Possible causes of unstable idle?

[knowley]

Hi everyone,

 

My R300s idle is a little bit unstable at the moment. I had a dodgy Throttle Pot which was changed. I had a remap which never really seemed to work well at cold start/hot idle/mot emmisions/idle with fan running etc but last night we switched it back to the standard map.

 

So far so good, she drives like a bat out of hell - seemed a lot more tame on the modified map?! And the idling / cold start is a little better behaved... but still not perfect.

 

After a 15 minute motorway jounrey the idle is a firm 900rpm, a brief blip of the throttle and they drop to just over 500rpm if left it will slowly climb back to 1000rpm+. A warm start showed a low idle of around 500rpm which did cut out once...

 

Just wondering if there are any sensors, or settings or anything else that might be on the blink causing this odd behaviour?

 

Cheers

 

My R300

[jackb_ms]

It also could be some air getting in?

 

Emily, The Very Yellow 21

[Julian Thompson]

Sounds like the IACV?

[knowley]

Air getting in where?

 

What the IACV? (I have seen that mentioend before but haven't a clue what it is).

 

Mark also thought the ecu sensor for the water temprature could cause issues?

 

Thanks

 

My R300

[knowley]

Apparently R300s with throttle bodies dont have an IACV (well according to other threads in techtalk).

 

My R300

[Kevsta]

I think it depends what r300 you have. If it is the early one with fancy TBs then no. But if you have the VVC engine then yes you do.

 

This may of course be wrong but I am pretty certain it is correct

[MattC]

It could just be the map, what ECU do you have?

 

Matt

[mav]

He's original R300 with RBTB and MBE ECU.

[MattC]

The blip of the throttle causing rpms to fall to 500 and struggle back up to 1000 can (I think) be rectified by adding ignition advance in the TP1 / RPM1 cell in the map (creating a ramp below normal idle speed)

 

It sounds like like the idle speed fuel / ignition settings are ok but the warm up map may be out a little (how warm was the warm start?). Normally making this a little richer and possibly a little more ignition advance will stabilize idle

 

Matt

 

Edited by - MattC on 4 Sep 2007 18:00:26

[Ian R]

 

It could also be that the new pot is not in the same position as the original one, and this is causing all the mapping sites to be out in conjunction with your map.

 

You might need a brief RR session to get the settings alighned again.

 

Regards

 

Ian

(If you want to go faster, you will have to add lightness!)