Isuzu trooper 3.2 petrol,1993 - Wont slow Run, Engine Light On.

Hi All, Can anyone offer any advice to this strange problem I am having ? Any suggestions greatly appreciated. Rgds s
Symptoms are: vehicle starts normally and runs normally on my 25km run to work in
the cool of the morning.temp 20deg C and Speed 80kph In the afternoon, temp 30deg C. It starts normally and runs normally for the first 20 minutes after which the "check engine" warning light often comes on and the engine will not slow run when the vehicle is stopped in traffic. If I then switch the ignition off completely and restart the engine, the warning light goes out and all becomes normal again. While this is all going on,the speedometer often stops working and will start registering again when it feels like it. I tried driving it home deliberately slowly at 70kph and at this speed all worked normally. Another thing I noticed was that if I accelerate away from a standing start with the revs getting up to three thousand or above in first gear, it often will not slow run afterwards. On the occasions when the engine does not stop entirely the rpm will hunt between 200 and 1100 RPM. The engine has been top overhauled runs very well at normal cruising speed and runs cool. The cooling system has been flushed,has new thermostat and new water pump. Oil pump and pressure sensors all recently replaced with new parts. New petrol pump and new petrol filters recently fitted.New timing belt plus all other belts renewed. Temperatures , pressures and alternator charging are all spot on. The fuel injection system has been checked cleaned and adjusted by the isuzu agents here in Doha.(or at least they charged me an enornmous bill for this work.) New spark plugs fitted. What is the solution?
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steve wrote:

likely needs FPR replacement
see http://forum.planetisuzoo.com/index.php as the NG is mostly dead
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