I have an 07 T4R SR5 4x4 with 150k on the clock. Its in great shape and the previous owner (single owner) kept all service records and its mostly highway miles.

The only real issue with the truck is at idle (stoplight) RPM's will sometimes dip below 500, causing a vibration/shudder. The ECM/PCM detects this and increases the idle speed back up to around 650 RPM. About 20 seconds later, the R's fall and the same thing repeats itself.

Is this just a quirk of a 150k engine or are there some steps I can take to correct it? Clean the MAF/TB? Seafoam treatment?

Airfilter is clean. Unsure how old the plugs are but I cant imagine that causing it. Vacuum leak maybe? I have a Bluetooth scanner and the Torque app. No codes or anything like that.

Thanks!

Is the AC or defroster on?

Does it with the AC on and off, though its more noticable with the AC off as the engine idles slower

Not sure if these cars have one or not but, search for "Idle Air Control Valve" Sounds similar to what my Honda Civic does with the valve stuck.

My 03 w/125K miles recently started doing the exact same thing. Cleaned the MAF and Throttle Body with cleaners specific to those items (CRC products). Fixed it right up. If you decide to do this, do buy a new TB gasket ($2.49 from RockAuto didn't check Amazon) or you'll end up with air leaks at the gasket. Mine was hard as a rock and I doubt it would have sealed again. The whole process took maybe 90 minutes and I may have fit an adult beverage in there somewhere. It now idles at 650 again unless the compressor is running, then it jumps to maybe 800. No dip and no erratic idle.

Nice! I'll give that a try. Did you buy the cleaners locally or online?

Rockauto - they were cheaper than Amazon and I also ordered the TB gasket at the same time.

I got the same CRC cleaners from my local auto parts store, so you should be able to find them at any major auto part chain stores.

i disconnect the efi ecu fuses, and start cleaning both maf sensor and throttle body, really need to give that throttle body a good cleaning.

then re plug in the fuses and also check air filter.

Update: I removed the airbox and TB, gave it a good cleaning with the CRC cleaner. It was covered in black, oily deposits.

I also pulled the MAF and sprayed it with MAF cleaner - it was a bit dirty but far less so than the TB.

Fired it up after ECU reset and its running much smoother!