This random two speed idle RPM comes back to irritate me every now and again and I usually get over it for a while by several days of fiddling with springs etc, and compromising in some way. Anyway having recently acquired what I perceived to be a better throttle body I went through the set up procedure again ensuring the little micro switch etc is set up properly and sure enough same problem exists with the "new" throttle body. I know one might be thinking the problem lies somewhere else but I have spent some time pondering on this and on the basis that most used throttle bodies will have similar wear I come to the following conclusion: If I let the throttle close in the normal way it will randomly add two or three hundred RPM over the setting of 750. But if I let the throttle flick back to the idle position it will always return to the correct setting. This happens even with the throttle cable disconnected. Note the idle micro switch is set correctly and the RPM drops down to the set value when the engine warms up. I suspect that an (albeit small) amount of wear in the shaft (bearings) allows a simultaneous engagement scenario to exist between the butterfly and the factory set throttle stop. On both throttle bodies I can feel/see this play by holding the throttle off its stop while moving the shaft about both radially and longitudinally. I suspect that due to wear over time the butterfly/spindle assembly can be arrested by the inner wall of the throttle body before the throttle stop contacts its landing face which incidentally has a dimple which, too has developed over time and could add to the problem. So flicking the throttle back or manually wiggling the spindle the butterfly by hand moves the spindle/butterfly assembly fully into that final position thus closing the air gap which is responsible the 200 or so RPM to the tick over. The solution therefore is clearly to re-bush the spindle and re-face the throttle stop landing face eliminating the play in the bearings – a job I have not been prepared to take on without having a spare throttle body to hand. In the meantime and seeking a way to test this theory I have backed off the throttle stop screw so that the butterfly centralises in the bore just before the throttle stop screw would make contact. As it happens the butterfly does not jam although clearly this would best only to be a short time trial. Another solution might be to lock the two butter fly retaining screws with just enough slack to allow the butterfly to float into proper relationship with the bore until the throttle stop comes into play although the prospect of the screws getting loose and being gobbled up by the engine doesn’t appeal. Plus it is not part of the design intent. Like I said earlier the ideal solution is clearly to re-bush/seal the spindle and resurfaces the throttle stop landing face. Top of my somewhat disorganised to do list I’d be interested if any fellow WBX'ers has suffered this lurgy and/or has any views around this wear issue.
Well-timed silence hath more eloquence than speech.
"A quiet shy boy who took little part in games or sport"
88 High top 2.1 WBX
I have but with a carb setup, sometimes I get about 1k
Sometimes it sits as is should around 800ish. Ive backed the stop off a turn to see if that helps.
When hot that is.. not at cold as I know the idle is higher for the first few mins.
Sadly I've no experience on digijet/fant systems. Other than books and YouTube vids
Mr Bean wrote:This random two speed idle RPM comes back to irritate me every now and again and I usually get over it for a while by several days of fiddling with springs etc, and compromising in some way. Anyway having recently acquired what I perceived to be a better throttle body I went through the set up procedure again ensuring the little micro switch etc is set up properly and sure enough same problem exists with the "new" throttle body. I know one might be thinking the problem lies somewhere else but I have spent some time pondering on this and on the basis that most used throttle bodies will have similar wear I come to the following conclusion: If I let the throttle close in the normal way it will randomly add two or three hundred RPM over the setting of 750. But if I let the throttle flick back to the idle position it will always return to the correct setting. This happens even with the throttle cable disconnected. Note the idle micro switch is set correctly and the RPM drops down to the set value when the engine warms up. I suspect that an (albeit small) amount of wear in the shaft (bearings) allows a simultaneous engagement scenario to exist between the butterfly and the factory set throttle stop. On both throttle bodies I can feel/see this play by holding the throttle off its stop while moving the shaft about both radially and longitudinally. I suspect that due to wear over time the butterfly/spindle assembly can be arrested by the inner wall of the throttle body before the throttle stop contacts its landing face which incidentally has a dimple which, too has developed over time and could add to the problem. So flicking the throttle back or manually wiggling the spindle the butterfly by hand moves the spindle/butterfly assembly fully into that final position thus closing the air gap which is responsible the 200 or so RPM to the tick over. The solution therefore is clearly to re-bush the spindle and re-face the throttle stop landing face eliminating the play in the bearings – a job I have not been prepared to take on without having a spare throttle body to hand. In the meantime and seeking a way to test this theory I have backed off the throttle stop screw so that the butterfly centralises in the bore just before the throttle stop screw would make contact. As it happens the butterfly does not jam although clearly this would best only to be a short time trial. Another solution might be to lock the two butter fly retaining screws with just enough slack to allow the butterfly to float into proper relationship with the bore until the throttle stop comes into play although the prospect of the screws getting loose and being gobbled up by the engine doesn’t appeal. Plus it is not part of the design intent. Like I said earlier the ideal solution is clearly to re-bush/seal the spindle and resurfaces the throttle stop landing face. Top of my somewhat disorganised to do list I’d be interested if any fellow WBX'ers has suffered this lurgy and/or has any views around this wear issue.
If you wind the stop screw right out, so it never touches the face, does that help?
I watched a good clip on YouTube about this, and they mentioned wiggling the spindle in the throttle body. The slightest movement will affect it, by either not fully closing, or not allowing the throttle switch to close.
It would be a huge help if someone could loan you a known good one.
At least then you absolutely know for sure this is the root of all the irritants, and you can then attempt a repair or buy the GoWesty replacement?
Sent from my iPhone using Tapatalk
'89 1.9 DG
“Some people die at 25 years old, and are buried at 75 yrs old” ~ Benjamin Franklin.
I am currently running with the factory set throttle stop backed off but unhappy as it is a bodge and questionable in the long term. So far the idle returns reliably to the set RPM. I believe that a TB with zero wear wil be rare as rocking horse poo and just for the shear hell of it have devised a Bean style upgrade which I an convinced will solve the problem:
1/Counterbore both Lip Seal apertures to 16mm by 6mm deep.
2/replace the Lip Seals with nitrile sealed stainless steel ball races. (E D I T: Remove old item 2)
3/Temporarily install the butterfly shaft and butterfly and pushing the butterfly firmly closed, determine the shim washer size required at the microswitch end.
4/Replace the shaft and butterfly with the shim in place.
5/Assemble the hardware at the throttle cable end of the shaft adding shim/s to eliminate logitudinal play in the shaft.
6/ Bring the factory set throttle stop to just contact the setting face.
Design intent:
Eliminate radial play in the butterfly shaft assembly - the ball races will achieve this.
Eliminate longitudinal float in the butterfly shaft assembly - the shimming will achieve this.
Eradicate leakage between TB body and butterfly shaft - the nitrile bearing seals will achieve this.
Reduce friction - new ball races are superior to plain bearings, particularly when side load from throttle cable is considered.
I have this modification under way and will be testing it shorly. Watch this space.
Well-timed silence hath more eloquence than speech.
"A quiet shy boy who took little part in games or sport"
88 High top 2.1 WBX
Mr Bean wrote:I am currently running with the factory set throttle stop backed off but unhappy as it is a bodge and questionable in the long term. So far the idle returns reliably to the set RPM. I believe that a TB with zero wear wil be rare as rocking horse poo and just for the shear hell of it have devised a Bean style upgrade which I an convinced will solve the problem:
1/Counterbore both Lip Seal apertures to 16mm by 6mm deep.
2/replace the Lip Seals with nitrile sealed stainless steel ball races. (E D I T: Remove old item 2)
3/Temporarily install the butterfly shaft and butterfly and pushing the butterfly firmly closed, determine the shim washer size required at the microswitch end.
4/Replace the shaft and butterfly with the shim in place.
5/Assemble the hardware at the throttle cable end of the shaft adding shim/s to eliminate logitudinal play in the shaft.
6/ Bring the factory set throttle stop to just contact the setting face.
Design intent:
Eliminate radial play in the butterfly shaft assembly - the ball races will achieve this.
Eliminate longitudinal float in the butterfly shaft assembly - the shimming will achieve this.
Eradicate leakage between TB body and butterfly shaft - the nitrile bearing seals will achieve this.
Reduce friction - new ball races are superior to plain bearings, particularly when side load from throttle cable is considered.
I have this modification under way and will be testing it shorly. Watch this space.
Sent from my iPhone using Tapatalk
'89 1.9 DG
“Some people die at 25 years old, and are buried at 75 yrs old” ~ Benjamin Franklin.
Can't see why I have no knowledge at all regarding that MacGyver character - must have wizzed completely over my head. Had to Google him to see what was meant.
Got to admit somewhat proudly that one of my KPI's is the ability to solve engineering problems in a ruthless back to basics kind of way often rearanging things using readily available alternative components to achieve the original designers objectives. Never actually blown anything up but had a few near misses .
Well-timed silence hath more eloquence than speech.
"A quiet shy boy who took little part in games or sport"
88 High top 2.1 WBX
Mr Bean wrote:Can't see why I have no knowledge at all regarding that MacGyver character - must have wizzed completely over my head. Had to Google him to see what was meant.
Got to admit somewhat proudly that one of my KPI's is the ability to solve engineering problems in a ruthless back to basics kind of way often rearanging things using readily available alternative components to achieve the original designers objectives. Never actually blown anything up but had a few near misses .
He was a part of my youth - would watch that program at my nan’s with my cousin. We watched in amazement
Sent from my iPhone using Tapatalk
'89 1.9 DG
“Some people die at 25 years old, and are buried at 75 yrs old” ~ Benjamin Franklin.
I finally completed the “upgrade” on my spare but worn WBX throttle body and road tested it this morning with very successful results. When I get time - and should any interest be expressed, I may set out a more detailed schedule of what it involved. (Not a job for the ill equipped or faint hearted though) Briefly: I replaced the lip seals with (dimensionally larger) sealed miniature ball races, custom made shims for both ends of the butterfly spindle and reassembled the whole caboose with borderline watchmaker care. Probably the most difficult job though, was machining the new ball race seats with line reaming accuracy.
Well-timed silence hath more eloquence than speech.
"A quiet shy boy who took little part in games or sport"
88 High top 2.1 WBX
Mr Bean wrote:I finally completed the “upgrade” on my spare but worn WBX throttle body and road tested it this morning with very successful results. When I get time - and should any interest be expressed, I may set out a more detailed schedule of what it involved. (Not a job for the ill equipped or faint hearted though) Briefly: I replaced the lip seals with (dimensionally larger) sealed miniature ball races, custom made shims for both ends of the butterfly spindle and reassembled the whole caboose with borderline watchmaker care. Probably the most difficult job though, was machining the new ball race seats with line reaming accuracy.
Well done - I’m impressed
Sent from my iPhone using Tapatalk
'89 1.9 DG
“Some people die at 25 years old, and are buried at 75 yrs old” ~ Benjamin Franklin.
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