Hesitation 2000-2700 rpm
Discussion
1. I belive that may be correct behavior (read that in the diag s/w user guide iirc). I think sudden changes in throttle make the ecu go open-loop for a moment
2. Noisy ignition timing trace sounds normal (nasty isn't it!)
Its my beleif that the poor behaviour at light throttle is just a function of the rather simplistic air/fuel control from the stock ECU coupled with small imbalances in the various parts. The best you can do is to tune and match everything the best you can. Replacing things like plugs, leads, coil packs etc is not really a fix but sometimes can improve matters just enough...but the underlying issue is still there. Mine still does it to a very small degree. Must say that the lightened finger followers and reduced pressure springs on the refurbed head seem to have made this problem very slightly better...but its all rather subjective. When my engine was doing this a year or so back it is very noticable...almost like a mild misfire on random cylinders.
But from your comment it sounds like yours is enough to be a pain right ?
One thing I've come to appreciate when you jump into a modern production car is just how amazingly smooth and refined everything is...the result of gazillions of r&d spend and fantastic tolerancing!
2. Noisy ignition timing trace sounds normal (nasty isn't it!)
Its my beleif that the poor behaviour at light throttle is just a function of the rather simplistic air/fuel control from the stock ECU coupled with small imbalances in the various parts. The best you can do is to tune and match everything the best you can. Replacing things like plugs, leads, coil packs etc is not really a fix but sometimes can improve matters just enough...but the underlying issue is still there. Mine still does it to a very small degree. Must say that the lightened finger followers and reduced pressure springs on the refurbed head seem to have made this problem very slightly better...but its all rather subjective. When my engine was doing this a year or so back it is very noticable...almost like a mild misfire on random cylinders.
But from your comment it sounds like yours is enough to be a pain right ?
One thing I've come to appreciate when you jump into a modern production car is just how amazingly smooth and refined everything is...the result of gazillions of r&d spend and fantastic tolerancing!
Cheers for your help Pete, I guess you know first hand how frustrating it is. I'm on the verge of taking it to Austec or RG now as I'm going nowhere, but one thing still bugs me. The adaptives on both banks go + right in the rev range where it hesitates pointing to an air leak but I'm damned if I can find one. I used Blue Hylomar to seal the throttle bodies to the head, do you think its worth taking them off again and sealing with RTV silicone? or could it be ignition. Dont want to do all that work again if I can avoid it.
Thanks for the support again - much appreciated.
Thanks for the support again - much appreciated.
PetrolHeadPete said:
Can you pm me the adaptives for the two banks
If you are saying the adaptives peak up at around 2k that might be similar to mine
Horsham is a little way from me in portsmouth
Thanks Pete, the only way I can make the diagnostics run is on a flakey old laptop I have, will try and transfer the maps from it to my PC and mail to you. Appreciate you are a way from me, would offer to drive down but the lean running on long runs makes me feel nervous about potential damage elsewhere in the engine. Look out for mail in the morning.If you are saying the adaptives peak up at around 2k that might be similar to mine
Horsham is a little way from me in portsmouth
Cheers
With regard to the adaptive's going more +ve and AFR faults, I had a similar issue with mine (2006 Tuscan S) and in the end it was the air temperature sensor that was giving an incorrect high reading, this is quiet easy to check though i.e. just disconnect the sensor to put it into a fault condition & the ECU will give a default value of 15 Deg.C.
I bit the bullet at lunchtime and decided to remove the throttle bodies and check the sealing faces. I'm glad I did, all the Blue Hylomar had been squeezed out (as I think PetrolHeadPete found) and more tellingly, there were traces of fuel/Hot Start etc in the joint. I also tested all 6 throttle body for air tightness on the bench - they were all excellent, no leaks through bearings/injector O ring/or other connections. One other point of note was that when I removed the fuel rail I spilt fuel into body No.6 and it stayed above the throttle butterfly for a good 30 seconds until I mopped it up? I.e. at tick-over no air was passing via the butterfly so it must have been coming from somewhere else!
All bodies are now back on with automotive petrol duty RTV silicone sealant and I am much more confident about the integrity of the seal. One final curve ball that's been thrown at me is all but one fuel rail/injector O rings have been damaged on assembly even though I was as careful as I could be and there were no fuel leaks. It is proving to be a right SOB to assemble them without shaving the o/d of the O ring, good job I have some spares.
Chad
All bodies are now back on with automotive petrol duty RTV silicone sealant and I am much more confident about the integrity of the seal. One final curve ball that's been thrown at me is all but one fuel rail/injector O rings have been damaged on assembly even though I was as careful as I could be and there were no fuel leaks. It is proving to be a right SOB to assemble them without shaving the o/d of the O ring, good job I have some spares.
Chad
hope you see progress now you have sealed them again.
One other check i thought of was the adjusters. I found the car went out of tune farily quickly just recently and upon investigation i found no. 3 adjuster thread to be stripped, so the arm was moving ever so slightly.
I tapped out to a larger thread (m5 to m6 if i remember correctly) and put in a larger grub screw, all sorted again
Also, can i suggest that you try Str8 Six for any diagnostic work in the same region as Austec and Racing Green, Jason knows these engines inside out, and will not charge you through the nose....others might
One other check i thought of was the adjusters. I found the car went out of tune farily quickly just recently and upon investigation i found no. 3 adjuster thread to be stripped, so the arm was moving ever so slightly.
I tapped out to a larger thread (m5 to m6 if i remember correctly) and put in a larger grub screw, all sorted again
Also, can i suggest that you try Str8 Six for any diagnostic work in the same region as Austec and Racing Green, Jason knows these engines inside out, and will not charge you through the nose....others might
Warming up the 'O' rings/fuel rail/injectors made assembly much easier, I think the 'O' rings were two hard to deform enough first time round. I now have it all assembled and been for a test drive and it's 60% better but not 100% yet. There were small flashes below 1 or 2 butterfly's before I re-sealed the bodies, there are none now and it was very easy to balance them (all adjustment screws ok thanks RobertJP). After a test drive I had a look at the real time graph for Adaptive/AFR, the trace for each bank is now, more or less, one over the other where as before, 456 was always above the other by about 5mm, I think this proves to some extent that I did have some small leaks between throttle body and head.
One thing that I did noticed is the throttle pots are now diverging by as much as 5% at 30% open, not sure if they did before but I will put a couple of new ones on tonight (just delivered from TVR Power). NCE61 the air temp sensor looks to function ok but its a good point.
If I cant get to the bottom of it soon I think a RR session to fault find/re-map may be on the cards. I am beginning to think the original TVR maps were less than ideal - anyone done this and care to comment?
As ever thanks for your contributions.
Chad
One thing that I did noticed is the throttle pots are now diverging by as much as 5% at 30% open, not sure if they did before but I will put a couple of new ones on tonight (just delivered from TVR Power). NCE61 the air temp sensor looks to function ok but its a good point.
If I cant get to the bottom of it soon I think a RR session to fault find/re-map may be on the cards. I am beginning to think the original TVR maps were less than ideal - anyone done this and care to comment?
As ever thanks for your contributions.
Chad
I have made significant progress in resolving the hesitation and will post a resume of what worked and what didn't in due course but for now a little more advice please.
I had the engine re-mapped which improved the hesitation but didn't cure it. I have noticed now that I have a constant AFR fault on 456 and an intermittent AFR fault on 123. Installing a standard chip myself for comparison instantly cured the AFR faults (adaptive's on the std chip range between 0 and +16. With the re-mapped chip -7 to -35). I will take the car back and have the re-mapped chip altered as clearly something is wrong and I have an MOT due soon as well.
The question for now, is the re-mapped chip doing the engine or lambda's or Cats any harm? We are off on a touring trip at the end of next week and I would prefer to leave the re-map chip in as it drives better with it, but obviously not if there is risk of any damage?
I had the engine re-mapped which improved the hesitation but didn't cure it. I have noticed now that I have a constant AFR fault on 456 and an intermittent AFR fault on 123. Installing a standard chip myself for comparison instantly cured the AFR faults (adaptive's on the std chip range between 0 and +16. With the re-mapped chip -7 to -35). I will take the car back and have the re-mapped chip altered as clearly something is wrong and I have an MOT due soon as well.
The question for now, is the re-mapped chip doing the engine or lambda's or Cats any harm? We are off on a touring trip at the end of next week and I would prefer to leave the re-map chip in as it drives better with it, but obviously not if there is risk of any damage?
Not sure about the decat chip etc.
A couple of weeks back I had a play with the diagnostics etc because I'd noticed a couple of unexplained "lumpy moments" and thought I'd try and track them down. My conclusion is that the low down running is just soooo critical on the throttle pot reset. With a very slight change to the throttle pot reset, i mean I'd just changed the idle screw and reset the pots, then made a tiny adjustment again bit didnt rese, I could exactly re-create the weird running: very slowly bring up the revs from idle...smooth until about 1500 then it got itself into an oscialltion mode with the adapatives and sensors see-sawing up and down, up and down with no change in throttle ! I think that there is always a place at light throttle where the mixture is not metered well enough...the closed loop is right on the edge of not working and you get a "lean spot". If you manually open the throttle very very gradually, you may find what I mean...the engine suddenly goes a bit rough and feels like it wants to die. When you drive it of course some of this gets smoothed out by the weight of the car so you dont notice it as much. And you can accelerate though it without even noticing.
I'm soon going to have another play and perhaps get the injectors tested.
A couple of weeks back I had a play with the diagnostics etc because I'd noticed a couple of unexplained "lumpy moments" and thought I'd try and track them down. My conclusion is that the low down running is just soooo critical on the throttle pot reset. With a very slight change to the throttle pot reset, i mean I'd just changed the idle screw and reset the pots, then made a tiny adjustment again bit didnt rese, I could exactly re-create the weird running: very slowly bring up the revs from idle...smooth until about 1500 then it got itself into an oscialltion mode with the adapatives and sensors see-sawing up and down, up and down with no change in throttle ! I think that there is always a place at light throttle where the mixture is not metered well enough...the closed loop is right on the edge of not working and you get a "lean spot". If you manually open the throttle very very gradually, you may find what I mean...the engine suddenly goes a bit rough and feels like it wants to die. When you drive it of course some of this gets smoothed out by the weight of the car so you dont notice it as much. And you can accelerate though it without even noticing.
I'm soon going to have another play and perhaps get the injectors tested.
PetrolHeadPete said:
Not sure about the decat chip etc.
A couple of weeks back I had a play with the diagnostics etc because I'd noticed a couple of unexplained "lumpy moments" and thought I'd try and track them down. My conclusion is that the low down running is just soooo critical on the throttle pot reset. With a very slight change to the throttle pot reset, i mean I'd just changed the idle screw and reset the pots, then made a tiny adjustment again bit didnt rese, I could exactly re-create the weird running: very slowly bring up the revs from idle...smooth until about 1500 then it got itself into an oscialltion mode with the adapatives and sensors see-sawing up and down, up and down with no change in throttle ! I think that there is always a place at light throttle where the mixture is not metered well enough...the closed loop is right on the edge of not working and you get a "lean spot". If you manually open the throttle very very gradually, you may find what I mean...the engine suddenly goes a bit rough and feels like it wants to die. When you drive it of course some of this gets smoothed out by the weight of the car so you dont notice it as much. And you can accelerate though it without even noticing.
I'm soon going to have another play and perhaps get the injectors tested.
When i was looking into my issues last year Dreadnought explained that the roller bearing throttle bodies did have a bit of an issue with 'pulsation' at part throttle due the greatly reduced stiction of the roller bearings. Maybe a symptom of this?? It resulted is inconsistent airflow for a given throttle settings. A couple of weeks back I had a play with the diagnostics etc because I'd noticed a couple of unexplained "lumpy moments" and thought I'd try and track them down. My conclusion is that the low down running is just soooo critical on the throttle pot reset. With a very slight change to the throttle pot reset, i mean I'd just changed the idle screw and reset the pots, then made a tiny adjustment again bit didnt rese, I could exactly re-create the weird running: very slowly bring up the revs from idle...smooth until about 1500 then it got itself into an oscialltion mode with the adapatives and sensors see-sawing up and down, up and down with no change in throttle ! I think that there is always a place at light throttle where the mixture is not metered well enough...the closed loop is right on the edge of not working and you get a "lean spot". If you manually open the throttle very very gradually, you may find what I mean...the engine suddenly goes a bit rough and feels like it wants to die. When you drive it of course some of this gets smoothed out by the weight of the car so you dont notice it as much. And you can accelerate though it without even noticing.
I'm soon going to have another play and perhaps get the injectors tested.
This is why Dreadnoughts offering was a hybrid of bushers / bearings, and cost over £1k!! From the discussions i had they had tested extensively. I just couldnt afford £1k after my engine rebuild
Edited by Robertjp on Tuesday 19th April 13:57
Chad speed said:
I have made significant progress in resolving the hesitation and will post a resume of what worked and what didn't in due course but for now a little more advice please.
I had the engine re-mapped which improved the hesitation but didn't cure it. I have noticed now that I have a constant AFR fault on 456 and an intermittent AFR fault on 123. Installing a standard chip myself for comparison instantly cured the AFR faults (adaptive's on the std chip range between 0 and +16. With the re-mapped chip -7 to -35). I will take the car back and have the re-mapped chip altered as clearly something is wrong and I have an MOT due soon as well.
The question for now, is the re-mapped chip doing the engine or lambda's or Cats any harm? We are off on a touring trip at the end of next week and I would prefer to leave the re-map chip in as it drives better with it, but obviously not if there is risk of any damage?
Would suggest a chat with Dom at TVR power. If the chip isnt the correct one...yes, it can do some real damage, one such problem is detonation, which can cause all sorts of issues from simple rough running to pistons with holes in them and thrown bearings. Dom has had a lot of experience with the maps. I had the engine re-mapped which improved the hesitation but didn't cure it. I have noticed now that I have a constant AFR fault on 456 and an intermittent AFR fault on 123. Installing a standard chip myself for comparison instantly cured the AFR faults (adaptive's on the std chip range between 0 and +16. With the re-mapped chip -7 to -35). I will take the car back and have the re-mapped chip altered as clearly something is wrong and I have an MOT due soon as well.
The question for now, is the re-mapped chip doing the engine or lambda's or Cats any harm? We are off on a touring trip at the end of next week and I would prefer to leave the re-map chip in as it drives better with it, but obviously not if there is risk of any damage?
Not scaremongering but its something you really need to check!!!
Since starting this thread I've spent 10 months on and off hunting down the cause of hesitation or a very slight misfire at light throttle openings (it seems a few other SP6 owners have the same issues as well). With the help of fellow Tivers on PH I’ve done the following that has improved things but I’m not there yet:
• Roller bearing throttle bodies
• Plugs, leads, coil pack, crank sensor, throttle pots
• Injectors cleaned and balanced
• Re-map (general improved driveability but little effect on the problem)
• Engine loom plug connections cleaned
Next I guess is to replace the Lambda sensors but the software graphs show all to be ok with them. Before doing the Lambdas, which is £300+, I have noticed a certain pattern to the problem which I’d like to get to the bottom of first.
The hesitation almost disappears after re-fuelling but gradually comes back after about 5 minutes. I’m not sure if it’s related to switching off the ignition, venting the fuel tank, or a rise in under bonnet temperatures.
Any thoughts welcome, I’m getting thoroughly hacked off with it now.
• Roller bearing throttle bodies
• Plugs, leads, coil pack, crank sensor, throttle pots
• Injectors cleaned and balanced
• Re-map (general improved driveability but little effect on the problem)
• Engine loom plug connections cleaned
Next I guess is to replace the Lambda sensors but the software graphs show all to be ok with them. Before doing the Lambdas, which is £300+, I have noticed a certain pattern to the problem which I’d like to get to the bottom of first.
The hesitation almost disappears after re-fuelling but gradually comes back after about 5 minutes. I’m not sure if it’s related to switching off the ignition, venting the fuel tank, or a rise in under bonnet temperatures.
Any thoughts welcome, I’m getting thoroughly hacked off with it now.
Chad speed said:
Since starting this thread I've spent 10 months on and off hunting down the cause of hesitation or a very slight misfire at light throttle openings (it seems a few other SP6 owners have the same issues as well). With the help of fellow Tivers on PH I’ve done the following that has improved things but I’m not there yet:
• Roller bearing throttle bodies
• Plugs, leads, coil pack, crank sensor, throttle pots
• Injectors cleaned and balanced
• Re-map (general improved driveability but little effect on the problem)
• Engine loom plug connections cleaned
Next I guess is to replace the Lambda sensors but the software graphs show all to be ok with them. Before doing the Lambdas, which is £300+, I have noticed a certain pattern to the problem which I’d like to get to the bottom of first.
The hesitation almost disappears after re-fuelling but gradually comes back after about 5 minutes. I’m not sure if it’s related to switching off the ignition, venting the fuel tank, or a rise in under bonnet temperatures.
Any thoughts welcome, I’m getting thoroughly hacked off with it now.
I have heard there are leakage issues with the roller bearing throttle body conversions? Could this be causing the issue?• Roller bearing throttle bodies
• Plugs, leads, coil pack, crank sensor, throttle pots
• Injectors cleaned and balanced
• Re-map (general improved driveability but little effect on the problem)
• Engine loom plug connections cleaned
Next I guess is to replace the Lambda sensors but the software graphs show all to be ok with them. Before doing the Lambdas, which is £300+, I have noticed a certain pattern to the problem which I’d like to get to the bottom of first.
The hesitation almost disappears after re-fuelling but gradually comes back after about 5 minutes. I’m not sure if it’s related to switching off the ignition, venting the fuel tank, or a rise in under bonnet temperatures.
Any thoughts welcome, I’m getting thoroughly hacked off with it now.
Thanks PipeNslippers, pretty sure the roller bearings are ok. Machined the throttle bodies and fitted the bearings myself. Not really sure where the view that they leak came from? Just look at the original set-up and compare it to the double sealed bearings. Thanks anyway, I'll do the dripping petrol onto the bearings whilst running test just to make sure.
Chad
Chad
Gassing Station | Speed Six Engine | Top of Page | What's New | My Stuff