V8S Rich running update and poss Throttle Pot issues
Discussion
Hi
Well I gave everything I could possibly check a thorough check in line with the bible then when all was ok i conceded and took it to the experts at TrackVRoad up here.
Just had them call to say they can't find anything wrong apart from the ECUmate they just bought showed v minor irregularities as the throttle went through its range and the vacuum advance was not working.
Before I go out and buy a throttle pot for £120 does anyone think that this is probably the issue and not something deeper that they haven't checked? Seems funny that the readout from the throttle pot is fine with throttle closed and only slight irregularities when opened would cause idling problems. Could even be wiring or connections to ECU from the pot that's causing funny signals at the ECU.
Also the how important have people found the vacuum advance? I'm skeptical its this too because its never worked properly since i've had it esp as the 1 way valve was wrong way round. And it ran fine when I first had the car.
Anyone got a spare compatible one that they would be so kind as to send over so that I could try it and eliminate it before I fork out more cash? Would obviously pay postage and a few beer vouchers for the trouble. Or know of where to get one for less than cost above?
Here's my original post on there a few weeks ago:
After trawling best I could on here using the less than perfect search facilities I've compiled what I think are the symptoms for suspecting rich running/overfuelling issues in my V8S.
1) Strong smell of petrol around esp when cold
2) Stalled recently when cold and wouldn’t restart for a while – suspect flooded engine
3) Big rise in fuel consumption – was about 250miles per tank, now about 180-200
4) MOT test shows HC figure 560 when 2 previous years show 150 which I believe is an indicator of unburnt fuel in exhaust. CO2 was fine.
5) Rough /lumpy idling when warm or cold and feeling like its going to die when throttle opened when cold
6) Jumpy / kangarooing when pulling away from cold start up. Sensation as if I had over sensitive throttle.
7) Pops and bangs through exhaust now a lot more frequent and noticable.
I'm after a list of things to check in order of difficulty, cost and equipment before I send it in to the professionals. Does anyone have anything to add or change to this below?
ECU coolant temp sensor - short this out and see if anything changes or just replace.
Throttle potentiometer - disconnect and run?
Lack of spark(s) / weak spark(s) - inline spark tester or arc to block?
Injectors jammed open - test with bulb across each one?
Fuel Rail pressure - need a garage for this one i think
AFM - wouldnt know how to test this tho?
ECU itself (ECU mate req'd?)
Oil & filter change & brand new B7ECS plugs about 200miles ago gapped to 0.9mm.
thanks for any help.
Well I gave everything I could possibly check a thorough check in line with the bible then when all was ok i conceded and took it to the experts at TrackVRoad up here.
Just had them call to say they can't find anything wrong apart from the ECUmate they just bought showed v minor irregularities as the throttle went through its range and the vacuum advance was not working.
Before I go out and buy a throttle pot for £120 does anyone think that this is probably the issue and not something deeper that they haven't checked? Seems funny that the readout from the throttle pot is fine with throttle closed and only slight irregularities when opened would cause idling problems. Could even be wiring or connections to ECU from the pot that's causing funny signals at the ECU.
Also the how important have people found the vacuum advance? I'm skeptical its this too because its never worked properly since i've had it esp as the 1 way valve was wrong way round. And it ran fine when I first had the car.
Anyone got a spare compatible one that they would be so kind as to send over so that I could try it and eliminate it before I fork out more cash? Would obviously pay postage and a few beer vouchers for the trouble. Or know of where to get one for less than cost above?
Here's my original post on there a few weeks ago:
After trawling best I could on here using the less than perfect search facilities I've compiled what I think are the symptoms for suspecting rich running/overfuelling issues in my V8S.
1) Strong smell of petrol around esp when cold
2) Stalled recently when cold and wouldn’t restart for a while – suspect flooded engine
3) Big rise in fuel consumption – was about 250miles per tank, now about 180-200
4) MOT test shows HC figure 560 when 2 previous years show 150 which I believe is an indicator of unburnt fuel in exhaust. CO2 was fine.
5) Rough /lumpy idling when warm or cold and feeling like its going to die when throttle opened when cold
6) Jumpy / kangarooing when pulling away from cold start up. Sensation as if I had over sensitive throttle.
7) Pops and bangs through exhaust now a lot more frequent and noticable.
I'm after a list of things to check in order of difficulty, cost and equipment before I send it in to the professionals. Does anyone have anything to add or change to this below?
ECU coolant temp sensor - short this out and see if anything changes or just replace.
Throttle potentiometer - disconnect and run?
Lack of spark(s) / weak spark(s) - inline spark tester or arc to block?
Injectors jammed open - test with bulb across each one?
Fuel Rail pressure - need a garage for this one i think
AFM - wouldnt know how to test this tho?
ECU itself (ECU mate req'd?)
Oil & filter change & brand new B7ECS plugs about 200miles ago gapped to 0.9mm.
thanks for any help.
As I understand it a high Hydrcarbon figure shows fuel is going in but not being burnt so either it is so rich it can’t burn ( unlikely) or the spark is not igniting it.
What do the plugs look like ? are they all black and sooty indicating it is very rich (or it is the wrong grade of plug for the engine ) or are one or two of them wet ? Once the plugs have become fouled it is very difficult to clean them and better to stick in a new set. Thing is if the plugs fouled on one or two cylinders I would be looking at plug leads / coil / dizzy cap.
You say the CO2 is ok but do you actually mean the CO ( Carbon Monoxide ) If the CO is good that suggests to me that the mixture is correct for the cylinders that are running but some sparks are missing from one or some others hence the poor running and high HC.
What do the plugs look like ? are they all black and sooty indicating it is very rich (or it is the wrong grade of plug for the engine ) or are one or two of them wet ? Once the plugs have become fouled it is very difficult to clean them and better to stick in a new set. Thing is if the plugs fouled on one or two cylinders I would be looking at plug leads / coil / dizzy cap.
You say the CO2 is ok but do you actually mean the CO ( Carbon Monoxide ) If the CO is good that suggests to me that the mixture is correct for the cylinders that are running but some sparks are missing from one or some others hence the poor running and high HC.
It looks like that is the price you pay for a throttle pot unfortunately. Maybe in time we will be adapting later ones to fit. The ones for the Speed 6 cars are a standard type and a fraction of the price, but you would need to adapt the throttle shaft fitting I think.
Back to your problem, if as Steve suggests it is an ignition-related problem, most garages should have a Sun diagnostic machine with which they can do basic checks to see if all the plugs are firing correctly. This is testing at the HT end, not looking at the ECU. On the Rover V8, the ignition is independent of the ECU anyway. Was this done? Also it should be possible for a properly equipped workshop to diagnose the injector firing and see if they are firing open too long.
Do all the plugs look the same colour, or are some black & fouled worse than others?
Another possibility is a wiring loom fault. These cars are 20 years old with a fibreglass body, so earthing problems can occur. If you strip back the insulation on the earthing wires, it's quite common to find the copper core has become corroded black. If the ECU is not getting a steady voltage supply, it will play up.
Back to your problem, if as Steve suggests it is an ignition-related problem, most garages should have a Sun diagnostic machine with which they can do basic checks to see if all the plugs are firing correctly. This is testing at the HT end, not looking at the ECU. On the Rover V8, the ignition is independent of the ECU anyway. Was this done? Also it should be possible for a properly equipped workshop to diagnose the injector firing and see if they are firing open too long.
Do all the plugs look the same colour, or are some black & fouled worse than others?
Another possibility is a wiring loom fault. These cars are 20 years old with a fibreglass body, so earthing problems can occur. If you strip back the insulation on the earthing wires, it's quite common to find the copper core has become corroded black. If the ECU is not getting a steady voltage supply, it will play up.
Potentiometers tend to go 'noisy' before they fail. You probably wouldn't see this on a meter if you were testing it's resistance. If you have access to an oscilloscope you should be able to test it by checking the wiper voltage in the time domain as you open/close the throttle. You could always try a multimeter, you might see a problem given how severe the symptoms are.
My old plenum is away at the moment but it has a throttle pot on it. If you haven't solved it in the next couple of weeks let me know and I'll send it up for a quick test when I get it back.
My old plenum is away at the moment but it has a throttle pot on it. If you haven't solved it in the next couple of weeks let me know and I'll send it up for a quick test when I get it back.
You can borrow my spare TP and see if it makes any difference. It was changed in the hunt for a problem but I was never convinced it was just the TP at fault. The positioning of the TP is critical to a smooth pick up as it "over-centers" when closed which means that as you ease the throttle open the butterfly actually goes from very slightly open (but in the wrong direction) through the fully closed position before opening again. If you do want to borrow the TP I'll try to find it over the weekend.
Have you ruled the connections to and from the ECU and the seating of the stepper motor as per my response to your earlier post?
Have you ruled the connections to and from the ECU and the seating of the stepper motor as per my response to your earlier post?
Hi All
First, thanks for the replies and ideas so far. I certainly need some if a TVR garage are struggling. They have spent 3 hours checking all the ignition and injection systems top to bottom inc fuel pressure, compression and timing. Why couldn't it have been that damn coolant sensor I checked first time round!
One thing not checked is a vacuum leak which could possibly be causing some of these symptoms though so I'll ask they carry this out next week. I didnt want to risk spraying carb cleaner everywhere as I have grown fond of owning a face!
In summary to what you've all asked:
Plugs - seemed fine apparently. No 'wet' or badly fouled plugs. All 8 cylinders are firing apparently. (just not too well..).
Wiring - not checked in depth, only at the ECU end of things in terms of continuity.
SteveV8s - If high HC rate is due to unburnt fuel then there are 2 causes - too much fuel or right amount and a faulty ignition. So its hard to say which of these it is from that readout I would imagine.
v8sforme - I would really appreciate the use of your TP. Might take some experimenting and fiddling with to calibrate but definitely worth a go. I will email you separately with my details and you will have to let me know how to pay you for your efforts mate.
To my mind, if I take the garage's word 100% now, then the ignition system is fine (and it does purr sweetly at 2000rpm and above esp accelerating) then something is causing too much fuel to enter the system. Just dont know what that something is.
Any thoughts on vacuum advance? Anyone else feel this is important to the car's running?
Thanks as ever.
Rob
First, thanks for the replies and ideas so far. I certainly need some if a TVR garage are struggling. They have spent 3 hours checking all the ignition and injection systems top to bottom inc fuel pressure, compression and timing. Why couldn't it have been that damn coolant sensor I checked first time round!
One thing not checked is a vacuum leak which could possibly be causing some of these symptoms though so I'll ask they carry this out next week. I didnt want to risk spraying carb cleaner everywhere as I have grown fond of owning a face!
In summary to what you've all asked:
Plugs - seemed fine apparently. No 'wet' or badly fouled plugs. All 8 cylinders are firing apparently. (just not too well..).
Wiring - not checked in depth, only at the ECU end of things in terms of continuity.
SteveV8s - If high HC rate is due to unburnt fuel then there are 2 causes - too much fuel or right amount and a faulty ignition. So its hard to say which of these it is from that readout I would imagine.
v8sforme - I would really appreciate the use of your TP. Might take some experimenting and fiddling with to calibrate but definitely worth a go. I will email you separately with my details and you will have to let me know how to pay you for your efforts mate.
To my mind, if I take the garage's word 100% now, then the ignition system is fine (and it does purr sweetly at 2000rpm and above esp accelerating) then something is causing too much fuel to enter the system. Just dont know what that something is.
Any thoughts on vacuum advance? Anyone else feel this is important to the car's running?
Thanks as ever.
Rob
Edited by gizzardio on Friday 10th August 17:58
The vacuum advance does not have much effect when you are accelerating on the throttle, it's when you throttle back it comes into play. Do your problems manifest themselves at the moments you come on/off the throttle? That might be worth checking, because that is when the vac advance will be active.
It can have an effect (depending exactly where the tapping is relative to the throttle plate) on advance when idling, hence you should always disconnect it when doing a timing check with a strobe. You could try disconnecting it and plugging the pipe to see if it helps. In the past, on old carburettor cars, I have run with/without vac advance and never noticed the difference!
If you have a pre-cat car, there is always the option to ditch the injection and run a good old Holley!!
See here for more info http://en.wikipedia.org/wiki/Ignition_timing
Here's another good article http://www.corvette-restoration.com/resources/tech...
It can have an effect (depending exactly where the tapping is relative to the throttle plate) on advance when idling, hence you should always disconnect it when doing a timing check with a strobe. You could try disconnecting it and plugging the pipe to see if it helps. In the past, on old carburettor cars, I have run with/without vac advance and never noticed the difference!
If you have a pre-cat car, there is always the option to ditch the injection and run a good old Holley!!
See here for more info http://en.wikipedia.org/wiki/Ignition_timing
Here's another good article http://www.corvette-restoration.com/resources/tech...
Edited by jwoffshore on Friday 10th August 20:23
No problem, I’ll wait for your email. I really, and I mean really really, urge you to check the permanent live feed to the ECU and the connection around the tune resistor. I spent hours and hours trying to solve similar faults to yours only to find a broken wire inside the little connector on the tune resistor and a dry joint in the loom where TVR bodged the live feed into the loom (and I do mean bodged). When you unwrap all that tape you’ll see what I mean. If I’d paid a garage to do what I did it would have cost around a grand because they’d have replaced loads of bits before they found the wiring faults. In the end all it took was a few drops of solder and replacing the washer on the stepper with goo. Good luck.
Rob one thing I didn't mention that has cropped up on griff and chims is the ecu needing to be resoldered. Better still would be to get hold of a known good pre cat 3.9 ECU to substitute might be worth asking on the griff forum (I am not sure if there are any pre cat chims as they came slightly later around the time cats were compulsory).
I'd happily re solder it if you are short of options.
Chris
I'd happily re solder it if you are short of options.
Chris
Hi
sorry been away so couldnt reply.
JW - I think the issues are at idle because when I'm accelerating it sounds fine and overfueling is so much of an issue. There is no hesitating or anything. Just rises up through the rev range. The garage did a timing check with strobe with vac advance operating as you suggest.
Barky - I'll check the elec connections and ask the garage if they have a sub ECU to replace mine with. If all this is down to electrical issues its gonna be a case of elimination and a lot of playing about. But not by the garage as it'll go on and on and some ££££'s. At least now its been checked over thoroughly by the experts I can proceed knowing what its NOT rather than what it could be.
This tune resistor connection seems to be something a few have mentioned now so I'll definitely be checking it out.
Cheers.
sorry been away so couldnt reply.
JW - I think the issues are at idle because when I'm accelerating it sounds fine and overfueling is so much of an issue. There is no hesitating or anything. Just rises up through the rev range. The garage did a timing check with strobe with vac advance operating as you suggest.
Barky - I'll check the elec connections and ask the garage if they have a sub ECU to replace mine with. If all this is down to electrical issues its gonna be a case of elimination and a lot of playing about. But not by the garage as it'll go on and on and some ££££'s. At least now its been checked over thoroughly by the experts I can proceed knowing what its NOT rather than what it could be.
This tune resistor connection seems to be something a few have mentioned now so I'll definitely be checking it out.
Cheers.
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