[jeepvolks]

I used to get 280 miles out of a tank around town. I'm now getting the fuel light at around 225 which gives me about 20 more miles before getting gas. I'd say that's quite a drop. In the past 6 months, I've replaced:

O2 Sensor
CTS
New Plugs
MAF
Cleaned TB
Cleaned IAT sensor

Not sure what else is left. I'm at 108,000 miles and the drop started around the time I changed the engine mounts 2 months ago.

 

[PZ]

Have you scanned for any codes? Is the CEL on? Did you test for boost leaks? Has power dropped off?

 

[jeepvolks]

No CEL. Scanned for codes with no returns. Maybe a little sluggish, but not drastic. Checked for vacuum leaks with starting fluid. Not sure about a boost leak or how to check for that. Did get a strange, light plume of smoke on start-up a few times. Also, sometimes it turns over several times before starting. I'll let off the starter and then back on again and it starts-up.

 

[PZ]

There is a thread on building a boost leak tester. Usually you get a code if the leak is large enough. The turbo outlet hose and the DV are the only thing I could think would be disturbed by a motor mount change on the 1.8T.

 

[Tomvw]

I suggest you check that the CTS is reporting the correct temp to the ECU.
If the CTS is not OEM it's likely to be the problem, if OEM it still should be checked.

 

[jeepvolks]

I did the pressure test just now. I found a significant leak at the connection where the PCV meets the TIP. I think that's what it's called. The gear clamp had not been tightened back after I did some other work and it was just there. Air and bubbles were very prominent at this location. Could this be enough to cause me problems?

 

[Tomvw]

Yes, could be.

 

[jeepvolks]

Air intake temperature sensor has now been replaced. When I filled up today, the mileage calculated until empty showed 355 miles. It used to say 425 miles until empty. I only got 240 miles from the last tank. Engine management is obviously not calculating the same as it used to.

 

[PZ]

That means nothing. It only shows based on your current mileage, calculated by the fuel level. Once the MPG improves due to repairs, the numbers should rise.

 

[B5 Money Pit]

Are you seeing any MPG improvement yet?

Our '02 variant 1.8t is still getting bad MPG (sub 20) since we inherited it 3 months ago. It was in rough shape mechanically, sister wanted to put it out to pasture after putting in a donor AWM motor three years ago (timing belt broke on the hwy), and then a rebuilt Tiptronic less than a year ago. 235K now on the odo. I figured it just needed a little TLC and a pretty hefty tune up.

So far:
Using only 91Octane.
New OEM NGK sparkplugs, new valve cover gasket, new coils
New air filter, new fuel filter
New Cat and both O2 sensors
New timing belt, thermostat, coolant temp sensor
New accessory belt, new a/c belt and tensioner
New pair of axles (Chinese)
Stock size Michelin Energy with 40K and inflated to spec.

No more CEL after P0420 cleared, and no more misfire codes after plugs/coils. But there is a stored code for brake booster vac pump.
Starts and runs smooth and strong. But it just gulps gas. No obvious leaks or cracks in hoses.

What's next?
Throttle body, MAF cleaning?
PCV, is there an actual valve somewhere? Take apart other PCV hoses?
What's a diverter valve?

 

[B5 Money Pit]

Are you seeing any MPG improvement yet?

Our '02 variant 1.8t is still getting bad MPG (sub 20) since we inherited it 3 months ago. It was in rough shape mechanically, sister wanted to put it out to pasture after putting in a donor AWM motor three years ago (timing belt broke on the hwy), and then a rebuilt Tiptronic less than a year ago. 225K now on the odo. I figured it just needed a little TLC and a pretty hefty tune up.

So far:
Using only 91Octane.
New OEM NGK sparkplugs, new valve cover gasket, new coils
New air filter, new fuel filter
New Cat and both O2 sensors
New timing belt, thermostat, coolant temp sensor
New accessory belt, new a/c belt and tensioner
New pair of axles (Chinese)
Stock size Michelin Energy with 40K and inflated to spec.

No more CEL after P0420 cleared, and no more misfire codes after plugs/coils. But there is a stored code for brake booster vac pump.
Starts and runs smooth and strong. But it just gulps gas. No obvious leaks or cracks in hoses.

What's next?
Throttle body, MAF cleaning?
PCV, is there an actual valve somewhere? Take apart other PCV hoses?
What's a diverter valve?

 

[Tomvw]

B5 Money Pit, I think you should edit both your posts back to this:

Are you seeing any MPG improvement yet?

And then start your own thread rather than messing up this one.

 

[Tomvw]

What temp does the CTS report to the ECU ?
Before first start for the day ?
What is the ambient temp ?
After driving for 10 minutes ?


Check the MAF sensor:
http://www.ross-tech.net/vag-com/advertising/DiagnosingA_MAF_TechTip.pdf