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Idle and Revving

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Hi - I have a problem with my Ford Escort Cabriolet 1997 1.8 Zetec Petrol.  I found your website and thought you might be able to help.  I have owned the car now for 11 years.   In between changing gear the revs are sometimes holding.  Prior to this I had a new idle control valve fitted as the car was dropping revs and cutting out.  Since the replacement control valve, the revs can sometimes go way above normal.  The car ticks over at just over 10 but sometimes, during tick over, it can drop to 8.  All the pipes have been cleaned as well as the electrical connections.  The car has been under a diagnostic test with no faults, apart from slight wear and tear on the mass meter.  No more than expected of a car this age.  Car starts fine, no loss of power driving, temperature gauge is fine.  Sprayed pipework with carb cleaner.  No difference to the running.  The idle control valve has been changed twice just in case the original supplied was faulty (done by the garage). The ECU was disconnected for a hour  after the new valve was fitted.  I have been advised the clutch could be causing the problem but this had been replaced within the last 20000 miles. Any thoughts or ideas would be most welcome.  Thank you

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Have you checked all the vacuum hoses? There is a t piece at the back of the engine on the right as you look at it which tend to split. Also the one on the front right where it connects to the crank  case breather. If ok then try replacing the crank case breather valve. These can be troublesome as well.

Cheers

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Hi Paul - thanks for the tip - I will take a look.  I am so sorry I didn't introduce myself.  My name is Sharon and I've had my car for 11 years now.  Every year it passed it's MOT, sometimes straight through.  I have had escorts all my life, the previous one was an XR31 Cabriolet too.  I'll get someone to take a look and let you know.  Thanks!

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Hi Paul - my sincere apologies for the delay - I've been working away.  Thanks again for the information, I have replaced the crank case breather pipe as this was partially collapsed.   You'll see on the first picture I have attached,  a little dent in the hose which may have been part of the problem.The car is still revving but not as frequently as before.  Is the valve where the pipe connects at the front of the engine? Can this be cleaned in situ or does it have to be removed.  This is a very modern car for my partner who I have working on it!  He's more used to the Cortina's. 

The other pipe with the t-piece - could you tell me exactly where this is as I cannot locate it.   

Many thanks.

Sharon

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Hi Sharon,

Yes the valve is on the front of he crankcase and the pipe attaches to it. They just pull out with a pair of pliers. 

They are sometimes called clacker valves as they make a clacking noise when you shake them! I would just replace it.

Incidentally Cortinas had them too!

If you still have a problem then I would be looking at he speed sensor on the gearbox.

Let me know how you get on.

Cheers

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Hi Paul - I have removed the breather from the engine and all seems clean and rattles quite nicely. Without taking more stuff off the car, the pipe must go into a joiner to meet the pipe from the inlet? - do you know if there is another vale in that joiner? I have noticed the revving seems to be when the car is warm.

I haven't checked if there is a speed sensor on the gear box but the revving can appear when the car is stationary in the garage.  I am thinking because of this, the gear box sensor is OK. 

My only other thought is whether the throttle position sensor is at fault? Your thoughts would be very much appreciated.

Thank you.

Sharon

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Hi Sharon,

The pipes go around the back of the engine and there is a t piece which also splits and gives trouble.. this is worth a check.

The speed sensor is fitted on the gearbox where the cable attaches and the harness goes up on to the baulkhead to a triangular 3 pin multiplug. The purpose of it is to provide a digital square wave to the ecu to inform road speed. The idea being to avoid cutting out due to throttle snap shut. In other words the revs should hang up until the car stops. 

The problem with these hall effect sensors is they develop an internal fault which gives supply voltage interference to the ecu which in turn thinks the car is moving when it is not, thus giving the high idle speed. The only real way to diagnose it properly is to check for interference with an oscilloscope. 

You could disconnect the speed sensor for a bit and see if it cures it however the engine may cut out when slowing down.

Cheers

Paul

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Hi Paul - still no luck I'm afraid with finding the t-piece.  I have noticed when spraying carb cleaner onto the fuel regulator increases engine speed but pipe and housing all seems to be intact with no damage. Also, I am having trouble locating a TPS to fit - do you know if any other ford part number covers this.  The part number on mine is 95BF 98989 DA 7F10A.  It would seem the TPS on my car is different to the ones recommended on Europarts for example.

Any suggestions most welcome!

Thanks

Sharon

 

 

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Hi Sharon.

So the t piece in a bit lower down then on your photos. As you look at the engine feel with your right hand around the the top of the gearbox to the back of the head. Then it's just below.

The carb cleaner must be getting in somewhere if it causes the engine speed to increase so you have definitely got an air leak. Fix this first as you may find you problem will be fixed.

Why do you want to replace the tps???

Regards 

Paul

 

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Hi Paul. So sorry but really struggling with this t piece lol. What does it connect to apart from the head. Tks

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Hi Paul. At the front of engine/crankcase theres a breather valve between two hoses. Should this be one way? Front on, and looking at the crankcase it's to the passenger side 

Thanks

Sharon

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Hi Paul - to explain better (rather than my last post) I removed the valve again from the crankcase to make sure it was still free.  I noticed you can blow both ways through it.  Am I correct in thinking this should be a one way valve? 

Thanks

Sharon

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Hi Sharon, the T piece connects breather pipes at the back of the head on the passenger side.

The breather valve is an oil separator and there is no real way of testing it unfortunately. I would just replace it. 

Cheers

Paul

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Hi Paul - you have been so helpful and patient during this time.  I have now joined the club!!

I went to Ford parts to buy the breather valve (part number 1065894).  I could not buy this anywhere else and the one that was in my car, had no part number.  I am so pleased!  I have completed two decent journeys and the car is now as it should be - so thank you.  The revving had gone. It was the first thing you mentioned.  

Whilst I was at the parts counter, I asked to see the exploded diagrams so that I could get an idea of where the T-Piece is.  Apparently, my particular car does not have one.  Even the Haynes manual stated there was one but for some reason, not my car.  Very strange.

Anyway, a big thank you - proud to be a member!

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Glad to hear all is well and thanks for the update. Perhaps the breather system changes with the model year. 

Happy cabriotleting 😉

 

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