P0505...this is getting annoying

Could this be the problem? Noticed a missing bolt where the plastic piece holds the spark plug wires in place. Near the PCV valve. Perhaps air is getting in through here to the engine???

@treyus30 @Andy01DblCabTacoma @96BlueTacos


Edit** Poured some water on the hole and it's not penetrating so air shouldnt be coming through here

 

It’s really easy, to check. Your AC SHOULD cause a slight increase in your idle. It speeds up your idle, so that the drag of the ac compressor doesn’t kill your engine. That is one of the few items to check in the FSM when you have the code you have…

I would check that if I were you.

 

Just checked and AC does not affect the idle. If anything, it ever so slightly decreases it (if you were to look really closely at the neelde). Swapped the IAC and now the truck is Idling steadily at 1000k rpm when warm (no jumping around). I ordered a new TPS, IAC gasket, and TB gasket from Rockauto. I will put those in on the weekend when they arrive and see if that loweres the idle to below 1000krpm

 

What I mean is that a properly operating AC idle up valve SHOULD increase your idle speed when you turn on your AC, and the fact that your are saying there is no change in your idle when you turn on your AC, sounds like the valve could be faulty

In the factory service manual, as far as the code you have, there are basically 5 options for the code when troubleshooting; air induction system, faulty IAC, faulty VSV AC idle up valve, short in harness connectors, or faulty ECM. The order which the manual says to check those for the 505 code is first check air induction system, then ac idle up, then harnesses, then IAC, then ECM.

hope that makes sense

 

so i found this quote in another thread: "the actual idle speed setting as well as increasing idle speed when a/c is turned on is ONLY controlled by the ECM adjusting the fuel air ratio

I learned all about this when I was trying to find a way to raise my idle speed to stay at 750 to solve my rough idle in gear issues, but I found out no matter what you do, the ECM decides what speed it will idle the engine at and nothing you do can change it short of finding the signal wire telling it the a/c is on and sending power to it all the time but I wasn't going to start messing with the ECM wiring (back then I had a 99 with a 2.4)".https://www.tacomaworld.com/threads/low-idle-when-ac-on.406096/

I'm gonna try and do some work on my truck this afternoon but if i'm being honest i don't know how to diagnose the ac idle up valve as per your photos of the repair maniual, i think thats a bit beyond my scope.

 

The ECU will raise your idle to combat the torque requirements of the A/C system. But correct, you cannot change idle points, which is why you're getting your code.

 

so just changing my tps and iac gasket right now and just realized that i was missing one of these black covers on the 2 vents on the TB… maybe this was causing my issue?? i put another cap on, i’ll figure out shortly if the problem is solved

 

Ok so update, after putting everything back together, truck is idling even higher now at 1100rpm. So I guess I can rule out anything to do with the TB, IAC, TPS, Vacuum Leak, Gaskets. @96BlueTacos could you point out where the ac idle up valve is in the picture, i couldn't find it? Also, if I replaced a working TPS with another working TPS, why would the idle raise by 100 rpm?

One thing I did notice is that there is a little play in the spring where the idle cables attached too. I have read in some other threads that some people have found putting a washer in the spring has solved their high idle. Could this potentially be what's causing my issue, or are we thinking its something to do with the ECM or AC Idle Up Valve?

@treyus30

Thanks

 

I actually ended up chasing down a high idle issue, and mine was quite a few odd cascading things. Basically boiled down to;
1. my radiator working poorly which was causing high engine temps
2. It was enough overheating to cause the thermostat to fail in open position.
3. After the thermostat failed, the coolant would continuously run and the radiator worked well enough to keep my engine temps too low and it stayed in warmup phase.
4. I had a sloppy butterfly valve in my throttle body, and after cleaning it realized there was a physical groove on the aluminum where the butterfly had worn in. Basically I shimmed the whole bitterly unit out so that the butterfly was centered again.
I also had some idle reduction with IAC valve cleaning.

The biggest thing for me was the temperature issues keeping the idle high because after the Tstat failure the ecm never received a high enough temperature code to bring the idle down. But after I solved that, the next main item was the air slipping around the butterfly valve.

I thought I read that you had your TB bored by max bore, so I figured the shimming on that wouldn’t be helpful to you.

I would put the maxbored TB back on, and then check the ac idle up.

let me do a little bit more digging on the FSM, and I will try to get you a bit more of a layman explanation for testing and show you where the valve is. Don’t feel bad… if you’ve never used an FSM before, they can be a little bit tricky.

stay posted

 

Also, did I see that you have done the PCV valve and checked that hose?

And as far as the shim to fix the idle, you would be able to pull on that spring mechanism, toward the radiator, while the engine is running, and hear the idle drop if that is the issue. Again, after max bore, they make a new butterfly, so that TB should have that issue

 

Your throttle cable should be firm, no slop, but not tight or tensioned. There is no separate A/C idle up valve, it is just a higher duty PWM on the IAc

 

Correct, so i did have it bored by maxbore and the TB is currently on the truck. I did pull on the spring and no change to the idle so i guess i can rule that out. I did change the PCV and checked the hose as well.

Also, i posted my temp readings on the last page, they seamed to look normal so can i rule out a thermostat/coolant/temp issue?

Thanks, appreciate it.

Throttle cable is firm, but enough slack not to have tension that would effect the idle. Interesting, @96BlueTacos posted a diagram on the last page with an ac idle up valve so i thought it was a thing in our engines?


*** Also i should add that no CEL light is on since i cleared the code a couple weeks ago

 

There is definitely an ac idle up valve…

 

I 100% do not have this

If you do I guess I would cap off the inlet and make sure it's not stuck open

 

I don't think i have it either from looking at my engine bay

 

so I will post an update for everyone who has followed along and offered they're help.

I took my truck to a highly regarded shop around an hour away. They diagnosed it as an issue with the non-factory IAC that was installed by the previous shop. They put in a used OEM factory IAC, and also removed my dash pot as it was sticking a bit, and now my truck is idling at a normal range finally ~750.

Here's the kicker. I took the aftermarket IAC back to the shop who charged me $600 for it, since they told me they would refund me if it didn't work; and the shop isn't standing behind their work or the part. They essentially accused me of lying, and said that the IAC looked too old for it to have been the one that they installed, and also accused me (or one of the other shops) of tampering with it. I even called the shop owner who just fixed me truck and diagnosed the faulty IAC, and had him on speaker phone, and they still chose to feed me BS, and not stand behind their work. Ridiculous.

I'm going to be leaving a real honest review for them.