Will the speed sensor affect mileage?
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Freshman User
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Will the speed sensor affect mileage?
I need to repalce the speed sensor on my 99 ranger. The apeedo doesn't work until you are over 75 mph and the ABS light is intermittantly on. Will the sensor affect the MPG as well? How about the overall running of the vehicle? I don't notice any shifting problems but MPG is out the window....Thanks
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Joined: Oct 2005
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From: Reno nv
probably.
VSS failures can cause the pcm to go into a "limp" mode and while it may still run OK, performance isn't going to be tuned to conditions actually in the car.
might be rich, delayed shifts, abs/airbag may not work, cruddy fuel mileage, etc.
VSS failures can cause the pcm to go into a "limp" mode and while it may still run OK, performance isn't going to be tuned to conditions actually in the car.
might be rich, delayed shifts, abs/airbag may not work, cruddy fuel mileage, etc.
Logistics Pro
Joined: Jan 2002
Posts: 4,907
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From: suburban atlanta
A failed speed sensor can really confuse the ECM, especially if you have an automatic trans. With valid rpm, throttle position, temp, throw in whacko speed readings and the ECM will drop out of torque converter lockup. Guaranteed. Watched the rpm's fiddle holding a steady 65 mph. They'd go up 2-300 rpm, then drop back, then rinse repeat.
Got an aftermarket, and the trans worked fine. Mpg improved back to where it had been. Engine temperature went back down too. That lockup truly makes a difference.
A similar, well different, symptom is caused by a TPS with dropouts. The trans will unlock the TC because it thinks the throttle is closed, the fuel will stutter off and on, but you'll still go down the road.
tom
Got an aftermarket, and the trans worked fine. Mpg improved back to where it had been. Engine temperature went back down too. That lockup truly makes a difference.
A similar, well different, symptom is caused by a TPS with dropouts. The trans will unlock the TC because it thinks the throttle is closed, the fuel will stutter off and on, but you'll still go down the road.
tom
Logistics Pro
Joined: Jan 2002
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From: suburban atlanta
DisturbedESV I read somewhere that the later model speedos can be reset or recalibrated a few times - like 4-5?? - to take into account a different tire size or a replaced differential with different ratio than original.
When I yakked about a failure, I meant one that gave wildly inaccurate information. The sensor that went blammo was in the transmission, transferring rotational motion to the cable that ran to the speedo, and generating a waveform to send to the ECM indicating velocity. It was in an 87 Sable, and I could watch the tach jump up and down all the way home from Florida. If you change tires/driveline, shifts and lockup may not occur as you expect. ABS and anti-skid could also be affected. I am not an engineer...
tom
When I yakked about a failure, I meant one that gave wildly inaccurate information. The sensor that went blammo was in the transmission, transferring rotational motion to the cable that ran to the speedo, and generating a waveform to send to the ECM indicating velocity. It was in an 87 Sable, and I could watch the tach jump up and down all the way home from Florida. If you change tires/driveline, shifts and lockup may not occur as you expect. ABS and anti-skid could also be affected. I am not an engineer...
tom
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