1987 YJ (2.5L TBI) after warming up, high idle speed and bogs down above 3000 RPM.

[Stever]

Starts, runs and drives really well.  Idle speed seems fine.  The problems seem to start after its warmed up, the idle runs at ~1500, and the engine hesitates above ~ 3000 rpm.  My plan is to test the throttle body position sensor and the fuel pressure.  I started on the position sensor this morning and found that I have a 4-wire sensor, but the wiring diagrams I've been able to find reference a 3-wire sensor.  https://wrangleryjforum.com/attachments/jeep-wrangler-yj-wiring-diagrams-pdf.115642/

So I guess its a 2-pot sensor and I'm reasonably sure that they are Black(GND), White/Black(Hot), Brown(Pot1) and Green/White(Pot2).  But I'm struggling to get any voltage readings with a back probe from ground to either pot.  I've removed and replaced the connector a couple of times to verify that I have good connection with the probes.  I'm measuring with the key in the on position.  I can't believe the sensor would be completely dead and the jeep would still start and run, so I have to believe I'm doing something wrong.

The jeep is new to me, I bought it maybe two months ago.  I've replaced the master cylinder and some brake lines, and resolved some tail/tow electrical problems.  

Anyway I'm going to go get a fuel pressure test kit and do that while I wait for someone here to hopefully illuminate me or at least tell me I'm on the wrong track.

 

[Moses Ludel]

Stever...What year YJ?  I'll furnish a wiring schematic if on hand. 

You're on the right track with a voltage probe/test of the sensor and verification of the TBI system fuel pressure.  Also look for a vacuum leak or a restriction on the return fuel flow to the fuel tank from the throttle body...We'll walk through this.

Moses