Thread: V8 hesitation on acceleration

Clean stepper motor.
Check TPS has .32-.36 volts at idle.

And vacuum hose leaks...
Even fuel filter. Being colder runs richer when first started requiring more fuel.

Thanks Discovery 39.


Have cleaned stepper motor, but not the housing it sits in. Is this worth doing?


Did fear it could be the TPS, not the cheapest and most readily available part it would seem. Am I right to assume that you can measure this voltage with a normal volt meter? Or do I need someone with diagnostic equipment. If it is outside the.32-.36 voltage range I also assume its time for a new one?

You can clean the Inside of the stepper housing. Very much worth doing. Three bolts is all it takes to get the housing off. Or some carby cleaner accurately sprayed inside while revving.!!!
Also check the Vac hose while ya there!
The TPS can be adjusted if it doesn't meet the required voltage at idle, but it should be made sure that its voltage is smooth while manually manipulating the throttle throughout the rev range. Can be done with normal digital multimeter. Its max voltage at full throttle should be just under 5.0 volts.
Will have to check which colour wire to stick the probe on......
It is the Green Wire.

Got the multi meter out and initially measured a voltage low of .26V. I have now been able to adjust it up to .33V, simply by turning it slightly within the two support screws. Encouragingly now I have voltage range of .33V - 4.87V and appears to increase smoothly through this range.


I also pulled the vacuum hose off and I think it could have been the original. It was as hard as plastic and was loose on the adjoining metal pipes with a crack beginning to form at one end.


I also noticed that the Allen keys holding on the stepper motor housing were just finger tight and there was no gasket in between the housing and plenum chamber. Might be some leakage there as well.


Will get a new hose and make a gasket and see how goes.


Thanks

Nice one Heley.
Buy yourself a little bottle of Permatex Form-A-Gasket.
Just lightly brush some of that on, and do it all back up.

So how did you go mate?

Thank you for your interest Discovery 39


After completing the tasks I outlined in my previous post I would say there has been a definite improvement. Idle is now down to about 800-850rpm when hot, I suppose it could still go lower?


There is still a slight hesitation but only when cold and the engine overcomes this hesitation noticeably sooner than before.


I am thinking that the stepper motor may have seen better days and perhaps will need replacement eventually.


Thanks