Basically after I've driven the Saph round for a bit and the engine has got nice and warm the engine will idle at about 1500 rpm. Also when this is happening the car will occassionally mis-fire. The mis-fire is more like a judder (similar to if you give the car some beans, then come off the accelarator quickly), it almost feels like it will stall but only lasts for a fraction of a second. This happpens at all speeds and rev ranges. Now the high idle and mis-fire comes and goes throughout a journey it can come and go 3 or 4 times over a 30 minute drive but one never happens without the other. If the car mis-fires, then I dip the clutch I can guarantee the revs will only drop to 1500 rpm.

I was advised it would more than likely be the phase sensor or crank sensor however I have had both replaced today with brand new ones and the problem still persists.

The car had a full service 9 months ago (plugs, fuel filter etc). It is totally standard engine wise apart from a Mongoose exhaust and has covered 78k and up until about 3 months ago never missed a beat.

I also had the garage check the earth points today and they have said there is nothing there that causes them any concern.

Please can somebody help me get to the bottom of this as I am mega pissed now and just want it sorting. This car hasn't missed a beat in 3 years of ownership and this is really starting to get me down.

Any advice much appreciated

 

Whoever advised you about it could be the phase or crank sensor, would be better off, not advising anyone of anything.
It sounds like a sticky ISCV, quite normal, just needs a good clean with carb cleaner then spraying with silicone to keep nicely lubed.
This is the sensor on top of the throttle housing with a two pin plug going to it and held on with a metal plate around it's base a with two screws.
Failing that could be a sticky throttle cable.
tabetha

 

Sounds like a defective coolant temp. sensor to me.
I had exactly the same problem with my own car.
Replacing the coolant temp sensor cured it.

 

Hi mate i had a similar fault on my car. When it was getting warm the engine used to misfire. I changed the water temp sensor and it was fine.

 

Sorry I really should try and slow down a bit, then I'd read the WHOLE question!!
Yes I agree about the cts!!
tabetha

 

Thanks for the reply and help offered

Out of interest, does that mean I should ignore your initial diagnosis and go with getting a replacement CTS?

 

Thanks


Thanks

 

I seem to only be able to find this kit with the CTS included

http://cgi.ebay.co.uk/RS-COSWORTH-YB...QQcmdZViewItem

Would you recommend changing them all anyway, or just look out a CTS and not bother with the others?

 

We are all on here to help each other out. If i know the answer to any of the questions i try and help out. Tabetha is the boy though,he knows his stuff. A mate of mine said he has seen the water temp sensors on Ebay for around 10 quid. The one i bought was 25 quid.

 

thats funny because the phase sensor sorted it out on my one!thats why i advised him could be the phase sensor!

 

soz to hear the phase sensor did not sort it paul!did they not check it out then before u took it?

 

No mate, I didn't have time to get it down to be looked at and thought as I'd already bought it and the crank sensor I'd just get them to change them anyway.

Back down again next Saturday me thinks!!

 

who fitted them ?

 

it could be a number of things but could be air related and very simlar to a problem i had once and it was the idle speed control valve that had developed a mind if its own.
a quick check just to isolate the problem is to simply disconnect the iscv plug when the engine is acting up. if nothing happens then give the valve a few taps. if the revs drop off then you know where to start.

 

Matt Lewis sells the sensors(CTS) seperately, it is a good idea to change it every couple of years anyway.
You could always buy a resistor(about 10P) and insert in the CTS plug so that the engine gets a fully hot signal, the resistor should be between 0.50K ohms to 0.30K ohms.
This wil simulate a warm/hot engine signal from CTS, or better still buy yourself a RESISTANCE WHEEL, for diagnostic work, about Ł6/8, few leads, job done.
tabetha
MATT LEWIS 01922 692424

 

with a vehicle of this sort of age you might as well change all the sensors including the tps

 

Sensors all changed this morning and everything is now sorted.

Thanks again for the spot on advice ppl

 

glad its sorted. nowt worse than when they act up