S1 revs stick - heater related?

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chrisdb
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S1 revs stick - heater related?

Post by chrisdb » Wed Aug 12, 2015 8:42 pm

odd one this. I had the car out for the first time in the evening yesterday and it was a bit cold so I put the heater on to the feet. It may have been coincidence but the revs then started sticking around 1500 and were slow or sticking on gear changes. I turned the heater off and it was soon ok again.

Is this a known quirk? Or heat doing something to the throttle pedal assembly?

It doesn't happen normally so think throttle bodies etc are fine (I think I have the alu one)

Cheers
Chris

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s29ttc
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Re: S1 revs stick - heater related?

Post by s29ttc » Wed Aug 12, 2015 9:13 pm

Is it under rev or on idle? There is also the idle air control valve that may be the source but don't believe it's in anyway related to the heaters.
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chrisdb
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Re: S1 revs stick - heater related?

Post by chrisdb » Wed Aug 12, 2015 9:51 pm

To get it to idle I needed to put it in gear to bring them down then it stayed at normal idle. When driving along the revs were slow to reduce between gear shifts and only got down to 1500 or so :?

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Ferg
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Re: S1 revs stick - heater related?

Post by Ferg » Wed Aug 12, 2015 10:32 pm

I would think the heater thing is unrelated, but no expert. Can't think how it would be. At a stretch maybe the ECU coolant temp sensor getting a shock of cold water but that wouldn't persist. Good to change the sensors out anyway BTW.

Were you able to reduce the revs by lifting the throttle pedal with your foot? The throttle cable can get sticky if it's on it's way out. Other thought is to check the throttle body and IACV. If the throttle spring is dirty etc is operation can be hampered. It should clean and dry. You can also take the IACV out easily and check its no sticking due to dirt etc.

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robin
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Re: S1 revs stick - heater related?

Post by robin » Thu Aug 13, 2015 7:46 am

It's pretty simple to diagnose some of this from the boot. You can open the throttle quadrant by hand (or press the accelerator from inside the car) until the revs stick (in neutral, obvz).

Once the revs are stuck, go to the boot and close the quadrant by hand. If closing the quadrant fixes it then you have a sticky cable or a sticky throttle. If you cannot close the quadrant because the throttle is already on the end stop DO NOT ATTEMPT TO FORCE IT.

Next problem can be the TPS (Throttle Position Sensor). If the ECU thinks that the throttle is slightly open (regardless of whether it is or is not open) then the ECU will stop controlling the idle and instead go into anti-stall - this could cause the revs to rise. There is a tiny possibility that if the TPS is borderline, the additional electrical load presented by the heater could make this problem slightly more likely to appear.

The way to "fix" that is to recalibrate the TPS and see if the issue goes away. Recalibration involves turning the ignition off, wait 30 seconds. Turn ignition on (but do not crank engine, so key should be in run position). Fully press and release the throttle 10 times. Note you should be careful to push the pedal to the deck and then completely take your foot off it. Turn the ignition off, wait 30 seconds. Now see whether the car behaves itself any better. If this does fix it, sometimes it can be only a temporary fix - if that's the case you probably need a new TPS.

It could also be the IACV sticking, as was mentioned above, or an inlet manifold airleak (split breather hose, inlet gasket failure).

Cheers,
Robin
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chrisdb
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Re: S1 revs stick - heater related?

Post by chrisdb » Thu Aug 13, 2015 9:31 am

Wow - thanks guys!

Will attempt to diagnose tonight and report back

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