Hello All,
Back Story:
I have a 89 Ranger 2.9l auto trans, P/S, A/C, it has about 90000+ miles. My mom bought it new, then gave it to me around the year 2000, and of those 90000 miles I myself maybe put 10000miles on it. It sat in the driveway most of the time since I used my work van for a daily driver ( would always start/drive Ranger 1-2 times a month), I did keep maintenance up on it always , also made sure had a full tank of gas....Truck would always fire right up , ran great, until a couple months ago.... now it has a crappy idle (cold and hot) almost " a stumble" runs great other than the idle and I cant seem to get rid of it , So I thought I would join this great forum hoping I can resolve this "issue"....

So over the past month I have done the following:
New= Tune up, including plugs & wires , cap/rotor, fuel filter, air filter, oil change w/filter. mapp and O2 sensors along with a new Air Bypass Valve....and has new exhaust/muffler ( checked cats, not plugged) also replaced brake booster ( vac leak) and check for other vac leaks ........compression test good , leak down test good....
also replaced P/S pump

and today I went and pulled off the intake and I have the injectors out for checking and/or replacing,............... I think I covered everything Ive done so far...

Some questions I have:
I tested fuel pump pressure at the rail and its about 80psi, manual says 40psi ...is 80psi normal for a Ranger with a intank fuel pump?
Whats the best way to test the Fuel Pressure Reg? I have a hand vac pump and with it hooked up the reg does not even try and move( -25hg) and me blowing thru the port .
Also the "piston " thats driven by that solenoid inside the Air bypass valve, is it supposed to have "space " around it inside the bore? or is it supposed to be a tight seal?

Im I missing anything?
Any help would be great ! Thanks all!

 

Welcome to the forum

Good work on the testing and diagnoses

Cleaning the injectors will help idle ALOT, good to put a can of Seafoam or similar cleaner in gas tank once a year, cleans my 1994 4.0l's idle right up

Replace FPR(fuel pressure regulator) that is also a source of your poor idle
System should run 30-40psi, FPR's spring valve is set for 43-45psi engine off, with 18-21" vacuum present(engine idle) should drop to 30-35psi

Fuel pump is capable of 70-90psi so your FPR is stuck closed, the hose attached(besides vacuum hose) is the Fuel Return hose, should have flow thru it all the time when fuel pump is on, sending fuel back to the tank

IAC Valve will feel loose inside that's OK
Best way to test is to start cold engine, RPMs should go high and then settle in at 1,000, computer is in Choke Mode, rich fuel mix and high idle(IAC Valve working), also means ECT sensor is working

Warm up engine and let it idle
Unplug IAC Valves 2 wire connector, RPMs should drop to 500 or engine may even stall, this means IAC Valve was working, computer is controlling it, and you have no Vacuum leaks causing poor or high idle

 

Thank You RonD , for your reply!....And another BIG thank you for not just giving a " one word reply" or something similar to that.....

So im off down the rabbit hole now...it started when I notice a crack in the wire insulation to No1 Injector .....then looking closer I found cracks in every wire in the harness that sits on top of the engine due to age ,heat , etc and also since it is the harness that connects the ecu to all the major sensors and fuel injectors ,etc,etc ....So im making a new harness up now, since Im not working right now, so I have the time, and all the new wire I need from my old job ( 100ft lengths of 20 conductor SO cord ,18 and 16 gauge ) I should have it done by Sat....Its not that many wires .

I will update when done, Thanks again Sir!