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911sc running problems

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Hi, I have only had my car a few months and I have a problem when the car is at low revs its not running smooth, but runs fine higher up the rev range.
Someone has told me it might be the warm up regulator (Bosch part number 0438140069) but I am not sure and I have had some crazy prices from £300 up over. It also runs ruff with the advance pipe connected to the distributer hence I am running round with it off. The car starts great when cold and when red hot, but not when its just warm
 
It could easily be the WUR but it could be one of the other components in the CIS system, none of the components are cheap, best advice is to get it checked by a Bosch specialist who knows this system, they should be looking to check hot and cold pressures.
 
Hi Daz,
A little more information please.
What happens when you start the engine from cold with your foot off the throttle.
i.e. will the engine tick over and run through the warm up stage without using the throttle ?
Cheers
John



 
Hi John sorry about not repleying sooner wanted to try it this morning, starts with no throttle and ticks over no problem till its warm, revs about 800 to 900
 
Hi Daz,
Thanks for the reply.
After starting the engine from cold do the revs rise to around 12 to 1500 after a couple of minutes or so then gradually fall back to your 800 to 900 figure say after 4 to 5 minutes. This is what my engine does.
You mention in your first message about the warm up regulator which could be at fault. I assume you are talking about the auxiliary air bypass valve ( as stated in the Bentley manual) which when starting from cold will be open to allow more air into the engine during the warm up stage to raise idle speed. A bi metal strip within the valve gradually closes the valve after 4 to 5 minutes which will reduce idle speed back to normal running. After the warm up stage this valve remains closed due to voltage on the bi metal strip. If this valve does not shut properly then a small amount af air could still be flowing into the engine. If your engine idle speed rises to 12 to 1500 during the warm up stage and falls to idle speed then valve is probably functioning correctly during the warm up stage.
To check that the valve is closed properly when the engine is hot all you need to do is clamp the rubber pipe which is connected to the valve when the engine is hot, the engine tick over revs should not change.
The valve is located on the top of the engine and toward the back of the engine on the right hand side, it has about a 20mm rubber pipe connected to both sides of the valve.
Before you spend any money I would recommend you check out the valve as described above.
Cheers
John
 
John, The revs dont go that high I will check the pipe like you said tommorow thank you
 
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