Running rough at idle - 2003 V6 3.4 Tundra

Hi Folks,

First time post here. 2003 V6 3.4 Tundra is the rig.

Original issue: Started running rough, check engine light came on. I took it to my shop and they diagnosed valve cover gasket leak (causing it to misfire). Ran my OBD scanner and found the P0306 error code.
Fix: I replaced valve cover gasket, o rings, spark plugs, plug wires and ignition coils (w/ NGK). I originally replaced only the 5/6 cylinder coil (cheap bastard) but still had the error code. I moved the new coil down to the 3/4 cylinder to see if the error code followed the coil or remained for 6. It stayed at 6. I put in two more new coils so I had all new coils (V6 3.4 has only 3)

Currently, check engine light is gone and no trouble code however it still feels like it is running rough and misfiring. When I fire it up initially a little rough but smoothes out for idling. After driving around it usually is intermittently rough at stop signs etc.

Any thoughts on what may still be going on / how to get it back to that sweet purring state.

Thanks guys

 

Hey Bud,

I had the same issue on my '99 4Runner (same engine), turned out to be an injector issue. I decided to replace all of the injectors and sure enough, it fixed the issue. The procedure is pretty easy, I was able to do it outside in Montana winter. There are plenty of youtube videos showing you how to go about replacing the injectors and if you are looking to save some money you could just replace cylinder six.

Let us know how it goes,

Mike

 

I don't know as much about the 3.4L but the common advice here is that it's a good idea to clean the MAF sensor and replace the PCV valve. You've already done a lot of the things that I can think of. You could try cleaning the throttle body as well. Try these things and let us know if you are still having issues.

 

Thanks guys, great insight. I just ordered a set of refurbished denso injectors to switch out and hopefully that cleans it up. I'll check out the situation situation with MAF and PCV valve as well.

Thanks again! Will post update when I get to changing out the injectors.

 

Hey guys,

Posting a quick update - New injectors in took care of misfire and rough running issue. However, a new problem has come up where it is not starting properly. It sputters to life only when I give it some gas, but runs great going down the road. Making a new post on the forum.

 

Glad to hear you were able to resolve the misfire. After you get it started does it idle fine?

 

Yeah it idles great (for the most part) and goes down the road fine pretty much just the initial fire up (even if i start, let run for a few minutes and then restart).

 

Your new rebuilt injectors the proper part#?

 

I too have encountered this problem on that engine. Try cleaning your IAC valve (Idle Air Control).

 

From what I've read and encountered I don't think my throttle body has an IAC valve (or at least one like the previous 3.4 versions). I've attached some pictures for reference. I was planning on cleaning it when I pulled the throttle body off but was somewhat surprised by what I found.

 

You’re correct. No IAC on a “drive-by-wire” throttle body.

I responded in your other thread.

 

I stand corrected. I assumed your 3.4L was the same as others I have worked on in 3rd gen 4Runners.

 

Hey, I would have thought the same until he posted the pic of the servo controlled throttle body.