Code 25 Lean - and VAF testing.

[JerseyCruiser]

The truck was running poorly, stumbling idle and lack of power. The idle would smooth out as I gave it gas. If your cats are glowing red, there is a very high possibility that you are getting too much o2 back there which would make it burn hotter. and really, the only culprits that I can think of that would introduce a lean mixture would be your VAF, PAIR, or a crack in the intake tube beyond the VAF. One thing that was happening when my PAIR was failed open that you could check really easily:
The silencer can that hangs off of the main Air intake Filter housing, was filling full of condensation. At first I thought it might be a by product of Seattle Snorkel ownership, but it turns out that with the PAIR valve constantly open, the Hot Exhaust gas interacting with the cool intake air was resulting in a ton of condensation gathered up in that little silencer can right off the intake. I would check that for any water, and would feel confident in saying that if you find any, your PAIR could be open more than it should be, (this could also be caused by whatever component tells the PAIR to open up failing as well.) Probably not your issue, but something more to check.

My idle is stumbling and low and when I dive the truck shutters with poor power. I do have a snorkle I'll check the silencer for the PAIR to.

 

[Timpanogos Slim]

my idle sometimes stumbles and is low and sometimes is fine.

it's always fine if the AC is going. And sometimes it just behaves for no reason.

I have codes but i don't know what they are other than the aft knock sensor, which has had it's wire fall off again. I suppose i should read them. again.

 

[JerseyCruiser]

The FSM diffidently has a typo on page EG-292 on what terminals to meter for the measuring plate resistance, the correct terminals are on page EG-290 thanks for catching that Timpanogos Slim. So with that said the VAF passed all the metering test and is fine. I disconnected the harness at the ECM and VAF and metered the wires for E2, VS, and VC and found they all have a half ohm of resistance with no opens shorts or grounds. So the wires from the ECM to VAF are fine, that eliminates any EGR valve pipe damage. I just need to meter the wire for going to terminal THA I ran out of daylight. I had poped the sealed cover of of the VAF before to see if it got wet inside and its OK and with the truck running if I slightly open or shut the measuring plate from under the cover it never evens out the idle just makes it stall. The PAIR valve seems fine too it cycles off after about a minute after you start it up from cold, I can hear the noise and then it goes quiet. I found no water in the No. 2 air hose and it passed the test by applying vacuum to the valve and blowing into the valve. Tomorrow I try the old ECM I have, it works but sometimes throws codes 81-83 and meter the THA wire. The only thing I can think of at this point is the O2 sensors or their wiring. The O2 sensors were replaced in the last 5 years and have about 10k on them and they are OEM. Report back later.

Thanks
George

 

[JerseyCruiser]

So The THA wire is good and it ran the same with the other ECM. I 'll be checking the injectors and O2 sensors next.

 

[Timpanogos Slim]

Good luck!

 

[JerseyCruiser]

Turned out to be a dead #6 injector, problem solved!