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Discussion Starter #1
Hi Folks,
I have an 03 ALH Jetta 375,000 km on an auto trans (200,000 and change in miles). Love it! I'm running into an issue with limp home mode.

Background: Well maintained by a good mechanic.. he's buffaloed on this one too and doesn't want to recommend throwing money at it based on what we're running in to. I have a background in large diesels... not automotive... and I'm buffaloed as well. The car is driven 2 x 50 kms every weekday at about 110 to 120 kms an hour (60 - 70mph). In the middle of each trip is a 2,000 foot climb and descent. Steep for around here.. but not for the mountains.

What's happening: At 100 - 120 km/hr on the ascent, if I punch it I get limp home happening. P0234 (16618). I restart on the fly and carry on. The situation doesn't often occur but if I need it it's dangerous not to have it. It will not do it in any other situation so it's only happening on testing in controlled conditions right now.

I've run the vcds for the at idle N75 and egr tests. Everything appears normal. I have fluttering in the MAP sensor (output of the intercooler) at idle that I don't like but it's possibly normal at idle - don't know. I think I'm going to throw a new map sensor in and see if there's a change. All vacuum lines have been checked or replaced if at all questionable. EGR is relatively clean (all carbon is less than 1/16" of an inch thick and the EGR tests correct. The Vacuum pump is 28" plus at idle with a T on the line to the vac system for testing. The vac system after the check valve holds 25" plus for over an hour at rest as measured at the vacuum "pot". There's light oil in the output of the Intercooler up to the EGR and I've drained it at the intercooler inlet to get nothing out (which bothers me). The EGR cooler seems clear with what I would call moderate carboning. The intake after the EGR is again moderately carboned from what I can see from the egr end. I don't have a boroscope so I can't see into the inlet manifold itself.

I can't detect any sticking in the vane lever (though the actuator is still attached when I'm feeling it by hand) and the actuator movement seems smooth as a whistle and in spec though potentially a little weak (Movement starts at 4" and stops at 16" using a mityvac).

I'm frankly starting to suspect the trans and possibly erratic punch downs.. Is this a red herring or a possible?
I'm also waiting until my my mechanic is free to do a test run with the vcds in his lap.

Any thoughts on what you would check next? Have I missed anything that you would check?

Thanks!
Rob
 

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Check this thread here from u he competing forum
Diagnosing and Fixing Limp mode for A4 1.9TDI [low power ...


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Oops


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First posts normally go in introductions else you could get a free fix and we never see you again!!!

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This is a new forum layout which is owned by a company last year that doesn't give a dam with loads of bugs which have been reported in the new thread. There is no TDI Wiki at the moment or original similes which they refuse to install. It doesn't show the car spec/location.

Add your car specs to your signature that will show on every post you make.

Car spec now shows not for all members.

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Manufacturer: VW, Date(s) Used: 11/1998-06/2004, Model: Jetta, Engine Code: ALH, 66Kw, 90PS, 1.9 Ltr, 4 Cyls, Remarks: USA ("USA"): Turbocharged Direct Injection (TDI) Timing belt
 

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Discussion Starter #5
Thanks for the response. I'm enjoying the forum and will try to play nice in the future! I didn't know there was such a thing till a while ago so I'll figure out the rules as I go. Lot's of good info so far and It's interesting to me that most of it seems to be pretty much the same overall path as my previous experience in bigger diesels (medium speed) would suggest. I'm very impressed with the ALH plant so far but there are significant differences when dealing with an engine you can walk around versus these ones! My last turbo dealings were with a unit that weighed more than I do and the sensor/control cabinet was located externally and opened up for testing. This is a much different environment and I look forward to learning more.
 

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03 Jetta. Nothing special. 380k miles
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I too have an 03 Jetta. Mine has about 380kmiles. I fought with limp mode for a long while. My first suggestion would have been the check valve but you’ve ruled that out. My problem was plugged intake manifold. Also consider plugged exhaust. I don’t think either is your problem because your symptoms are infrequent. Do consider the temp and pressure sensors (IAT) for example. Good luck!
 

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Go to Malone Tuning's site and use their guide for performance logging. If you have VCDS then you CAN find the problem: just need to do proper testing/data collection.

With 01m trans just shift it manually to take command of the shifting: pretty sure that's what Malone's guide says. If behavior is different between allowing the trans to shift on its own vs manually shifting then consider the trans to be part of the problem (and here it becomes a lot more difficult to track down the problem, though it's still possible to get closer to it). I was responsible for a car with an 01m in it which had an issue with the valve body (not sure what code it was throwing- I had the valve body replaced, not knowing if it would solve the issue [thankfully it did], and I wasn't aware of it hitting any limp mode- it was my wife's daughter's wagon and was not readily available to me).

Perhaps the N75? Quick test is to swap it and the N18 (EGR) to see if that has any effect: assumes, of course, that one of them is good. MAF connection might be an issue.

Based on what you've said and that would seem like best places to look. BUT, you must do some serious data logging with VCDS in order to really see what's going on. If it's not related to the trans then it's almost certain that VCDS will expose the problem (sticking vanes that you might not think is happening will show up).

I have 208k miles on my car and none of the lines or valves have been touched: I'm still able to crank out 50+ mpg, get over 800 miles on a tank of fuel [manual trans, of course; with DLC520s and a Malone Stage 2 tune to boot]; this means that the engine continues to run flawlessly. I cleaned the intake and EGR valve at around 120k miles (not long after I bought it); performance had been abysmal, but NO check engine light or codes.
 
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