10mpg what could it be

1875 Views 10 Replies 5 Participants Last post by Scared4life, Jul 5, 2017

Scared4life

Discussion Starter · Mar 7, 2015

Hey there everybody I have a 2002 1.8 bug and I've been having some serious gas mileage issues, i used to get 19mpg in city and 25 highway until i hit 100k miles in october, at 100k I replaced the plugs, valve cover gasket, t hose, fuel pump, speed sensor, camshaft position sensor, put new front and rear ceramic breaks and rotors, and cleaned my k&n filter (airbox style) before the mileage dropped, at 100250 a code popped up p1176 and gas mileage dropped to 16mpg in town instead of doing research i said screw it and replaced both 02 sensors, code hasnt popped up since but my gas mileage slowly went down from 16 to 15 and now im at 102k miles getting on average 10-13 mpg. I'm going to clean the MAF and the throttle body either tomorrow or sunday and see if i have any improvement,fingers are crossed, i know i should get a vagcom but im being tight on money just in case

Also i have a hunch there's a small exhaust leak in the flex pipe, i can feel it in my foot when on the brake pedal so my question is
any recommendations on a turbo back exhaust with no cat or resonator? link would be appreciated want a vagcom and turbo back with my tax return funds

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billymade

· #2 · Mar 7, 2015 (Edited)

I would scan the car for trouble codes; also, check your fuel trim levels and your maf readings are ok. Your exhaust leak; can be fixed by just having the flex portion of the pipe sectioned out and a new one welded in. Fix the exhaust; you can buy a performance stuff later. Get the car running right and then, add performance parts after you get the car running at its best in stock form. Be sure to align your throttle body; after cleaning, you intake temp sensor, is a easy to clean sensor as well. Once you tune up your car and get it running correctly, you might be surprised how well it runs. I would also check your diverter valve and the Wastegate Bypass Regulator Valve (N75). Read this thread for more info and testing ideas (the DV's can stick, have a hole in them and the N75 valves can get worn, have soft failure and not work at the level that they need to):

http://newbeetle.org/forums/1-8-lit...ock-motor-apr-aftermarket-vs-stock-bosch.html

17584/P1176/004470 - Ross-Tech Wiki

One thing; that really seemed to affect my gas mileage was a bad coolant temp sensor. Another basic maintenance item; did you replace your fuel filter?

Fix your flex pipe, get us those codes and what your fuel trims are; we can go from there...

http://wiki.ross-tech.com/wiki/index.php/Fuel_Trim_Info

https://www.youtube.com/watch?v=yM3iarhSP68

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Scared4life

Discussion Starter · #3 · Mar 7, 2015

aligned and cleaned throttle, did fuel filter, and cleaned MAF today lets see how it goes

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billymade

· #4 · Mar 7, 2015

Here is a great 1.8T troubleshooting guide:

VW VOLKSWAGEN AUDI 1.8T TROUBLESHOOTING GUIDE READ ME | eBay

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turboturbo

· #5 · Mar 7, 2015

Check rear (and fronts, but rears are far more common) calipers for a dragging brake.

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Scared4life

Discussion Starter · #6 · Mar 8, 2015

Gas mileage jumped up to 19 mpg city, how can I tell if I have a dragging brake? Cuz now that you mention it I get a noise as if the brake is catching when in reverse

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turboturbo

· #7 · Mar 8, 2015

I would highly suspect a dragging brake. It can be caused by three common things:
- pads that get stuck on the sliders
- stuck slider pins
- e brake not releasing all the way

I've dealt with all three. To check, jack the car up and spin the wheel by hand (parking brake off). Any resistance means you have a problem. Take the wheel off, and spin the rotor, it should spin easily.

For each problem there are write ups here on the forum, but for quick help:

- pads that get stuck on the sliders: remove pads and grind down the "ears" where they fit in the mounts. Or, leave out the top shim (I did this, and it works perfectly)
- stuck slider pins: remove hardware, clean, lube, reassemble
- e brake not releasing all the way: ensure cable is releasing at caliper, then take apart console inside and back off the nuts for attaching the cable to the lever. Our brake was fully on at one click, I backed it off to the specified 3 clicks. Mileage jumped immediately.

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Scared4life

Discussion Starter · #8 · Mar 9, 2015

they seem to spin smoothly but i did notice my wheel bearing is going bad on the passenger side as well as a loose tie rod end, ran it good tonight gas mileage seems to have revived, our master tech here told me to throw some gum out in it and that should complete the rest, now i found that on the down pipe is leaking in 2 different spots and the cat smells like straight boiled eggs, also noticed when i put it in park you can hear a small idle bog. other than that i smoke tested it and found no leaks im going to hook it up for the next couple days see if i find something

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esse10

· #9 · Mar 11, 2015

1.8t

Scared4life said:
they seem to spin smoothly but i did notice my wheel bearing is going bad on the passenger side as well as a loose tie rod end, ran it good tonight gas mileage seems to have revived, our master tech here told me to throw some gum out in it and that should complete the rest, now i found that on the down pipe is leaking in 2 different spots and the cat smells like straight boiled eggs, also noticed when i put it in park you can hear a small idle bog. other than that i smoke tested it and found no leaks im going to hook it up for the next couple days see if i find something

We suspected you didn't have a leak otherwise you'd have a too lean or too rich code.

If I were you I would Seafoam that poppy. There is a really cool video in utube on how to do that to a 1.8t engine, I think it's in a vw Passat. I did it to mine and it really helped out. I think I'm gonna make that an annual spring cleaning for my little bug.

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jfoj

· #10 · Mar 13, 2015

Verify the engine coolant temperature.

My bet is a bad thermostat. It will only be a problem once the local temps drop below 70F. Once above 70F you will not notice much of an issue.

Albuquerque February Weather 2015 - AccuWeather Forecast for NM 87102

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Scared4life

Discussion Starter · #11 · Jul 5, 2017

Sorry for the late...late update but this is what we did to fix this issue,first was the coolant temp sensor, increased by 6mpg. Then thermostat for 2mpg increase. Fuel filter for a 3 mpg increase, and finally not mpg related but there was 2 boost leaks in the boost lines closest to the firewall and after all this, the water outlet started leaking. As of right now the car is running great, and the autotragic still lives

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