Occasional complete miss fire
Discussion
Any one experienced this...?
Three times, the engine has not miss fired as such, but seemingly gone quiet for half a second when accelerating. Its happened in 1st gear, 3rd gear... oil temp is at least 45+ (ie not cold). When it happened in 1st gear, I was accelerating fairly swiftly (but not hard), and the "quiet spot" was harsh enough to throw my hands forward of the steering wheel and gear knob (sudden power turn off!), before coming back to life and throwing me back into the seat as before....
Other than this freak event, the engine runs and goes extremely well.
Confused as to what it could be!! Its like stalling the car whilst going along except without me using the clutch at the time!!
Three times, the engine has not miss fired as such, but seemingly gone quiet for half a second when accelerating. Its happened in 1st gear, 3rd gear... oil temp is at least 45+ (ie not cold). When it happened in 1st gear, I was accelerating fairly swiftly (but not hard), and the "quiet spot" was harsh enough to throw my hands forward of the steering wheel and gear knob (sudden power turn off!), before coming back to life and throwing me back into the seat as before....
Other than this freak event, the engine runs and goes extremely well.
Confused as to what it could be!! Its like stalling the car whilst going along except without me using the clutch at the time!!
matt_c said:
Any one experienced this...?
Three times, the engine has not miss fired as such, but seemingly gone quiet for half a second when accelerating. Its happened in 1st gear, 3rd gear... oil temp is at least 45+ (ie not cold). When it happened in 1st gear, I was accelerating fairly swiftly (but not hard), and the "quiet spot" was harsh enough to throw my hands forward of the steering wheel and gear knob (sudden power turn off!), before coming back to life and throwing me back into the seat as before....
Other than this freak event, the engine runs and goes extremely well.
Confused as to what it could be!! Its like stalling the car whilst going along except without me using the clutch at the time!!
My July 2000 car does this sometimes too. It doesn't seem to follow any pattern though and may do it a couple of times in one drive and then not again for a month or so. I have had fuel supply problems in the past though so may be related.
James here:
I'm assuming it's at roughly 6000rpm under heavy acceleration. It is a known problem with the speed six caused due to vibrations down the number 1 throttle spindle into the potentiometer. It is resolved with a new throttle body with bearings not bushes and a 'dethrottled' ECU chip.
There are plenty of threads I did before going into greater detail.
I'm assuming it's at roughly 6000rpm under heavy acceleration. It is a known problem with the speed six caused due to vibrations down the number 1 throttle spindle into the potentiometer. It is resolved with a new throttle body with bearings not bushes and a 'dethrottled' ECU chip.
There are plenty of threads I did before going into greater detail.
Mine used to stumble a little at 2000-2800 rpm under moderate acceleration. I got the throttle bodies rebalanced - cost £40, and no longer any problem. Nice and smooth. Maybe worth getting it looked at if it is bothering you. As James say, there is a dethrottle chip available from TVR that smooths the response with the potentiometer. There are also some aftermarket upgrades available for the the throttle body assemby from Dreadnought - cost £500 IIRC and makes the S6 silky smooth.
I had a similar problem once. Car would suddenly lose all power, at around 2-3000 rpm, then come back on. Happened 3 or 4 times over the course of about 5 minutes when the car was not fully warmed up, then was fine.
Dealer traced it to water getting into the water temperature sender(I think). They sealed it up and all ok.
Dealer traced it to water getting into the water temperature sender(I think). They sealed it up and all ok.
TUS 373 said:
Mine used to stumble a little at 2000-2800 rpm under moderate acceleration. I got the throttle bodies rebalanced - cost £40, and no longer any problem. Nice and smooth. Maybe worth getting it looked at if it is bothering you. As James say, there is a dethrottle chip available from TVR that smooths the response with the potentiometer. There are also some aftermarket upgrades available for the the throttle body assemby from Dreadnought - cost £500 IIRC and makes the S6 silky smooth.
It is more than a stumble Bryan (I've had that too) it's like turning the ignition off for a second and then back on again. It can be quite violent if your are accelerating hard at the time.
Marcus
Hmmmmm. Had something happen like that - but only once. I was charging hard up a long uphill slope on the motorway - at the same time as the low fuel warning was showing on the dash. I put that down to fuel startvation, high altitude, gravity and g-force! (Delete where non-applicable).
TUS 373 said:
Hmmmmm. Had something happen like that - but only once. I was charging hard up a long uphill slope on the motorway - at the same time as the low fuel warning was showing on the dash. I put that down to fuel startvation, high altitude, gravity and g-force! (Delete where non-applicable).
I had this on my chimp, and it was the coil breaking down. Two day's later the coil gave up totally. Don't know if the same could be happening on the Tusc ignition system...
This could be a number of things. How hot was your engine and were you gunning it ? 45 degrees oil temp is a little low for grand prix acceleration and if the engine isn't convinced its warmed up yet it can throw its toys out of the pram. I've pasted in the guidelines below.
If not the water temperature sensor could be giving a wrong reading, causing the wrong map to the be used, a lambda sensor could be playing up, the tappets could need adjusting, an HT lead could need replacing, a coil could be on the way out, a throttle pot could need replacing or the pots could need balancing. As it's at low revs I don't think the vibrating throttle boddies come into play (usually about 6000rpm at full throttle, solved with a dethrottle chip). I think (but am not certain) that changing the throttle boddies solves the constant speed/light throttle stuttering you can get between 2500 and 3500 rpm as the butterflys flutter a little bit as there is a little bit of play in the mechanism.
Editted to add, you've reminded me of a test drive I had in a Cerbera Speed 6. The dealer drove the car (from stone cold) to a changeover place for me to have a go. On the way, and after less than 2 miles the A-road slip road beckoned and he gave me the full onslaught of acceleration. The car had an enormous hickup halfway up the rev range. "Hmmm", he said, "a slight pause in acceleration". I bought a new Tuscan instead of any of the dealer stock!
Cheers,
Andy.
JOHN RAVENSCROFT’S TIPS ON MECHANICAL SYMPATHY AND HIS ENGINES!
RUNNING IN
Most importantly, drive fairly normally. Being too gentle with an engine when running in can be as bad as being too rough.
Although it is important to avoid full throttle or over 4,000 rpm during the first 1,000 miles, occasional bursts (c.5 seconds) of 75% throttle up to 4,000 rpm, will help to bed the piston rings in.
FROM COLD
When starting, please be careful not to let it rev straight up so please make sure that you do not give it anything more than a tiny bit of throttle while cranking it over and then lift off as soon as it catches.
Then try to avoid more than 3,000 rpm until the oil (not water) temperature has exceeded 40°C, 4,000 rpm until 60°C and 7,000 rpm until 80°C. If it climbs above 110°C, please keep the revs below 5,000 rpm until the oil temperature returns to normal.
>> Edited by andyvdg on Monday 26th January 22:35
If not the water temperature sensor could be giving a wrong reading, causing the wrong map to the be used, a lambda sensor could be playing up, the tappets could need adjusting, an HT lead could need replacing, a coil could be on the way out, a throttle pot could need replacing or the pots could need balancing. As it's at low revs I don't think the vibrating throttle boddies come into play (usually about 6000rpm at full throttle, solved with a dethrottle chip). I think (but am not certain) that changing the throttle boddies solves the constant speed/light throttle stuttering you can get between 2500 and 3500 rpm as the butterflys flutter a little bit as there is a little bit of play in the mechanism.
Editted to add, you've reminded me of a test drive I had in a Cerbera Speed 6. The dealer drove the car (from stone cold) to a changeover place for me to have a go. On the way, and after less than 2 miles the A-road slip road beckoned and he gave me the full onslaught of acceleration. The car had an enormous hickup halfway up the rev range. "Hmmm", he said, "a slight pause in acceleration". I bought a new Tuscan instead of any of the dealer stock!
Cheers,
Andy.
JOHN RAVENSCROFT’S TIPS ON MECHANICAL SYMPATHY AND HIS ENGINES!
RUNNING IN
Most importantly, drive fairly normally. Being too gentle with an engine when running in can be as bad as being too rough.
Although it is important to avoid full throttle or over 4,000 rpm during the first 1,000 miles, occasional bursts (c.5 seconds) of 75% throttle up to 4,000 rpm, will help to bed the piston rings in.
FROM COLD
When starting, please be careful not to let it rev straight up so please make sure that you do not give it anything more than a tiny bit of throttle while cranking it over and then lift off as soon as it catches.
Then try to avoid more than 3,000 rpm until the oil (not water) temperature has exceeded 40°C, 4,000 rpm until 60°C and 7,000 rpm until 80°C. If it climbs above 110°C, please keep the revs below 5,000 rpm until the oil temperature returns to normal.
>> Edited by andyvdg on Monday 26th January 22:35
Thanks Andy.
I don't tend to gun the engine under 60degC. The water temp sender I think is ok, as it gives a steady read out and shows running hot after the normal expected amount of time.
As Marcus says, its like turning the ingnition off and on. So perhaps it could be a coil etc fault. Although at all other times the engine runs really sweet, hot or cold (starts very well without any throttle, doesn't die) right upto 7000rpm.
Its just been serviced 1000miles ago, so I would hope the major components like throttle pots to be ok.
I don't tend to gun the engine under 60degC. The water temp sender I think is ok, as it gives a steady read out and shows running hot after the normal expected amount of time.
As Marcus says, its like turning the ingnition off and on. So perhaps it could be a coil etc fault. Although at all other times the engine runs really sweet, hot or cold (starts very well without any throttle, doesn't die) right upto 7000rpm.
Its just been serviced 1000miles ago, so I would hope the major components like throttle pots to be ok.
When mine was serviced by the factory, I mentioned the stuttering to them and they fitted the dethrottle chip. It still wasn't quite right. I then took it to Shane at SFR who found the throttle pots were way out, rebalanced them, and its been fine ever since. I am amazed that the throttle pots were apparently untouched/unchecked by TVR at service time.
matt_c, the water temperature sensor connected to the ECU is a different one to the display. Don't ask me why. You can test the one that matters by checking to see if the first cooling fan comes on about 92, and the second fan about 94. If they come on much earlier, or not at all, or are on all the time then that's the problem. Otherwise all should be OK with that sensor.
Cheers,
Andy.
Cheers,
Andy.
What I've never worked out Bryan is why the the two pots go out of balance in the first place. I imagine that there is a potentiometer at each end of the throttle bearings. What is there to go wrong ? Do the pots move on the mountings ? Anyway, my car seems to need to have it done every now and again.
Cheers,
Andy.
Cheers,
Andy.
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