Throttle position sensor issue?

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27 May 2003
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Hi all

Ford Focus Mk1 1.6.
Can a faulty Throttle Position Sensor cause the rpm to increase when moving in neutral in the period of wanting to go up or down a gear?

I ask as if I'm in a gear at say 2000rpm and put the clutch pedal down, in that period the rpm creeps up, where as before it would immediately drop.

As a test I coasted at 25mph from 3rd gear and the rpm kept creeping up to over 3500rpm until I had to brake and drop down a gear.

A new Idle control valve was put in recently due to some rough idling and cold starts but no issues with starting or idling now. When stationary and I rev the engine it immediatly drops to normal idle rpms. Possibly crap replacement ICV?

I've tried an OBD scan and no errors are coming up.

However, a new sensor is a tenner so might just try a new one anyway.

Ta
 
Funnily enough my previous mk.2 1.8T Focus had a similar issue. Garage quoted me around £50 to fit a new throttle component. Though I traded the car in before I ever got it fixed!
 
Phil W said:
Do revs increase or just hold? Could be a sticky throttle body.
Click to expand...
Sticky throttle is unlikely to cause a steady rise in revs. A cable throttle, which I think a MK1 focus has, is relatively easy to do a manual throttle sweep check with a hand, and the inlet pipe removed.

Electronic throttles may open with the ignition on and engine not running, but requires either a helper to witness or a camera recording the movement. Modern vehicles with stationary rev limiters may not fully open, so the full range of motion can't be checked.

Engine temperature may factor into a sticky throttle fault.
 
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Thanks all, think I sorted it, however to answer the questions, possibly to help anyone else in a search in the future......

MatteH Oxford said:
I'd be looking at the clutch switch potentially, by coast are you referring to having the clutch down whilst in gear? Or selecting neutral and clutch up?
Click to expand...

It was either, coasting with clutch up or down.

Phil W said:
Do revs increase or just hold? Could be a sticky throttle body.
Click to expand...

Revs were increasing but I didn't see what limit, just that it was at around 2000rpm and crept up to around 3500rpm and stopped it there.

FIX:
I had a hunch about the new ICV installation.
I did one years ago myself (2 min job) and reset the ECU to make the new ICV learn the engine.
I disconnected the battery for a while to do the reset, let the car sit at idle for a few minutes and it sorted out the whole issue. A few test drives and around 40 miles of driving later, the issue appears to have gone.
So I'm guessing the garage didn't do this reset and as such the rpms was so erratic?

Got a spare TPS now if anything comes back and could swap that of need be. Fortunately that's also a 2 minute job as it's right the front of the engine bay on the throttle body.

My chariot lives another day!
 
Moving while out of gear can confuse the ecu, keeps getting a signal from the speed sensor that dosent match the other info from the engine. It will increase the engine speed, normally I would only worry about it if it was doing this at idle then remove throttle body and strip it , soak in a cleaner and clean all the componants.
 
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