Rough idle

[mrMUMU]

Hi I have a isuzu mu 2.8lt with 235xxxkms, I have this constant rough idle at the lights or just on start up. Any ideas on where to start. I've taken it on long trips and it seems to be fuel efficient, and still has plenty of punch in her.
All pollution gear is connected.

Thinking
Tappets

Any help would be great

Cheers

[turnturn]

What revs is it currently idling at?

Injectors?

Is your air conditioning on? Is the fast idle actuator functioning correctly?

[geeves]

try placinf a thin aluminium sheet between the egr valves and manifold. A leaky egr valve can cause this.
Otherwise 1 low compression cylinder 1 bad injector a worn cam a worn pump can all cause it. Does it smoke or burn oil?

[mrMUMU]

Hi thanks for the replies

The engine blows a little bit of white smoke on start up, and then a bit of black when u take off. At the lights once the engine is warm it does seem to blow smoke but is still idling rough. It does use a little oil but nothing major.

Revs about 500-750

Air con off its a little better

Adrian

[WestOz]

I have a very similar problem with my 2.6l 4ZE1 1995. I have checked plugs, valve clearances, timing, vacuum hoses, replaced fuel filter, air filter, cleaned the MAFS, cleaned the Throttle Body and run a can of injector cleaner through (Toyota Stuff, which I am told is the best), all with very little or no change. Idle is steady at 900 rpm though it does vary slightly. I haven't checked compression, fuel pressure or the injectors, so could be one or more of those, she doesn't blow any smoke and seems fuel efficient (400km on a tank), she runs very nicely at all other rpms. Fast Idle works at cold start up and when Air con is switched on, so I believe those parts are working ok, though they do seem to leak a little vacuum when checked but it is very minor and a finger over the vacuum points makes no difference. I have not been able to locate the ERG valve and don't appear to have an exhaust gas take off on the exhaust or exhaust manifold that I can see, so not sure if its been removed or if there ever was one. Its not on the firewall end of the manifold which is where I think its supposed to be.

Any other thoughts? Should I pull the injectors and clean them in an ultrasonic bath with new filters and seals or am I looking for something else?

[slightlydodgy]

Chances are the issues aren't related the 2.8 being diesel and the 2.6 petrol