Running Rich / Idle problem

[law262 0]

Hi all,

 

I would really appreciate if you people could help me out.

 

[The Problem]

My G60 wont idle, runs really rich and is eating lambda’s (I think) (IMG:style_emoticons/default/sad.gif)

 

I picked the car up last year, I was told by the previous owner that it had a misfire problem which had been recently resolved by fitting a new head and ECU. I drove the car 30 miles I found it was running ok. I didn’t drive it again until this April.

 

In the past 3 weeks the car has develop a progressive rough idle and been running rich, it got so bad I stopped driving it.

 

Done some searching on this problem and tested the ISV, blue temp cts, CO Pot and throttle body switches, all returned factory set values except for the CO pot which was approximately set to 350 ohms. I changed this to 480 ohms, made no improvement. (IMG:style_emoticons/default/sad.gif)

 

Ok so it’s looking like a lambda problem, so I tested that and found the heater circuit was faulty – no continuity. Ordered a new Bosch lambda, cracked the old one off and found it to be like… “B: Rich Fuel Mixture” in the picture on… http://www.lambdasensor.com/main/mfaults.htm it also rattled so must be well mullered. It had all the VAG and Made in Germany stamps on it, could this be the original one? The car has done 142,000mi.

 

(If I remember right, the resistance of the new lambda correctly read 3.5 ohms across the heater cores)

 

Anyway, started the car up with the new lambda in and the idle was a perfect 850rpm for about a week (IMG:style_emoticons/default/sad.gif)

 

[Current Status]

It now runs very similar to before the new lambda went in.

 

Had an MOT this Saturday and at the end I asked if we could look at the emissions, found CO level was 8.5, it should be 0.7 +/- 0.4% at idle correct? (I was told the hydrocarbon ppm emissions are ok)

 

We followed the VW Set Idle and CO Content guide and adjusted the CO content to 0.7%. The problem now is to get it down to this level the CO pot is set to 1900 ohms. (I believe the timing is ok.)

 

The car goes really well when the lambda is in open circuit i.e. toe’in it.

 

When I restarted the engine after about 3 hours it wouldn’t idle and badly surged in the 1000 – 2000rpm range. I’ve had to disconnect the lambda to be able to drive it now, am I correct in thinking the ECU is now using default set values when running? Will this cause it to run rich?

 

Due to it having a new head, is it likely someone has incorrectly set the CO content, which has been the root cause of the death of the original lambda and possibly my new one? If running to rich kills the lambda, the lambda then affects the idle as ECU gets incorrect readings – correct?

 

(When setting the CO Pot resistance does this need to be adjusted when the ECU is in service mode i.e. blue temp cts off?)

(Going by the back of a Haynes book the plugs only look slightly carbon fouled when compared to the normal plug)

Do the CO Pot's tend to fail or is it if you can adjust them they are generally are ok?

 

 

Any help will be much appreciated