Stock Engine, ODB-I Reporting Lean Condition

[Canyonero]

Working on one of my Troopers, a stock 1989 with a 2.8L Gen-I TBI. I was getting an intermittent CEL with O2 sensor codes (DTC-13 and DTC-44)*, so I went ahead and upgraded to a new 4-wire HO2S yesterday. Now I get a consistent CEL with just DTC-44.

*DTC-13 Oxygen sensor circuit open or no activity
DTC-44 Oxygen sensor error (lean condition indicated)

On a totally stock engine like this, what would be likely make it lean?
I'm thinking maybe unmetered air from a vacuum leak, maybe a poorly flowing injector. Think I'm on the right track? I'm going to do the 4.3 TBI swap eventually, so I'm thinking of mailing off a pair of 2.8 TBI injectors to get cleaned/flowmatched.

I've probably put 1500-2000 miles on this truck since I bought it. Seems to run pretty well. Had been sitting for about 7 years before I got it though. I expected it to get better MPG, but figured that was related to the O2S problem.

[robertisaar]

yeah, it sounds like you're probably right, its either getting too much air or too little fuel somehow. vacuum leaks/clogged or worn out injectors aren't that rare so i would start with that...

[Canyonero]

Couldn't find any vacuum leaks. Injector patterns don't look great, so I'll get a pair or two mailed off and see what that does.

[geoffinbc]

Ever looked at the fuel filter? Hows the fuel pressure?

[Canyonero]

I replaced the fuel filter when I first got it. Truck seems to run good, just getting the CEL. I might get a can of seafoam to run through first, but I think a proper off-engine cleaning might be what they need.

[Canyonero]

I mailed off a spare pair of injectors to WitchHunter Performance for cleaning, that should be an easy way to tell. Can't hurt anyway.

[TiredGXP]

Exhaust leak?

[ForcedFirebird]

True, exhaust leak before the sensor could cause excessive o2 to get in that the sensor is seeing.

Where is it placed in the exhaust stream?

[NArtissimus]

Hey guys, back again... Now looking at the hybrid build

Funny you'd mention those codes. I have the exact codes on my 3.4 swap and was looking at doing the 4 wire o2. I have headers and I know I have a minor leak at the crossover pipe joint that opens up when it's hot. I'll have to close it up and see what happens.

If not... I'm running the stock 3.4 (19lb I believe) injectors with the 2.8 intake p&p, and a distributor but I can't see it getting too much air or not enough fuel. I've got a brand new fuel pump and filter. I was wondering if a problem ECM would be causing this problem instead and if an upgrade to the DIS and the Beretta/Cavalier??? ECM would be beneficial now? Like I said I'm looking at doing the 3400 alum heads and intake, a cam, and timing chain next and then definitely go DIS.

Thanks, Art

The 4.10's sure made a difference from the 3.42's... I think I'll have to go 4.56 though with the 20's