Volkswagen Jetta Junkies banner
1 - 20 of 41 Posts

·
Registered
Joined
·
31 Posts
Discussion Starter · #1 ·
I have a 2.0L BBW Engine and periodically the check Engine light comes on. When I check the OBDII message (P2177) it is defined as "System too lean off idle bank 1". Has anyone experienced this error message? I suspect that it has something to do with low fuel pressure. I suppose the best thing to do would be to buy a fuel pressure gauge set so that I can check. Alternatively, I could try replacing the O2 sensors. But either route seems like an expensive guess. The car has 104K Miles on it and we've owned it for the last 8K Miles. Any thoughts would be appreciated.:confused:
 

·
Eur0wn3d
Joined
·
1,846 Posts
well this is somethin i found searching around...



1) first step is to make absolutely sure that there are no intake or vacuum leaks. You can start with a visual check of all of the hoses and check valves, but in my experience, this may lead to success about 25% of the time. There are just far too many components to be able to see without removing parts. In this case, as a shop, I would hook up my inert smoke generator to the intake air hose, fill the intake and vacuum system with smoke and see where, or if it comes out.
2) then I would check the air mass meter, which would require a vw-specific scan tool such as Ross Tech's Vag-Com. Easiest way to check it using this tool would be to get into the engine control module screen, then measuring blocks, then group 002 to monitor the amount of air passing over the sensor in grams/second, at redline, in 3rd gear, wide-open throttle. I would expect to see approximately 100 g/s. If significantly lower, I would replace the meter.
3) Then it's time to monitor the front oxygen sensor to see if there's a good clean lean-rich-lean cycle being generated, as you're wanting to see a very tight sine curve that dithers between approximately 0.1v and 0.9v, and the frequency should be less than 1hz.
 

·
Eur0wn3d
Joined
·
1,846 Posts
yeah..i mean ur suppose to change them anyways..nothing lasts forever...can maybe try cleaning them if you wanna try and save money..might or might not work
 

·
Registered
Joined
·
31 Posts
Discussion Starter · #5 ·
Hi Jedduh, Thanks for the reply!
This afternoon (before receiving your reply) I spent some time locating the O2 sensors (I didn't expect there would be three!) and took some Voltage measurements.

The first O2 sensor connected to the exhaust manifold had six wires; the following voltage measurements were taken with a DMM (no O-scope readily available - but can probably borrow one from work next week if needed). Pin 1 = 3V, Pin 2 = 2.2V, Pins 3 and 4 ~ 13V, Pin 5 = 2.5V and Pin 6 varied from 2.1 to 2.8V. It is not clear from the schematic as to which pins are inputs and which is the output, but it was clear that pin 3 is the + side of the internal heater and Pin 4 is the negative side of the heater. The schematic indicates the remaining pins (1, 2, 5 & 6) all connect to the ECM through the 121 pin connector.

The second O2 sensor positioned in the middle of the Cat Conv had ~ 13V at pins 1 and 2 and pin 4 measured 0.4V.

The third O2 sensor located after the Cat Conv had the same voltage readings as the second sensor.

Not knowing what the voltage levels should be on the first sensor I can't say if it's good or bad. But it would seem that the 2nd and 3rd Sensors are OK.

I will take a close look at the vacuum hoses and the fittings tomorrow. Do you have any suggestions on how to DIY a Smoke generator? I thought of reversing my shop vac or using my compressor, but they seem to make so much noise it would be impossible to listen for a leak. If you have any thoughts on how to do that please let me know.

Regarding the suggestion of taking my car to a dealer, I just can't. A year ago when we first bought the car we took it to the dealer because I couldn't figure out this error code (P2177) problem. They told me it was the MAF sensor and wanted to charge me $450 for the part and install. Obviously that was a simple pop and swap so I did it myself. The total Estimate they gave me was $1300 to r/r MAF sensor, axle boot, radiator fan, and a side marker bulb. Well I got all the things fixed myself and it cost a little over $300. Up until a few days ago we thought I'd fixed the problem with the replacement MAF sensor. So, I don't know where your located, but if you or anyone else knows of a reputable shop near Simi Valley CA please let me know. If you or anyone else thinks of anything else to look at please let me know.
 

·
Registered
Joined
·
49 Posts
There's a lot of things that could make it run lean. The key is to check the simple things first, because that's usually what it is. Don't go replacing expensive things like o2 sensors before you check the simple things. Like mentioned before, do a boost leak test, make sure everything is clamped down tight, and check the spark plugs, and make sure they are gapped correctly.

Edit: Just saw that you have a 2.0. Ignore the boost leak test comment, but yes, make sure there are no vacuum leaks anywhere.
 

·
Registered
Joined
·
31 Posts
Discussion Starter · #8 ·
Well, I tried checking for vacuum leaks today, but whenever I discharged some compressed air into any of the lines I could hear it leaking or rather passing into the system but coming out somewhere..possibly into the intake manifold. Just couldn't tell without the smoke. Today I was at a Autoparts store and opened a Chilton manual and it talked about how to test the O2 sensor in the Exhaust manifold. It said that at below 600F the O2 sensor should read about 400mV. Once the sensor temperature goes over 600 (normal operating engine temp) the voltage should begin toggling between 100 to 900 mV. So with the engine running I climbed back under the car and took the measurements for each of the six pins on the connector to GND. Here's what I found: Pin 1 (Grn wire) = 2.95V, Pin 2 (Blk wire) oscillating between 2.1 and 2.9V at 8 sec interval, Pin 3 (Blk/Ylw wire) 13.3V, Pin 4 (Lg Wht wire) oscillating between 1V and 12V at 1 sec intervals, Pin 5 (Sm Wht wire) = 2.5V, Pin 6 (Grn wire) 2.1 to 2.8V (same as pin 2). Funny thing was the book said to check between the brown and the Black wires - I didn't find any brown wires so I guess I have to throw that info out the window.

I cleared the code and drove the car around and the light didn't come back. I expect it will be gone for a couple weeks to make me believe the problem is gone and then will re-appear just to drive me nuts again. Appreciate everyone's comments thus far. ForceFed/AJSnow - thanks for your comments, I will try checking the gap.

Can someone answer this question for me - If I have a vacuum leak, shouldn't it show up as an abnormally high RPM at idle? The car seems to be idling ok at 750-800RPM. Also the code indicates too lean "OFF IDLE"..... so I was thinking it might be too low a fuel pressure at say highway speeds or during higher/full throttle acceleration. This sort of brings me back to Fuel filter since I just replaced the fuel pump last Spring. Any thoughts my friends?
 

·
Registered
Joined
·
761 Posts
the easiest way to check for a vacuum leak is to take a propane torch and turn it on but do not light it and while your engine is running trace the vacuum lines and if your engine revs high you just found the leak. another thing to try it maybe cleaning your maf sensor. use either maf cleaner or alcohol but just make sure you don't tough the wires inside the maf with anything. here is a DIY http://jettajunkie.com/vw-jetta/showthread.php?6548-Cleaning-your-MAF

i could have missed it but is your car running rough? if so to rule out the maf just unplug the maf connector and if it runs better then its your maf. if it doesn't run better than its probably not it.

by the way i have the same engine as you and it seems to be the only mkiv with three o2 sensors and it appears that the fuel filter is located inside the tank.
 

·
Registered
Joined
·
31 Posts
Discussion Starter · #10 ·
Hi Bill H.,

Thanks for the tip about checking for vacuum leak. That is a novel idea. I will give that a try. When we bought the car last summer, the error code came up nearly on the drive home from the dealer if I remember correctly. Funny how it didn't show up on the test drive! Anyway, we took it to the dealer when I couldn't find the problem and they said it was the MAF Sensor. So I replaced it to the tune of about $200, cleared the code and everything was fine for a few months and then the light came on again and the code was the same (P2177). I did a lot of poking and proding but never found the source. A few months ago (this spring) I replaced the fuel pump (not because of a warning light - the car just died). So I traced it to the fuel pump. I replaced the pump and everthing worked fine...until last week. Can you tell me if you replaced the O2 sensors on your car and if so what mileage you did it at? Also, do you think the MAF sensor needs to be cleaned if it was just replaced last summer? Can't wait to try out that vacuum leak test. Truely a clever idea.

Not sure if this is a correct assumption, but I believe the BBW engine is the PZEV engine? Maybe someone out there can confirm. That might explain the sensitivity that this engine has to Emission problems. I personally drive a '98 Dakota with the I4 engine with 195K Miles on it and I've never had the engine light ever come on - but then again, I have replaced the Cat converter twice (both times under warranty). I did the O2 sensors on that vehicle at around 150K miles. Thanks a lot, Chris
 

·
Registered
Joined
·
761 Posts
i would love to take credit for the vacuum leak test but i can't i learned that from another member of this forum boostaddicted. What i have learned is that the MAF is a very sensitive sensor. it is possible that if it get oil/dirt on it that it could cause a problem. if that fixed the problem before it could be the issue again. does the car run rough?

if it does try disconnecting the MAF connector from the housing and see if it runs better. if it runs better then the MAF may be dirty. I don't see that being the problem but its something easy to test. how is your air filter any oil on it? that could be a sign that your MAF may be dirty. i wish i could be more help but, knock on wood, i haven't had too many problems with my car so far.

as far as the o2 sensors go i have replaced the one on the cat and the one post-cat at about 95000. i have about 97000 now.

the only thing i could ever find about the BBW engine is that it could have been a C.A.R.B. friendly vehicle for california emission which would make sense if it is PZEV. i am making an educated guess because when i looked for parts a lot of them came up C.A.R.B. friendly but i could not find any concrete evidence.

oh and i will let you know now that the dealership, at least mine, really isn't a lot of help when getting info about the engine either because i told them it had 3 o2 sensors and they looked at me like i had 2 heads until they looked it up themselves and found out i was right.
 

·
Registered
Joined
·
31 Posts
Discussion Starter · #12 ·
Well I tried the removing the connector to the MAF sensor and it ran almost indistinguishably different. Meaning, I could tell that it ran only very slightly rough with it unplugged. As I recall it was supposed to run BETTER if the MAF was dirty/contaminated. I still have this nagging feeling it has something to do with a fuel delivery problem. A question I have for all those Jetta experts: At the right side of the fuel rail is what looks like a valve stem. Can I connect a pressure gauge to that stem and measure the fuel pressure? My suspicion is that the fuel pressure is low at higher rpm/full throttle condition and if the Engine management computer gets a few low pressure readings it triggers the MIL warning light and stores the P2177 code. I would like to check this theory but I need to know if my hunch is worth investigating and if so, how much pressure should I expect for a normal system? This is a connection to fuel which is nothing to mess around with unless completely confident of a secure connection, otherwise the results could be disastrous.
 

·
Registered
Joined
·
761 Posts
if it would be your MAF then when it is unplugged it should use a default setting for air/fuel mixture. if it doesn't run better then it probably isn't your MAF. Have you had a chance to test for a vacuum leak? i wish i could be more help with the fuel pressure test but that is something i don't have experience with. Hopefully someone with a little more knowledge will help you out there.
 

·
Registered
Joined
·
31 Posts
Discussion Starter · #14 ·
I tried that Propane tank experiment and found no difference. I could see gas flowing out from the nozzle of my propane torch and position the nozzle about the same distance as I would if were lit and followed the one vacuum hose from the top of the Throttle body to the runner that goes to each of the fuel injectors (Below the fuel rail) and the other vacuum hose from the left side of the intake manifold to some other vacuum thing and from there to a few other places. There was no change in the RPM. Next I removed the hose connector that goes from the exhaust gas air pump to the air filter box and allowed the gas to enter into the air cleaner area. I expected that would cause an increase in RPM, but it did not. Tonight I might try disconnecting the large diameter tube from the air cleaner box and try leaking the gas into the area before the MAF or possible after the MAF to see how the Propane changes the RPM. Thus far all I have noticed is "no change". I need to see what a positive result to the gas is so I know what to expect if there is intake of the propane. The saga continues.
 

·
Registered
Joined
·
761 Posts
i have not done the test myself but from what i understand is that you will be able to tell right away if you have a leak using the propane torch. have you tried any injector cleaner or seafoam to see if that makes a difference? i wish i could be more help but i don't have much experience with this type of issue. i will try to find some more info for you that might help.

as far as the avatar goes you need to click on settings at the top and then on the left under my settings there is a link to edit avatar and then just choose your picture.
 

·
Registered
Joined
·
31 Posts
Discussion Starter · #17 ·
I am going out on a limb and asking for a huge favor. How would you like to check the voltages coming from the first O2 sensor so that I can compare to my readings? The way I tested it was to undue the connector cover located on the underside of the car on the passenger side. I llocated the 6 pin connector and then connected a partially expanded paperclip to my voltmeter and inserted the expanded end of the paperclip between the foam and wire coming from the connector. I connected the other end of the voltmeter with an alligator clip to a bolt that was extending through the floorboard (it was something I felt should be an adequate GND and near by the area of the connectors). The most unfortunate part of this is having to go under the car when the engine is warmed up and running. I then wrote down the measurements and reported them above. I know that this is not a fun thing but I think it will help me know if the O2 sensor is the problem. The intake doesn't seem to be the problem based on the results of the visual and Propane test for Vacuum leaks.
 

·
Registered
Joined
·
761 Posts
I should have some time later on today to give this a try but i can't make any promises. I will measure the voltage on each of the pins and see what it comes up while the car is warmed up and running and then report back to you as soon as i can. just to make sure i do it the same way, did you disconnect the o2 sensor and just measure the car side connector voltage or did you leave the sensor connected and measure the voltage on wires headed to the sensor? i would assume that you measured the voltage of the wires on the sensor side of the connector without disconnecting it.
 

·
Registered
Joined
·
31 Posts
Discussion Starter · #19 ·
The voltage measurements were made without disconnecting the connector (both male/female connectors were mated). Thanks in advance for your help.
 

·
Registered
Joined
·
761 Posts
i was going to attempt his last night but we had a big thunderstorm move through and i didn't have access to a garage. i can still try this for you but i won't be until next weekend because i work all week. sorry man
 
1 - 20 of 41 Posts
Top