Test it before you condemn it! If the truck is running better, especially at idle, it probably works right! Unplug it when running and see what it does.

 

Tried that earlier - no change when its unplugged when running. When engine is started with it unplugged, engine high idles normally and then drops down to a slow, rough idle.

 

Earlier as in after cleaning the throttle body? It shouldn’t idle any higher with IAC unplugged. Even if it was in warmup enrichment for a minute, then it’s just running really rich for that period.

 

yes, after i got back from my test drive after cleaning TB and replacing TPS.

If i unplug IAC while engine is running, idle doesn't change at all. If i start engine with IAC unplugged, I get a very slow, rough idle.

 

I would test it. When it’s unplugged, the truck should indeed barely idle. Around 550 rpm if you have a gauge.

 

Performed a sanity check after work today.

Pulled the IAC off, checked gasket (its good, brand new), made sure connector and valve was clean. All good there. When I put it back on, I noticed the idle screw on the throttle body was in by about halfway. With IAC unplugged, engine ran rough, and was slow, but not 500 rpm slow like I keep seeing online.

So, I ran the truck with IAC unplugged and unscrewed the idle screw until I got a pretty dog slow idle... never could get the truck to die, but it came close. After that, I plugged in the IAC and have a much calmer engine at idle. Again, no tach, not sure what RPM is. But this seems much better than what it was - it might be close to half the speed it was before.

 

Now that you’ve done that, verify idle tps voltage on signal and adjust as close to .9v as possible! If it’s close, then I would leave it.

 

I was able to get it down to about 1.004V. It had to be way higher before I turned out the idle screw... I was also able to adjust the TPS itself just a tiny bit without pulling the throttle body. I see some people recommending anything under 1V... Hopefully I'm close enough. If not, I can pull the throttle body again the next large chunk of time I get to mess with the truck.

Truck idles better, maybe feels a bit more gutless with today's adjustments. Worth it to not be idling at 1200+, though. Transmission still shifts about the same - i crawled under the truck to check the MLPS alignment and it was perfect.

Really looking like you may be right about my lean code being a fuel system issue. Noticed I've got a few intermittently noisy injectors - louder than normal for these, anyway - and I have seen some people say the fuel solenoid is a common failure point. Just gotta will myself to tackle that next.

 

I have a permanently mounted fuel pressure gauge on the rail. I got tired of finding the tester, hooking it up and hoping the same issues were still there. It’s a preliminary part. When I’ve had issues, I still use the main tester to diagnose where the pressure loss is coming from. With the rail gauge, I can be anywhere and pop the hood and immediately see the pressure. Helped when my second fuel pump In 3 years started failing 2.5 hours away from home. That coupled with a wideband AFR gauge, I was able to limp the truck home and save a tow bill. Made a nasty mess in my pants on the ride, but that’s what a working washer is for!

 

Did you buy a permanent gauge, or find some way to mount a normal gauge?

 

I can take a pic of it tomorrow if you’d like, but the video shows it.

I was diagnosing a problem when I took it.