Stumbling acceleration

Hey all,
Running a 2002 jetta tdi 286,000 miles.
Recently upon acceleration it seems to be stumbling. there is no noise to be heard, just an obvious rhythmic, kind of pulsating feel to it.
Dropped it off at a shop. he claimed the MAF was bad. but even when disconnecting the MAF the stumble continues. Changed air, and fuel filters. cleaned the MAF. there was a considerable amount of sand in the air box. CV boots are solid. one thing to note. several months ago, the car had violent acceleration on the highway. decided to do a transmission flush. turns out there was no fluid. as i bought the car at 215k i had no idea what kind of service she had. so who knows how long the car was without transmission fluid. since the addition of fluid, the clutch whistles when pressed. grinds going into reverse. ive owned several cars with worn throwout bearings, and non stumbled on acceleration.

the only recent work on the car was cross drilled and slotted rotors. which she doesnt seem to like.

Check your actuator on the turbo

If you have vcds you can watch the resistance on the accelerator pedal, I inadvertently got water in mine through a hole in the firewall and it acted really funny...

Or you may have a QA that's not sweeping smoothly

Do you shoot smoke when it stumbles?

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No smoke. The turbo is funny. the actuator sticks, for a day or two. its done this ever since ive owned the car. generally twice a year. spring and fall, no joke.
This morning i noticed it doesn't stumble in corners.

Unsure of what "QA" means

QA is quantity adjustor, it changes the amount of fuel injected.

Turbo is likely to be dirty as heck with it sticking.
When the actuator is sticky it's usually the turbo sticking, sometimes it is the actuator.

I would start with the turb, actuator, and vacuum lines that move the turbo.

Another question is if you have cleaned, or looked at, the ASV (anti-shudder vavle)

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Thanks, i'll take a look at those things.
But it honestly feels more drivetrain related. this morning i accelerated hard through through a long uphill corner. no stumble. hit a straightaway. stumbled. idk maybe im just paranoid

Cleaning the MAF doesn't usually fix anything. I assume you do not have VCDS.
A couple hundred $ for one could save you from parts throwing.
Try to find a VCDS owner near you and look at injector balance.
At 300k miles they might need attention.

jbruAT09 said:

Thanks, i'll take a look at those things.
But it honestly feels more drivetrain related. this morning i accelerated hard through through a long uphill corner. no stumble. hit a straightaway. stumbled. idk maybe im just paranoid

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If it were a vibration I'd agree but hesitations typically aren't driveline related. If you had a boost gauge you could see if the hesitation was boost related or if you had vcds you could log the map sensor and see it that way.

I'm having an off idle boost issue that gives me a little smoke when I pull off from a dead stop, I'm just not to the point where I want to fool with it at the moment.



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Where do i find a VCDS owner?

There's a link in tdi 101, or you can make a post stating the location you're looking for one at.

http://forums.tdiclub.com/showthread.php?t=296841

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If you were close to sw Arkansas I'd hook it up...love e Maine but no idea when I'll be back

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Thanks guys, going to do vacuum lines. easiest fix at this point. after that ill just wait for it to break. then ill definitely know what it was lol

i had a stumbling issue for a LONG time on my ALH jetta. It turned out someone had gutted the check valve on the fuel pump pickup and installed an inline check valve in the supply line just on top of the sending unit (under the seat). The valve has slowly collected stuff over time and eventually it would collect ice crystals and kill the car. I finally found it when it left me stranded in the winter at night in -20F weather.

The pickup in the tank was also a bit blocked up with plastic from someone gutting the check valve.

Not likely, but worth a look for you.

My car now has more bottom end power and response than it ever has in my 100k mile ownership.

jbruAT09 said:

......................... several months ago, the car had violent acceleration on the highway. decided to do a transmission flush. turns out there was no fluid.......................

Click to expand...

Do you suppose it was a run away? That could be trouble. If the gear box ran dry chances are it's leaking now. Any chance a leak like that could contaminant the clutch? That might cause slippage. Just interweb guessing...........

Check to see if your actuator is holding vacuum! Its easy

If you disconnected the MAF and it didn't make any difference I would be looking at your VNT actuator next. My guess is your actuator isn't holding vacuum like it should. When mine was bad it would still accelerate the car but it would hit a wall, and then kick back in i thought it was strange considering it would BARELY hold vacuum.

It's a very quick check but you need a vacuum gauge.

also...

as previously mentioned there is a check valve (looks like an acorn) by the N75 that could be bad but i would check the actuator first.. The check valve is secondary problem if your actuator is leaking all the vacuum out.

For the check valve, take it off try(lightly) blowing through both sides, if you can blow or suck through both sides then you need a new check valve. I found a good check valve at my local pick n pull. I didnt feel like dropping 45 bucks on one....

Does your cruise control keep the car up to speed on a hill????????

Goodluck!

Mine was doing the same thing, my Catalytic Converter was plugged. I cut min off and its been smooth ever since.

I am also curious if you have any issues with the accelerator pedal
Drive by wire can cause some issues if worn.

You can check with a multimeter.
Unplug the pedal, stick probes in on resistance setting and check for smooth operation.
If it skips, or does anything funny, it's not working properly.
It should move smoothly increasing and decreasing resistance.
Anything irratic can cause stumbling by sending faulty readings.

Just a thought.

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Have you checked/adjusted your i.q.? My car had a dead ass miss and slow down shudder before adjusting it.

Thanks guys,
i havent had any time to poke around. i did empty my transmission, 2 quarts came back out. so i dont think thats leaking. the issue was still present afterwards. latley it hasnt been acting as bad. one thing to note, it doesnt stumble on corners, ive got some big uphill s cruves where im living to test that out. also the temperature has cooled of considerably. which has always been suspect when my turbo temporarily stops working. i bought vacuum hose but havent had a chance to replace.