P0300 after throttle body replacement

I recently replaced the throttle body on 2002 2.7L, which partially fixed the high idle issue I was having. After replacing the throttle body the RPMs are very low after start. On a cold day it bogs between 400-800 and you have to give it a little gas to get the RPMs up for about a minute. Then it run at 800-900 and increases to about 1,200 when its warm.

Additionally I got a P0300 multiple random misfire. The truck run fine, even at low RPM on cold days it runs nice and smooth. Acceleration is normal through about the first half of gas pedal travel, but the second half theres some hesitation. Im guessing thats a fuel issue. I was thinking replacing the fuel filter and testing the injectors.

Heres the link to the previous issue:
https://www.tacomaworld.com/threads/stuck-high-idle.509642/

Any thoughts?

-Tanner

 

Did you reset ecu after new tb? It needs to learn that it now has a functioning TB.

 

imho, the random misfire points to something that affects all cylinders as opposed to a single one. I would start with the intake tube from the MAF to the throttle body. Take it off and look for cracks or places where the wire clamp might have cut through it. Bend it around, flex it etc.
There is still the possibility that you are still chasing prior issues.

 

Yeah I reset the ECM. The throttle body swap took about 20-30 minutes. Ill disconnect the battery for a night just to be sure.

Ill take a peek at the intake manifold as well. I know the MAF is clean and working properly. Ill have to look for any cracks or anything, its all in pretty good shape so i'm doubting its that, but a good thing to look for.

Im going to start simple and change the fuel filter and test the pressure from the fuel pump.

 

Alright, so i'm kind of baffled with this issue. I changed the fuel filter and it made the problem better, now once the engine is warm I have normal acceleration again! Sweet!

But my check engine light came back on and now I still have the P0300 and P505 is back. So i'm really not sure what the issue is here. I have a good throttle body on there, with a brand new IAC and my idle is still doing the same thing. Additionally its still having that weird low idle on start.

The ECM has definitely been reset, I disconnected the battery overnight. No change at all and i've gone through a couple tanks of gas since then. So I'm open to ideas if anybody has any. Really its just this idle issue that is the only problem. I know i'm getting a P0300 code, but the engine runs like a top even at low RPM. Sometimes it will get a sputter here and there, but nothing consistent that I can really nail down.

Additionally I tested the fuel pressure when I changed the fuel filter and at idle I was getting between 40-50 PSI, which seems sufficient.

Maybe the fuel pressure regulator?

I don't think its an injector issue, because its multiple cylinders getting the misfire. I checked for manifold leaks and couldn't find anything. I've gone over the vacuum lines multiple times and blown them all out. Nothing there.

Any ideas are greatly appreciated!