Limp mode after long stop-and-go

After a long time stuck in stop-n-go traffic (1 hr+), the car would go into limp mode. The RPM revs up high (4K+ easily) but the car barely speeds up. After I pull over, stop and restart the engine, the car drives fine as long as I keep moving. Outside air temp was a cool 68 F.

The car idles perfectly, but the power is a bit less than I remembered. When not hot, the car revs and shifts smoothly. No codes on ECU/TCU.

I've changed the air filter recently with no effect. ATF has been drained/fill 3 times in last 3 months. Never had a burnt smell, no bits/particles.

Going to change the fuel filter (36K since last) and MAF (186K original). I cleaned the MAF and the car was rocking for a few days. The MAF connector retaining clip (red plastic) has broken off a bit, but still plugs in tight to MAF. Also planning on cleaning intake, but not until next year.

What else should I look into?

Thanks.

Alex

Are you able to check for codes? Sometimes limp mode will set a fault, label it intermittent, but not turn on the CEL.

No codes for both engine and transmission on VCDS.

I did a quick test run just now and noticed that the ATF temperature was around 112/113 C, but the coolant temperature gauge was steady and pointing straight up on the dash (190 F or 90 C).

Could I have a clogged transmission ATF cooler?

alex_tdi said:

No codes for both engine and transmission on VCDS.

I did a quick test run just now and noticed that the ATF temperature was around 112/113 C, but the coolant temperature gauge was steady and pointing straight up on the dash (190 F or 90 C).

Could I have a clogged transmission ATF cooler?

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Anything is possible, but usually the transmission would overheat then start to shudder/drop out of gear. But it would. Also discolor the fluid and yours is clean. Course I'm not very familiar with the 01M, I disposed of mine when I started getting torque converter chatter.