Codes P0300, P0507, P0171 P0174, P0304, P0302, P0301, P0306

Tiny
IFYUSER
  • MEMBER
  • 2003 VOLKSWAGEN PASSAT
  • 2.8L
  • V6
  • 2WD
  • AUTOMATIC
  • 170,000 MILES
Can these codes be caused by bent exhaust valves and how can I tell?
Friday, January 24th, 2020 AT 7:40 PM

2 Replies

Tiny
JIS001
  • MECHANIC
  • 3,411 POSTS
I do not believe that those codes could be mechanical. P0171 and P0174 indicate system running lean. I would recommend checking for vacuum leaks, low fuel pressure, contaminated fuel/too much ethanol in fuel, or faulty mass air flow sensor.

I am posting some guides on basic checks for vacuum leaks and fuel pressure.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

To check the mass air flow sensor your scan tool will need to be able to read live data. With engine warmed up and all loads off example: lights off, A/C off. You need to look at the mass air flow data in grams per second. The reading should be close to what your engine size is. You have a 2.8L engine. In theory your mass air flow should read 2.8 grams per second but you will most likely see something of a range of 2.3 - 3.2 grams per seconds. That is a rough estimate but if you post the readings we should be able to see if your within normal range.

If okay then take a fuel sample and see if the fuel is clear or cloudy. If cloudy then your fuel is bad and will cause lean running codes which could cause a misfire. Let us know those readings. If all looks good I will let you know another test for the mass air flow sensor when at cruising speeds. For that test you will need a co pilot to read the data off the scan tool.
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Friday, January 24th, 2020 AT 10:38 PM
Tiny
IFYUSER
  • MEMBER
  • 54 POSTS
Hehe, it is ten dollars like the scan tool says. I know the original one can take for heat and abuse it had a new one but that can do for now. Thanks
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Friday, December 4th, 2020 AT 10:51 PM

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