Volkswagen Jetta Junkies banner

emmissions malfunction indicator lamp...turning out to be a huge headache...help!

28K views 12 replies 4 participants last post by  Mill-pie 
#1 ·
I have an '04 Jetta tdi, with 137,000 mi. I have had it since '06ish , and put almost 100,000 of those miles on it. I have been changing the oil about every 8,000, using synthetic oil. It has had a few minor repairs done on it in the last couple years. So, of course, I've just been braggin' up a storm over this car, how much I love it and so on.
THEN, Just recently the emmissions malfunction indicator lamp comes on as I'm driving over a steep mtn. pass. It's really blowin out smoke, and feeling gutless. So I take it to my mechanic and they clean the maas air flow sensor. The light stays off for about 2 days. I take it back to the mechanic, and decide to have him replace the sensor. The light comes back on about a week later. I take it back to the mechanic, he comes up with a list of things to fix on it (totaling around $500) but does not guarantee that will solve the problem.
So I take it to another mechanic to get a 2nd opinion, he says to just trade it in , that it could be a broken ring , (and something about back blow? can't remember exactly) that would cost around $4,000 to repair.
I'm wondering, now what do I do? It is currently at a 3rd mechanic getting a more thorough diagnostic. This is my first diesel , so I am clueless and want to understand what is going on with this engine.
Any thoughts, comments, suggestions, answers???
 
See less See more
#2 ·
lol blowby, you mean? Blowby is when your cylinder is compressing the air/fuel mixture, and some of it slips past the piston rings, into the crankcase... If fuel content is high enough, it can contaminate your oil and really screw things up... Probably not your case.

The PCV (positive crankcase ventilation) valve is used to evacuate these gasses and relieve pressure from the crankcase itself. IF what you were told is that you have a blowby problem, it could have to do with your PCV system... However, excessive blowby is caused by bad piston rings, however bad rings don't cause CEL's to come on.

Anyway, what you need to do is first, pray to whoever you pray to that they didn't erase your diagnostic trouble codes (if your check engine light (CEL) is on, you're good to go) and second, bring it to advance auto, autozone, or pep boys and have them scan it for free. They'll give you a list of stored codes. Once you have those, we can go from there.

However, if you get a P0440 and nothing else, you'll have to take it to a shop where they can print out a diagnostic tree for that particular code, and go from there. Typically, however, if a P0440 shows, more come with it that help the situation.
 
#3 ·
LOL yes blowby. Ok thank-you for explaining all that to me! That totally makes sense.
I was on the right path, I initially took it to auto zone and the diagnostic said it was only the maas air sensor, The 2nd time the light came on I had it scanned again before going back to the mechanic and it was the same readout. ( therefore I was so confident , thats why I spent the $ and let the mechanic replace it right off the bat, after only cleaning it didn't work)
Question: is the CEL same as the MIL lamp? My owners manual is in my car, so I'm a little unsure of all my warning lamps. (Especially since they've never come on till now).
I'm hoping for word this eve on what they find. I just want to be educated so the mechanic doesn't try to pull one over on me. So I appreciate your advice and knowledge.
 
#4 ·
No problem, thats what we're here for =)

MIL and CEL are the same thing, malfunction indicator lamp, check engine lamp/light. It only comes on for emissions purposes, so thats why some refer to it as emissions lamp, but they're all the same.

So, can you actually tell that the MAF is replaced? Because if you had a code for the MAF, replacement should definitly be the fix, unless somewhere there's a wiring issue.

Did the code description say anything about high voltage, low voltage, or no signal? You could have a wiring problem... Though its not too likely.

Do you have an air intake modification by any chance?
 
#5 ·
If my mechanic is honest , then I know for sure the MAF was replaced b/c he gave me the old one back. I can't find my readout from the auto store. But if I can find it I will tell you exactly what it says.
I do not have an air intake modification.
If this info is of any use.....It's really cold in the winters here, and I don't have a block heater. I've never had a problem tho getting the car to start, until one time this winter when it was like 20 below and I park outside. I also moved closer to work this winter and only had to drive 5 miles to and from work. Is this really hard on the car? Do you think it could have initiated the cause of the problem?
 
#6 ·
Well, short trips, especially in the winter time can be harmful to the engine. While the block is very cold to start, combustion temperatures are very hot. So, if you don't heat the block up completely before you get to your destination, the two temperature differences (in the right conditions) can actually form water vapor (due to condensation) inside the cylinders. The water collects, and drips down onto the pistons. When the piston rings cool and contract, that water seeps into your oil....

So in short, it's certainly not a good thing... For a diesel especially, it'd be a good early xmas gift to get a block heater. But for purposes of this thread, that won't have any affect on your mass airflow sensor.

Try scanning her again, and let me know what the P code is. It may not be real specific... But if its a general MAF sensor code (no low/high voltage, etc), and it WAS replaced, you probably have a wiring problem.

Try this - Unplug the MAF but don't take the sensor out. Does the car run better with the MAF unplugged, or plugged in?

Make sure to do that little test after you get codes, b/c driving with a MAF unplugged will definitly throw a code.
 
#7 ·
The latest...So car has been at a mechanic who could not get any codes, he took it straight to the dealership. They found a broken main hose. The part should be in today and once they get that put on I will find out if that is the only culprit to this wild goosechase. I'm praying that it is all that is wrong. I have a good feeling. Will you explain to me this hoses job and if and how it would make the sensor go off? Nobody( mechanics) seems to want to explain anything into detail for me, maybe assuming since I'm a girl I don't care or want to understand, but I do.
 
#8 ·
What hose job?

There are alotta hoses lol. Vacuum hoses, coolant hoses....
 
#10 ·
Well at least YOU didn't get "hosed". :cool:

Glad your baby is running right again.

I always learn a ton whenever Boost gets into diagnostics with a member so thanks to both of you.
 
#11 ·
Oh no, 4 days after she came out of the shop the MIL came back on again, and it is running the same way - which is rough, lack of power, and excessive black smoke when I put the pedal to the metal. I'm back to square one.ugh. SO she's got a new MAF, and a cupling on the intercoolant hose...and still the problem. NOW WHAT? Just dropped her back off at the vw dealership this am. The only code I was getting was the MAF so I'm letting the vw guys take over. But why does this seem to be a goosechase? What else could it be???
 
#13 ·
......The saga continues......a new turbo,and other misc. repairs and 4 days later, the mil comes back on , so back in the shop and i'm told it's the cam, b/c i've been putting in the wrong oil. so i go back to the manual and it specifically calls for vw 505 01. ive been using a synthetic oil. but now that i look at it closer it says vw 505 00. Is that a big enough differance to ruin the cam?
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top