Hesitation after gear-change when tanking it...
15 April 2006, 09:12 AM
#32
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Hi mate,
I'd forgotten all about this post
I never fully resolved this problem although I can work around it using the technique described by AndyF earlier in the thread. I'm not sure if it's a mechanical or mapping problem. Maybe Andy F or John Banks made some progress with it - they probably just upgraded to new ages instead
I am hoping to enlist Andy's mapping services later this year so perhaps we may look at the issue again then.
Good luck with finding a solution.
Andy.
I'd forgotten all about this post
I never fully resolved this problem although I can work around it using the technique described by AndyF earlier in the thread. I'm not sure if it's a mechanical or mapping problem. Maybe Andy F or John Banks made some progress with it - they probably just upgraded to new ages instead
I am hoping to enlist Andy's mapping services later this year so perhaps we may look at the issue again then.
Good luck with finding a solution.
Andy.
15 April 2006, 04:47 PM
#33
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Cheers for posting. I think after I'd had my WRX for a couple of weeks I kind of used the same slight slipping technique without realising, suppose I just put it down to a sharp clutch (I used to run a 4-paddle cerametallic on a road car so I kind of got used to adjusting the way I drive to suit the clutch). But now I'm noticing it again, and I'm aware that I'm doing it every time I change gear or give it a little throttle and I'm sure it can't be doing my clutch any good.
Just took it out again for another run and it's definitely nothing to do with acceleration enrichment. One other thing I HAVE noticed this time is that it only does it in ONE throttle position, which I suppose is helpful. My accelerator pedal has a tiny bit of free play at the top but in general I can cruise along quite easily with the pedal down only 1 or 2 cm at most. It's in this position where if I suddenly floor it, I get the momentary hesitation then the drive suddenly comes in with a bang. Any further than this point, at say 1/4 throttle, 1/3, 1/2 etc and it will NOT do it at all. It just drives perfectly normally. Perhaps that's why I seem to have noticed the effect more in low gears at relatively slow speeds because you've got to be just tickling the accelerator and this is the exact point at which the problems happen. Something like manouevering slowly around a car park has the transmission jerking and shunting around the whole time.
So I wonder if it is to do with throttle position itself? Perhaps when they wear out, the first bit to go out of alignment is the low range where the throttle plate is hardly cracked open? This would make sense because the jerkiness seems to ONLY happen at the very top of the pedal travel, ONLY when the manifold's in vacuum. If you're on a fast cruise at a few psi of boost, any sudden flooring of the pedal results in an instantaneous response from the engine.
Just took it out again for another run and it's definitely nothing to do with acceleration enrichment. One other thing I HAVE noticed this time is that it only does it in ONE throttle position, which I suppose is helpful. My accelerator pedal has a tiny bit of free play at the top but in general I can cruise along quite easily with the pedal down only 1 or 2 cm at most. It's in this position where if I suddenly floor it, I get the momentary hesitation then the drive suddenly comes in with a bang. Any further than this point, at say 1/4 throttle, 1/3, 1/2 etc and it will NOT do it at all. It just drives perfectly normally. Perhaps that's why I seem to have noticed the effect more in low gears at relatively slow speeds because you've got to be just tickling the accelerator and this is the exact point at which the problems happen. Something like manouevering slowly around a car park has the transmission jerking and shunting around the whole time.
So I wonder if it is to do with throttle position itself? Perhaps when they wear out, the first bit to go out of alignment is the low range where the throttle plate is hardly cracked open? This would make sense because the jerkiness seems to ONLY happen at the very top of the pedal travel, ONLY when the manifold's in vacuum. If you're on a fast cruise at a few psi of boost, any sudden flooring of the pedal results in an instantaneous response from the engine.
15 April 2006, 06:00 PM
#34
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Just did a search on throttle position sensors and mine was showing 0.3 v at idle which seems too low, so I've set it for 0.55 (what I'd do without an offset screwdriver I don't know!)...I'm taking it out now and crossing my fingers that the light throttle problem will be fixed...
Well, it does seem a little better now, even though I can still get it to hesitate if I get the throttle position just right. A sudden throttle opening from anwhere between zero to 1/10 throttle will do it. Once cruising steady with 1v or more showing on the TPS it doesn't have the problem at all.
Well, it does seem a little better now, even though I can still get it to hesitate if I get the throttle position just right. A sudden throttle opening from anwhere between zero to 1/10 throttle will do it. Once cruising steady with 1v or more showing on the TPS it doesn't have the problem at all.
Last edited by silent running; 15 April 2006 at 07:46 PM.
16 April 2006, 02:35 PM
#35
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Originally Posted by Andy.F
I believe this is a fairly common problem on 99/00 cars. John Bank's car does this when I drive it and ****** it through the gears, John has learned to drive it differently, he slips the clutch a little bit between gears and there is no power cut.
It's not turbo lag, I logged it on the AP22 and it is an instantaneous power cut, then back on power, just like someone turned the key off/on.
As Bob says, possibly a weak/rich blip with the fueling when using VTA. John however uses a recirc dump valve, I guess it could still be backrush expansion of air confusing the MAF signal to the ECU.(although it was not detected on deltadash)
As you say, even at full rpm, with a 'slightly' slower shift it doesn't happen, the power is there instantly
Andy
It's not turbo lag, I logged it on the AP22 and it is an instantaneous power cut, then back on power, just like someone turned the key off/on.
As Bob says, possibly a weak/rich blip with the fueling when using VTA. John however uses a recirc dump valve, I guess it could still be backrush expansion of air confusing the MAF signal to the ECU.(although it was not detected on deltadash)
As you say, even at full rpm, with a 'slightly' slower shift it doesn't happen, the power is there instantly
Andy
16 April 2006, 07:52 PM
#36
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Well after a lot of knuckle scraping and making home-made cranked screwdrivers (no, I didn't remove the entire throttle body to get at the bottom TPS screw!) I finally removed it and I can't see what there is that can really go wrong. It must be a rotary potentiometer with a spring loaded return and I can't see how to get at the innards and clean them out or check them. A blast of carb cleaner hasn't revealed any muck or oil.
Just refitted and I've adjusted the range to 0.7v -4.6v, slightly over the recommendation but thought I'd give it a go and see if throttle response is improved...test drive reveals it's the same as when it was set at 0.55 v on idle.
Bollocks. Now what? Try a new TPS? It's getting really annoying now.
Just refitted and I've adjusted the range to 0.7v -4.6v, slightly over the recommendation but thought I'd give it a go and see if throttle response is improved...test drive reveals it's the same as when it was set at 0.55 v on idle.
Bollocks. Now what? Try a new TPS? It's getting really annoying now.
Last edited by silent running; 17 April 2006 at 02:02 PM.
24 April 2006, 08:55 PM
#37
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Hi Mate,
Sorry to hear that didn't help I was hoping for a easy fix ! I'd love to know what causes it. To me it feels like the fuel cut you get on over-boost but it's momentary. I can't help thinking it's hitting the wrong part of the fuelling map or something. I note there's another similar MY00 thread here:
http://bbs.scoobynet.co.uk/showthread.php?p=5727327
Andy.
Sorry to hear that didn't help I was hoping for a easy fix ! I'd love to know what causes it. To me it feels like the fuel cut you get on over-boost but it's momentary. I can't help thinking it's hitting the wrong part of the fuelling map or something. I note there's another similar MY00 thread here:
http://bbs.scoobynet.co.uk/showthread.php?p=5727327
Andy.
02 May 2006, 01:16 AM
#38
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we all using shell optimax? perhaps a bad batch? My CRX just started hesitating tonight, never noticed it before.
My WRX has had problems since my exhaust install. I've run the diagnostic test and found ECU error code 32 O2 Sensor fault, And 12 which I think may be down to my Turbo Timer connected through my CAT1 Alarm?
My Hesitation got so bad tonight it was almost stalling, had to drive the Honda. I'll get it to a garage tomorrow and get my Manifold leak sorted as well
My WRX has had problems since my exhaust install. I've run the diagnostic test and found ECU error code 32 O2 Sensor fault, And 12 which I think may be down to my Turbo Timer connected through my CAT1 Alarm?
My Hesitation got so bad tonight it was almost stalling, had to drive the Honda. I'll get it to a garage tomorrow and get my Manifold leak sorted as well
07 May 2006, 09:28 PM
#39
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I used to have an L reg WRX with a Full system on.After a little while i noticed my throttle cable was slack at the top end of the pedal so i sorted it so it had no travel but not to much so it raised the idle and it helped a lot with the overall drivability of the car.
BUT i've just got my new M reg WRX and i'm having the same problems as you guys are explaining here.I'm going to adjust my throttle cable in the week as it's the same as my old one was before i sorted it.
The thing is i rekon it's due to the exhaust.Due to my old one having a HUGE bore the turbo spool was instant with my new one having a sort of 'Lag' when i first floor it...standard exhaust mind.A new clutch has been fitted to mine recently and i'm not sure if this has anything to do with the problem ie not being set right.Pedal seems fine.
What exhaust is everyone running?
BUT i've just got my new M reg WRX and i'm having the same problems as you guys are explaining here.I'm going to adjust my throttle cable in the week as it's the same as my old one was before i sorted it.
The thing is i rekon it's due to the exhaust.Due to my old one having a HUGE bore the turbo spool was instant with my new one having a sort of 'Lag' when i first floor it...standard exhaust mind.A new clutch has been fitted to mine recently and i'm not sure if this has anything to do with the problem ie not being set right.Pedal seems fine.
What exhaust is everyone running?
09 May 2006, 03:27 PM
#40
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I'll have a look at the throttle cable and throttle body in general this weekend. Any tips for getting the thing off in one piece?
The thing that's weird about mine is that it doesn't happen at all if you're starting from any position other than closed throttle/full vacuum. You get INSTANT engine response anywhere else in the throttle travel. But from closed throttle you get NOTHING but a rushing of air, then half a second later, the revs come up in one big blip. The bigger the difference in throttle position whilst the engine is hesitating, the bigger the rise in revs after half a second. I've so far changed fuel filter, plugs, lambda sensor, checked the air filter, boost, temperatures, cleaned the IACV and TPS as well as I could etc etc. Nothing seems to help! Next up is replacing the TPS, leads and throttle body along with looking at the fuel pressure regulator and having the injectors out for a service.
The thing that's weird about mine is that it doesn't happen at all if you're starting from any position other than closed throttle/full vacuum. You get INSTANT engine response anywhere else in the throttle travel. But from closed throttle you get NOTHING but a rushing of air, then half a second later, the revs come up in one big blip. The bigger the difference in throttle position whilst the engine is hesitating, the bigger the rise in revs after half a second. I've so far changed fuel filter, plugs, lambda sensor, checked the air filter, boost, temperatures, cleaned the IACV and TPS as well as I could etc etc. Nothing seems to help! Next up is replacing the TPS, leads and throttle body along with looking at the fuel pressure regulator and having the injectors out for a service.
10 May 2006, 06:24 PM
#42
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I'll get right on it. In fact I've got an entire spare throttle body sitting here so I might swap the whole thing.
BTW - why are there TWO independent throttle quadrants? I've seen double quadrants before, but usually they're a 'sequential' system - i.e. the one attached to the throttle cable handles small throttle openings and then at a certain point, it engages with the second quadrant which does the rest of the throttle travel. But the Subaru ones are totally separate in operation?! So what's the point? Different spring strengths or something?
BTW - why are there TWO independent throttle quadrants? I've seen double quadrants before, but usually they're a 'sequential' system - i.e. the one attached to the throttle cable handles small throttle openings and then at a certain point, it engages with the second quadrant which does the rest of the throttle travel. But the Subaru ones are totally separate in operation?! So what's the point? Different spring strengths or something?
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