Hesitation/slight hiccup at around 3,000 RPM

I've only owned the car for a few weeks and I didn't start to notice until I began driving it a bit harder, but I detect a noticeable stutter/hiccup/hesitation on hard acceleration.

In first gear it is not noticeable at all. Second gear only slightly. Third and fourth definitely more pronounced. (I haven't accelerated through 5th gear to 3,000 RPM yet.)

It's a minor annoyance and I'm not ready to tear the car apart to correct it, but my guess is it will not go away on its own and may get worse with time.

Any ideas where to start looking?

If you don't know the history of the car, and if it doesn't totally lose power (limp mode) then it may fix itself with the way you drive it. The wastegate may be a tad sticky. Driving it hard will exercise it and may fix the issue. Of course, I'm an optimist.

I would start with some VCDS logs.
Check injector imbalance in Measuring block 13.

rdkern said:

If you don't know the history of the car, and if it doesn't totally lose power (limp mode) then it may fix itself with the way you drive it. The wastegate may be a tad sticky. Driving it hard will exercise it and may fix the issue. Of course, I'm an optimist.

Click to expand...

No, definitely not limp mode. It just happens briefly then back to normal boost. (Does not require the ignition to be turned off.)

I'd characterize it as noticeable but not annoying.

DanG144 said:

I would start with some VCDS logs.
Check injector imbalance in Measuring block 13.

Click to expand...

I will take a look. Thanks.

Getting Worse

rdkern said:

If you don't know the history of the car, and if it doesn't totally lose power (limp mode) then it may fix itself with the way you drive it. The wastegate may be a tad sticky. Driving it hard will exercise it and may fix the issue. Of course, I'm an optimist.

Click to expand...

I was hoping this might happen but the opposite has occurred. It has gotten much worse to the point that it feels like limp mode most of the time with the turbo cutting in and out intermittently. Pretty sure it is not limp mode because shutting off and restarting does not fix it.

I am planning to hook up the VAG-COM after work tonight. I felt around under the dash where my A4 Jetta connects but did not feel anything there. Where does the cable connect?

On the B4, there is a little "texas-shaped" plastic cover that is between the steering wheel and ashtray. It pops off, and the plug goes there. You'll see the engine impression on it. Good luck. Intermittant issues are a pain - might be in the wiring to a variety of places. Cleaning grounds sometimes helps, and at least it would help you look at the various connectors, etc. VCDS may also help - if you log you might see odd things happening with one system.

Group 013 Log

DanG144 said:

I would start with some VCDS logs.
Check injector imbalance in Measuring block 13.

Click to expand...

The extent of my VCDS experience is checking for and clearing Fault Codes, so I am now officially in over my head.
Hooked it up just now and started the engine. No Fault Codes, but Group 13 shows this:
Monday,21,May,2012,17:10:35:30519
VCDS Version: Release 11.11.3 (x64)
Data version: 20120401
--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
Address 01: Engine (028 906 021 BK)
17:08:28 Group 013: Idle speed smooth running adjustments
-0.28 mg/str Cyl 1 -2 to +2
-0.45 mg/str Cyl 2 -2 to +2
-0.40 mg/str Cyl 3 -2 to +2
Cyl 4 -2 to +2
VCDS shows only three of four cylinders reading. Cyl 4 is blank. Any idea what this means? Is there an actual problem with Cyl 4 or is there a bad sensor or sending unit?
Any suggestions what to look at?

On this older car, I think this is normal. My best guess is that #3 is actually assumed to be zero (not #4) and everything else is adjusted to it. So I generally put little trust in the cylinder numbering system. In any case the readings you have are not at all bad. I consider any thing less than an absolute magnitude of 0.5 mg/stroke to be "Good".
In each case your ECU is raising or lowering the fuel demanded from each injection by the given amount - a correction.

So it would appear that injector imbalance is not your primary issue.

While you have your VCDS hooked up, go to ENGINE, then Basic Settings, then 011 and test your turbo controls. Then go to 003 and test your EGR.

I would probably also start looking for vacuum leaks from your control system,

No trouble codes at all in the engine module?

Stay Tuned

DanG144 said:

No trouble codes at all in the engine module?

Click to expand...

ZERO fault codes. If it were going into limp mode it would have thrown a code, right? I seem to remember getting fault codes when I was chasing a bad MAF on my A4.

I will go back and look at 011 and 003.

I will also continue through the FAQ on power loss and see if I can find it on my own without bothering all you nice folks.

Thanks!

While driving your car, and trying to accelerate (pedal to the floor) make a log (not "add to log", but create a CSV file) of measuring value blocks 3, 4, 11. Then email me the file.

We can tell if you need a new MAF (or have air flow restrictions) or not from that data, plus the EGR basic settings data (it should have two stages - low and high on air flow -note the "eyeball average" for each stage of the Basic settings 003 test and post it here.)

The basic settings tests are NOT measuring value blocks. The engine controls should cycle between two definite high and low states. Not the average readings of each state and pass it on.

Yeah, the lack of codes seem to indicate not a limp mode issue, and not an unexpected lack of boost pressure issue. Nick's input is looking pretty good. But I would do the air flow, fuel and boost log to help pin it down.

Any results on the basic settings tests?

richmondvatdi i did some logs and have them graphed. you can compare yours to mine and then we can have dang144 explain what he sees.

Logan, you can also post a link to the PDF file, as if it was a photo. Then we can see the graphs full size, and read the numbers.

Fixed it. Thanks

Logan, your engine seems to be very slow to build boost to me. I am not very knowledgeable on the B4. I don't think I have any graphs to compare these to. The wastegate is noted for being slower to boost than the VNT, but this seems awfully slow.

The OP's engine never reaches target boost, and is at least as slow as yours to ramp. I only had the boost graph, not the air flow for him, but I wondered if his had a boost leak. He never mentioned smoking, which I would expect for a boost leak.

I was glad to make the graphs for you both; I would have posted them for you but my photo account is too full to allow another to be added.

Perhaps someone who is more familiar with your engine's performance can teach us both what is normal. I am always ready to learn.

DanG144 said:

He never mentioned smoking, which I would expect for a boost leak.

Click to expand...

Correct. No noticeable smoke. I will log the air flow tonight.

Your log shows reported air flow very low, half of idle value.
Unplug the MAF, see if it works better, check for smoke.
I do not know what flow value the B4's use for a substitute when the MAF is unplugged, but it is likely more than twice the air flow you presently show. So you should get twice the present power - still only about 65% of normal.
If you get no smoke, then in looks as if Nick is right.

I'm out of town today. If I get home in time to disconnect the MAF and re-log I will. If not it will be tomorrow. Thanks for all your help so far.

If you have time, check MVB 003 for air flow values (specified and actual) with the MAF unplugged.

UPDATE: No Internet at home for the last couple days so I am typing this on my phone. (Thanks Verizon.)

Went out to log Thurs evening and VCDS started acting squirrelly. Right in the middle of driving/logging I hear the "ding" you hear when you shut off the engine with VCDS still connected. Wire snug on both ends. Tried several times to log (unsuccessfully) before laptop battery died.

Went out again last night again but car had some power right out of the gate. Nowhere near as bad as it was before. Disconnected MAF but little or no change. No noticeable smoke. Reconnected MAF and cleared fault. I tried accelerating hard and I could feel the power cutting in and out.

This appears to be intermittent and may be hard to track down. Disconnecting/reconnecting the MAF seems to have had some impact. Should I try to clean or just replace MAF? I guess it could also be a vaccuum leak.

One more note: the turbo is new and the intake manifold was recently cleaned.

Sorry this post may be hard to follow but editing on a phone is kind of tough. Ideas?

I had the same problem it stutterad under load like a hickup not all the time it was randem any gear and i had no codes when scaned with vagcom.I bought a second hand maf put it on and all has been well for the last 3 weeks.I think this is your problem.Hope this helps.

I pulled the MAF and found the intake probably 20% clogged with leaves and other junk, so I opened up the air filter to find this:



I am going to change the air filter and clean out the MAF as best I can.

UPDATE: Put everything back together and took it out for a road test. There is still a hesitation so I did another log of 003, 004, and 010. I will try to graph and post the results.

Holy moly! There's your problem. I bet your turbo is eating leaves! No wonder it's intermittent.

I've never seen an air filter collapse. Is it an aftermarket brand?

You need to take out the air box, snorkel, filter, turbo inlet pipe and accordion, and clean them all out. Check for debris in the turbo. You also need to disconnect the IC inlet "pancake pipe" because you probably have a ton of leaf debris in the IC input side clogging airflow.

Lastly, your EGR assembly and intake is almost certainly going to need to be removed and cleaned.

And it goes without saying your MAF is trashed and needs to be replaced. Get the revision "C" part#. It's very robust.

nicklockard said:

Holy moly! There's your problem. I bet your turbo is eating leaves! No wonder it's intermittent.
I've never seen an air filter collapse. Is it an aftermarket brand?
You need to take out the air box, snorkel, filter, turbo inlet pipe and accordion, and clean them all out. Check for debris in the turbo. You also need to disconnect the IC inlet "pancake pipe" because you probably have a ton of leaf debris in the IC input side clogging airflow.
Lastly, your EGR assembly and intake is almost certainly going to need to be removed and cleaned.

Click to expand...

The air filter was a Mann.
I checked the air path before the air filter and it was clean.
I will check for debris that may have gotten past the MAF and clean everything out this weekend if I can find the time. I doubt there is much though. Even though there were a couple leaves on the air box side of the MAF, there was zero debris inside the MAF (on the screen on the outlet end of the MAF).
After replacing the filter, the engine runs better and has decent power. It still hesitates at higher RPM's. It feels like the engine is rapidly cutting in and out as I accelerate through 2,500 RPM and up. It almost feels like a fuel issue.
Is it consensus among all you B4 gurus that the MAF must be replaced? I hate to spend $200 in a wild goose chase, only to find out the MAF was not bad.

Do the reading again with the intake cleaned. The odd MAF readings could be correct readings of poor airflow.

Latest LOGS

rdkern said:

Do the reading again with the intake cleaned. The odd MAF readings could be correct readings of poor airflow.

Click to expand...

Sunday evening I logged measuring blocks 001, 003, and 010 while accelerating through 2nd and 3rd gear. I saved them as CSV file, but I am not sure what I am looking at.

Anyone want to take a look? I can email the file to you.