2006 Jetta running bad

tdipwr

Well-known member
Joined
Feb 27, 2009
Location
ohio
TDI
1996 tdi passat wagon,1991 jetta 2 door diesel
Ok I just bought a 06 tdi with 187,000 miles it was in limp mode pretty much my intire 6 hr trip home. I found a vacuum line that was off and that fixed the limp mode still ran kinda bad. Cel was on two codes one was mass air flow and one was o2 sensor. I replaced the mass air sensor but still running bad. It runs great as long as you don’t push the pedal down much past 1/4 throttle then it starts acting up. My question is can a bad o2 sensor do this? It almost acts like something restricting it under load. It will rev fine in neautral but struggles under a load. Any suggestions would be greatly appreciated.
 

dandywriter

Veteran Member
Joined
Jul 18, 2007
Location
Ottawa (Kanata), Canada, eh?
TDI
2014 Golf Wagon 6M
If the car is new to you, a good start would be changing the fuel filter and air filter. If it is cold, add a couple of ounces of power service white in case you have gelled fuel (also, adds a bit of cetane). An oil change to a known type (lots of info on here about which) - 505.01 or T6 are frequently recommended on the forums - also a good idea.

If you don't know the last timing belt service, it would be a good idea to change the timing belt/check the cam and lifters; if they haven't been done yet, you are overdue for the timing belt and associated internals (water pump etc).

A VCDS scan, as Windjammers says, helps a lot.
 

tdipwr

Well-known member
Joined
Feb 27, 2009
Location
ohio
TDI
1996 tdi passat wagon,1991 jetta 2 door diesel
Jetta

So today I removed the o2 sensor and cleaned it and it appeared to be almost new but I’m not sure the plug was plugged in all the way. I also changed fuel filter and air filter and started the car and CEL went off shortly after. I took car for a drive and it runs great not sure what fixed it but it’s fixed.
 

James & Son

Veteran Member
Joined
Oct 10, 2008
Location
Maryhill, Ontario, Canada
TDI
2006 Jetta
It runs great as long as you don’t push the pedal down much past 1/4 throttle then it starts acting up. My question is can a bad o2 sensor do this? It almost acts like something restricting it under load. It will rev fine in neautral but struggles under a load. Any suggestions would be greatly appreciated.
So today I removed the o2 sensor and cleaned it and it appeared to be almost new but I’m not sure the plug was plugged in all the way. I also changed fuel filter and air filter and started the car and CEL went off shortly after. I took car for a drive and it runs great not sure what fixed it but it’s fixed.
The likely order would be Fuel filter, air filter, egr clogged, leaks in intercooler hoses screwing up boost and as you found out vacuum leaks screwing up turbo actuator function.

O2 sensor I don't think will have very much an effect, other than to warn there are other problems. Even though the Mass flow sensor measures the problem(s), it normally is not the problem. There is an easy test to verify it is not the MAF
 

James & Son

Veteran Member
Joined
Oct 10, 2008
Location
Maryhill, Ontario, Canada
TDI
2006 Jetta
Just an aside to the above post. If you pay Terry Dyson 150.00 for an oil analysis he is able to tell if it was air filter or fuel filter by his oil analysis.
He tunes high performance cars this way not for all out power but overall efficient performance.
 
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