ZD30 wont rev past 2000 RPM any suggestions?

[Gary65]

My ZD30 developed this fault without any warning, I took of from traffic lights and it would not go over 2000 RPM, holding full throttle it ran like it only had 2 cylinders, back off and hold under 2000 RPM and it runs normally. I managed to creep home and while I was sitting in the driveway I tried full throttle again. After a couple of small surges it suddenly went to full RPM, revved up and down normally. I thought that it had cleared itself. Had a coffee and came back to move it and the fault was back and won't go away. I checked the fuel filter, clean as. Changed the filter anyway, no change. No knocks or rattles, just feels like there is a governor limiting RPM to 2000. Could the EGR cause this??

[mudski]

How did you check the fuel filter? They are a sealed unit.

[Gary65]

I had a dirty fuel filter once before, when I drained the fuel from the filter into a clean dish you could see the muck, Anyway I put on a new filter anyway but it made no difference.

[mudski]

So assuming its not the fuel filter, things it might be is, air in the line from the filter to the pump, mass air flow meter is shot (doesn't seem like it to me though), the Throttle position sensor on the acc pedal has dirty contacts, can be cleaned, you need to drill a small hole in the housing just big enough to fit the nozzle straw in from a can of contact cleaner, spray and clean out. This may work, or replace the TPS. Could be a simple as a bad earth connection to the motor or to the body. Doubt it but its a ZD30, they carry on like a two bob watch about anything...

[the evil twin]

Try the easy stuff first... Clean the MAF sensor, disconnect the battery for 30 mins to force an ECU relearn, check all boost hoses etc for a boost leak then see if it still does it again.

Also a bit more info may help... how many K's on the vehicle, have you done any recent mods, how long have you had the vehicle, have you cleaned MAF in the past etc

[Gary65]

I have had the ZD30 for 10 years, motor rebuild about 5 years ago. Done nothing to it recently, only a crankcase breather filter and a Dawes valve fitted.
This happened suddenly. I pulled up for a red light, everything normal. Light goes green and suddenly it simply starts to chug and vibrate at 2000 RPM, drives normally below 2000 RPM. Feels just like the old hoof governor on a VW Kombi van.
I think it unlikely that the MAF sensor would cause a problem so abruptly and then clear and re appear but I will clean it anyway.

[mudski]

Dirty contacts on the TPS maybe


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[happygu]

Gary,

I am leaning towards the MAF being the cause, or possibly the TPS Sensor....but you might be better off backtracking back to the last thing you have done.

Maybe take the Dawes Valve out of the Boost Piping, and put it back to factory, to see if the valve is not performing as it should.

If this has happened soon after changing something, usually the best way to fault find an issue, is to backtrack.

[the evil twin]

Is it a Di or a CRD engine?