Jumpy Speedometer

[rionredinger]

I have a 94 Ford Escort the original motor had 348,000 miles on it before I blew it up the new motor has 70,000 miles on it only 5,000 of those have been put on since I put the new motor in. No matter, i have had a problem reading the speedometer because it jumps around all the time. For example it will be jumping between 80-90 mph, what would cause this? I thought maybe it is just worn out and maybe I should replace the whole unit. Another problem that bugs me is that the idle is screwed up and I have had the timing belt adjusted but it still does the same thing. Help me out I'm lost. Thanks in advance.

[josmith]

Usually a spedo will jump because the cable is bad or needs lubrication. I don't know what you mean about the timing belt. They should be replaced at aronud 70k but other than tension there is no adjustment.
Idle and tuneup adjustments should be in the service manual.

[Externet]

Hi.
This will be the nuts part of Nuts&Volts.
Remove the speedometer cable form inside its jacket and straigthen it with your fingers while keeping it hanged vertically from one end.
The cable has a kink due to careless overbending or hit.
Be VERY thorough to eliminate the slightest deformity you can sense with your fingers while spinning it and reinstall VERY carefully to avoid creating more kinks again. Lubricate with transmission fluid.
Miguel

[Bernius1]

It also may have an inductive speedo sensor & an electric speedo. In this case, check wiring for faults. If so, the komputer will read the sensor wrong, & trans./fuel/spark signals may be off.
Re: idle, clean the throttle plate and surrounding bore, & check the komputer with a scanner for error codes. Also, use a 10 Meg voltmeter when checking the oxy sensor. Should be .5v to 1.5v hot.

[dacflyer]

speedo sensor might be dirty also,,causing eronious errors too...if it has one...just advising... friend had a car do this once...sensor couldn't see the emitter
they cleaned it,, worked fine then...hope this helps...

[rionredinger]

Thanks for the idea's I think I'll work on it tonight!!

[Edd]

Tux…the Magic Penguin :<p>One more slant on the speedo problem that I did not see mentioned, considering the unit is the conventional spinning magnet inducing eddy currents into your aluminum disc or cup that couples to your meter pointer.. Since the speedo cable is a spiraled bundle of hi tensile wires in the order of aircraft cable ,what I have found in the past to cause that problem is for a peripheral wire in the cluster , typically on the apex of a bend in the routing of the cable, to snap and break after eighty six thousand four hundred and ‘lebenteen cramped revolutions..The pointed end then splays outward and gets engaged into the convoluted outer housing resulting in the the cable builds up rotary tension until such time that it springs free with a resultant wild spin of the cable and a fast/ intermittent/ high reading of the speedometer display.
If it were a kinked cable typically the cause /effect should have been noticed after the unit was worked on, however that cable is rather well armored in its outer housing, except possibly in the case of violent manhandling. My lubricant of choice is pulling the cable and working on a covering of molybdium disulfide by virtue of it being as slippery as
greased owl feces and also its cohesivity and temperature specs.
I remain Puff the Magic Dragon ….or…..
73's de Edd
[email protected] ............(Interstellar~~~~Warp~~~Speed)
[email protected]........(Firewalled-Spam*Cookies*Crumbs)
(However in lieu of my 90% system down time in conversion over
by Comcast…more apropos would be:
[ UNSTELLAR !~~WARPED !~~SPEEDLESS ! ]