Negative long term fuel trims indicate the ECU wants to reduce fuel, so the engine is running rich on average. My mechanic says normal long term trims should be between -5 and +5%, closer to zero is ideal. Max allowed is +/-25%. Long term adjusts (ratchets) when the short term trims hit the 25% limit regularly. Reasons for negative LTFT might include leaky injectors (very rare I hear), bad O2s, and others (maybe bad MAF, TPS, Google may help). Maybe running in limp mode?

Short term trim trying to add fuel at idle may indicate a vacuum leak. You didn't show bank 1 short term trim data? Short trims can vary a lot during a drive, but generally, positive at idle, then negative when the throttle opens up (relieves vacuum) indicates a vacuum leak. I had a self inflicted vacuum leak when I forgot to connect the tube for the fuel pressure regulator, the trims swung negative 15 to 25% back towards center when I reconnected it.

Sometimes crud builds up on the tiny MAF sensor elements, that can be sprayed, but a pick can be used to gently pry off the hard crust on the hot wire (I need to use a magnifying glass).

I have taken to leaving my coolant caps a bit loose (per this Forum), so pressure doesn't build up in the D1 cooling systems (and I know that lowers the boiling point of the coolant). Good luck with Indy!

 

I think the issue is finally resolved. I purchased a new Walker MAF which was total crap and caused the stft to stay at +25 and ltft to increase to the -20 range. Luckily Rock Auto provided a refund for that unit. A local LR specialty shop had a used MAF from a Defender that I installed yesterday and the ltft is now -0.8%, and the stft is near zero. I have an appointment with the State Emissions Technical Center tomorrow for a free in-depth analysis to see if it passes.

I replaced the coolant overflow tank, top radiator hose, and thermostat (Stant 45858 180 degree) and a few days later the temps were creeping into the low 200's while the a/c was on. One of the auxiliary fans in front of the radiator was dead, so that has also now been replaced with a VDO/CONTINENTAL PM9115. When it rains, it pours......