[Cirillex]

Hi there,

It's me again I've been trying to get my 1.8t running again, and just recently I replaced the air filter, injector cups & injector o-rings, painted the intake manifold & throttle body, cleaned and painted the PCV hard pipes, and installed a post-cat O2 spacer (I have a high flow cat).

After putting everything back together, the car started right up but I noticed a more delayed throttle response after the cold start ended and it now it won't rev past 3k rpm and it takes forever getting there even when flooring the gas pedal. The car idles fine and until like 1800rpm I can say it behaves pretty much normal except for the little delay I feel in the throttle pedal. All this testing was done with the car parked and sitting on jack stands.

I checked the boost levels in measuring block 115 and it's not building boost at all. I thought maybe it could be a bad N75. Unplugged it and engine ran the same way. Then I measured the resistance and it's at 30ohms, which seems to be within the expected range.

Then, I checked for vacuum/boost leaks in all the hoses around the intake manifold and everything seems to be fine.

Then, I ran a scan using my OBDEleven and found a P0101 code relating to the MAF sensor. So I went ahead and unplugged the MAF sensor and the engine ran the exact same way which means there's something going on with my MAF.

Using a multimeter I measured the voltage on the connector pins, and I think I found the culprit, though I don't know what to do with it:
- pin 2 measured only 3.33v when it should measure 12v.

• pin 3 (ground) measured 12v (good)
• pin 4 measured close to 5v (good),
• pin 5 measured 0v (which is expected because the key was on but engine was off).

My connector is the 5-pin style with an empty pin 1.

For reference, my battery was measuring 12.86v with key ON and engine OFF.

Question 1: is this a boost limp mode?

Question 2: What should I do next given that the power source to the MAF is way lower than it should be (3.33v vs 12v)? I have no idea what to trace it to, my guess is that I should look at the fuse panel next but other than that I have no clue where to go.

It's discouraging because it was running fine before I did all of that, but I guess that's just how it goes

 

[VAGguy]

Check/replace fuses #29, 32, and 34 and also check the wiring to the downstream O2 sensor as it shares that main wire connection on #34 with the injectors and MAF. Reading more above, it sounds like the O2 sensor wiring would be the first thing to look at. The wiring may be rubbing on something or have burned through with it now being in a slightly different position due to the spacer.

Does the SAIP come on at all?

 

[Cirillex]

The post-cat O2 sensor was also replaced with a used one during this job since I ruined the previous one due to the lack of a spacer. Now with a 45 degree spacer it sits in with plenty of space and I’m sure the wire is not touching anything it shouldn’t be.

Maybe I’ll try to disconnect the O2 sensor and see what happens.

The SAIP comes on normally for like a minute or two on cold starts, so it is working.

Thanks for your input - I’ll go buy some extra fuses and I’ll post the results.

 

[Cirillex]

Well, I just checked (visually) the fuses #29, #32, and #34 and they look fine.

I tried unplugging the post-cat O2 sensor and the car ran exactly the same and wouldn’t rev past 2000 rpm.

The only difference I noticed now is that the SAIP didn’t kick in.

Not sure where to go from here

 

[Cirillex]

Update: I just tested the voltage on pin 2 using pin 3 as ground with the engine running and now I’m getting 14.4v which seems to be right.

I just read somewhere that apparently the MAF is only powered when the fuel pump is running, which would explain the lower voltage I was getting with just the key on.

So I guess I can narrow it down to a problematic MAF sensor?

I’ll try to stop by the local junkyard tomorrow and pick up a used MAF.

 

[Cirillex]

Update: I pulled a used MAF from a junkyard car and it didn't change a thing. The MAF code hasn't come up anymore, but now I'm thinking it might have come up because of me hyper-focusing into thinking that the MAF was the problem, and I probably forgot to clear out the codes in between connecting/disconnecting the MAF.

I am currently getting a P1857 when reading codes from the transmission module. I found my passenger side carpet a bit soaked in water last week and traced the leak to the door panel. Yesterday I took it apart and resealed it with silicone, though I could see a trace of rust down from the bottom of the speaker, so I'm not sure it'll resolve the leak.

The gears still show up fine and they're not highlighted on the dash, but I'm thinking the car is in limp mode because of a soaked TCM. What do you guys think?

What else could cause it to stay in limp mode?

 

[Tomvw]

18265/P1857/006231 - Ross-Tech Wiki

wiki.ross-tech.com

Scan the engine and post all codes.

 

[Cirillex]

Update:

After a week of not touching it because of all my school work, I finally got to put in a decent amount of time in the car.

I was able to borrow my friend's air compressor, so I did a boost leak test. I found out that my 3-way check valve was completely busted (as in, air could be blown in any direction) and another check valve under the intake manifold was making some funny noises. Luckily, I already had replacements for both, as I anticipated this could be an issue at some point.

However, this did not solve my problem. I tried driving the car around the parking lot and it has no power at all. Even flooring the gas pedal, it will stay around 1200rpms and move around very slowly. Limp Mode? When parked it revs up to ~2500/3000rpms and idles perfectly fine. Unplugging the MAF makes no difference either.

Reading blocks 002 and 032, I see the MAF reading around 3.4g/s when idling, and idle fuel trims +1.5%. Correct me if I'm wrong, but I think the engine is adding fuel, which means the MAF is detecting less air than it should be, right?

Luckily (if I can say so?), this time around the P0101 code came back. So I am assuming it just so happened that the MAF decided to give up coincidently as I disassembled and repainted the intake manifold, granted it was still the one original to the car from 2002 (MAF manufacturing year).

I pulled the trigger and bought both a new MAF connector (1J0973775A) which I hope to be able to rewire (not a big fan of splicing wires) and a new Bosch MAF (06A906461N). I'll try and replace the connector first, since mine is all brittle and most of that red plastic locking mechanism is gone. If that doesn't do it, I'll try the new MAF.

What makes me think it may be the connector is that the junkyard MAF didn't change anything - the car just ignored it too. Though, it's also from 2002, so maybe I just had back luck and it happened to be faulty too.

Any other thoughts or ideas of things I should investigate?

Thanks guys!

 

[Cirillex]

Final update:

I though I'd get over myself and just post the resolution here - I have to say it's embarrassing to do so. I hope this serves as a warning/reminder for some.

A few weeks before I ran into this issue, I had the intake manifold and the air filter box out. I did injector cups and repainted the manifold and had the airbox out because I was installing an secondary O2 spacer.

Anyways, every time I take things apart in the engine bay, I put blue shop towels in the hoses so I don't get any debris or anything to fall inside of them, and specifically blue ones so I see them when installing it back later (!).

Fast forward to when I had everything ready to be put together, I was really excited I had the time to put the whole engine bay together and start the car. I think what happened is that when moving the hoses around to install the airbox, the shop towel fell deeper in the turbo inlet pipe and I didn't notice it (I know, pretty bad).

So before I reconnect everything I take the shop towels out, but I think I was blinded by my excitement to see the engine running and didn't notice I hadn't taken it out of the TIP.

So now for the funny part of how I figured out that there was a shop towel chocking my intake: I decided to do another boost leak test, BUT I didn't tighten the boost leak tester (2" pvc end cap with a tire valve stem) enough on the TIP, and as pressure built up to like about 1 bar (~14 psi) the boost leak tester came out flying - luckily, my head was not in the way - but also with it, came an entire blue shop towel.

At this point, you can imagine how confused I was, trying to understand what happened and seeing if I had messed something up because the "explosion" made a super loud noise. As I inspected everything, it seemed fine to me but I was still wondering where the heck did that blue shop towel come out of.

It didn't take me long to realize this was in the TIP and I might have just hit the jackpot and solved the problem "accidentally". I inspected the shop towel and for my surprise it came out pretty much intact except one of the corners had been "eaten" a little bit, but since it was just a tiny piece, I thought that was my luckiest day and felt really blessed by God haha

I put everything together again, and cranked the car and ta-da: it ran perfectly fine!!! Boost was back, the engine breathed normally again, MAF code was gone.

I cancelled my order for the new MAF, but kept the new connector that came in. I ended up just replacing the red part (locking mechanism) for good measure because mine was totally brittle but the connector housing was just fine.

I also vacuumed the TIP for good measure to make sure there were no pieces of shop towel left. I believe there might be a few bits stuck in the intercooler but I decided not to worry about it too much because the "eaten" part of the shop towel was fairly small (surprisingly).

To conclude this saga, now two weeks and about 600 miles later since the fix, the car drives amazing. Thanks for everybody that pitched in.

The itch now is with the transmission, I'm hating it so much now that the engine is runs like it should. So you'll likely hear from me in the near future as I was encouraged by my fiancé (!!!) and friends to do a manual swap.

Stay tuned and watch out for shop towels haha

 

[VAGguy]

Final update:

I though I'd get over myself and just post the resolution here - I have to say it's embarrassing to do so. I hope this serves as a warning/reminder for some.

A few weeks before I ran into this issue, I had the intake manifold and the air filter box out. I did injector cups and repainted the manifold and had the airbox out because I was installing an secondary O2 spacer.

Anyways, every time I take things apart in the engine pay, I put blue shop towels in the hoses so I don't get any debris or anything to fall inside of them, and specifically blue ones so I see them when installing it back later (!).

Fast forward to when I had everything ready to be put together, I was really excited I had the time to put the whole engine bay together and start the car. I think what happened is that when moving the hoses around to install the airbox, the shop towel fell deeper in the turbo inlet pipe and I didn't notice it (I know, pretty bad).

So before I reconnect everything I take the shop towels out, but I think I was blinded by my excitement to see the engine running and didn't notice I hadn't taken it out of the TIP.

So now for the funny part of how I figured out that there was a shop towel chocking my intake: I decided to do another boost leak test, BUT I didn't tighten the boost leak tester (2" pvc end cap with a tire valve stem) enough on the TIP, and as pressure built up to like about 1 bar (~14 psi) the boost leak tester came out flying - luckily, my head was not in the way - but also with it, came an entire blue shop towel.

At this point, you can imagine how confused I was, trying to understand what happened and seeing if I had messed something up because the "explosion" made a super loud noise. As I inspected everything, it seemed fine to me but I was still wondering where the heck did that blue shop towel come out of.

It didn't take me long to realize this was in the TIP and I might have just hit the jackpot and solved the problem "accidentally". I inspected the shop towel and for my surprise it came out pretty much intact except one of the corners had been "eaten" a little bit, but since it was just a tiny piece, I thought that was my luckiest day and felt really blessed by God haha

I put everything together again, and cranked the car and ta-da: it ran perfectly fine!!! Boost was back, the engine breathed normally again, MAF code was gone.

I cancelled my order for the new MAF, but kept the new connector that came in. I ended up just replacing the red part (locking mechanism) for good measure because mine was totally brittle but the connector housing was just fine.

I also vacuumed the TIP for good measure to make sure there were no pieces of shop towel left. I believe there might be a few bits stuck in the intercooler but I decided not to worry about it too much because the "eaten" part of the shop towel was fairly small (surprisingly).

To conclude this saga, now two weeks and about 600 miles later since the fix, the car drives amazing. Thanks for everybody that pitched in.

The itch now is with the transmission, I'm hating it so much now that the engine is runs like it should. So you'll likely hear from me in the near future as I was encouraged by my fiancé (!!!) and friends to do a manual swap.

Stay tuned and watch out for shop towels haha

Love it! Never be embarrassed about something like that. Most if not all of us have been there. Glad it all worked out and you are back in business again.