Adjust CO or how much petrol my 740 is using?

[Jonny Jones]

Hi everybody! Im after some advice on how to reduce the amount of petrol my 740 GLE (B23OE, Manual) is using! Driving it normally the petrol just seems to be gulped down! I remember my mechanic mentioning something about adjusting the CO level - mainly for MOT emissions requirements - but after he had done this the fuel economy got better! Any suggestions? Many thanks in advance! Jonny.

[CTCNetwork]

Hi,

Will help to know what year/engine and fuel system your car has to be able to help...

Des. . .

[Citizen.Agfa]

First things first, you need accurate measurements of fuel consumption and short of fitting fuel-flow metering equipment the only reasonably accurate method goes as follows:

Fill fuel tank to brim.

Re-set trip meter.

Drive car.

Fill fuel tank to brim.

Note mileage driven then re-set trip meter.

Divide miles travelled by gallons of fuel used. (For test purposes 4.546 litres = 1 gallon.)

Repeat as required.

Post MPG figures on here for analysis and comment.

Regards, C.A.

[Tom85]

Well, since your engine is K-jetronic, all you can do to adjust mixture is to follow the instructions in the attachment. It can be done without CO analyzer, but it is not easy. ;-)

[Jonny Jones]

Originally Posted by Tom85

Well, since your engine is K-jetronic, all you can do to adjust mixture is to follow the instructions in the attachment. It can be done without CO analyzer, but it is not easy. ;-)

Thanks for the info everybody, I'll be attempting to follow those instructions...

I know the engine is using more fuel because I've always kept an eye on the fuel gauge since I bought the car two years ago and the consumption has always been up and down - down usually after the CO has been adjusted by the garage, so yes, I'll be having a go! Thanks again

[Tom85]

Be careful when doing this adjustment. Just let the engine warm up, prepare the long 3mm allen wrench, insert it into adjustment hole carefully, only to get the end of the wrench into the screw, do not press down as it will move the lever and close the fuel flow to engine entirely. Adjust by only a small bits (only few degrees) of screw rotation, since it's extremely sensitive, remove the wrench, open the throttle few times as the distributor lever must settle itself and observe the engine smoothness. If the engine retains it's smoothness after making your adjustments you definitely need to drive test it. Most noticeable is the engine torque in high RPM - if the mixture is too lean, the engine won't have power. Another thing after this adjustment is that there might be problem with cold start (if the cold start valve isn't working 100%) - the mixture will be lean and engine will not start. Hot starts shouldn't be big deal. You might need to readjust your idle speed (black knob on throttle body) after adjusting the mixture. Clockwise rotation = richer mixture, counter-clockwise = leaner mixture.

Make at least some notes (how much you rotated the adjustment screw) so you can retrace your steps back, when your car won't idle or start ;-)

This adjustment can be done without any other tools, major part is patience.

And = carry this wrench with you, wherever you go after making your adjustment and testing the car, so you don't get stranded in the fields with flooded engine like me ;-D

[Jonny Jones]

Thanks for that major piece of advice! I haven't yet touched anything because, frankly, I need to make sure people know what engine I have in case any of the info you just gave me needs to change. I've got some photos below of my engine, I've circled also what I believe to be the Idle Control Valve - the engine is idling WAY too high, even after a long motorway journey, my rev counter doesn't work but at a guess its idling at 2000rpm give or take.

So basically I need somebody to point out the rough area where the 3mm allen key hole is and whether or not the circled knob is the idle control valve, many thanks! Photos below... (feel free to download and photoshop any of the photos if this helps with showing me where things are located!)







Idle Control Valve?

[Tom85]

Whee a K-Jetronic engine

Well, the thing you circled is idle air regulation, correct.
I attached the picture with circled mixture adjustment hole.
It's right behind the big black hose under the intake.

Also, i see several leaks (intake manifold gasket, throttle body gasket) and it's quite probable that engine will suck air through them (making idle high). So you better be replacing them.

[Jonny Jones]

Originally Posted by Tom85

Whee a K-Jetronic engine

Well, the thing you circled is idle air regulation, correct.
I attached the picture with circled mixture adjustment hole.
It's right behind the big black hose under the intake.

Also, i see several leaks (intake manifold gasket, throttle body gasket) and it's quite probable that engine will suck air through them (making idle high). So you better be replacing them.

Thats great thank you! Yeah the 'leaks' have been there ever since I've had the car (2 years now) but its never had a problem... I guess it must have gotten worse, I'll look into replacing them

[OldBlueVolvo]

Completely off topic (sorry)...It looks like your car has cruise control. That's very rare for a k-jet engine. Thought you might like to know.