Yesterday I installed URD's Thottle Body Gasket .

While installing, I took out the EFI fuse as recommended. When I started it up a while later, the idle was relatively rough, and the RPMs occasionally bounce between ~500-700. I figured it was no big deal, and that when the computer relearned some things, everything would smooth out. Well, that didn't happen. And this morning, I started my truck, and after a couple minutes of driving it the check engine light came on. I tried taking the EFI fuse out again to see if that would help, left it out for a long time, and it didn't help. I think the check engine light was off for a few seconds when I started it up, but it immediately came back on.

Just a while ago I took it to Autozone to find out what codes it was spittin out.

PO171: The PCM has determined that during testing, the fuel system for bank 1 was too lean. (Ok, so my cylinder 1 is lean.)

And another code, PO300. The guy told me this was a Random/Multiple Cylinder Misfire.

Here are a few other notes that may be helpful:

Amsoil air filter. Cleaned both the throttle body and MAF a couple weeks ago. Gasoline is BP (good stuff from busy gas station), 1/3 87 octane, and 2/3 85 octane (figured it would be ok to throw some 85 in since it's higher elevation. I also put a can of seafoam in this tank of gas. This problem didn't appear until immediately after I put the new TB gasket in.

Thanx in advance!

-YB

EDIT: Problem solved. Sorry for wasting your time. Rotated gasket 90 degrees and all is well.

 

maybe some new plugs? or coil

 

I will be putting in new plugs and plug wires in a few days. I'm thinking there may be something else though. Everything is fine while I'm driving, it's just the idle is rough, and the CEL...

 

Are you sure you connected all the hoses and stuff? I did the same mod you did and the truck idled really rough. I looked all over for loose connection and finally found a loose vacuum hose right under the throttle body I didn't see when I was removing the TB.

 

I just went and triple checked all of the hoses around the TB, and checked for other loose connections etc. Everything looks good to me.

 

check to see that in moving things out of the way you didn't crack a hose or wire.

 

Checked that. Everything is in very good condition.

 

Did it have the code previously? If not, you probably buggered the TB gasket in some way and now have a vacuum leak. And P0171 is for Bank #1 of the engine running lean, not just cylinder #1. You didnt say what you drive, but most Toyota's only have 1 upstream O2 sensor, so that means the entire engine is considered bank #1.

 

That's what I thought too, but here is what the printout of the tester said:

TROUBLESHOOTING PO171
The PCM has determined that during testing, the fuel system for bank 1 was too lean. (Bank 1 identifies the location of cylinder #1, while bank 2 identifies the cylinders on the opposite bank.)


Sounds like the machine is giving a bad description. It refers to bank 1 as a single cylinder (cylinder #1) and then kinda condradicts itself saying that bank to identifies cylinders (plural) on the opposite bank.

Oh well. I am going to go check out the gasket, and make sure I don't need to rotate it 90 degrees or something. If not, I'll try and see if putting the old gasket back in changes something.

Edit: Forgot to say that I don't think it had a code before. At least everything worked perfect and that there was no check engine light. Also, it is a 2001 Tacoma TRD, 5vz-fe.

Edit #2: Problem solved. Sorry for wasting your time. Rotated gasket 90 degrees and all is well.