Idle quality problems

[Richmond]

Note: This was a problem of a melted wiring harness connector on a fuel injector due to it having been twisted wrong after an intake manifold gasket installation.

Hello everyone, been scouring the boards for a resolution for this but nothing really jumped out at me.

Basics: 88 FJ62, 156K, rust where the mud usually hides.

The computer is throwing one trouble code, a 28, O2 sensor. The engine isn't giving me much diagnostics to look at, no fouled plugs, no obvious vacuum leaks.

Problem: After changing and properly adjusting my throttle position sensor, my idle quality has gone south. It is around 800 in drive and when I stop at stop lights it will run, then drop a couple revs, run like normal, drop a couple revs, then sometimes gets locked in to around 600 rpm, and a very lumpy idle, feels like its missing on one or maybe even two cylinders. I still can't find anything wrong with the spark delivery, even got out my coil tester.

Any ideas of where to look next? This has been going on for more than one tank of gas so I assume this is not a problem of bad gas.

Thanks in advance

 

[slcfj62]

An error code 26 is not O2 sensors. The book says "injector circuit, injector, fuel line pressure, air flow meter, cold start injector, or ECU. I would start with doing the air flow meter (AFM) checks since it won't cost you any money. If that checks out OK, then I would replace the fuel pulstation dampener if you haven't already, followed closely by the fuel pressure regulator. If it isn't fixed by then, pull the fuel injectors and send them off for a cleaning. And if you haven't already, get a Toyota repair manual, also called a factory service manual (FSM).

 

[Richmond]

I apologize for the typo, its a code 28, not a code 26, still oxygen sensor

 

[slcfj62]

Did you replace the Oxygen Sensors?

 

[Richmond]

No, the light has been on for some time with that code, and I haven't had the 94.99 to pony up for the sensor. The idle problem has started more recently. The O2 has been throwing a code since I got the vehicle and I just have had to suffer with less than optimal gas mileage.

 

[Downey]

I could be way off base here, but:
(a) It has been my experience that the o2 sensor deals with rich or lean conditions, but would have little to do with idle fluctuations.
(b) On GM TBI engines the VSS and Ignition Module working together control idle functions. Don't know if your fluctuation problem might be in this area???