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Discussion Starter · #1 · (Edited)
Hi, can anyone help please. I have an intermittent fault which is getting more frequent, the revs are limited to 1200 sometimes when in any gear, when the clutch is depressed the engine will rev freely. There is no engine management light, I have changed the fuel and air filter, added 'diesel detox' to the fuel, disconnected the maf sensor and the brake light switch appears to be ok.
Any help would be greatly appreciated, thanks lesmac.
 

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Hmm, sounds very much like the throttle position sensor might be playing up, although you should be getting the management light on. The TPS is the normal culprit for the revs being limited to 1200rpm, certainly was on my SDi! It would rev quite freely in neutral most of the time too, but try to drive off and it would stick at a high idle.

Unplug it, give the contacts and plug a good clean, then plug back in, and you might find your problems go away. :)
 

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Discussion Starter · #3 ·
Hmm, sounds very much like the throttle position sensor might be playing up, although you should be getting the management light on. The TPS is the normal culprit for the revs being limited to 1200rpm, certainly was on my SDi! It would rev quite freely in neutral most of the time too, but try to drive off and it would stick at a high idle.

Unplug it, give the contacts and plug a good clean, then plug back in, and you might find your problems go away. :)
Thanks FuzzWoof, I'll give it a try and report back.
 

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I'd double check the brake light switch, and also the bulbs too. If the TPS goes faulty then I think the revs hang at 1200rpm. If the brake light switch is faulty then the revs get limited to 1200rpm but the idle speed is still normal.
Try when stationary in neutral applying the footbrake and then the throttle at the same time. If this gives the same symptoms then I'd change the brake lamp switch as the TPS is quite expensive.
 

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Discussion Starter · #5 · (Edited)
I'd double check the brake light switch, and also the bulbs too. If the TPS goes faulty then I think the revs hang at 1200rpm. If the brake light switch is faulty then the revs get limited to 1200rpm but the idle speed is still normal.
Try when stationary in neutral applying the footbrake and then the throttle at the same time. If this gives the same symptoms then I'd change the brake lamp switch as the TPS is quite expensive.
Thanks E_T_V I've not been able to work on the car today, but will have a play over the weekend and let you know how I get on. By the way what would happen if I pulled the plug off the brake light switch to disconnect it?

I can confirm that the idle speed will always return to normal (800-900) the brake pedal has to travel about 15mm before the switch is made, the bulbs are OK, and the engine revs freely when in neutral with the footbrake applied, the only time the revs are limited is when in gear and driving. Will rev freely when clutch depressed.
 

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If you remove the plug and the problem goes away then its pretty conclusive that the switch is faulty or adjusted wrongly. However your brake lights won't work so drive with caution!
 

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Discussion Starter · #7 ·
If you remove the plug and the problem goes away then its pretty conclusive that the switch is faulty or adjusted wrongly. However your brake lights won't work so drive with caution!
thanks for your help E_T_V disconnecting the switch made no difference, the revs do stick in neutral and with the clutch in if you take the revs up slowly, so I have come to the conclusion that the tps is the problem.
 

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Discussion Starter · #8 ·
Hmm, sounds very much like the throttle position sensor might be playing up, although you should be getting the management light on. The TPS is the normal culprit for the revs being limited to 1200rpm, certainly was on my SDi! It would rev quite freely in neutral most of the time too, but try to drive off and it would stick at a high idle.

Unplug it, give the contacts and plug a good clean, then plug back in, and you might find your problems go away. :)
Thanks for your help FoozWoof, the revs do stick in neutral and with the clutch in if you take the revs up slowly, so I have come to the conclusion that the tps is the problem.
 

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Time to check it is adjusted right and the connections are all ok(they are very fussy about the adjustment) and then if it is faulty look for one from a scrap car as they aren't cheap new.
 

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i dont think you can just disconect the switch because when my went they had to rewirer it to last me a few days untill the new 1 came in as it wouldnt work as an open circit or closed 1 witch ever way round it was lol. so it might be worth buying 1 and trying it. i think there only £15 or so. it would be alot cheaper than a new tps.

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