This has got me totally confused. Over the past 9 months my 1989 w124 300te seems to run happily then gradually runs richer and richer until MPG drops to single figures.
It started last year, the mpg dropped and the garage adjusted the mixture. all was well for a couple of weeks until full throttle was accompanied by clouds of black smoke from the exhaust. The coolant temp sensor was replaced and then the entire metering head (with a secondhand unit). The car ran ok-ish until March when the black smoke started again and it failed the MOT on emissions being "off the scale" - co2 was more than 10. The scrapyard was very understanding, (thanks mercland) and supplied another metering head. The car passed the MOT but still seemed to hesitate.
Fast forward to July when the dreaded black smoke poor driveability and single figure fuel consumption returned with a vengence. A different garage was chosen who came to the conclusion that it was the pressure actuator (small black box) on the side of the metering head; this was replaced with a new one and the car immediatley ran much better but on taking it back for a check on emissions last week, just to be sure, the following was noted:
If the mixture is adjusted correctly at idle, when revs are applied co2 rises alarmingly. The only way to get the car to run properly is to weaken the mixture to stalling point at idle which gives a sort of acceptable level of drivability though not particualarly good fuel economy.
So the mixture gets richer and richer as the weeks pass until the car is barely drivable.
The garage is stumped.
What can be killing the pressure actuaters? Or is replacing them simply treating a symptom.
What should I be checking next?
What is the function of the fuel pressure reguator in front of the metering head?
Any suggestions, ideas or similar tales of woe welcomed.
I also managed to lock myself out of the car last night - is it trying to tell me something?
Thanks in advance
It started last year, the mpg dropped and the garage adjusted the mixture. all was well for a couple of weeks until full throttle was accompanied by clouds of black smoke from the exhaust. The coolant temp sensor was replaced and then the entire metering head (with a secondhand unit). The car ran ok-ish until March when the black smoke started again and it failed the MOT on emissions being "off the scale" - co2 was more than 10. The scrapyard was very understanding, (thanks mercland) and supplied another metering head. The car passed the MOT but still seemed to hesitate.
Fast forward to July when the dreaded black smoke poor driveability and single figure fuel consumption returned with a vengence. A different garage was chosen who came to the conclusion that it was the pressure actuator (small black box) on the side of the metering head; this was replaced with a new one and the car immediatley ran much better but on taking it back for a check on emissions last week, just to be sure, the following was noted:
If the mixture is adjusted correctly at idle, when revs are applied co2 rises alarmingly. The only way to get the car to run properly is to weaken the mixture to stalling point at idle which gives a sort of acceptable level of drivability though not particualarly good fuel economy.
So the mixture gets richer and richer as the weeks pass until the car is barely drivable.
The garage is stumped.
What can be killing the pressure actuaters? Or is replacing them simply treating a symptom.
What should I be checking next?
What is the function of the fuel pressure reguator in front of the metering head?
Any suggestions, ideas or similar tales of woe welcomed.
I also managed to lock myself out of the car last night - is it trying to tell me something?
Thanks in advance
