Hello everyone, so the other day i bought a 90 ford ranger off my buddy for dirt cheap. When he got the thing it was running decent, we changed the oil pressure sending unit and put the engine all back together and it started running bad. He said he plugged something in and it started running better but im not sure what he plugged in. The truck ran good all the way up till when i bought it. I went to his apartment complex and warmed up the truck, then proceeded to drive it back to my house. It was running great and all of the sudden the rpm started to rapidly drop and the trucks mph dropped as well. I was petal to the medal in first gear trying to get this thin to a parking lot going 10 miles an hour. The thing went from good to bad in a literal blink of an eye. I had my dad tow me back to my house and i did some research and came to the conclusion it was my cat. I did a vacuum test on the engine and wasn't getting a solid reading at idle, nor at a constant 2000 rpm. I unbolted the exhaust system and did the same thing, Rpm at idle wasnt stable but it was at 2000 rpm. I havent ruled it out yet but i dont think it is the cat, it looks like its been replaced. Next i chase the fuel pressure but im sitting on a solid 35 psi. The vacuum lines are all on and my truck isnt kicking any codes. The only thing left that i think it could be are the plugs or the fuel filter. I only checked one easily accessable plug and it looked fine but you never know. Any suggestions? Thanks for helping!!

 

Welcome to the forum

1990 Ranger will have the 2.3l SOHC Lima engine, not to be confused with the 2.3l DOHC Duratec engines Rangers started getting in mid-2001.

So if you google: "Ranger 2.3l" you will get conflicting information because there were two different 2.3l engines

OK, 2.3l Lima
Has 2 spark plugs per cylinder, BOTH spark plugs fire(spark) at every TDC, compression and exhaust stroke.
They do not alternate.
So you need two bad spark plugs in one cylinder for it to misfire from a spark issue.

But you can mis-wire spark plugs on Coil Packs, so double check that

Clogged exhaust will certainly cause a problem, but that problem gets worse as RPMs go up, doesn't get better.

Vacuum leak causes engine to run worse at lower RPMs, then it can smooth out at higher RPMs because small amount of air leaking in doesn't cause as much of a problem as engine air volume increases, i.e. a drop of poison in a swimming pool or in a shot glass.

You will need to do a compression test to take a few other things off the table.

The fact it "was running good" then suddenly wasn't could be bad gas, when was last time you got gas?

 

Ok, today i will check the compression and the coil packs. He had filled the truck up about two days before i got it and the thing gets killer gas milage so id imagine it is fine. I can run the thing for quite a while. Might jut change the fuel filter just to be on the safe side.

 

throttle position sensor

 

Cheese man you are a genius. Thank you!!

 

you are welcome

oh replace the fuel filter as soon as possible , if you do not know if it has ever been replaced