B6 1.8T Cabriolet/System Too Lean/Random Multiple Missfire + more

[bellaxxmorte]

Hello,
Somewhat recently my coolant and oil leaks were finally fixed, however now there seems to be some other kind of vacuum issue. When vacuum issues first appeared I had some broken hoses that were replaced. Currently I am replacing the PCV pipe again in case for some reason that one that I recently replaced is faulty. Also recently replaced ignition coils, spark plugs, throttle body, MAF sensor, upstream O2 sensor. I still have the MAP sensor and downstream O2 sensor; however, I haven't found where the MAP sensor is located & the downstream O2 sensor is difficult to reach, so I saved it for another time.

These were the codes I was getting:
17887 Brake Boost Vacuum System: Mechanical Failure
16684 Random/multiple Cylinder Misfire Detected
17705 Pressure drop between Turbo and Throttle Valve (Check D.V.)
17700 MAP Controlled Engine Cooling Thermostat (F265): Open Circuit

(Note the Thermostat and housing was changed also (It's been a year or so), when I had the coolant leak issue and overheating. My thermostat continued to break until everything up to the radiator was changed. Temp was fine after and no leaks. Currently temp was fine also)

(Other random parts changed within last 2 years: Engine Coolant hose flange, engine vacuum system suction pump valve, Water pump (2nd time)[belt was changed more than 2 yrs ago], Crankcase PCV hoses, Head Gasket Set, intake exhaust Valve Silicone kit, Belt Chain Tensioner, Tensioner Gasket, Head bolt socket ribe polydrive spine bit, HVAC Heater Hose CRP, Engine Coolant Water Outlet Dorman, Thermostat housing plug, ECU has been reprogramed, over 2 years)

After replacing the O2 sensor nothing changed. I didn't mention that the car idles terribly and the engine shakes/vibrates when idling (due to incorrect air fuel mixture, misfires), also a burning smell would be coming from the car. Also, has been experiencing loss of power when the vehicle is not driven for a while. Checked battery (battery is fairly new) and alternator (working-has never been replaced), they both were working fine. Due to running poorly, I did not use the vehicle for approx. 2 weeks while trying to find time to work on it and in fear of causing engine damage. Recently I took the car out of the garage to work out. I happen to clear the codes with VAG.COM and when I tried to move the car back in the garage, it would not stay on. The vehicle drained my battery somehow over the 2 weeks. I charge the battery, but now it starts, then loses power within seconds and shuts off. If I rev the engine it will stay on and if I keep it around 3rpms. I did that for a couple minutes and white smoke (not very thick) started coming out in the area where the O2 sensor is plugged in (passenger side). No codes now, because I can't keep it running long enough to detect anything and I don’t feel good about running it or turning it on due to how it’s running. I’m afraid of damaging the engine.
Note: Before I started having the current issues car ran fine, except when going high speeds once in a while the check oil light would come on. I haven't seen it since the car started running terribly.

There may be more parts that were changed. There were so many parts changed on this car, I have lost track.
One more weird issue I should mention. When I'm filling up gas, the gas pump dispenser will not stay in place, I have to hold it by hand. It seems whatever holds it up, has broken off or fallen off. But this has been present for a couple years now, as I am unsure of how to fix that and if it affect anything else.
Have to stay tuned after new PCV valve install. I will change the MAP sensor if I can find it. If anyone knows where it is located, please let me know. Not sure if any of these are going to do me any good. Going to try a Thermal intake gasket also, since that had to be removed to reach all the hoses under/behind it.
Any suggestions please let me know.

[Arnie91]

Have you checked the vacuum suction jet pump? Is it still connected or broken?

[ECS Tuning-Audi]

Sounds like you have a major boost/vacuum leak somewhere.

I'd start first with a boost leak test.

Also seems like you have a bad coolant temp sensor so it is probably a good idea to replace that as well.

I hope this helps!

Jason

[bellaxxmorte]

Arnie, yes, that was replaced earlier this year.



Jason, thank you. I will look into that. I was just looking at the coolant temp sensor.

[bellaxxmorte]

Hey all,

Update Switched out the upstream O2 sensor and replaced the MAF sensor twice...the first one was faulty.. I figured that the first maf replacement was faulty after doing a boost leak test, changing the pcv valve, alternator, and throttle body...lol

The MAF sensor was shutting my car down below 3000 rpms. Now turns on and stays on. Haven't driven it yet though, have to reattach the bumper and headlights.

[Dcheney]

Sent from my iPhone using Audizine

[vier_Ringe]

To those future souls that find themselves stumbling on this forum with similar issues, if VAG-COM says check DV (Diverter Valve) after you have checked all your vacuum hoses and your short term fuel trims show +25, then the issue is a broken DV. I had this issue a while back after having to install several DV's. DV's from a B5 S4 will work on this B6 1.8 FYI.