Hmmmm how strange

[DodgyDave]

Just wondering if anyone's had a similar problem.
Well not really a problem, the car drives fine.
Its just when I'm slowing down and press the clutch the engine ticks over at 1500rpm. As soon as I stop it drops to the normal thousand???
If I slow the car down in gear to just above a thousand rpm and push the clutch the revs rise to the 1500 till I stop.
And it only is when I completely stop.
I can roll along doing only a couple of mph with the engine still at 1500???
It must be sensors as anything above tick over is ECU controlled, but does anybody have an idea what could cause this?

Thanks for any help

[tvrgit]

Mine does this after I disconnect the battery, for a couple of days - then the first time the engine gets really hot, it settles down for good until the next time the battery is disconnected (which I suppose resets the ecu)

I thought it was the idle speed control valve or the throttle pot, because if I disconnect the ISCV it doesn't do it - but I renewed both of mine, so it can't be. Might be a wiring fault?

Overall, though, I reckon it's a coolant temperature sensor - maybe it's trying to maintain a "fast idle" because the ecu is receiving a "cold" signal and adjusting the ISCV to suit. I can't be bothered playing about changing sensors - it's all right at the moment.

[DodgyDave]

tvrgit said:

Mine does this after I disconnect the battery, for a couple of days - then the first time the engine gets really hot, it settles down for good until the next time the battery is disconnected (which I suppose resets the ecu) I thought it was the idle speed control valve or the throttle pot, because if I disconnect the ISCV it doesn't do it - but I renewed both of mine, so it can't be. Might be a wiring fault? Overall, though, I reckon it's a coolant temperature sensor - maybe it's trying to maintain a "fast idle" because the ecu is receiving a "cold" signal and adjusting the ISCV to suit. I can't be bothered playing about changing sensors - it's all right at the moment.

Cheers TVRGit
I did disconnect the battery a couple of weeks ago and the car has only been back on the road a couple of days because both the master and his slave both died so that sounds very possible!
Gives me a good excuse to go out and drive the balls off it!
I did think it was running on choke but why does it immediately tick over at the correct rpm as soon as I come to a complete standstill.
Where is the coolant temperature sensor located on the engine?
Tempted just to renew every bloody sensor on it!!!!

[F908 Tim]

I seem to remember someone posting that this is correct when the engine is not yet up to full temperature, something to do with burning off excess exhaust gasses when the engine is cold and running rich until you come to a complete stop when the ECU returns engine to tickover.Disconnecting the TP would have the same effect.
It sort of made sense and I think everyones V6 does it until all is up to full operating temp, regardless of recent battery disconnection? my penniesworth.

[59fan]

Mine does the exact same thing, with the addition of some intermittent hunting between 500 and a 1000rpm. I suspected the idle control valve, but if you repleced that than perhaps you are right about the temp sensor.

Ian

[tvrgit]

F908 Tim said:

I seem to remember someone posting that this is correct when the engine is not yet up to full temperature, something to do with burning off excess exhaust gasses when the engine is cold and running rich until you come to a complete stop when the ECU returns engine to tickover.Disconnecting the TP would have the same effect. It sort of made sense and I think everyones V6 does it until all is up to full operating temp, regardless of recent battery disconnection? my penniesworth.

No, I know it's meant to do that when it's cold.

I am talking about when the engine is at full temperature - it does this for a few hot/cold cycles after the battery has been reconnected, as if it is relearning the fuel map or sensor ranges or something - then after it gets really hot (ie to the point where the fan cuts in) it seems to settle and run normally.

[DodgyDave]

I havent had the engine hot enough yet to see if it settles down (Fingers crossed)
But Im thinking it probably is going to be some kind of sensor liying to the ECU as 59fan is having the same problem and Ive disconnected the battery a few times and not noticed this before.
Is there anyway of testing the coolant sensor? I bet it wont be as easy as my mini, chuck the stat in a bowl of hot water haha

[59fan]

Still, at least you don't need double jointed fingers to work in the TVR's engine bay

Ian

[DodgyDave]

59fan said:

Still, at least you don't need double jointed fingers to work in the TVR's engine bay Ian

Haha, your so right
When I first popped the bonnet to look at the engine I thought YES Wooooo Woooooo
This is gonna be easy to service!!
The only thing Im tempted to get done in a garage is changing the gearbox and diff oil.
Even my mechanic mate said it would take him all day and dont worry because the oil looks in good nick anyway!
Yeah right I believe you haha

[grumpytvr]

Hi Dave

I had a similar problem with the car running at around 1500rpm on idle irrespective of engine temperature. I traced it to a faulty connection to the throttle pot. If you can get the car to exhibit the fault whilst stationary, pop the bonnet with the engine running and give the wiring loom running along the top of the engine a wiggle (if you'll pardon the expression)- Watch your fingers on hot bits and fan belts. If the idle speed drops then its likely you've got a wiring fault in this area. I replaced the idle control valve connector (as it was damaged on closer inspection) and throttle pot connector (as it was causing the problem!) and hey presto the idle speed dropped to around 850ish.

Cheers

Tom

[big Ian]

Mine did that after a particularly rainy day this winter (not may of those).
It cured itself! Dodgy wiring to the throttle pot get my vote.

[roy c]

When this has occurred in the past it's been an early symptom of TP failure, proved by unplugging the TP.

[tvrgit]

roy c said:

When this has occurred in the past it's been an early symptom of TP failure, proved by unplugging the TP.

Mine does it and TP and ISCV are both new. Once the engine has been through a couple of hot/cold cycles it settles down.

Unplugging the TP might simply produce an error code and bypass the fuel maps, so that the symptom goes away, but not the problem.

You might be right, I'm not saying you're wrong. Just that diagnosis might not necessarily be as simple as that. But it might be.

Ford ECUs eh? Don't you just love em?

[F908 Tim]

My other half away last week so used her car. Gave me the chance to test so disconnected the battery for two days and then took it for a drive in the evening. Once the car had warmed through,(Temp guage half way from cold) the revs dropped back as normal.Tried it again later in the week... normal again.
Mine will only keep revs up at 1000 when cold and rolling to a stop.Then drops to 800 directly you stop.When warm it drops to 800 directly you start to coast.
Wiggle those wires about in the front wiring loom, suspect they may have cooked or have a bad connection to sensor?

[DodgyDave]

F908 Tim said:

My other half away last week so used her car. Gave me the chance to test so disconnected the battery for two days and then took it for a drive in the evening. Once the car had warmed through,(Temp guage half way from cold) the revs dropped back as normal.Tried it again later in the week... normal again. Mine will only keep revs up at 1000 when cold and rolling to a stop.Then drops to 800 directly you stop.When warm it drops to 800 directly you start to coast. Wiggle those wires about in the front wiring loom, suspect they may have cooked or have a bad connection to sensor?

Well something must be a miss then, mine is ticking over at 1200 to 1500 rpm then dropping to a 1000 when stopped.
I guess Ill start with the temp sensor then the TP and if that doesnt cure it Ill start scratching my head again.

[johns3]

exact same thing is happening to mine now. The master and slave cylinder also were leaking. Turns out the friction material on the clutch is virtually non existant now too so lots of cash needed.

[F908 Tim]

I know i have recounted this before,
but at risk of being a bore

When mine did the same I changed the TP,then the air-bypass valve,then the water temp sender and then the petrol temp sender,lastly I changed the front wiring loom for a better replacement breakers one.
Somewhere along the line the combination worked...

I think it was probably the TP in combination with the loom that sorted it. My old loom was pretty shabby and the wires brittle.
Mounted the replacement well off the head so it did not get so hot,and made a rubber cover flap over the TP.
Fingers crossed,...that was a couple of years ago and she has been fine since.

[DodgyDave]

johns3 said:

exact same thing is happening to mine now. The master and slave cylinder also were leaking. Turns out the friction material on the clutch is virtually non existant now too so lots of cash needed.

Weird, ive just had to change my master and slave.
They cant be connected.............Can they????

[DodgyDave]

F908 Tim said:

I know i have recounted this before, but at risk of being a bore When mine did the same I changed the TP,then the air-bypass valve,then the water temp sender and then the petrol temp sender,lastly I changed the front wiring loom for a better replacement breakers one. Somewhere along the line the combination worked... I think it was probably the TP in combination with the loom that sorted it. My old loom was pretty shabby and the wires brittle. Mounted the replacement well off the head so it did not get so hot,and made a rubber cover flap over the TP. Fingers crossed,...that was a couple of years ago and she has been fine since.

Well if I do the water temp first, then the air by-pass valve then TP, leaving the loom till the next owner We can see what that cures if anything.