Okay, this whole ordeal started a few months back. My 92 5.8 auto started idling pretty high. I took a guess and replaced the IAC valve, didn't fix it. My next plan was to replace the TPS sensor. I had to wait a few weeks, so I UNhooked the IAC, which brought the idle back down to below normal. It's been running this way for a little while, but now my transmission is not shifting as it should. It's going up just over 3K rpm before shifting. I am just wondering if this is a transmission issue, or is it connected to the idle issue? Thanks

 

 

Did you try to pull codes?

T-stat stuck open will cause a high idle.

Get a Haynes manual and a multimeter, you'll figure it out!

 

pull codes and engine vac.Vac should be 17-22.

 

I don't have my own code reader, will any of them work? And How do I test Vac?

 

https://www.f150forum.com/f10/how-re...es-obdi-10907/
Use a vac gauge on the hose off the brake booster. If you got to buy a gauge get the one with the hand pump.

 

Okay, I attempted to pull codes, and if I did it right, I think the ect sensor is bad, so I will replace that next. I did a fluid and filter change on the tranny today, and it still runs up to about 3K rpm before shifting. Any other ideas on this?

 

Could be the vss. For your trans. Ect is easy to replace. And you still need to pull engine vac.