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Discussion Starter #1
Posting this to help others find their problem I had gotten a rich code one day on my 2005 tundra (2uzV8) for only one bank. Although both banks were rich, bank 1 was worse. Ltft was -30 and -33 this was a real cause for concern even though my truck was running fine. The code went away shortly after and wasn’t accompanied by another code. I started to look at all my sensors and I decided that maybe my o2s needed replacing(maf tested good) tried new Denso upstreams and it didn’t help. I decided that since there were no other codes with the p0172 it had to be something either not electronically controlled or something that’s slowly going out. So I had the injectors cleaned and flow matched also didn’t help although it smoothed the idle out some. After driving it like this for a while the idle got worse and worse and had a slight random miss. I thought since bank 1 was worse maybe bad coil packs, changed them and didn’t fix it. Started to worry so I checked timing belt for any jumped teeth and everything was perfect. So I started to look elsewhere and found I had some fuel in the fpr changed it and still nothing. Tested fuel pressure and it held at about 44 for a long time. I started to lose my mind about it for a bit and I got to doing some research. I knew my truck didn’t have an egr but I looked anyways and found out it had a smog pump setup by looking at the diaphragm check valves behind the heads. Tested vsvs all were good, pulled the manifold and checked the smog pump as they are typical to go bad on these trucks. All was good. I decided to suck on the vacuum lines to see if the valves were stuck closed from carbon. First one slammed right shut after I let off the vacuum line. Second one pulled some vacuum but tasted like exhaust and I couldn’t hear the valve shut. So I removed it and looked closely. It was clean but had a pin hole in the diaphragm. Replaced it and BAM finally fuel trims dropped back to 0% and the truck runs like a dream. Decided to do the timing belt and water pump as it has 140k on it and it’s 15 years old. This truck runs fantastic again and will do so for many miles to come. I wasted a lot of money on other parts and hopefully this post will help someone as the stuff I read never mentioned the smog/secondary injection system. Just shows you should always test before you buy parts but at least I have brand new Denso everything and won’t have to worry about the new stuff I put on going out for another 10-20 years.
 

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Just an explanation of the secondary air injection(smog) setup on these trucks new and old both have it. All it does is blow fresh air down the exhaust to thin the fuel gassed entering the exhaust. Similar to a regular egr. So because one valve was blown and another worked it wasn’t adding fresh air to one bank so the o2 read high. Plus since the diaphragm was blown it was sucking exhaust into the intake at idle making both banks run rich but one bank slightly higher than the other due to no added fresh air to the exhaust.
 
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