vtraudt

Update:

New O2 sensors (no code) did not change a thing.
Gas mileage is still 12 mpg highway (and 10-12 mpg mixed driving).

I pulled the spark plugs out (less than 5k since new) and had an 'expert' take a look. They show NO signs of running rich.

Also cut the catalytic converters out (one was rattling anyway) to rule out 'plugged cat'. Inside of the exhaust pipes looked also 'normal' (no signs of running rich).

Last time I checked the vacuum, it was at -18 (which seem normal, or?) at idle.

I had replaced the fuel pressure regulator, no change.

a) could I still have a vacuum leak that is causing the terrible gas mileage?

b) when I did the timing belt service, I checked compression, which was ok and fairly uniform across the 6 cylinders. I will check again

Key question: what could (any ideas are very welcome) cause such terrible gas mileage?

- dirty injectors?
- leaking injector O rings?
- EGR system (I would expect a code, even on this very basic Hitachi ECU)?
- air pump or other evap stuff?
- resonator or muffler plugged (maybe from cat 'debris'?)?

Without obvious signs (or codes), I am at a loss.
Power seems poor, but it is hard for me to judge (my other cars are 2.7T 6spd stage 2, 1.8T manual stage 3, 1.8T manual stage 2, so yes: this 2.8 A4 with auto trans seems awfully slow, but I have not comparison.

Suggestions, PLEASE!

vtraudt

Does the 2.8 have EGT sensors that could go bad and tellung the ECU to run rich to 'cool', causing the high gas consumption?

Prospeeder

pull the injectors out, but leave them attatched to the fuel line and rail, and turn the key on so the fuel pump primes. but dont start! and put paper towels under each injector, and any that get wet, are leaky and bad. also you can use an ohm meter, and check the resistance of each injector. They can electrically short out.

Bosch injectors - 15-17 ohms
Siemens injector - 13.5-14.5 ohms

Anything dramatically less is junk.

vtraudt

Will do.
Get a set of O-rings (number/specification to order the correct ones? Source?) and change them out while at it?

goodys90

would the injectors make the check engine light come on if bad. got the same white slim on oil cap and in breather hoses. my check engine light will come on if it sits and idles for 10-15 mins. car also wants to die right after starting will rum real rough at around 3-4 hundred rpm for about 5 mins then it seems to come out of it. Then at low rpm wile driving it hesitates. at about 2000 rpm it seems to come out of it but still dont feel like it has full power. and what would symptoms of one clogged cat and the other free flowing. exhaust makes weird high pitched kackle. caused by misfire? or what

goodys90

I have 2.5" exaust from right behind the cats into a cherry bomb glass pack for resinator then into a pilot dual 3" tipped muffler

Jeffsg605

So I know this is a super old thread but was there any resolution to this problem? I went to do my coolant temp sensor today and when I took off that hose at the rear of the valve cover (1.8T) it was full of that white crap.

Any help would be appreciate, thanks.

uberwgn

Jeff, is it cold where you are operating the car?

Jeffsg605

Yes, Chicago.

So a little background, at the end of last winter, I changed the thermostat, J-plug, coolant temp sensor, and that weird coolant connection at the rear of the engine. Car ran great until maybe September. Then I realized the temp gauge on the dash took a bit longer to reach operating temperature. Once it started getting cooler, it took a lot longer and now that its been cold, it'll often never reach operating temperature, even after driving 30-40 minutes. I do get heat pretty quickly although it never gets as hot as it usually does in the winter so I'm not sure its the thermostat. I do have a P3081 "Engine temperature too low" and a P2181 "Cooling System Performance".

Jeffsg605

I guess I don't know if any of that is related but the point is that I went to change the Coolant Temp Sensor when I noticed that weird white crap.