Hey folks!

Today I did some routine maintenance on my 2000 4runner:

Changed plugs using OEM Denso's
Changed fuel filter using OEM filter
Drained Radiator, flushed with a garden hose, filled with yota red stuff and burped. (1 gallon of red stuff filled the radiator. After the first and second burp, it hardly went down, I only had to add a 1/4 gallon of water, then I filled the overflow to the top mark)

Everything went smooth until the two hour ride back to Philly from the Poconos. After about 20 minutes of driving, I got a P0125 (coolant temp too low for closed loop operation).

I pull over, turned car off, checked rad hoses - upper hose was hot and rock hard, lower hose was soft and not even warm. I opened the radiator and burped the system again, got a few more bubbles. I cleared the code and got back on the road.

20 minutes later...I get P0125 again, and P0171 (fuel trim - bank 1 - system too lean). I pull over and shut down. Upper rad hose a little softer than before and hot, lower hose is still cool and soft. Jacked up front end about 8", burped system again, cleared code, back to driving.

A few minutes later I get the same 2 codes again, but continued home. Car ran perfect, but it was sucking down a lot more fuel than usual. Once I got home, I checked hoses - upper one is hot and feeling normal (not rock hard), lower hose is again soft and not even warm. Burped the system another 2 times and still getting the same codes and the cool lower rad hose. Also, nothing got sucked from the overflow.

A little related info: A few months ago I had a bad A/F sensor (front sensor). I put in a new one from toyota, it's been good for over 1,000 miles now. So...not sure why i'm getting P0171.

Any ideas gentleman? The car was running perfect before I did all the work. I was trying to get the car ready for a trip to North Carolina, and figured I should take care of some maintenance I've been putting off, and now this! I know the usual issues with these codes (map sensor, a/f sensor, vac leak), but it's odd that they popped up after this maintenance.

I'm thinking when you did your plugs you didn't get everything hooked back up nice and tight. Check your air intake tubing and vacuum hoses and make sure everything is hooked up.

Yea i'm going to double check everything again. The only driveability issues are the really bad fuel economy, and a slight pulsing at idle while in Drive or Reverse.

If the upper hose is hot and the lower not even warm, have you checked the thermostat? I have had one go bad with a rad flush before...

SO...I picked up some plug wires. As I'm installing them I noticed a dangling ground strap for the diagnostic socket next to the intake...the one I removed when installing the plugs!!!!!

It now makes sense why I was getting all kinds of DTC's. I hooked it back up, and after 30 minutes of driving and 3 on/off cycles, no CEL. The slight pulsing is gone, she's smooth as butter

LESSON LEARNED! lol

Ha ha, yeah, I've never done that! My friend who used to work at a chevy dealer years ago always jokes, "you know you've been working on a chevy if you have left over nuts and bolts when you're through"... But on Toy's there should not be any leftovers!

hahaha yea I'm usually good about that stuff, I guess the bolt took off ;)