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2002 mercury sable dohc
The car wants to accelerate slightly on it’s own when it’s being driven down the road. You can let off the gas and it stays at speed on its own and sometimes accelerates. I can put it in neutral when it does this and watch the rpms rise on their own for about 20 seconds then return to normal. It attempts to continue accelerating like this on stops which I’m sure isn’t helping the brakes. I have access to a scanner with detailed information. There’s no check engine light on. The pedal itself doesn’t seem to be sticking. I’ve cleaned the throttle body. I’ve also unhooked the cruise cable in case it was binding or creating tension. That didn’t help. The throttle position rests at around 17% though I’ve read this can be normal. I’m not sure how to approach this any further. Any input would be appreciated. I’m familiar with most diagnosing methods. I just need some direction
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It’s seems to me that Ford/Merc TPS numbers are always up higher than I would think, though you might have a TPS that has a bad return on it, you might want to watch how fast the TPS numbers fall from WOT, which of course you can watch with the Key On Engine OFF ( KOEO ) See if it’s hitting 100% at WOT, and then modulate the throttle to see how the numbers react in real time. I’ve heard that the return spring can get janky on Ford TPS’s.
The tps only went up to a maximum of 92% on the floor WOT. It seemed to return decently fast but the obd scanner im using isn’t the fastest. The tps is only an idea. Any other thoughts?
Bump for help. You can be driving down the road and let off the throttle and it keeps slightly accelerating on its own. I put it in neutral and the rpms shoot up to 3500 for about 15 to 20 seconds then immediately back down to normal. I cleaned the throttle body. I didn’t consider vacuum leaks because itTruns perfectly fine otherwise and immediately returns to normal operation when the rpms drop back down
You can eliminate vacuum leaks by hooking up a volt meter to the tps. With the engine off, gradually open the throttle by hand and watch the voltage. Then immediately let go of the throttle to see if the voltage increases or decreases depending on the specifications for the car.
I’d be checking for sticking linkage. Also make sure the carpet isn’t binding up the accelerator pedal. You can check for a binding throttle cable by removing it from the throttle body and activating it. It should move smoothly and not stick at all.
I am NOT advocating you clean the throttle body, just check the throttle cable and linkage.
Good luck and please keep us updated on your progress.
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