Hi All,
I'm looking for some advice on what looks like a pretty serious issue that our 2004 Passat is experiencing. First, a little background: this is an '04-model B5.5 Passat wagon powered by the 2.0L TDI-PD motor and 5-speed Tiptronic automatic. We bought it in July of 2004 and have put on 16,500 miles since then. That has included a few long-distance trips, but mostly this car has to do in-town errand duty, meaning it rarely gets fully warmed up. I have changed the oil every 5000 miles, it has had the PD tandem pump recall done but has never been to the dealer other than that (so no ECU reflash, replacement injectors, etc). Since about 4000 miles, we have run B99 in it at all times, except for a couple tanks we had to fill with straight diesel when out of town on trips (those tanks probably ended up being somewhere beteween B5 and B10 I guess). Always the best fuel suppliers, OEM parts, expensive oil, etc.
When I was around (before I went to college in September), I regularly took it out maybe once or twice a week and gave it a long drive, to fully warm it up, and used full throttle and boost. However, for the past 4 months, it has had exclusively short drives, and absolutely no full-throttle runs (Mom's a very conservative driver). When I got home, I checked the lifetime average on the MFA, and was horrified to discover that it has been getting, on average, 18.5 mpg. When it was brand new, I could easily get above 40 mpg on the highway, and it was averaging in the 28-31 range.
The very first morning I was back, I changed the oil, using Elf Excillium DID 505.01 5w40. I then spent all day driving it around the area picking up parts for my Rabbit, mostly freeway driving, with many full-throttle blasts to the redline once it was warmed up. The car is an absolute dog. It feels like the engine has maybe 80 hp. It can barely accelerate uphill with one person onboard, and with five aboard, a little luggage, and highway driving, it is dangerously slow to accelerate. Even now, with one aboard, it cannot manage to get more than about 25 mpg on the highway. Other than this, it seems fine. Runs smooth and quiet, no obvious smoking, no check-engine light, and so on. It does not enjoy cold starts (even 45 degree Seattle mornings cause it to stumble and shudder for the first 30 seconds), but it's always been like that. Also, it does occasionally go into a no-boost "limp" mode (usually a little while after starting up, not after long hard driving), which is cured by shutting the engine off and starting it up again.
I have been trying to figure out where to start on diagnosing this problem. Here are the ideas I have come up with so far--let me know if any of you have input about these:
--Bad MAF sensor? It runs OK like I said, but low power and awful mileage make me suspect it...how could I test this for sure? Vag-com? Maybe this is also causing the occasional limp-home situation?
--Bad MAP sensor/boost sensor/N75 valve? No idea if these could affect things, these just came up a lot in searches about bad mileage and low power. And again, something has got to be causing that occasional limp-home deal even though there appears to be no overboost (unless my turbo vanes are sticking, it hasn't happened since I thrashed it hard on the highway when I got home and got the boost way up).
--Plugged intake manifold? I do have plans to install a Racor or Provent CCV filter eventually, but haven't done it yet. Is it easy to check this on a B5.5 PD motor? Since it has mostly been run on soot-free B99, I don't see how the clogging could be bad enough to cause the problems I'm seeing, but I guess it's worth considering. I can see a bunch of oil dripping from the intake hoses where they connect to the intercooler, and it does use about 1/2 liter of oil every 6000 miles, so I know there is at least oil getting in there.
--Restricted intake/exhaust? I have no reason to believe the exhaust is clogged, since it sounds fine and the turbo seems to be spooling without any trouble, but it is true that I have never cleaned the snowscreen. I will do this very soon; any chance it could cause this much trouble?
--Injectors, computer, or other electrical device having trouble? I know there have been recalls for ECU flashes and injector replacements on some PD motors; is mine among them?
--Fuel problems? Our biodiesel has come from Laurelhurst Oil, which gets a lot of business and uses a large commercial-style underground tank; it's not some grassroots operation with a tank in someone's backyard shed. It should be good stuff. However, my parents never think about their cars, they just drive them; as a result, even when there was a cold snap with mornings in the high 20s (fahrenheit), they used B99. I know they should have mixed with diesel. They said it always started OK (though very unhappy/smoky/shaky on the colder mornings), but could this have done permanent damage to the injectors? At those temps, I'm sure there was at least some gelling/waxing going on. My next tank will be straight diesel to see if that makes a big difference. Should we be using some Stanadyne or PowerService (if so which kind?) mixed with our fuel, or do you think biodiesel will already provide those benefits without addatives?
--Internal engine problems? I am continually appalled by how much blowby this engine has. If you take the oil cap off when the car is running, it pumps out a steady pulsing torrent of gray smoke, and you can feel it strongly if you put your hand over it. Every time I check the oil I notice that the area around the fill cap is all greasy, presumably because internal crankcase pressure is pushing oil out through the cap seal. When I bought my '81 Rabbit diesel, it had 224k on the original engine and was using a quart of oil every 100 miles. It had nowhere near as much blowby as this Passat engine does. The Passat uses about half a quart every 6000 miles, which I think is normal for a diesel. But maybe it was never totally broken in? If so, am I totally screwed, or will it eventually wear in? I guess bad compression could cause the rough cold starting and bad efficiency and power, but we broke it in carefully, and I don't understand how it could be this bad. How much blowby do you guys notice on your engines?
I bought a Bentley CD manual, and will check out what it says about this tonight. Also, I am going to try to get someone to hook their Vag-Com up to the car and see what the computer is saying (anyone in the Seattle area have one?).
I have a digital camera, any pictures that would help you guys help me, let me know and I'll get them taken.
OK, if anyone got this far, THANKS!!!!! This is driving me out of my mind, and I only have 3 weeks to fix it before I have to go back to school. Let me know if you have any ideas!
I'm looking for some advice on what looks like a pretty serious issue that our 2004 Passat is experiencing. First, a little background: this is an '04-model B5.5 Passat wagon powered by the 2.0L TDI-PD motor and 5-speed Tiptronic automatic. We bought it in July of 2004 and have put on 16,500 miles since then. That has included a few long-distance trips, but mostly this car has to do in-town errand duty, meaning it rarely gets fully warmed up. I have changed the oil every 5000 miles, it has had the PD tandem pump recall done but has never been to the dealer other than that (so no ECU reflash, replacement injectors, etc). Since about 4000 miles, we have run B99 in it at all times, except for a couple tanks we had to fill with straight diesel when out of town on trips (those tanks probably ended up being somewhere beteween B5 and B10 I guess). Always the best fuel suppliers, OEM parts, expensive oil, etc.
When I was around (before I went to college in September), I regularly took it out maybe once or twice a week and gave it a long drive, to fully warm it up, and used full throttle and boost. However, for the past 4 months, it has had exclusively short drives, and absolutely no full-throttle runs (Mom's a very conservative driver). When I got home, I checked the lifetime average on the MFA, and was horrified to discover that it has been getting, on average, 18.5 mpg. When it was brand new, I could easily get above 40 mpg on the highway, and it was averaging in the 28-31 range.
The very first morning I was back, I changed the oil, using Elf Excillium DID 505.01 5w40. I then spent all day driving it around the area picking up parts for my Rabbit, mostly freeway driving, with many full-throttle blasts to the redline once it was warmed up. The car is an absolute dog. It feels like the engine has maybe 80 hp. It can barely accelerate uphill with one person onboard, and with five aboard, a little luggage, and highway driving, it is dangerously slow to accelerate. Even now, with one aboard, it cannot manage to get more than about 25 mpg on the highway. Other than this, it seems fine. Runs smooth and quiet, no obvious smoking, no check-engine light, and so on. It does not enjoy cold starts (even 45 degree Seattle mornings cause it to stumble and shudder for the first 30 seconds), but it's always been like that. Also, it does occasionally go into a no-boost "limp" mode (usually a little while after starting up, not after long hard driving), which is cured by shutting the engine off and starting it up again.
I have been trying to figure out where to start on diagnosing this problem. Here are the ideas I have come up with so far--let me know if any of you have input about these:
--Bad MAF sensor? It runs OK like I said, but low power and awful mileage make me suspect it...how could I test this for sure? Vag-com? Maybe this is also causing the occasional limp-home situation?
--Bad MAP sensor/boost sensor/N75 valve? No idea if these could affect things, these just came up a lot in searches about bad mileage and low power. And again, something has got to be causing that occasional limp-home deal even though there appears to be no overboost (unless my turbo vanes are sticking, it hasn't happened since I thrashed it hard on the highway when I got home and got the boost way up).
--Plugged intake manifold? I do have plans to install a Racor or Provent CCV filter eventually, but haven't done it yet. Is it easy to check this on a B5.5 PD motor? Since it has mostly been run on soot-free B99, I don't see how the clogging could be bad enough to cause the problems I'm seeing, but I guess it's worth considering. I can see a bunch of oil dripping from the intake hoses where they connect to the intercooler, and it does use about 1/2 liter of oil every 6000 miles, so I know there is at least oil getting in there.
--Restricted intake/exhaust? I have no reason to believe the exhaust is clogged, since it sounds fine and the turbo seems to be spooling without any trouble, but it is true that I have never cleaned the snowscreen. I will do this very soon; any chance it could cause this much trouble?
--Injectors, computer, or other electrical device having trouble? I know there have been recalls for ECU flashes and injector replacements on some PD motors; is mine among them?
--Fuel problems? Our biodiesel has come from Laurelhurst Oil, which gets a lot of business and uses a large commercial-style underground tank; it's not some grassroots operation with a tank in someone's backyard shed. It should be good stuff. However, my parents never think about their cars, they just drive them; as a result, even when there was a cold snap with mornings in the high 20s (fahrenheit), they used B99. I know they should have mixed with diesel. They said it always started OK (though very unhappy/smoky/shaky on the colder mornings), but could this have done permanent damage to the injectors? At those temps, I'm sure there was at least some gelling/waxing going on. My next tank will be straight diesel to see if that makes a big difference. Should we be using some Stanadyne or PowerService (if so which kind?) mixed with our fuel, or do you think biodiesel will already provide those benefits without addatives?
--Internal engine problems? I am continually appalled by how much blowby this engine has. If you take the oil cap off when the car is running, it pumps out a steady pulsing torrent of gray smoke, and you can feel it strongly if you put your hand over it. Every time I check the oil I notice that the area around the fill cap is all greasy, presumably because internal crankcase pressure is pushing oil out through the cap seal. When I bought my '81 Rabbit diesel, it had 224k on the original engine and was using a quart of oil every 100 miles. It had nowhere near as much blowby as this Passat engine does. The Passat uses about half a quart every 6000 miles, which I think is normal for a diesel. But maybe it was never totally broken in? If so, am I totally screwed, or will it eventually wear in? I guess bad compression could cause the rough cold starting and bad efficiency and power, but we broke it in carefully, and I don't understand how it could be this bad. How much blowby do you guys notice on your engines?
I bought a Bentley CD manual, and will check out what it says about this tonight. Also, I am going to try to get someone to hook their Vag-Com up to the car and see what the computer is saying (anyone in the Seattle area have one?).
I have a digital camera, any pictures that would help you guys help me, let me know and I'll get them taken.
OK, if anyone got this far, THANKS!!!!! This is driving me out of my mind, and I only have 3 weeks to fix it before I have to go back to school. Let me know if you have any ideas!
