larppaxyz wrote:Mandrake wrote:
larppaxyz: does yours do this too if you quickly tap the throttle ?
Not quite like that, but thats exactly what it does sometimes when i'm just idling.
Now that i have been thinking this TPS issue (and watched some youtube videos about TPS problems and reading some articles) i think my lower end (idle part) of TPS is open circuit most of the time and ECU detects this and ignores or calibrates TPS more or less randomly because of this. I haven't seen any error codes about TPS, but maybe they get clearead everytime ECU detects TPS is ok again, or maybe it's not bad enough to trigger code.
Yes I think that's exactly what happens. An intermittent dead spot that makes the wiper connection go open circuit at some locations. With these types of inputs the ECU is self calibrating - minimum and maximum throttle are not at the extremes of the potentiometer range, they're about 1v and 4.5v respectively, the ECU learns this over time by observing the minimum and maximum voltages seen during operation.
If it never sees a voltage under 1v then 1v is calibrated as idle / closed throttle. Then if the voltage suddenly drops to 0v due to the wiper going open this represents a "less than idle" throttle opening - the initial response is to cut back fuelling and the engine attempts to stall, (you can actually hear it cut out completely on mine) when the rpm gets dangerously low the anti-stall function kicks in and the ECU opens the ICV and boosts the fuelling - the idle then surges above normal as my video showed.
As you say, sometimes this surging behaviour can happen with the throttle closed. Mine hasn't done that recently but it was doing that surging at idle after a hot start quite a lot until recently.
If the 0v reading persists after a few surge and stall cycles the ECU recalibrates the TPS input to accept 0v as the new closed throttle position. This means you now have a large discontinuity in the calibration at the bottom end of the throttle range, (if its only open circuit close to the bottom) and the scaling of the entire throttle range will be thrown way out.
Once this bogus recalibration happens I believe poor low rpm performance and throttle response occurs until the ECU is reset.
Anyway, it's 5min job max to replace TPS on my Pug, but i have no quick access to (new) replacement part. I'm thinking about opening up my TPS (i know it's glued/molted, but should be possible anyway) to clean it and just slightly twist those "legs" that are in contact with "resistance" part. I will do some resistance measuring and visually inspect it. I assume construction is similar to this
http://www.4crawler.com/4x4/CheapTricks/TPS/tps2.gif" onclick="window.open(this.href);return false; (this is however 4-wire version).
I don't know why, but i have feeling this could be it finally
(Yeah... right)
I don't think its a good idea to try dismantling your TPS, if it breaks your car is off the road...
Although a lack of wiper tension could be the problem, on a carbon track potentiometer the usual failure mode is the carbon track itself wears out at points where the potentiometer spends a lot of time - for example at closed throttle. In that case tensioning the wiper won't help.
Will that ebay seller I linked to not ship to your country ? (Where are you again ?)
If you're really stuck and can't find one for a good price anywhere let me know and I could get another one from the same seller and post it to you if you're willing to pay the extra postage...(I have no idea what the postage would be but its very small and light and would fit in a bubble bag)
I reckon I can have this car fixed by page 100 otherwise...)
)
