Surge when under load??

Funrover

Expedition Leader
Rig: 1993 Range Rover LWB
Engine: 4.2

Did the head gasket job about a 6 weeks ago, while there also cleaned up the stepper motor.Here lately it seems to have a surge issue in the 2000 - 2400 RPM range while on a climb. Seems most common on a sustained climb, worse when colder. Normally I can give it gas and it'll downshift and be fine, this morning however that was not the case. Also had one day, 2 weeks ago, where it did not want to start, however you could smell fuel was getting there. Then after a quick bump it started right up.

Thanks for any help/tips
 

Funrover

Expedition Leader
Well i just had to go out and use the Rover to tow another rig home, did just fine, afterwards went up the hill to get gas, and it was surging pretty bad, seemed to have some bad hesitation. Would that still be O2?
 

Colin Hughes

Explorer
Stepper motor, mounted on rear of plenum, flame trap, on pass side valve cover and the hose from it to the plenum. With a RRC, it's a case of working through the engine bay. I had one one time that kept trying to stall turning right, turned out it was the coil on the inside fender.
 

Funrover

Expedition Leader
The hoses are all new, I cleaned the stepper. I did tonight find that wire o the condenser from the coil is destroyed. Will fix that since it is needed.
 

cosmic88

Observationalist
the stepper (idle air control valve) only comes into play when the vehicle is not in motion. The VSS tells the computer when the vehicle is not longer moving. then opens or closes the bybass valve depending on conditions. did the idle control screw get reset after the head job? it should have been...

The simple stuff can lead to that surging. More involved checks should be done after you eliminate the basics. Fuel Filter, Air Filter, Vacuum hose from the intake plenum to the distributor vacuum advance module. loose or cracked air intake hoses... downstream of the MAF.

After that stuff is confirmed to be new or clean... you could be looking at fuel pressure / fuel pump. since this issue is occurring during load and normal RPM it could also be timing related. After the headjob did you set the timing personally or a garage?

Also, I assume you checked the error display under the passenger seat and it is showing nothing?
 
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Funrover

Expedition Leader
So a quick update. The fuel filter was bad (Forgot the K.I.S.S. method) as well as timing being off. However there are other issues also being taken care of. Front seal, timing cover seal, etc etc.
 

cosmic88

Observationalist
better late than....

Just happened across this thread again. Good to hear it was the simple (not expensive ) stuff.
 
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