begging help from the TDI gods (or you ;) )

OK I am frustrated!!! I have had an odd stumble on acceleration with CEL (MAF unplausable intermittant) for a couple weeks now and am having trouble figuring it out. I thought at first (using the vag-com and logging it) it was a fuel delivery issue, so I replaced the filter (about 20k miles and 1 year old so it was time any way) but it didn't help. I did the following in the following order, cleaned the snow screen (about 60 to 70% blocked), replaced the air filter (not filthy but getting dirty) , replaced the MAF (had a brand new one on hand), completely dismantled the intake from the front of the car to the MAF, checked the EGR (clean with some oil but no sooty build up), replaced every vacuum line on the car, swapped the ERG and the N75, replaced the N75, cleaned the MAF connector with a good contact cleaner, gooped the MAF connector up with di-electric grease. I am at a loss and don't know what or where to go next. I can reproduce the issue time and time again, it is the easiest to reproduce in 3rd gear if I hold the rpm's at 2800 to 3000 for a couple seconds and then floor it, it will climb for about 400rpm then it will still climb but SLOWLY (feels like 30 to 50% throttle) for about 200rpm, then take off to redline. this happens in every gear but like I said it is most noticeable in 3rd.

I have logged quite a bit with the vag-com and it appears I am truly getting an overboost, but the weird part is that sometimes the fuel IQ will drop to about 65% during the "over boost" and then jump back up to 100% when boost is back to normal. The MAF A vs S shows 1200+ vs 850 requested for 1 to 4 samples, at the same time the MAP A vs S varies by about the % so it truly looks like an overboost, but shouldn't that cause limp mode instead of throwing a CEL for MAF???

Thanks in advance
Bill

you have a pm..

Sorry I forgot to mention that the VTN rod moves freely. I tested this while replacing al the vacuum lines

Bill

What does oil accumulation in the intercooler feel like? could that cause issues like this?

I had a similar problem after letting a local dealer change my timing belt. Car would rev to around 3000 just fine then, for a couple seconds, sort of 'think' about it and then go to redline. Next time I replaced the timing belt it was done by someone who knew what he was doing and this problem went away. This might not be it but I thought I would throw it at you.

The TB has about 45K (APPROX) on it, I bought the car with 93K and I spoke to the dealer and they were able to pull the sevice records and the TB was done at about 80K so that places the current TB at about 45K, I was planning on doing the TB this summer or fall to be safe. Looking at some other recent postings I will check all pullies and tensioners also.

Bill

Sorry I forgot to mention that the VTN rod moves freely. I tested this while replacing al the vacuum lines

Click to expand...

OK How freely should the VNT rod move? Mine moves VERY EASLY with a finger and thumb. Is it possiable something in my turbo, having to to the VNT, broke or came disconnected? Could this cause this type of issue? On the way home from work I noticed that the stumble does happen under almost any acceleration, in every gear. Would a disconnected VNT rod cause self correcting over boost??

Thanks again
Bill

any other ideas before I take this to a shop

Bill

OK so I called 3 VW shops today, and the lost likely causes I heard were 1. plugged intake 2. bad MAF ground under battery. 3. who knows we'll need to look at it

OK so is there any way this could be a plugged intake, I looked through the EGR (from the intercooler end) into the intake and it looked oily but I didn't see any black crud, I will take out the battery tonight and clean up the ground (even though this was done less then 1 year ago ).

Thanks
Bill

looking for help... new forum entrant here... direct me to a new forum if appropriate
Just had the Timing belt replaced on my '01 TDI... check engine light had come on... coincidentally at the same time as it rolled over 126,000km - any connection there? Upon getting the car back, it sounded MUCH louder... rattly... and when I attempted to drive away, it would'nt accelerate beyond 1900 rpm... took it back... mechanic took apart the air intake - almost completely plugged with black gunk... What's Up? And is it possible he didn't set the timing right after the timing belt replacement?

How familiar is the mechanic with ALH engines (1999.5-2003) ?? Did he "lock-down" the crank, cam, and fuel pump? Does he have the computer equipment (Vag-Com or equivalent) to actually check the timing??? (I'm not even going to harp on replacing the 1-use bolts...)

It's possible that one of the pipes going to/from the intercooler became detached, which could make the car louder, but...

You should have it checked out by someone who knows these engines !!!

As for the intake clogging... happens to all TDI's...


PS: please post your location, and we could possibly help you better...
Yuri.

You can't imagine what I'm learning these days!
I'm in Saskatchewan, near Saskatoon, and can't say if he has the equipment that you've mentioned, nor the single use bolts you mentioned...

Question - what's an ALH engine? I've read A4 and A3 - don't know what the differences are...

Yeah he probably did the mark and swap timing belt approach which doesn't work with the TDI. He must have the correct diagnostic equipment. The timing of these engines is very precise.

OH Sure get me excited thinking some actualy replied to my thread LOL . I cleaned the 3 grounds under the battery last night with a wire brush sand paper and contact cleaner. No help I am now to the point of taking the EGR off the intake so I can hopefully get a better look in the intake to make sure it is not plugged up. I really don't want to take my baby into a shop but at this point I am about out of ideas and am not getting too many new ideas from anyone here .

ANY ideas no matter how off the wall they seem would be appreciated.

Bill

There are a number of TDI guys in Saskatoon who are members of the TDI-Club... Try and do a search... perhaps one of them would have a Vag-Com and could lend a hand. (go to the "Meets" section - top of this page on the right - and search on "Sask" and you'll find someone...)

I'm not feeling terribly good about your mechanic... as Cage said, the mechanical timing on these engines is CRITICAL... (the ALH engine is what you've got in the A4 cars from 1999.9 - 2003) It's easy to wreck the engine by getting the belt on incorrectly!!

I would ask the mechanic to first check whether there's a loose pipe in the turbo pathway, and then to double-check the mechanical timing...

Good luck !!!!

Yuri.

OK guys, weirdness tonight.

I filled up tonight, and the CEL didn't come back on for over 1 mile, and the stumble/hesitation was considerably less. Is it possible that I got a couple tanks of bad diesel?? My last tank of fuel was from a different fleet farm then my usual. The CEL did start about the same time as my last fill up (not 100% sure if it was the same day or a day or two before or after, but it was around the same time). I know that "bad" or contaminated fuel can cause goofy power issues, but is there any way this would be related to the cel for MAF???

Thanks
Bill

OK I lied, driving to work this AM the stumble is still there

Bill