mpg
 

What mpg are you guys getting? I think I have a duff sensor or something as I'm only getting 21mpg :frusty: It's a motorway cruising commute so it shouldn't be that bad, I was getting over 40mpg from my Libra and 50mpg from our passat tdi for comparison.

The only reference I've found was possibly a duff coolant sensor but I have checked the warm resistance and it is smack in the middle of specs, the supply voltage from the ECU was significantly down though, the ECU should be giving it 5V but it is barely over 1V measured out of the ECU, the sensor ground is fine. Is it possible part fo my ECU is knackered? The theory I am working on is that it is constantly running rich as it thinks it is always warming up. It drives fine.. Maybe I should chek the condition of the plugs too? They did mention the CO reading was near the max at the MOT..

Any suggestions gratefully received!

Rich

I'm hoping it is a dodgy thermostat that is not letting the engine get up to full operating temperature so always running on rich warm up cycle, will change it this weekend and keep my fingers crossed! My big rad (for future upgrades) and the cold weather is probably making things worse..

Thought I'd update this for the record... It ended up being a blocked water line in the idle control valve so all the bypass circuit was blocked, new valve sorted it and I now get about 32mpg for my commute...
I think this must be a problem wiht leaving engines to stand for a while, without the coolant in there it soon furrs up!

Rich

That sounds a bit more reasonable :hippie:

How did you find the fault, was it trial and error?

John

I was also getting a blippy idle once the car had warmed up which eventually went away, I presume through heat soak into the valve. There are two idle control valves on the engine, one is controlled by the ECU and another works like a wax thermostat which closes off an extra idle air path when warm. What was happening was the extra idle air flow path was staying open due to no warm water flow and the ECU didn't have proper control of idle speed which resulted in the blipping, I also noticed that the small bore water pipe of the bypass circuit wasn't getting very warm. The bypass circuit warms up the intake manifold, throttle body and some other parts so this must have affected warm up too. When I took this valve off to clean it I needed a drill to get through all the corrosion!
I sorted all this out ages ago now, just thought it was worth pointing out to others as it took me ages to work out and I have seen the same problem on 3 engines now...