Diagnosing and Fixing Limp mode for A4 1.9TDI [low power troubleshooting]

[rdkern]

I wish I had an idea, but at least this will bump the question up.

Perhaps looking at the differences between the two trips might be helpful.

Was the AC used during the day? Different radio station? Uphill one way?

How did you get 428K miles in Canada? I didn't thing those things were allowed up there.

My WAG is that the N75 may be going, and the hotter engine bay caused it to get worse with the increased heat. If so, it should eventually get worse at all times.

Not a good guess, but a "bumpable" one.

 

[ymz]

When I post, I usually convert things to units used by the majority of members... The current "mileage" reading is 690477 km...

True to my reputation... I do have a spare N75, so perhaps I'll try throwing it in the car... Of course, I won't be able to "test" it for a while... the car drives just fine... for at least 30 minutes...

Air conditioner was being used both in the day and at night - of course, it was working harder during the day... Perhaps I should hook up VCDS and monitor/log the actual temperature of the motor...

Yuri

 

[rdkern]

When I post, I usually convert things to units used by the majority of members... The current "mileage" reading is 690477 km...

I'm new here. I've got to learn how to use the little smiles

And my WAG makes the assumption that the new actuator is good.

Did you lose oil on that trip?

 

[dilkie]

I hope folks still follow this thread.

I've read all 21 pages and followed some advice but I have a few questions.

First, ( have an '01 Golf TDI, 5-speed manual, with 440K Kms on it (~250K miles)

I just finished replacing the tranny with one from an '03 but the job got interrupted in the middle for 3 weeks so I only just got the new tranny in last week. Another story..

So when it's all back together I fire her up and it runs fine for a bit and then totally looses power and a lot of blue smokes come from the tailpipe (blue = oil? and my exhaust ends in the middle of the car just past the resonator so the smoke was coming from there).

Found that the vacuum line from the vacuum pump had severed at the pump side of the rubber line, victim of the tranny job. I cut it off and used a regular hose clamp on the remainder.

However, no joy, no power, surging when I try to accelerate in neutral, lots of blue smoke. Also, could no longer hear the turbo whine which is normally easy to hear due to exhaust configuration. Worried that the turbo went south.

Car was throwing a maf code, 101. Read this thread. Tried out a number of things.

- vacuum hoses look shot. the one to the turbo is chafed but used a hand vac pump and the actuator seems to move the full range.
- vacuum in the "vac" side of the piping is around 20-25 mm Hg. varies with rpm.
- vacuum on the "out" side of the N75 is 5 mm Hg at idle, climing modestly to 8 mm Hg with 2500 rpm and in neutral. Does that sound right?
- pulled the hose off the intake manifold so I could check to see if the turbo was pushing air. It wasn't pushing much at all. So I put my hand vac on the line to the vane actuator (ie, the test above but when the car running) and when I manually operated the vanes, lots of air moved so that sounded somewhat positive to me.
- this morning I pulled the maf (or map or whatever it's called) and it was dirty so I cleaned it with non-chlorine brake cleaner. Reinstalled.
- went for a drive and the car seemed fine... Popped the intake manifold off because I hadn't reattached the hose clamp when I pushed the hose back on. This was deliberate, figured it was a poor mans boost pressure gauge...
- clamped it and it seemed fairly good. Only thing I could feel was some turbo lag that I don't remember being there and sometimes it seemed to have less power than I remember. But I'm pretty hyper-sensitive right now to every hiccup so it could be imagination.

so question. could a bad MAF lead to the symptoms. I mean total loss of power (barely enough to get going at low rpm and takes forever to get up to speed, all the while blowing huge clouds of blue smoke).

does my N75 sound faulty too? any way to be sure?

I'm going to replace the MAF, it's on order, and likely will order the N75 too and replace the hoses while I'm at it but I'm curious if this was the culprit or if I should look elsewhere.

thanks,

-lee

PS. bought my wife an '06 TDI a week before my tranny replacement and spent the last 4 weeks driving it, put 8000 Kms on it with a trip to newfoundland. The BEW engine has a way different torque feel to it and maybe the lag I feel on my ALH is normal and I'm just not used to it... Just went for a test drive and what I feel is a ~1 second lag on the power when shifting.

 

[ymz]

Follow-up

after about 45 minutes or so, the car would start going into limp mode - usually while on the cruise control at about 65 mph... as the trip continued, it got worse - until recycling it would not help at the very end... The trip back, at night, was flawless... whether on cruise or driving in a "spirited" manner, the car wouldn't go into limp mode...

The following week I found that the N75 was defective, as well as the one-way valve near it... Replaced them both and while I was at it, I replaced all the vacuum lines... (takes longer than I anticipated... at least now I understand the system...) It helped a little, but the car was acting worse... now it was constantly under-boosting.

Took it to regional Guru (Brandon)... He took a look at the turbo impeller and the clearance between it and the adjoining input flange and declared the turbo finished... (there was no end-play in the shaft... just "wear" on the blades...) Threw a good used one in there, and... voila... car's driving just fine again... I guess our factory original didn't want to make it to 429,000 miles...

Yuri

 

[bobbyo]

code po 234 & 252

we go into limp mode on long uphill climbs.eventually i get a 252.i replaced the injector pump and on my 1st long trip i went into limp mode and got a check light.the code was 234.how to proceed?

 

[Geobmx4life]

Maybe go see the Organic Mechanic?
Are you using Vag-com to read the codes?

 

[cowhand74]

Help!!! Just R and R the head, now my jetta has no power

So I just replaced the head on my 2002 jetta, that frank06 repaired(beautiful work!!!) and finally got the car put back together and finally got it started. Now it has no power. It sounds good, idles good, everything seems fine but it takes a mile to get up to 60mph. Theres no "get up and go". Is there some kind of sensor i forgot to reset after the overhaul. Ive never experienced limp mode but this seems like this is in a limp mode. I accidentally broke the plastic nipple on the acuator for the shutter valve but the valve is staying open. just need to replace the acuator...would this cause lack of power. Any ideas.....I love this car too... just getting frusterated. What about the ip timing. could it be off a bit even though the car runs and i pinned it in place when i timed it. Thanks everyone! Cowhand 74

 

[Canadian_Grizzly]

Did you plug the vacuum hose going to the antishutter actuator. A golf tee works nicely. I'm thinking this is vacuum related.

 

[whitedog]

You need to get the timing dialed in with VCDS. First though, go over your work and check that all of the vacuum lines are installed in the correct place, and are in good condition. Also, check that the vacuum check valve is installed in the correct direction. I have heard of bad doggies that put them in backwards and had no power.

 

[2ManyKMfor1Tank]

I have a bit of a strange thing going on in my car. I have replaced all of the vacuum lines in the past year, no problems since then. Minor overboost issues occasionally - I know that I need to clean my turbo at some point, about a month ago a hole wore through my boost gauge line going into the upper IP pipe to my race-pipe, replaced it as I noticed lack of boost. Back to normal. A week or so ago, have a strange power loss. Still have 15 psi boost, though a few days before had some huge spikes which I had meant to check into. Occasionally I feel the turbo surge, then dial back and a power loss - I have nozzles and RC3 tuned, it feels as though the car has gone back to stock power. No engine light on, so its got me stumped somewhat. Could there be codes with no CEL on? Anyone care to take a shot at what it could be? Going to try unplugging the MAF on my way home and see if that is the problem.

Thanks in advance.

Aaron

 

[2ManyKMfor1Tank]

Just a quick update. I tried unplugging the MAF with no change, am really stumped. The stranger part is it seems(Could be just my imagination) that when I go WOT it has less power, if I back off the throttle some it actually seems to accelerate faster. Did a quick check of the vacuum lines, everything looks ok to me.

 

[Canadian_Grizzly]

Aaron it should run worse with Maf unplugged.

 

[2ManyKMfor1Tank]

Aaron it should run worse with Maf unplugged.

Why wouldn't I be getting a CEL with the MAF unplugged though??

 

[Canadian_Grizzly]

It seems hit or miss. Most do get a CEL but others have experienced no CEL.

 

[ymz]

Why wouldn't I be getting a CEL with the MAF unplugged though??

It could be the particular implementation of your tune... I'd try to borrow a MAFs and swap... as a test...

Yuri

 

[2ManyKMfor1Tank]

It could be the particular implementation of your tune... I'd try to borrow a MAFs and swap... as a test...

Yuri

I just bought a spare last week, I'll try throwing it on and update.

Thanks

 

[TMC]

I replaced MAF, N75 and the vacuum lines but the CE light still comes on. Does the fault code need to be cleared before the light will stay out?

 

[Canadian_Grizzly]

Maf code usually needs to be reset. Search for folks with vagcom in your area to reset. Hope its running better.

 

[taugust]

Well, I am back here. This seems to be the best place for my current problem.

While driving to work the other day, climbing a short and moderately steep hill, something under the hood "popped." Suddenly, I had no power, and the engine speed was surging with a steady throttle position. Almost immediately, I pulled over. The engine idled normally, but any attempt to accelerate met with the surging. I turned around and limped for home, since I was in the middle of nowhere with no help available. It was surging and smoking somewhat for several miles, then the engine speed smoothed out and was somewhat normal, albeit with no boost. Upon restart tonight, idle is normal, but any increase in throttle results in the surging engine speed.

In reviewing the original post here, following are the results: I got no CEL at the original failure, or later. Hooking up VAG-COM showed only Boost Pressure, Negative Deviation. After reset, it does not return. Removing the vac hose at N75 to actuator, it actuates and holds vacuum on Mighty Vac. Input vac line with engine running is 25mm Hg. Checking N75 with VAG-COM, the turbo actuates normally. Removing the MAF connector caused no CEL, but resulted in a change. The surging went away, but there is still no boost pressure (I have a standalone guage). The turbo whistle is noticably louder. Reconnecting the MAF results in the surging again.

Some history: Current mileage is 287,658. Timing belt was changed recently at 286,517. Fuel filter replaced and LM Diesel Purge done after belt change, due to hard start. I was having loss of fuel system prime due to leaking fuel lines at the filter.

I had buildup and sticking of vanes on the turbo, causing limp mode. Cleaned several times, but not recently. I used to run homemade B100 and the turbo would carbon up every 20K miles. Last time cleaned was at 141K miles

Last time I was having limp mode, infrequently, it seemed to be caused by a combination of several factors. I replaced all vacuum lines with silicone, replaced MAF at 235K. Replaced main vacuum line at brake booster at 236K. Cleaned intake manifold at 237K. Limp stopped. Inproved running but did not solve sluggish power. Replaced catalytic converter with a good used one at 267K. That combined with the other fixes brought back performance, mostly.

My current thought is that there is somehow a blowout in the boost intake lines somewhere, but haven't been able to locate it.

Thanks for any help you can provide.

Tim

 

[whitedog]

Start pulling the hoses off after the turbo and inspect each part. They can hide and only a visual inspection off the car can show you. Did you check that the turbo spins?

 

[dilkie]

I had a hose pop off a couple of times and that makes a "pop" for sure, but the after effects didn't include surging. Also, if you have a major air leak, you'd hear the leak.

I also had "sluggesh power" (boost/turbo lag). Like you, I replaced all the parts, MAF, MAP, vacuum hoses, N75 but to no effect. I found some time later that it was a sticky EGR valve. It was too slow closing up. I clamped off the vacuum line to it and problem was imediately solved.

Only other thing I can think of for this problem, perhaps TB jumped a tooth? Can you check the TB timing with VAGCOM? Just a wild guess.

Does VAGCOM show actual boost == requested boost?

 

[rdkern]

Did you check your oil?

Most likely place for the boost hose to "pop" would be at the innercooler. While there, take off the hose (if it's not already off" and check for puddling oil. Like several tablespoons.

I agree that a boost hose separation would not likely cause the "surging".

 

[MCR]

Some history: Current mileage is 287,658. Timing belt was changed recently at 286,517. Fuel filter replaced and LM Diesel Purge done after belt change, due to hard start. I was having loss of fuel system prime due to leaking fuel lines at the filter.

You had a hard start after a timing belt change? And it's now about 850 miles after your timing belt?

I wouldn't start it until you check the belt tension. You might even see if you can get the injector pump pin in to show it's in the right spot. Or Vag-com.

Scary.

 

[taugust]

Well, I was finally able to get underneath today and found the problem. As I suspected, it was a boost hose disconnected. Between the turbo and the intercooler there is a rubber hose that connects to the hard tube with a hard connector secured by a clip. This apparently wasn't completely secured after the TB change. It's mount to the body is broken. After removing both tubes from the vehicle, I was able to secure that connection. and replace. Everything works well now.

I did check for oil in the intercooler and found maybe a tablespoon. I am somewhat surprised by this, because I had used Vag-Com to adjust the EGR cycle at 118K and the oil problem was supposed to go away. I have noticed also that since cleaning the intake manifold, I have a lot more oil coming out of the weep hole in the EGR.

Thanks for the input.

 

[whitedog]

The oil does not come from the EGR, so the adaption that you did will have no effect on the oil, just the exhaust soot entering the intake during cold idle.

 

[rdkern]

Glad you found the problem. Small amounts of oil will come through the seals of the turbo while it's not under boost. You were checking for bunches of oil coming from the turbo - a much more expensive problem than you actually found.

 

[steviemac]

What a great thread. I had a boost problem that was solved by reading through this awesome thread. Thanks fellow TDI'ers!

 

[Sappington]

I would like opinions in my situation. I have been experiencing the following code for some time:
16618 - Boost Pressure Regulation: Limit Exceeded (Overboost Condition)
P0234 - 35-10 - - - Intermittent

I have went through the following:

• Checked MAF - ok
• Vacuum Leaks - ok
• Faulty N75 solenoid
  • The actuator does not move during key on, only when I start the car. Does this single out the solenoid to be the root cause?
  • I attempt to go to move the actuator via Vag-com, but I am not confident that I am on the right page. First I go to the '01 Engine', then to the 'Login - 11', which requires the password of 12233 to login. Is this what is meant to be 'Group 11' on the original email?
• Faulty Actuator
  • Holds 20in of Hg.
  • Mine actuator starts moving at 10in of Hg, not the 3-5 that was mentioned in the first post. Once it starts moving it jerks 1/4" within 1in of Hg. If anything this seems to be reduce boost according to prior responses.

Should I replace the N75? I stopped at the 'Sticking turbo vanes'. Any help or comments are helpful.

That is the same code I have. I had a guru (ninedee_golf_tdi) look at it and verify that the MAF is fine and the turbo vacuum is fine. My limp mode hits usually around 3500-4000 rpm, and persists until I restart the car, then it's fine for a while.

He recommended I exercise the car's turbo by revving up and down, but frankly, I have a hard time doing that when it keeps triggering limp mode. Could weak hose clamps or sticky EGR valve could cause this?

 

[sarwar92]

tdi has no power, makes a rattle or knocking noise,

hello, I'm new to the forum, I have a tdi vw golf 1999 1.9 liter, manual transmission, love this car but recently got a scary sound from the engine, I heard a tap sound and smelled burning one morning. After that I got the following problems, engine starts slow, it takes a long crank time, 3 to 4 seconds in sacramento California area weather, after starting it, it runs smooth but has a knocking or rattle sound at the motor, this knocking sound increases as I put a load under the motor, the engine knocks at every speed, once in a while this knocking sound might go away for 2 seconds and come right back when i'm going down the highway, but it will only go away for this random 2 seconds at highway speeds, otherwise it's alway knocking or rattling. I saw some of the knocking sounds on youtube and their just a little louder than mine. Mine runs smooth, just the knocing noise and slow start up and slow acceleration. It used to be really quiet with lots of power, i got it smogged at a smog shop 2 weeks prior.

Every time i put it under a load, for example 1st gear, it will make this knocking rattle noise even more, especially if i put it in 1st gear partially let off the clutch with the break peddle pressed down, it aggitates the noise full blast (i did this just to diagnose where the noise is coming from). It sounds like an exhaust leak but the exhaust and motor mounts look good.

I checked the timing-it's dead on
I changed the fuel filter-no difference
I put in a new mass air flow sensor-still does it.
I opened the fuel lines just above the injectors while running the motor-plenty of diesel fuel comes out.
I took the cam cover off and ran the engine-it threw oil everywhere but i didn't see anything wrong in the cam shaft area.

While the engine is running in idle if i partially close the shutter valve where the engine shut off is (next to the egr) it will agitate the noise too. I can live with the slow start up and slow speed but the knocking sound is too serious to ignore. Sure would appreciate any help. Thank you