I have a 1988 ford ranger 2.9 auto. When I start the engine cold it idles high for a second then engine light comes on and it idles low. It runs fine has little rough idle to it. Any ideas?

 

Welcome to the forum

Have you tried to get the code from the computer?

Some auto parts store can read OBD1 codes, that will narrow it down alot

If you just want to replace parts to see, then I would start with ECT(engine coolant temp) sensor, NOT ECT sender(used for dash board temp gauge, has just 1 wire)

ECT sensor tells computer when engine is cold and it needs to run high idle and Rich fuel mix, Choke mode

Any time engine starts idle should go high(1,500rpms) and then drop, that's normal, but when it's cold it should only drop to 1,100rpms, and then once ECT sensor shows its warmed up, 150+deg, then idle should be down to 750rpm with automatic in Park



You can use a Test light to read codes, info here: https://www.therangerstation.com/tec...ry/OBD_I.shtml

Replace analog meter with 12volt test light
Light will flash a 2 digit code for 1988 Rangers OBD1 system

2-digit Ford codes seen here: https://www.therangerstation.com/tec...gitcodes.shtml