Rookie mistake - used upstream O2 sensors for all four sensors - lean code

[08EddieCA]

SOLVED: Installed four new o2 sensors. Two upstream and Two downstream. Also replace intake manifold gaskets. While I was at it I changed the trans filter and replaced six quarts of Mobil 1 synthetic ATF. I'm beat. No more codes. Truck runs better than it has in months. Hope to see and increase in gas mileage too. I feel pretty silly installing upstreams in the downstream ports. I'll watch the catalyst temps over the next couple of days too. Thanks for the kind criticism. I own this mistake. Toughest part of was reconnecting the exhaust tube to the EGR.

 

[gdgiordano]

SOLVED: Installed four new o2 sensors. Two upstream and Two downstream. Also replace intake manifold gaskets. While I was at it I changed the trans filter and replaced six quarts of Mobil 1 synthetic ATF. I'm beat. No more codes. Truck runs better than it has in months. Hope to see and increase in gas mileage too. I feel pretty silly installing upstreams in the downstream ports. I'll watch the catalyst temps over the next couple of days too. Thanks for the kind criticism. I own this mistake. Toughest part of was reconnecting the exhaust tube to the EGR.

Glad it worked out

 

[Mbrooks420]

Why did you install 4 new ones, and not just the downstream ones?

 

[08EddieCA]

Just in case I fried the upstreams in the process of utilizing the upstreams on the downstream. I guess I didn't have to but I had an opportunity to do so. Car idles so much smoother.

 

[08EddieCA]

Your catalytic converters are overheating because your wide band sensors are out of spec and the truck thinks it’s running lean, so it’s dumping excess fuel in trying to reach its O2 sensor voltage target, which it can’t reach due to the incorrect sensors.

My catalyst temps are causing cyl 1 misfires under load. I think I may have fried my catalytic converters. Much less of an issue is the pcv rubber o-ring isn't keeping the seal tight and causing a lean code plus it looks like oil is slowly coming out of the intake manifold.

 

[bob m]

Sorry For jumping in late here, but I have a question. I am also getting lean codes and have looked at 100 things trying to find the answer. I was under the impression that the O2 sensors that are in front of the upstream towards the motor Cat is what is sending the feedback for the Fuel Trims and that the ones downstream of the Cat are basically measuring Cat Performance so that if the Cat Gets Plugged or Contaminated it will generate a code. Is this correct or no?


I was under this impression as it is the only place that can tell the efficiency of the ignition without some effect from the Cat.

Was also told at least on my 2002 that the difference between front and rear O2 sensors is the length of the connector wire.

 

[bob m]

Sorry For jumping in late here, but I have a question. I am also getting lean codes and have looked at 100 things trying to find the answer. I was under the impression that the O2 sensors that are in front of the upstream towards the motor Cat is what is sending the feedback for the Fuel Trims and that the ones downstream of the Cat are basically measuring Cat Performance so that if the Cat Gets Plugged or Contaminated it will generate a code. Is this correct or no?


I was under this impression as it is the only place that can tell the efficiency of the ignition without some effect from the Cat.

Was also told at least on my 2002 that the difference between front and rear O2 sensors is the length of the connector wire.

 

[08EddieCA]

I'll have to measure the length, which I will do. Not sure about the condition of the Cat, per your question. I have looked at Catalyst temperature from my scanner as an indicator of Cat health - my Cats run hot, very hot, and that's not good. A post above references the computer trying to figure out the proper fuel trim and, based on the assumption the Lean Code is caused by a vacuum leak, dumping fuel - Rich - and resulting in poor MPG. I think he is correct.

I recently smoke tested my intake and found that I did not tighten the rear intake manifold bolt when I changed the intake seals - most difficult to approach. And, I needed a new O-ring on my PCV. Before the smoke test, I struggled to address every vacuum line I could.

Unfortunately, in my case, with all vacuum leaks addressed, I discovered I have coolant being burned during combustion as a result of a "blown" head gasket or cracked head between cyl 4 & 5. I read a post that stated coolant within the combustion gasses can cause an O2 sensor to have a faulty reading, possibly causing the lean code. Luckily the head that has the issue is the driver side head. I hope to receive a rebuilt head within the week. Total hassle.