R53 idling fluctuations at stand still

21113 Views 43 Replies 19 Participants Last post by  casper911ca
My R53 has developed a new gremlin.

The past month or so Iv noticed when the car idles at stand still for more than 5 minutes or so the revs start fluctuating on the verge of cutting out and then picks itself back up again and down /up etc Temperature gauge is always at half when it's at temperature and the fan is working ( even though Iv only heard it once with the air temp still being pretty cold ) if I rev the car it settles back to normal . It's almost like the car Is running out of fuel . Its had a recent full service including fuel filter .

There's no issues when the car is driving it just seems to be at idle for anytime over 5/10mins waiting for work with the heaters on mainly . I'm abit concerned as its intermittent but probably happening more often in the same situations and I really need it reliable .

Any ideas ?
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This is related to cansiter purge. It could happen with aftermarket badly tuned injectors, problem with canister purge lines, valve, map sensor... Anything that could disturb air/fuel ratio during canister purge at idle.

for example my car never had the issue before , then I installed 550cc with approximate dead times tuning and it started to randomly "die" at idle. Then I set more precise dead times (still trying to find the OEM certified values on the internet....) and never had the issue again
Mine doesn't do it anymore after I stopped filling the tank up to the top. Someone suggested that in another thread. Sounded silly but after filling couple of times until the first "click", idle problem is gone :confused1:
I guess you hadn't completely fucked up the activated charcoal canister yet. :D
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I guess you hadn't completely fucked up the activated charcoal canister yet. :D
Any idea where the canisters purge valve is located in 2007 base model?
Just had a quick look about there seems to be a “t map sensor” or a “map sensor”. I’m assuming it would just be a map sensor, or did you replace both?
You can back probe the sensors and check them with a voltmeter. Put a very thin nail or sewing needle through the back of the sensor pin 3 (3rd of the driver's side, port side) on the TMAP sensor and pin 4 on the MAP sensor (closest to the front) and connect with a voltmeter, then check the voltages at key in (not running), idle and 2500 rpm. Note: Voltages will go to zero after a few minutes after key in, so don't take forever to take that data point. There are also redline values, but three points should be enough to show they are functional. I think PIN 2 on the TMAP is a 5V reference, so you can check that first if you doubt your back probe isn't making contact. And keep an eye on your ground contact, I kept getting 0V, but discovered my multimeter ground contact kept falling off.

Nominal values:
TMAP: 1.9V @ key in, 0.9V @ idle, 0.6V @ 2500rpm
MAP: 4.0V @ key in, 1.8V @ idle, 1.1V @ 2500rpm
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