Mk3 1.8 Fuel Consumption

[camhaz]

G'day,

I have been driving our Mk3 the last 2 weeks, which we recently bought for our kids to learn to drive in. I have noticed that the fuel consumption is particularly poor, chewing through a tank of premium in about 300km, which does not seem normal at all.

Last weekend I found a few things, notably a loose timing belt (a reminder to all to check theirs perhaps?), and ignition timing that was out a fair bit. Those fixed, the car felt much better, with noticeably more power. This weekend I have checked the resistance of the coolant temperature sensor both hot and cold and it seems to be functioning correctly.

What I did find was a broken dipstick extension, which means that the dipstick was flopping around with no seal to stop air getting into the crankcase. Given these car's engine recirculation and ventilation systems, could this cause poor consumption?

Any pointers on what else to check? Thanks.

Rob.

[Water Boy]

They dipstick tube is an easy replacement. They around around $15 from Volkswagen.

I have a CL and can get a tad over 700km's when highway driving.

Around town I normally get around 450km's and that me ringing it neck, like full chock necking.

I found when I replaced the base plate between the throttle body and inlet manifold it made a huge difference. If this does need replacing as the rubber cracks also spend some time cleaning the throttle body (Is just used carby clean and it worked wounders)

Also if its using a bit of oil valve stem seals/guide and a quick head clean does wounders.

The ADZ in the CL is a bullet proof motor. I have had mine 2 years, done 13 track days, 2 trips to Sydney plus a trip to QLD the long way and had no problems.

[camhaz]

Thanks Water Boy,

Your economy is what I would have expected, nice to know it is capable of that. Giving the throttle body a clean was going to be my next course of action as the top of it is rather gunky and I suspect something may be blocked up there, your message is confirmation that I need to give it a go. I have visually checked the baseplate from the outside, but it sounds like I need to remove it properly and have a closer look.

Thanks again.

[MrJohn]

hey guys, ive read what u guys wrote and i have a problem with my mk3 - its like its not misfiring but the timing aint right.. when my car is parked on idile, it idiles only up to 800rpm? =s shouldnt it be on 1,000rpm?? the idiling goes up and down from 650 - 800rpm.

[camhaz]

G'day MrJohn,

As far as I know, idle speed should be about 800rpm, but can be as high as 1000rpm according to the Bentley manual.

My issue which I have not documented here was incorrect timing caused the poor consumption. My car is an auto and the timing marks are not as obvious as on the manual gearbox version, as there are 2 holes in the top of the bell-housing in the auto, and I have yet to discover which hole I am meant to be looking through and what marks I should be lining up!

If anyone can enlighten me, I would appreciate it, as I know it is meant to be 6 degress BTC, but can't find the marks to aim the strobe at. Through a bit on guestimation I have got it close and it is using heaps less fuel, but would like to time it properly.

Regards,
Rob