Golf 2.0 8V SE - POOR Fuel Consumption

[CraigR]

Just picked up a 2003 mk4 Golf 2.0 SE at the weekend, and noticed that the fuel consumption was sitting in the high teens per 100km. After filling the tank with 95 (straight after a minor service - oil, filter and air filter) I reset the trip computer and ran it for 100km - at 100km on the dot it was telling me 17.7l/100km. I pulled into shell and topped the tank off with 95 to make sure - 17.2l to brim the tank.

What. The. Hell. How can a 2L golf be using that much fuel (we have been driving it like nanas). I can't get my golf R to use anywhere near that!

Does any one know what the cause could be. Pouring through receipts (and there are a lot), the lamba sensor has been replaced, along with the coolant temperature sensor. It could be that one of these has failed again? No engine light.

Auto, 172k kms, FSH.

[Umai Naa!!]

MAF? Also, check all the vacuum hoses, including the larger plastic one from the brake booster. These crack at the fittings.

They're not that great on fuel. Being an auto won't help, either.

My Beetle with the same motor, but manual gets about 650kms from a tank on E10.

Ex wife's old Mk4 Golf 2L manual was getting roughly the same.

[gldgti]

2nd MAF. Ive seen these with dirty maf make them basically blow black smoke like a diesel.
You can clean it with carbie cleaner.


If it has an aftermarket cotton air filter its probably the cause - change it for a paper stock one if it isnt already.

[CraigR]

I replaced the air filter with a new ryco one (I believe these are paper type), and I cleaned the MAF while in the process. I also took the intake pipe off and cleaned the throttle body. I will check all the vacuum lines again tomorrow, I did see one hanging off that felt loose that I reattached.

It actually runs "okay", maybe a little rough sometimes, and doesn't blow any noticeable smoke.

[gldgti]

Plugs are also worth a look, but its a bit of an arse because you have to take off the upper half of the intake manifold. Its not a big job but it still takes a little time.

[Umai Naa!!]

Nah, you can leave it on.

Although, if you're going to pull it, do the rocker cover gasket at the same time.

[CraigR]

I actually have plugs ready to go in but it was starting to get dark so decided not to start taking the intake manifold off. You have to take the manifold off to get to the plugs surely? There's no way to get your socket in otherwise!

[Bug_racer]

Did they check lambda probe operation at the service ?
Small checks like that are the difference between a good mechanic and an average one .

[CraigR]

My wife took the car today, so I will check to see when the o2 sensor was replaced. I'm not sure if they checked it, but it definately was replaced within the last 50,000kms as I remember seeing it in the paperwork, along with a note saying "customer complaining of high fuel usage"

[Umai Naa!!]

I actually have plugs ready to go in but it was starting to get dark so decided not to start taking the intake manifold off. You have to take the manifold off to get to the plugs surely? There's no way to get your socket in otherwise!

You need a wobble extension, and some long long-nose pliers. Be very gentle with the leads. Twist the boots, before pulling them off the plugs.

[CraigR]

I'll give that a bash this coming weekend. Part of me is thinking I should just do a complete ignition service...

[CraigR]

Just had a read through the car's service history, and not only am I surprised the the service history is complete and never missed a service, but this car has had some serious coin spent on it!

However, this heavy fuel usage and rough running thing has been going on for years...

08/2007 - Running rough, black smoke. New o2 sensor
05/2012 - o2 sensor replaced, coolant temp sensor replaced
11/2013 - coolant temp sensor replaced, leads & plugs replaced, MAF replaced, o2 sensor fault code noted

Might get the car scanned and see what vcds can tell me. I don't mind spending a little bit of money on this car to get it where it needs to be.

[Umai Naa!!]

Check the evaporative purge solenoid on the charcoal canister, too.

It should start ticking away after a few minutes of running.

[CraigR]

I wondered what that was! Yep - ticks away once is begins to warm up.

[CraigR]

Took the car to VW and got it on the VCDS. They told me it looks like a new MAF is required, however it logged a lean condition, but you can smell how rich it is running. I've ordered a new MAF anyway in a bid to achieve more than 295km from a full tank of 95, which we just got yesterday. My main issue here is I plugged my ELM327 and using the Torque app, monitored what the MAF was doing and seemed to be behaving how it should.