Engine Idle fluctuates.

Hi there, I’m having an issue with the engine idle in my 1993, KZH106, 4WD, diesel, auto supercustom. Sometimes I’ll be sitting in my Van at a paderstrian crossing or in traffic and the idle will start rising and lowering. But as soon as I put the throttle down it runs as usual. This issue has it caused any problems as such but I’m aware it’s obviously not normal haha. Any help is greatly appreciated. I’ll try get an update as to exactly the Rpm’s it’s sitting at and fluctuating too and I’ll post it up. Cheers

maybe tps

Does it sit at one RPM a few seconds, then drops to by a couple-hundred for a while before going back up - then repeat? if you have the aircon on, try turning it off to see if that helps.

If it does, it may be the idle control (that kicks in when the aircon adds extra load). The petrol has a vacuum valve that does that but I'm not sure how the diesel does it. So it could be as simple as a vacuum leak.

Hey mate,
Thanks for your help, I’ll look into it more. It happens mostly when it’s starting from cold. But yes that sounds about right, RPM sits for a few seconds then drops a couple hundred before going back up. This is something I haven’t dealt with before so I’ll have a look into remedies regarding a vacuum leak.

Something else to check - which I need to do - and that is to lift the engine cover and listen to / watch the AC compressor when it's warning up. (Assuming the revs problem only happens when the AC is on).

If the higher revs are when the compressor is running/spinning and then drops when the compressor clutch lifts, then it may be low refrigerant in the AC system (and the vacuum hoses are working properly - as the rev boost is cut/increased in line with the compressor switching on and off).