a stocko or yours?
Does it do it more so when its at running temp or at cold start up?
Have you done a injector clean (the nulon stuff is ok)
Is it blowing any smoke at all? Start up or anything if so what color?
If it is a stock one what is it normally used for? as in is it a highway driver or a stop go work ute?
Does the problem go away if you have a lot of weight in it or towing a trailer?
Can you rev it out as in when it starts give the go go pedal a bit of a romp and it clears?

[joshy]

Its my pos.
equal between running temp and cold start.
Havent touched the injectors in anyway yet.
no more smoke then its ever blown, bit of black on start up.
And it doesnt go away if i rev it.


edit: only started doing it last time i took it for a wheel. And the couple of times ive started it in the shed since.

[V.W.Dave]

So its been doing it since your big role over?
Does it go away when you turn the heater off?
Since then did you have a good once over on the motor? Have a good look over the intake and make sure there aren't any air leaks.

Now I am only talking from my VW experience. I found the EGRs would get a little clogged up with some build up would that would cause the revs to fluctuate.

The things you put your rig through and the adverse angles it is put on it may be worth putting some injector clean through it. It is going to be a pain in the ass to get but well worth the effort, look up a product called One Shot. It is not sold in Australia. In my training with VW we spent 3 weeks in a diesel engine training course and they showed us some very detailed tests on different "additive" style diesel injector cleaners. (there were over 30 tested) The One Shot was hands down the best. Back in the states we called it goat piss because thats what it looked like and smelt like but its worth its weight in gold. I have seen it go into a engine running rough as guts with 500k on the clock and after one treatment it was running like it was a week old.

A second little secret I will share for the first time in 10 years. Cut off your fuel supply, run the engine till it runs out of fuel. Get a can of spray Silicone. With a warm to hot engine take the intake off (after the turbo) and spray a fine mist of the silicone into the intake. Then crank it over, the engine will start and run like normal keep it running like that using the silicone as fuel. Keep it running for between 20 and 30 seconds keeping the revs between 1300 and 1500rpm. Doing this does 2 things It makes it run a little "rich" doing this it burns off any extra build up on the valves and the silicone is also good for the valve seats. Be sure not to spray to much Silicone down its guts just keep it running.

That little trick is also a little trick if you have a diesel that will not start due to changing a fuel filter or air in the lines. It will start any diesel.

[joshy]

Yeah only since the big roll. Due for a service.
Its there when the heater is on or off or if im actually driving it.
Ive had a bit of a look over the motor for any major leaks, ill have to have a look n make sure theres no pinholes anywhere.

Ive grabbed some injector cleaner, see if that makes any difference at all.
Thanks.

[V.W.Dave]

If its only been since the role over I would be taking a few of the intake tubes off and intercooler off and looking if they need a clean out. With it being on its lid and laying on its side for however long. oil may have made its way into the intake.
Is the check engine light on? Even if its not do you know anyone that has a code reader? Being on its lid oil may have gotten into one of the wrong sensors causing your problems.

[joshy]

when it rolled it had enough momentum it kept going back onto its wheels, was on its side longer at TT. No engine lights on. ill give the injector cleaner a go and then maybe pull some pipes off.

[joshy]

small update. Couldnt find an air leak. gave it some injector cleaner. Took it for another run, went fine for the first 2 hours, then it started surging pretty bad. Started it up again yesterday, turned the lift pump off and it was struggling to keep running. So ill change all the fuel filters and see what happens, otherwise its probably the pump..