just bought a 98 gt for 4200 bucks,its got 100 thou on it and while im driving it the tach jumps all over the place then it will stick at 2900 no matter if your driving or idling.the car runs normal its just the tach needle thats doing this,not the motor.anyone else experienced this problem?if so what was the cause,im lost here.the car has been oiled sprayed,id like to kill the guy for doing that,and i was thinkin maybe some oil got into something it wasnt supposed to and screwed it up.any help
what the heck is oil sprayed? I never heard of that before or just maybe i have heard called something else. It might that the rpm gauge is going bad or it a sensor on the trans. I don't know if yours is elect controlled or not but if it is then it might be that.
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88 LX 50 Blue 5spd notchback
3:73 gears, true loc diff,
31 spline axles, Aluminum driveshaft
BBK headers, hi flow cat h-pipe, flowmaster mufflers
K&N, FMS B springs, energy suspension (everything)
It could be the throttle body is stuck open?
I would take it to your local Ford Dealership and have them
take a look at it and fix the problem/problems.
It sounds like an electrical gremlin to me. So the engine was sprayed down with oily stuff to make it look clean? Its possible that got into the wire connectors. If it was me I would degrease the whole engine bay and then disconnect the wire connectors and dry them out with a hair dryer or something and put them all back together with dielectric grease. If thats not it maybe its something called a tach driver? Not to sure about what it is or if a stock car it but maybe others will help.
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DHG #01434 Bullitt - full JLT intake, MGW shifter, Accel coils (I wish I had 4.10s, o/r H, tune)
Black 89 LX(the drag car) best 8.75 at 80 mph in the 1/8
97 Mountaineer V8 AWD
oil spray is where they spray the undercarriage of the entire car with what looks like used motor oil,sounds wonderful dont it?it looks even worse and it gets everywhere.they do this instead of undercoating sometimes for whatever reason.if it has gears i cant really tell,not like my the 3.73 in my 94.around town they seem stock but on the highway when the speedo says 70 im still gettin passed like im doing 50.so if it has gears installed they aint to steep.when i got it the guy said it was a stock car,never touched,heck it stiil has the stock mufflers.but he did say he pulled the 17 inch rims off it and put a set of 16 inch stock 5 stars on it,but i wouldnt think just the tire size would throw off the speedo that bad would it.i checked the tb,its not stickin at all.i guess ill go from there.thanks for takin the time to answer
My tachs doing that too. Except it doesn't stick. It works freely through its range. But it pulses it will read 3300 for a second and then jump to 3500 for a second or so and then read 3600... I have noticed this is even worse on hard acceleration. My car Is a 95 GT. I think the problem is a loss of signal. I think the tach has to recieve a signal in order to move either direction. Funny butits fine under 2900 RPM
tach needle jumps,then sticks at 2900 
