New owner armed with a question ....
Discussion
Hi all,
Just wanted to say hello as a new S3 owner. I'm not new to the TVR way of life having previously owned a 350 wedge so I understand/accept their ' undocumented features '
So far I'm very impressed, last time I sat in one was at the 1989 Motorshow and I was 13 .....
Having just taken ownership I have a question though ......
Idling ...... should it ?
Switch it on and it idles around 900rpm. Drive it, come off the throttle, and it drops to about 2000rpm and stays there for about 20 - 30 seconds before dropping down to 900 again, occasionally rising back up a little as it drops. I've checked that the throttle cable isn't getting caught on anything. I've also taken the idle stabilisation valve off, cleaned it with carb cleaner and replaced it. I've also cleaned the main multi plug connector between that valve and the main loom on top of the inlet if that makes sense but it's made no noticeable difference. I didn't take the actual stabilisation valve apart as I use the car everyday and didn't want to risk making it un useable as I didn't know what was inside it ........ 
Any ideas ?
Normally I would have searched and I apologise if it's been covered a million times before but it's a bit tricky at the moment.
Thanks in advance
Al
Just wanted to say hello as a new S3 owner. I'm not new to the TVR way of life having previously owned a 350 wedge so I understand/accept their ' undocumented features '
So far I'm very impressed, last time I sat in one was at the 1989 Motorshow and I was 13 .....
Having just taken ownership I have a question though ......
Idling ...... should it ?
Switch it on and it idles around 900rpm. Drive it, come off the throttle, and it drops to about 2000rpm and stays there for about 20 - 30 seconds before dropping down to 900 again, occasionally rising back up a little as it drops. I've checked that the throttle cable isn't getting caught on anything. I've also taken the idle stabilisation valve off, cleaned it with carb cleaner and replaced it. I've also cleaned the main multi plug connector between that valve and the main loom on top of the inlet if that makes sense but it's made no noticeable difference. I didn't take the actual stabilisation valve apart as I use the car everyday and didn't want to risk making it un useable as I didn't know what was inside it ........ Any ideas ?
Normally I would have searched and I apologise if it's been covered a million times before but it's a bit tricky at the moment.
Thanks in advance
Al
Welcome to back to the fold!
Re the idling - most snags in this area seem to be solved by a new Throttle Potentiometer (Throttle Pot or TP). As to which replacement is best - you'll get a variety of answers.
I got mine from 'Tuneparts' (can't find link at mo). Worth a shot as they seem to fail at random intervals.
Re the idling - most snags in this area seem to be solved by a new Throttle Potentiometer (Throttle Pot or TP). As to which replacement is best - you'll get a variety of answers.
I got mine from 'Tuneparts' (can't find link at mo). Worth a shot as they seem to fail at random intervals.
I'm guessing if it is the TP, when you disconnect it not a lot will change! If you look at the 'misfire' threads below some guys haven't even got one connected. In that case I'm thinking the ECU is just using 'default' values for the TP readings. Handy if you can 'borrow' one rather than buy one to test but not sure if anyone near enough to you.
Mine did exactly what yours is doing, and I disconnected the idle speed control valve and it ran fine. Bought a new valve and that also worked fine when it was reconnected. I also replaced the throttle pot later for a separate reason.
Then I discovered that if I disconnect the battery, the ECU seems to reset itself somehow, and the engine idles too fast before it settles each time. So the symptoms you have, reappear on mine each time the battery is reconnected.
What I found is that, if I leave the car idling until the fan cuts in (ie until the engine has been through a complete cold->really hot cycle), the idle speed is fine after that, for weeks or months - until the next time I disconnect the battery.
So in my case, the problem seems to be a temperature sensor whose range has to be reset every time the ecu is re-booted. This causes the ecu to hold the ISCV slightly open because it thinks the engine is cold.
You'll find that nearly every engine running fault or misfire tends to be blamed on here, on the throttle pot or the idle speed valve, when in reality, there could be dozens of reasons, and disconnecting one of those two might mask the symptoms but not necessarily point to the cause.
Then I discovered that if I disconnect the battery, the ECU seems to reset itself somehow, and the engine idles too fast before it settles each time. So the symptoms you have, reappear on mine each time the battery is reconnected.
What I found is that, if I leave the car idling until the fan cuts in (ie until the engine has been through a complete cold->really hot cycle), the idle speed is fine after that, for weeks or months - until the next time I disconnect the battery.
So in my case, the problem seems to be a temperature sensor whose range has to be reset every time the ecu is re-booted. This causes the ecu to hold the ISCV slightly open because it thinks the engine is cold.
You'll find that nearly every engine running fault or misfire tends to be blamed on here, on the throttle pot or the idle speed valve, when in reality, there could be dozens of reasons, and disconnecting one of those two might mask the symptoms but not necessarily point to the cause.
See how it goes. If necessary, cleaning the ISCV is worth a try.
1. disconnect wiring
2. remove two 10mm bolts holding valve to throttle casing and remove (try to keep gasket intact!
3. two (very tight) screws hold valve onto solenoid - remove and watch you don't lose the rubber o-ring inside when you split them.
4. clean out the inside of the valve with carb cleaner. Hold the valve open by pressing the end with your finger while you spray. Wear gloves because it's bloody freezing.
5. clean out the two airways in the plenum with carb cleaner.
6. leave to dry (doesn't take long) and reassemble. Make sure that you have an airtight seal between the valve and the throttle body (business cards are ideal for making gaskets - ahem)
1. disconnect wiring
2. remove two 10mm bolts holding valve to throttle casing and remove (try to keep gasket intact!
3. two (very tight) screws hold valve onto solenoid - remove and watch you don't lose the rubber o-ring inside when you split them.
4. clean out the inside of the valve with carb cleaner. Hold the valve open by pressing the end with your finger while you spray. Wear gloves because it's bloody freezing.
5. clean out the two airways in the plenum with carb cleaner.
6. leave to dry (doesn't take long) and reassemble. Make sure that you have an airtight seal between the valve and the throttle body (business cards are ideal for making gaskets - ahem)
Thanks again ....
I took it off, cleaned the plenum and the valve with carb cleaner but I didn't take the valve apart incase springs and valves exploded into the street
I cleaned the connecting plug as well.
Put it back with a little gasket sealer and it was the same
I'll try the whole disassembly if letting it warm up doesn't sort it.
Is there any test that can check if the idle valve is working correctly ?
Cheers
Al
I took it off, cleaned the plenum and the valve with carb cleaner but I didn't take the valve apart incase springs and valves exploded into the street
I cleaned the connecting plug as well.
Put it back with a little gasket sealer and it was the same
I'll try the whole disassembly if letting it warm up doesn't sort it.
Is there any test that can check if the idle valve is working correctly ?
Cheers
Al
It's funny you should say that. I've just been out at lunch and ran it up to temperature then drove it and it was the same. I did have to blip the throttle a couple of times though to make the battery light go out ( another little issue 
) unless that has messed it up .... ?
So I disconnected it when I got back and tried it and it seems to work a lot better. I didn't have time to test drive it but it re started ok, returned to an acceptible idle but it wasn't struggling to idle ..... ?
As an aside, the fuel economy has being surprisingly good since I got it ( over 35mpg on a run ) so maybe it's been running too lean if the idle valve has been open all the time ?
Maybe it's been setup to ' accomodate ' an issue with the idle valve / TPS / air flow meter / day of the week / colour of the sky etc etc .......
Cheers
Al
) unless that has messed it up .... ? So I disconnected it when I got back and tried it and it seems to work a lot better. I didn't have time to test drive it but it re started ok, returned to an acceptible idle but it wasn't struggling to idle ..... ?
As an aside, the fuel economy has being surprisingly good since I got it ( over 35mpg on a run ) so maybe it's been running too lean if the idle valve has been open all the time ?
Maybe it's been setup to ' accomodate ' an issue with the idle valve / TPS / air flow meter / day of the week / colour of the sky etc etc .......
Cheers
Al
hargo said:
It's funny you should say that. I've just been out at lunch and ran it up to temperature then drove it and it was the same. I did have to blip the throttle a couple of times though to make the battery light go out ( another little issue ) unless that has messed it up .... ?
) unless that has messed it up .... ? Unusual feature of TVR S types (maybe all TVRs, I dunno) - they don't start charging until they have been over 2,000 revs. So the red light stays on, goes off at 2000 revs and then stays off. TADTS
tvrgit said:
hargo said:
It's funny you should say that. I've just been out at lunch and ran it up to temperature then drove it and it was the same. I did have to blip the throttle a couple of times though to make the battery light go out ( another little issue ) unless that has messed it up .... ?
) unless that has messed it up .... ? Unusual feature of TVR S types (maybe all TVRs, I dunno) - they don't start charging until they have been over 2,000 revs. So the red light stays on, goes off at 2000 revs and then stays off. TADTS
When I first got the S I booked it into an engine tuner/modifier just to give the engine a once over as the previous owner was a self servicer. I started to mention that you had to rev to over 2000 when you start it. He said that he was aware of that as the seirra 4*4 and XR4i was the same. He did explain why but it was to early in the morning for me to remember.
Edited by russ35 on Friday 20th October 17:02
russ35 said:
tvrgit said:
hargo said:
It's funny you should say that. I've just been out at lunch and ran it up to temperature then drove it and it was the same. I did have to blip the throttle a couple of times though to make the battery light go out ( another little issue ) unless that has messed it up .... ?
) unless that has messed it up .... ? Unusual feature of TVR S types (maybe all TVRs, I dunno) - they don't start charging until they have been over 2,000 revs. So the red light stays on, goes off at 2000 revs and then stays off. TADTS
When I fist got the S I booked it into an engine tuner/modifier just to give the engine a once over as the previous owner was a self servicer. I started to mention that you had to rev to over 2000 when you start it. He said that he was aware of that as the seirra 4*4 and XR4i was the same. He did explain why but it was to early in the morning for me to remember.
That's interesting - the same engine and ECU in the Granada worked normally - ie light off as soon as it started.
I did read somewhere why it does it but I can't remember - i just know it does.
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