Poor Fuel economy on ALH TDI

[Moses Buckwalter]

Hello all! I have an '02 ALH TDI Golf that's fairly stock. It has like 10% over injectors that were installed when I bought it, but that's about it. Timing done ~40K ago, new AC, idler, and tensioner in the past year. I mainly drive it between 45-80 mph on a pretty much straight 15 minute commute. In the ~15 months of owning it, I've never got much better than 35mpg while frequently nearing 30 mpg mark or even lower. Other than my right foot... anyone have an ideas on things to check as to why I'm not getting the "50 mpg" that people talk about with these ALH's?

 

[IndigoBlueWagon]

There a a lot of possible reasons: turbo may not be boosting properly, mechanical timing might be off, intake or cat may be clogged, even alignment might be off. Usually it's a lot of little things, not one big thing.

I'd also wonder about those injectors. They might be worn and dumping more fuel than they should, and balance may be off.

It's also winter, and your engine probably is barely warm after 15 minutes. Does the temp gauge make it to straight up and down? If it doesn't move much your thermostat may be shot, which will also hurt FE.

Time to do some diagnostic work.

 

[oilhammer]

Start here:

tips for fuel economy | TDIClub Forums

 

[Moses Buckwalter]

Intake *should* be clean. It got clogged last winter and I disconnected the EGR hose after cleaning it out. The alignment is off slightly, I've been meaning to take it in for a proper alignment.

I hope the turbo's not at fault...

And ya, these TDI's hate this weather. Usually about 10 minutes in it get's up to temp. Thermostats all good.

 

[ZippyNH]

Your roof rack is hurting you just like it's mentioned in the tips for fuel economy. Tires are another thing... careful selection based on pro's and cons, both in changing sizes and picking brands make a similar big difference. Between those two alone you can see 3-5 mpg change

 

[oilhammer]

That short drive isn't helping either. Zero chance that engine is at full operating temp after 15 minutes. Just the temp gauge pointing straight up means very little. Full operating temp is defined as the oil temp is as high as it can get and is being regulated along with the coolant thermostat. After 15 minutes, your thermostat hasn't even had to open. Shoot, in single digit temps you could drive for 30+ minutes and the hoses to the radiator will still be cold.

And if you disabled the EGR, and did nothing else, you've now lost that heating as well.

 

[Moses Buckwalter]

That short drive isn't helping either. Zero chance that engine is at full operating temp after 15 minutes. Just the temp gauge pointing straight up means very little. Full operating temp is defined as the oil temp is as high as it can get and is being regulated along with the coolant thermostat. After 15 minutes, your thermostat hasn't even had to open. Shoot, in single digit temps you could drive for 30+ minutes and the hoses to the radiator will still be cold.

And if you disabled the EGR, and did nothing else, you've now lost that heating as well.

Got it.

As for the EGR, it's not disabled. Just disconnected the vacuum hose so that it can't open up for recirculation into the engine, but the heat can still benefit from it.

 

[oilhammer]

No, that is most certainly disabled.

 

[IndigoBlueWagon]

I will say that a winter front helps in this weather.

 

[oilhammer]

Yeah, except they are NLA now.

I feel like I could sell a couple a week if I had them available here. Little display stand or something.

 

[Moses Buckwalter]

No, that is most certainly disabled.

Interesting. I guess the divergent to the coolant happens after the valve opens? My mechanic gave me the impression that this would still aid in warming up the coolant, but I hadn't done too much research into it.

 

[oilhammer]

If no EGR is flowing, then no heat will be going though the cooler, which means no heat will be exchanged. Also, the ECU is now seeing ALL the incoming air through the MAF, so it is not able to do the fueling, timing, boost, etc. calculations like it was designed to do.

Having a tune change those things is how you would do an EGR delete, not just pulling a vacuum line off. Because then you can change some other parameters that could possibly get the economy back up or even better, even if the cabin heat might still suffer a bit.

 

[Sting]

Hmmm... I have an ALH as well. Manual Wagon. I also have a shorter commute these days, but not nearly as cold as PA. It's about 25 km and 30 minutes to drive, and about half is city driving. My FE has not been less than 40MPG at any point. I know it'll suck, but turning the heat knob down will help the engine pick up heat quicker. I always start my drive with the heat off, and generally I get it up to temp (needle up and down) within 5-6 km. I try to keep the engine going around 2000 RPM ish until I hit full operating temp.

I have done the same with my EGR, pulling the line. I haven't seen any downside. I also recently did a 8000 km US road trip and the car was great.

Even on the coldest days back in Ontario, my FE was always in the 40s. I found that the FE hit in winter was about 10-15%, depending on the cold. I have the stock fore to aft roof racks. The ones like in your profile pic will definitely hit the FE a bit too.

 

[Moses Buckwalter]

Hmmm... I have an ALH as well. Manual Wagon. I also have a shorter commute these days, but not nearly as cold as PA. It's about 25 km and 30 minutes to drive, and about half is city driving. My FE has not been less than 40MPG at any point. I know it'll suck, but turning the heat knob down will help the engine pick up heat quicker. I always start my drive with the heat off, and generally I get it up to temp (needle up and down) within 5-6 km. I try to keep the engine going around 2000 RPM ish until I hit full operating temp.

I have done the same with my EGR, pulling the line. I haven't seen any downside. I also recently did a 8000 km US road trip and the car was great.

Even on the coldest days back in Ontario, my FE was always in the 40s. I found that the FE hit in winter was about 10-15%, depending on the cold. I have the stock fore to aft roof racks. The ones like in your profile pic will definitely hit the FE a bit too.

Same here on keeping the heat down. If the windshields fogging up I'll turn it on at the 10 o'clock position, but otherwise it stays off till it's straight up and down.

This winter has been especially rough, it was 12 degrees when I started it this morning.

 

[oilhammer]

It was 6F here. I'll take that over 90+ any day. My fat ass doesn't like the heat.