Popping Back At Idle
Discussion
Hi All,
I’m v. worried about my Cerb S6.
Last weekend I noticed “popping-back” sounds coming through the exhaust system for the first time whilst idling at <50c water temp, not sure oil temp. I warmed the engine up to running temp and checked again - the same irregular (say every 10-15 secs on average) popping-back noises. There is no smoke or obvious funny business going on from the outside.
I had just upped my idle speed to nearly 950rpm - it had steadily dropped from c700rpm to below 450rpm (i.e stall speed) in the last 6 months/4500 miles - don’t know if upping the idle could be connected to the noises (or for that matter whether a gradually falling idle speed itself is to be expected) ? My girlfriend tells that she’s heard the same noise ‘since before Christmas’ when the car idles from cold, so I don’t think something has suddenly happened/changed/blown or that changing the idle speed has brought this on.
The engine has always idled evenly and smoothly whether hot or cold (though obviously it is noisier when cold), and the engine appears to run perfectly, so could this be normal ? - some by-product of a performance cam or the fuelling arrangement ?
Or does this sound like trouble ? Could it be a product of over/mis-fuelling, or worn valve seats, or stretched exhaust values, or what ? I’ve also read that throttle pots commonly wear/fail causing problems with fuelling, or could it be some ECU/sensor voodoo mischief ?
Do the symptoms sound familiar to anyone, do I need to have it investigated by the garage, can I still drive it ?
Thanks in advance,
Stressed And
And,
I posted a thread a while back called "Not Happy Christmas to me" (I think). Had the same problem, mine turned out to be the Speed Six Engine problem of valve seats moving.
Cure = rebuild in Blackpool.
Hope yours isn't as sinister a problem! The thread goes through what you need to do to check for this problem.
I posted a thread a while back called "Not Happy Christmas to me" (I think). Had the same problem, mine turned out to be the Speed Six Engine problem of valve seats moving.
Cure = rebuild in Blackpool.
Hope yours isn't as sinister a problem! The thread goes through what you need to do to check for this problem.
Would any of these possibilities mean I risk damaging other components if I drive it before getting it sorted ? My dealer is 250 miles away - Is this a pre-cautionary flat-loader job ?
If it turns out to be valve seats, or valve clearances / re-shimming would you expect these to be covered under warranty ? (Warranty Holdings)
If it turns out to be valve seats, or valve clearances / re-shimming would you expect these to be covered under warranty ? (Warranty Holdings)
Shouldn't do any harm to drive it there.
been through the mill with WH trying to get engine work covered on warranty. Didn't have any joy I'm afraid.
Best bet is to get your dealer to negotiate with TVR on your behalf if its an engine problem. If you have a full TVRSH they may be able to help you out a bit with the costs.
... anyways, lets hope its not the engine hey
!
been through the mill with WH trying to get engine work covered on warranty. Didn't have any joy I'm afraid.
Best bet is to get your dealer to negotiate with TVR on your behalf if its an engine problem. If you have a full TVRSH they may be able to help you out a bit with the costs.
... anyways, lets hope its not the engine hey
! Just spoken to the dealership servicing mgr.
Obviously they haven't seen the car but based on what I could tell him on the phone they think it sounds like a throttle balancing problem. Apparently the throttles on each cylinder are independently adjustable and need to be aligned or you could potentially have an individually mis-fuelled cylinder.
If an imbalance is present increasing the overall idle speed (two-fold) on the main screw would make it more noticeable at stand still - my missus did notice it months ago so it sort of ties in. I don't understand why I don't (appear to) get any popping through the rev range though ? They think that the lack of misfire supports this rather than valve prob, but again I'm not sure why.
I asked explicitly about the idle speed declining over the mileage (5k) and was told that "..they all do that because high perf engine state of tune etc.." which doesn't sound too scientific or satisfactory, but I guess it's possible.
Recommended course of action is to have the throttles balanced at the next service, but to bring it in immediately if it develops a misfire.
Does this sound plausible / sensible ?
Obviously they haven't seen the car but based on what I could tell him on the phone they think it sounds like a throttle balancing problem. Apparently the throttles on each cylinder are independently adjustable and need to be aligned or you could potentially have an individually mis-fuelled cylinder.
If an imbalance is present increasing the overall idle speed (two-fold) on the main screw would make it more noticeable at stand still - my missus did notice it months ago so it sort of ties in. I don't understand why I don't (appear to) get any popping through the rev range though ? They think that the lack of misfire supports this rather than valve prob, but again I'm not sure why.
I asked explicitly about the idle speed declining over the mileage (5k) and was told that "..they all do that because high perf engine state of tune etc.." which doesn't sound too scientific or satisfactory, but I guess it's possible.
Recommended course of action is to have the throttles balanced at the next service, but to bring it in immediately if it develops a misfire.
Does this sound plausible / sensible ?
And,
Is the car still under any form of warranty?
I.e. is the garage you bought from going to be responsible for the repair costs?
The throttle bodies could be causing an issue but you tend to notice a rather lumpy ride in all gears at all speeds (in my experience)
Replacing the throttle bodies isn't very expensive or time consuming so this could be a quick win to find out if it cures the problem. The car WILL feel better after it has been re-tuned, but if this isn't the root cause of the problem the symptoms will return (over a few months)
When my car was on song the idle speed didn't go down at all .. but again, ever car is different.
If things deteriorate over time then I'd get the compression tests done to check the valves. This only cost me £60 from APM Automotive and of course gave me peace of mind.... and found the real cause of the problems I was getting.
Good luck!
Is the car still under any form of warranty?
I.e. is the garage you bought from going to be responsible for the repair costs?
The throttle bodies could be causing an issue but you tend to notice a rather lumpy ride in all gears at all speeds (in my experience)
Replacing the throttle bodies isn't very expensive or time consuming so this could be a quick win to find out if it cures the problem. The car WILL feel better after it has been re-tuned, but if this isn't the root cause of the problem the symptoms will return (over a few months)
When my car was on song the idle speed didn't go down at all .. but again, ever car is different.
If things deteriorate over time then I'd get the compression tests done to check the valves. This only cost me £60 from APM Automotive and of course gave me peace of mind.... and found the real cause of the problems I was getting.
Good luck!
and said:
I asked explicitly about the idle speed declining over the mileage (5k) and was told that "..they all do that because high perf engine state of tune etc.." which doesn't sound too scientific or satisfactory, but I guess it's possible.
Recommended course of action is to have the throttles balanced at the next service, but to bring it in immediately if it develops a misfire.
Does this sound plausible / sensible ?
sounds bollox to me. if the throttles are out it's cos they weren't set right last time. there is an issue with the throttles collecting oil mist from the breather on the oil catch tank, but if the relative air flows are different cyl to cyl (and assuming they were set right last time .. si non pourquoi pas?) then it's more likely to be because the cyls are drawing different airflow levels because the trapping efficiency is different, valve clearance issue i still say.
PS you can mask valve issues by increasing the airflows - If you can why not stay and watch them check the clearances anyway, just to make sure?? 8 thou inlet, 10 thou exhaust ...
“...if the throttles are out it's cos they weren't set right last...” (joolz)
If only I knew – I guess this is a new owner risk. I planned to bring it to you for servicing next time so I can eliminate risking any dodgy set-up or funny business! I bought in September ‘post-service’, but the car had covered only 1000 miles in the previous year. I suppose the temptation would be to skip some items on the service, but sincerely hope not.... let’s not go there.
“...valve clearance issue i still say...” (joolz) - how much should I pay to have them independently checked ? I assume it’s a case of getting the head off, measuring and reassembling, how long should it take ?
“..is the garage you bought from going to be responsible for the repair costs?” (Bandit)
Am I entitled to insist that the dealer checks the valve clearances FOC and fixes the root cause ? hmm - no idea what my buyer rights are, but I suspect technically I would have to pay unless I could demonstrate the fault was there at time of purchase. At the end of the day I don’t mind paying someone else I know will do the investigation meticulously for peace of mind. I have 8 months left of WH warranty if investigation shows something up, cross that bridge if it comes to it BUT I do worry about peeing off the dealer in case I do need them on-side to push WH/TVR eng. on my behalf.
I want to eliminate the possibility that it’s not a dodgy plug as in Martin’s case, I guess I just let it idle on 5 cylinders to diagnose which cylinder has the pop, then swap-in a good plug and see if it disappears. Anything I should be wary of ?
By the way, if I do any checks myself I’m not giving anyone a way to wriggle out of responsibility at some point in the future am I ?
If only I knew – I guess this is a new owner risk. I planned to bring it to you for servicing next time so I can eliminate risking any dodgy set-up or funny business! I bought in September ‘post-service’, but the car had covered only 1000 miles in the previous year. I suppose the temptation would be to skip some items on the service, but sincerely hope not.... let’s not go there.
“...valve clearance issue i still say...” (joolz) - how much should I pay to have them independently checked ? I assume it’s a case of getting the head off, measuring and reassembling, how long should it take ?
“..is the garage you bought from going to be responsible for the repair costs?” (Bandit)
Am I entitled to insist that the dealer checks the valve clearances FOC and fixes the root cause ? hmm - no idea what my buyer rights are, but I suspect technically I would have to pay unless I could demonstrate the fault was there at time of purchase. At the end of the day I don’t mind paying someone else I know will do the investigation meticulously for peace of mind. I have 8 months left of WH warranty if investigation shows something up, cross that bridge if it comes to it BUT I do worry about peeing off the dealer in case I do need them on-side to push WH/TVR eng. on my behalf.
I want to eliminate the possibility that it’s not a dodgy plug as in Martin’s case, I guess I just let it idle on 5 cylinders to diagnose which cylinder has the pop, then swap-in a good plug and see if it disappears. Anything I should be wary of ?
By the way, if I do any checks myself I’m not giving anyone a way to wriggle out of responsibility at some point in the future am I ?
I think I would go back to the dealer you bought it off and ask them to investigate the root of the problem .. say you're concerned about valve issues and that you insist the clearances are checked - it only take about an hour to do the check so that'd be 50 pounds well spent .. however if they found that some needed adjusting that's proof the last service wasn't done properly (since all tvr dealers manitain there's no more engine probs or valve issues they can't have closed up, therefore must have been wrong when you bought it .. QED)- you therefore shouldn't have to pay the additional labour to set them correctly. make sure the blinking awkward ones at the back are done too!! (often get missed by "mistake").
Check with WH that they warranty the SP6 engine .. I thought there was a rumour somewhere that they didn't cover that engine anymore (please correct me if this is wrong .. not wishing to malign WH in any way, merely trying to work out if they do or not). I also heard that Car Care Plan (or something) was much better at paying out on warranty issues than WH ..
Check with WH that they warranty the SP6 engine .. I thought there was a rumour somewhere that they didn't cover that engine anymore (please correct me if this is wrong .. not wishing to malign WH in any way, merely trying to work out if they do or not). I also heard that Car Care Plan (or something) was much better at paying out on warranty issues than WH ..
I see you are in Surrey. Give Andy at APM a ring, get him to check it out and then you can go back to dealer or to WH and get it sorted. Andy is a top man re TVRs and their own engines. 07740 723673.
He can do warranty work (vat registered) and has strong relations with the factory if needed.
I am sure he will be able to look at your car in the next couple of weeks and this will put your mind at rest.
He can do warranty work (vat registered) and has strong relations with the factory if needed.
I am sure he will be able to look at your car in the next couple of weeks and this will put your mind at rest.
I was away on business for a while so I hadn't chance to take it to Andy yet (or drive it).
No MIL Light, the Oil light flicked on and the pressure went straight to zero. I must have had it switched off within 5-10 seconds but no noises or bangs.
Car probably going to MV Redhill - no final arrangement yet. I obviously want the best chance of getting as much engine work covered by the warranty / TVR as poss - no idea what the best way to do this is.
No MIL Light, the Oil light flicked on and the pressure went straight to zero. I must have had it switched off within 5-10 seconds but no noises or bangs.
Car probably going to MV Redhill - no final arrangement yet. I obviously want the best chance of getting as much engine work covered by the warranty / TVR as poss - no idea what the best way to do this is.
sorry to hear that and. re the throttle balancing. I had a similar problem with my tuscan and the dealer told me it was throttle balancing. They had it in but a few weeks later it was back and worse, wouldn;t tick over and didn't sound good. It is now having a rebuild as it turned out the cam was 'breaking down'. Moral...treat talk of throttle balancing as a cure with suspicion!
TVR are contributing (i didn't even have to ask, the delaer spoke to them and thye divvied up) but it is still costing me 3k. after 13000 miles that is a bit of a sickener
>> Edited by gutted on Monday 3rd March 15:56
TVR are contributing (i didn't even have to ask, the delaer spoke to them and thye divvied up) but it is still costing me 3k. after 13000 miles that is a bit of a sickener
>> Edited by gutted on Monday 3rd March 15:56
Dealers and independents can both deal with the warranty co and the factory for rebuild stuff. I am sure MV redhill are a good choice as would other dealers and independents be. Just dont let them start work on anything without written permission from the warranty company ie if they strip then WH will say no way. Ensure you really push WH for a valid response. ensure you ask the factory to contribute. Assuming this is a biggish bill.
Personally I would use APM. You may end up paying for stuff on top of a rebuild eg clutch, service, ancillary work etc - this can soon mount up. Unless of course you are against the independent route.
Personally I would use APM. You may end up paying for stuff on top of a rebuild eg clutch, service, ancillary work etc - this can soon mount up. Unless of course you are against the independent route.
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