kangarooing/stumbling/stuttering
Discussion
Not sure wat the right description is of the ailement, nor am I sure if it is a real ailment....
When barely touching the throttle (keeping speed stable) my 4.2 kangaroes.... its most obvious between 2500-3000 rpm and in lower gears, however I can feel the stuble or stutter also at 60 mph up (around 3000 rpm).
The car has been remapped (at Austec) and Paul has put quite some time in it, also to alleviate this problem, but it has not disappeared, so I am wondering if it can be solved at all....
Has anybody had the same issues and has he been able to solve them? Is it just the nature of the 4.2 and should I learn to live with it? Its a bit of a pain though as much of the driving is done barely touching the throttle anyway (only takes a couple of seconds to get up to speed.....).
I'd like to think that there should be a solution for it, might it be a flaw of the inlet manifold design: no bearings, spindles start to move a bit, butterflies may not open exactly at the same time, throttlepot readings become more erratic...? Or does it have to do with the lambda (saw a discussion elsewhere suggesting that at low rpms it's to slow giving signals about lean/rich mixture)?
thx
wiebe
When barely touching the throttle (keeping speed stable) my 4.2 kangaroes.... its most obvious between 2500-3000 rpm and in lower gears, however I can feel the stuble or stutter also at 60 mph up (around 3000 rpm).
The car has been remapped (at Austec) and Paul has put quite some time in it, also to alleviate this problem, but it has not disappeared, so I am wondering if it can be solved at all....
Has anybody had the same issues and has he been able to solve them? Is it just the nature of the 4.2 and should I learn to live with it? Its a bit of a pain though as much of the driving is done barely touching the throttle anyway (only takes a couple of seconds to get up to speed.....).
I'd like to think that there should be a solution for it, might it be a flaw of the inlet manifold design: no bearings, spindles start to move a bit, butterflies may not open exactly at the same time, throttlepot readings become more erratic...? Or does it have to do with the lambda (saw a discussion elsewhere suggesting that at low rpms it's to slow giving signals about lean/rich mixture)?
thx
wiebe
One of the problems with the 4.2 is the way the throttle linkage and stop is designed.
The cable pulls the N/S bank rod but the thottle stop is on the O/S bank rod.
So if there is any play at all in the linkage the first part of the throttle movement opens the N/S bank and takes up play in the linkage before opening the O/S bank. Lots of slop makes for a lumpy throttle response. The ball joints wear very quickly. A new pair on my car lasted less than a year.
Solution 1 is to replace the ball joints with rod ends. Ondrive do some nice 5mm rode ends in LH and RH threads but close to £20 each. And they will still wear out although a lot less noticeable than the ball joints.
Solution 2 is to remove the design flaw and fit a throttle stop to the N/S bank so that the tension of the O/S bank spring takes up any slop in the linkage.
The cable pulls the N/S bank rod but the thottle stop is on the O/S bank rod.
So if there is any play at all in the linkage the first part of the throttle movement opens the N/S bank and takes up play in the linkage before opening the O/S bank. Lots of slop makes for a lumpy throttle response. The ball joints wear very quickly. A new pair on my car lasted less than a year.
Solution 1 is to replace the ball joints with rod ends. Ondrive do some nice 5mm rode ends in LH and RH threads but close to £20 each. And they will still wear out although a lot less noticeable than the ball joints.
Solution 2 is to remove the design flaw and fit a throttle stop to the N/S bank so that the tension of the O/S bank spring takes up any slop in the linkage.
mikesr said:
One of the problems with the 4.2 is the way the throttle linkage and stop is designed.
The cable pulls the N/S bank rod but the thottle stop is on the O/S bank rod.
So if there is any play at all in the linkage the first part of the throttle movement opens the N/S bank and takes up play in the linkage before opening the O/S bank. Lots of slop makes for a lumpy throttle response. The ball joints wear very quickly. A new pair on my car lasted less than a year.
Solution 1 is to replace the ball joints with rod ends. Ondrive do some nice 5mm rode ends in LH and RH threads but close to £20 each. And they will still wear out although a lot less noticeable than the ball joints.
Solution 2 is to remove the design flaw and fit a throttle stop to the N/S bank so that the tension of the O/S bank spring takes up any slop in the linkage.
Could also be the throttle pots...? They pick up interference and need adjusting / replacing...quite common apparently? This results in hunting as constant throttle, espcially at low speeds, or at least it is more noticable then.The cable pulls the N/S bank rod but the thottle stop is on the O/S bank rod.
So if there is any play at all in the linkage the first part of the throttle movement opens the N/S bank and takes up play in the linkage before opening the O/S bank. Lots of slop makes for a lumpy throttle response. The ball joints wear very quickly. A new pair on my car lasted less than a year.
Solution 1 is to replace the ball joints with rod ends. Ondrive do some nice 5mm rode ends in LH and RH threads but close to £20 each. And they will still wear out although a lot less noticeable than the ball joints.
Solution 2 is to remove the design flaw and fit a throttle stop to the N/S bank so that the tension of the O/S bank spring takes up any slop in the linkage.
Good luck
I am looking at the website of ondrives right now, but there is a lot to choose from: Any suggestions?
Creating the extra stop seems fairly straightforward but if anybody has done that before i'd appreciate any advice beforehand how to do that. My first idea was I would simply drill a small diameter hole, tap a thread and screw in a bolt, however I would not have an idle control. Is there any part readily available to make the stop from or will I have to machine one myself? If the latter: Any suggestions on the material (thinking corrosion)?
Now how about the spindles over time sitting looser in the manifolds, messing up the throttle pot's, would that make a difference? And what about the butterflies not opening at the same time: is there a chance of play building up by which the butterfly closest to the windscreen opens first, followed by the ones further away?
Last but not least I am still wondering what the sequence of events is what causes the stumbling: Is it not all cilinders getting the same fuel mixture (by any of the above discussed possibilities) causing the lambda's to become confused, creating a less frequent change in mixture (after all even at idle there are still about 13/16rps, where a lambda sends a signal every half a second?).
The more I think about it: Is the stop and rod end issue really a big think, after all the ajp fires two cilinders at the same time each time, one in each bank. So if the cilinder banks get a diffrent mixture, should that not be averaged out simply by the fact that both banks are firing at the same time and that you you should not feel a thing?
thx
Wiebe
Creating the extra stop seems fairly straightforward but if anybody has done that before i'd appreciate any advice beforehand how to do that. My first idea was I would simply drill a small diameter hole, tap a thread and screw in a bolt, however I would not have an idle control. Is there any part readily available to make the stop from or will I have to machine one myself? If the latter: Any suggestions on the material (thinking corrosion)?
Now how about the spindles over time sitting looser in the manifolds, messing up the throttle pot's, would that make a difference? And what about the butterflies not opening at the same time: is there a chance of play building up by which the butterfly closest to the windscreen opens first, followed by the ones further away?
Last but not least I am still wondering what the sequence of events is what causes the stumbling: Is it not all cilinders getting the same fuel mixture (by any of the above discussed possibilities) causing the lambda's to become confused, creating a less frequent change in mixture (after all even at idle there are still about 13/16rps, where a lambda sends a signal every half a second?).
The more I think about it: Is the stop and rod end issue really a big think, after all the ajp fires two cilinders at the same time each time, one in each bank. So if the cilinder banks get a diffrent mixture, should that not be averaged out simply by the fact that both banks are firing at the same time and that you you should not feel a thing?
thx
Wiebe
turfclubroad said:
I am looking at the website of ondrives right now, but there is a lot to choose from: Any suggestions?
Creating the extra stop seems fairly straightforward but if anybody has done that before i'd appreciate any advice beforehand how to do that. My first idea was I would simply drill a small diameter hole, tap a thread and screw in a bolt, however I would not have an idle control. Is there any part readily available to make the stop from or will I have to machine one myself? If the latter: Any suggestions on the material (thinking corrosion)?
Now how about the spindles over time sitting looser in the manifolds, messing up the throttle pot's, would that make a difference? And what about the butterflies not opening at the same time: is there a chance of play building up by which the butterfly closest to the windscreen opens first, followed by the ones further away?
Last but not least I am still wondering what the sequence of events is what causes the stumbling: Is it not all cilinders getting the same fuel mixture (by any of the above discussed possibilities) causing the lambda's to become confused, creating a less frequent change in mixture (after all even at idle there are still about 13/16rps, where a lambda sends a signal every half a second?).
The more I think about it: Is the stop and rod end issue really a big think, after all the ajp fires two cilinders at the same time each time, one in each bank. So if the cilinder banks get a diffrent mixture, should that not be averaged out simply by the fact that both banks are firing at the same time and that you you should not feel a thing?
thx
sounds like a good thorough rolling road tune is in order...?
Wiebe
Creating the extra stop seems fairly straightforward but if anybody has done that before i'd appreciate any advice beforehand how to do that. My first idea was I would simply drill a small diameter hole, tap a thread and screw in a bolt, however I would not have an idle control. Is there any part readily available to make the stop from or will I have to machine one myself? If the latter: Any suggestions on the material (thinking corrosion)?
Now how about the spindles over time sitting looser in the manifolds, messing up the throttle pot's, would that make a difference? And what about the butterflies not opening at the same time: is there a chance of play building up by which the butterfly closest to the windscreen opens first, followed by the ones further away?
Last but not least I am still wondering what the sequence of events is what causes the stumbling: Is it not all cilinders getting the same fuel mixture (by any of the above discussed possibilities) causing the lambda's to become confused, creating a less frequent change in mixture (after all even at idle there are still about 13/16rps, where a lambda sends a signal every half a second?).
The more I think about it: Is the stop and rod end issue really a big think, after all the ajp fires two cilinders at the same time each time, one in each bank. So if the cilinder banks get a diffrent mixture, should that not be averaged out simply by the fact that both banks are firing at the same time and that you you should not feel a thing?
thx
sounds like a good thorough rolling road tune is in order...?
Wiebe
Replying to the initial post, my 2003 4.2 does this and i was lead to believe that this was a charachteristic of the engine. when accelerating every thing is responsive and works well. At constant speed however there is a jerkiness when at relatively low reves. Even at at say 100mph in top gear. It's like the engine just wants to accelerate all the time. That's what i tell my wife any way!
Same here, also at 100 mph, or maybe I should say any gear at about 2500-3000+... Characteristic of the engine? Well of the 4 4.2's that I test drove at least one of them did not have it at all, so if it is a characteristic it must be something which is not in the genes. Sounds more like something wearing (oh I just checked but I have no play in my rod ends) like the spindle, or some engines having spindles being more stable than the others (assuming it has anything to do with that)leading to less erratic potentio meter readings etc etc
Wiebe
Wiebe
Mine started doing this about 500 miles ago and becoming more noticable each time I drive it, I figured it was the ball ends but have to much on at the mo to get it sorted. still pulls strong on mid to full throttle. let us know if the joints cure it and how easy it is to set up the t.pots. with a ohms meter. Cheers and good luck.
I'm more than convinced that the Kangorooing of the 4.2 is an engine characteristic. I have had mine re-mapped at Austec twice for various issues,but never managed to eradicate the jerkiness. The problem is made worse with the fittment of race cams,which mine has. I have just managed to have this smoothed out the best as possible,which is a hell of a lot better than it was. Its still slightly there though. never been a problem under load,or on the over run. but at part throttle and low revs,especially town driving. Its there.
Paul (Austec) had another look at the car and found that one of the new throttle pots (They had been replaced prior the remap) readings was way of.. Maybe it had not been properly fixed. Anyway, with that rectified and more work on the map the problem has become much less noticeable. It still needs a little work by Paul, but so far so good. I have to say that I am impressed by their service.
By the way I will also go the rod end way and second throttle stop. May be a bit of over engineering, but it just seemed the right way to go.
thx
Wiebe
By the way I will also go the rod end way and second throttle stop. May be a bit of over engineering, but it just seemed the right way to go.
thx
Wiebe
Glad you've got it sorted . . . almost! Its an engine out jobbie on mine though - crankshaft oil seals (both ends) explains the slipping clutch when hot under load & so new clutch plates too as a consequence plus various other bits as well . . . once this is all done and the paint sorted it'll be up for grabs . . . form an orderly queue 
unfortunately I can't afford to run the Cerb and race too! 
. . . still smiling - just 
unfortunately I can't afford to run the Cerb and race too! . . . still smiling - just Edited by Keithyboy on Thursday 9th April 09:27
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