Checked the air filter, now no power.

02 Jetta TDI O1M

Just purchased it, so I was checking the condition of the air filter. Lifted the lid out of the way, pulled the filter, vacuumed out the lower portion of the air cleaner box and put everything back together.

Took it into town and noticed it's very low on power.
-Very consistent in the way it runs and performs. This may sound odd, but I feel like it's being electronically governed. It accelerates (smoothly but slowly) to about 2100 rpm, then its like someone flips a switch off.
-I can clearly hear the turbo, but the Jetta falls on it's face just over 2k rpm in 1st and 2nd gear. 3rd gear I can run the rpm's out, but it's very slow getting there.
-While in park or neutral I can rev it up, but again the rpm's are slow to climb.
-No check engine light and my Scangauge doesn't show any codes.
-Turning the ignition off then back on doesn't "reset" anything.

I read about a test drive with the MAF unplugged, but haven't tried that yet.
I also read threads about low power/limp mode, but those seems to me resolved by restarting the car.

Thank you,
-Jason

Perhaps you should try the drive w/o MAF. It would give you a chance to check on whether the MAF is indeed properly plugged in, whether the vacuum lines are all properly in place, and whether the intake air plumbing is securely in place.

That's all I can think of without being there and having a look-see in person. Otherwise, it makes no sense to lose power after not having done anything.

Cheers,

PH

I agree. Makes no sense.
I didn't unplug the MAF when I checked the air filter.

I'll drive with the MAF unplugged and report back.

Thank you,
-Jason

Jason, were these same issues existing prior to digging into the airbox?

There's a hose that connects up to the airbox. Maybe you forgot to connect that up?

A bad MAF can cause low power. As Powder Hound notes, unplug it and see if that makes any difference. In park/neutral a bad MAF won't allow you to get full revs.

Next in line for consideration would be a clogged intake.

Fuel restriction could also be an issue for concern if there's a very consistent drop off in power (rpm-related).

How many miles? What do you know/were you told about this car? Any history would help.

Limp mode is most commonly triggered by over boosting or some times under boosting for a period of time (about 5-10 seconds). This is the most common issue. its usually caused by a bad vac (boost) line to something that causes the waste gate actuator to not work properly when commanded.
Common issues and the fix for them.
For just about every issue there is a code. you have to look it up. Its not very difficult if you google the right terms like "code 1234~ and your make and engine"

Vacuum lines or boost lines: Inspect or replace them all. usually 3mm, 4mm and 5mm hoses. dont use cheep ones, get quality silicone or VW braided lines from IDparts.com or where ever. Not sure about your ECU but on MK3's there is a boost line going into the ecu and inside the ecu to the MAP sensor and it needs replacing too, if you have one.

N75 Valve: you should have a slight clicking from it, kinda like a CCV valve. some times you can clean them, they are not very cheep ($75) for an OEM. usually replacing it is best.

MAF: this is the sensor on the intake air duct right after the filter. ONLY CLEAN WITH MAF cleaner. A cold air intake usually is the culprit for killing them. Check out this link to understand why. Disconnect it and if driving conditions do not improve then its bad. (only after you make sure you have no boost leaks and all your lines are perfect shape.) http://forums.tdiclub.com/showthread.php?t=290373

Boost leaks: Check all your pipes after the turbo to and from the intercooler and to the intake manifold. take them apart, and put back together to make sure no cracks etc. inspect the intercooler too. You will see some oil on the pipes. Its normal. Just wipe off the parts your connecting with a light amount of brake clean on a rag. DO NOT spray it into or on the pipe. it could cause a temporary runaway. Happend to me lol, i was lucky, kinda.

When you take your intake pipe off the intake manifold, inspect the intake and see how much soot and crud is caked up. This is caused by the CCV (crank Case Vent) it mixes with the EGR (Exhaust Gas Recirculate) and caused crap to build up. A small amount is ok. Recommend a EGR delete and a tune or hack to remove the CEL (Check Engine Light.) This wont cause limp mode unless its Really bad to the point of causing an over boost. the ECU knows the engine to take in enough air and charges the turbo to supply. This is very uncommon but eh its worth a look. Newer fuels dont cuase this issue as much anymore. To properly clean it you need to take the head off. Again this is probably not the issue but worth inspecting.

thats about it. Fix and inspect those items. in that order one at a time with test drive in between to make sure you dont jsut thorw parts at it.

Get someone with VCDS and a VAG-COM connector, or you can autozone it with one of the diagnostic computers they lone you, or a amazon Bluetooth OBDII device. Look up the code you are getting. Limp mode usually does not trigger a CEL (check engine light.)

UhOh:
No way. Ran awesome before I cleaned out the air box.
I didn't disconnect anything. Not the hose to the airbox or the plug to the MAF. I simply unscrewed the cover and set it off to the side a bit.

I have a lot of history on the car and purchased it from an honest seller.
-Stock air cleaner assembly (snow screen removed) using Mann air filter
-Intake was recently cleaned
-All new silicone (BMW) vacuum lines
-EGR delete
-Malone eco tune
-5-speed injectors
-Hammer mod
-Cat & mufflerectomy
-196k miles

Mongler 98:
-This issue didn't begin until after I checked the stock air filter and vacuumed out the bottom of the air box.
-No CEL
-My Scangauge shows no codes

Thanks again,
-Jason

nomorotors said:

UhOh:
No way. Ran awesome before I cleaned out the air box.
I didn't disconnect anything. Not the hose to the airbox or the plug to the MAF. I simply unscrewed the cover and set it off to the side a bit.

I have a lot of history on the car and purchased it from an honest seller.
-Stock air cleaner assembly (snow screen removed) using Mann air filter
-Intake was recently cleaned
-All new silicone (BMW) vacuum lines
-EGR delete
-Malone eco tune
-5-speed injectors
-Hammer mod
-Cat & mufflerectomy
-196k miles

Mongler 98:
-This issue didn't begin until after I checked the stock air filter and vacuumed out the bottom of the air box.
-No CEL
-My Scangauge shows no codes

Thanks again,
-Jason

Click to expand...

Not that there could be the coincidence that something just decided to impale itself with this simple operation, but it does seem like something with the MAF or the hoses has been disrupted. I'd check that the nipple on the N75 didn't get tweaked. Also look at the stuff around the vacuum pump. Well, if you have a vacuum gauge it might be best to just do some vacuum checks.

The most obvious place to look is the sealing of the airbox itself. I won't open one up unless I am putting in a new filter. IF it's not sealing up well then it's possible that the MAF might not get proper readings?

Not sure about Scangauges, but my Ultragauges can show me boost numbers.

At this point you pretty much have to start at square one and painstakingly prove that everything is as you believe it to be: thinking or assuming it is isn't good enough- have to measure/check.

10/4 on the n75 vlave. I snapped one off, somehow! was crazy brittle for no reason.

ok if your 100% sure you checked all your hoses, and everything is perfect and your 100% sure that it was caused by working on the air filter, than check your turbo fins. MAYBE some crap got sucked into the turbo. its either that or a issue with limp mode and a vacuum or MAF, maybe n75

or 100% coincidence. maybe broken fuel line underneath?

I *disunplugged* the MAF and gained **some** power. Probably 60%. Also been getting a CEL for the first time. PO102 for the MAF, both when plugged in and unplugged. I’ve been clearing it with the Scangauge.

I’ll clean it when I get home.

Thanks,
-Jason

>disunplugged

95% chance cleaning won't help, if you have VCDS you can check for a dead maf.
I tried cleaning with mine and it didn't make a difference, new MAF sure did the trick!

I carefully pulled the MAF, cleaned it with CRC MAF Cleaner, reassembled everything, cleared the PO102 and BOOM...full power restored.

Before getting home to clean the MAF, I put about 50 miles on it this evening going back and forth between having the MAF connected/disconnected. Both ways the PO102 would pop up, but the Jetta always had more power with the MAF disconnected.

I really appreciate all the help,
-Jason

nomorotors said:

I carefully pulled the MAF, cleaned it with CRC MAF Cleaner, reassembled everything, cleared the PO102 and BOOM...full power restored.

Before getting home to clean the MAF, I put about 50 miles on it this evening going back and forth between having the MAF connected/disconnected. Both ways the PO102 would pop up, but the Jetta always had more power with the MAF disconnected.

I really appreciate all the help,
-Jason

Click to expand...

If power is better with the MAF unplugged then it's the MAF or its wiring. As important as a properly operating MAF is it's really not worth trying to salvage a marginal one.

UhOh said:

it's really not worth trying to salvage a marginal one.

Click to expand...

It depends on a person's situation. For me, it would be worth it in this situation. I now know it's the MAF and I can run it until it happens again or doesn't. If it happens again, throw a new MAF in it then. If it doesn't happen again, I'm golden.

But, my situation is that I'm not driving this car across country all the time, nor do I have important cargo on board. Some people would need a more reliable car and in that situation, it certainly makes sense to install a new MAF.

Doing this for someone else, I would discuss it with them, and understand their situation and make a recommendation to fix or clean based on that.

Dog, the near complete failure of a MAF in the wife's car convinced me to not even chance running what I know to be a marginal MAF. There had been little advance warning other than the Ultragauge's instantaneous MPG was getting a bit goofy (I think it was reporting a fair bit lower FE). The car started really bucking; I wouldn't have wanted to try and operate it in any traffic. For people like you and I we know that we can just disconnect the MAF and continue down the road. I'll admit, I don't believe that this kind of failure is common; but, it's the only encounter with a bad MAF that I've had: I put a new one in the daughter's car because the existing one wasn't showing to be fully healthy and she's a couple hours away (won't send her off with anything that I know if marginal- Downtown Vancouver, BC is no place to have car issues): the one I pulled ended up going into the wife's car in place of that failed MAF until I got a new one.

Going back to the original activity which seems to have lead to a MAF fault, the air box lid removal is more likely to have strained the wires going into the MAF plug. Fatigue at that point is likely in normal use and I would want to check the wires very carefully for internal fractures which may not be apparent from external examination.

I'd bet internet money it was the plug contacts. After re-connecting for the removal, MAF clean, the contacts cleaned up a bit.

BobnOH said:

I'd bet internet money it was the plug contacts. After re-connecting for the removal, MAF clean, the contacts cleaned up a bit.

Click to expand...

I thought the same or perhaps he yanked the maf when opening the air filter. I did that once. Plug was out just a little and power was gone. Popped the hood and pushed the maf back together and presto!

Cause and effect. I don't think I've ever popped off/moved the top of the airbox w/o disconnecting the MAF connector: my pea brain seems to think that it cannot be done; but, IF it can be done, it think that it ought NOT be done.

I wonder if the corrugated intake hose could have developed a crack or the seal was compromised while trying to set the air box lid aside.

i just replaced my air box filter yesterday - it would be pretty awkward to sneak it out and the new one in with the MAF harness connected.

You didn't stuff a rag into the intake while the filter was off....that you forgot to remove?