Short burst of poor engine sound

[rreegg]

Had a weird engine sound/noise event today driving 2002 tdi. Engine warmed, maybe 45* out, start driving up a mild hill and randomly the engine/exhaust sounded really poor for a couple seconds. A coughing sound almost like initially firing over on a cold start. Was maybe going 2300 rpms and giving slight throttle increase for hill. It only lasted a couple seconds and decreased to a slight chuffing sound. It sounded rotational and seemed to get louder/faster while revving in neutral.

Was able to pull over maybe 10 seconds after this happened. At this point the engine sounded much better almost normal.
Viewed the engine area after turning off and only thing I could notice was signs of rodents above the battery (scat and like dried walnut shell/pit)

After driving later the engine sounded and performed well as usual.

havent yet done a more extensive survey of engine area but any ideas or thoughts of things to check? This just a blip? Somehow operator error?

Serp belt and tensioner seem fine. Did not view timing belt/oil. Coolant color and level seems normal. 198k miles basically the whole engine/injectors/ip are stock. New timing belt kit at 178k, fuel filter at 182k miles, oil change 195k. At about 1/3 tank

Just gonna monitor things, check oil, and fill tank..

 

[Nero]

Do you still have egr? Chances are a chunk of buildup in the intake got sucked into the valves and the engine munched it up. Very similar symptoms.

 

[rreegg]

Interesting. So far have left egr probably needs to be drivin harder though usually is

 

[DaveBen]

These engines don't like to be babied. Get on it. Rev it up and drive it like you stole it. Being too "kind" to it just causes all sorts of small problems, like carbon build up on the valves and pistons.

 

[rreegg]

For sure. Usually pull around 3400 rpms up hills but gave'r th beans up to 4k rpms last night. about 55 total miles of freeway gogo. engine seems good, fun to drive it like its stolen. probably a bit too much city miles lately... putting in an online order for some maint items like trunk struts, air filter, 2x glow plugs, and various exterior bulbs

 

[rreegg]

Ended up getting a check engine with MAF and egr related codes (P0101, P0401) this morning haha. Was surprised it wasn’t glow plug related.

Gonna start with cleaning MAF and replacing air filter. Engine performance has felt fine but mpgs have been slightly down past quarter tank I think.

 

[rreegg]

Replaced air filter and cleaned MAF and same codes persist. Spent half of yesterday getting a windows xp virtual machine and vcds working on a new m4 laptop. The old one used before for vcds batteri died.
No reason to think MAF is bad yet but at 199k maybe rational to just replace. I am able to rev engine up to 5k rpms at idle, have not tested with vcds yet. Only other thing thinking of doing is intake manifold cleaning protocol. Any other suggestions?

The car is still very drive able. If anything I just notice less boost in the mid-to-high 2k rpm range. Maybe MAF is just starting to go out

 

[rreegg]

New Maf seems to have resolved things so far. Really nice to have boost in the 2-3k range again