Spaz

I just picked up a stock 1992 LX 5.0 that has 2 "lean" codes in the computer (41 & 91). It has long tube headers, off-road h-pipe and Flowmaster cat-back but is otherwise completely stock. I have to put a cat h-pipe on to pass inspection. So I'm wondering if you think that will be enough to stop the lean codes or should I add 65mm TB/EGR as well? Thanks

skunk21

you are going to have to do some testing because faulty O2's and a vacuum leak can cause this. simply replacing the O2's may not fix the problem. the oxygen sensor generates its own voltage, never apply voltage and never measure resistance of the sensor circuit, use an analog voltmeter.Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. You'll have to pull the passenger side kick panel off to gain access to the computer connector. Remove the plastic wiring cover to get to the back side of the wiring. Use a safety pin or paper clip to probe the connections from the rear. The computer pins are 29 (LH O2 with a dark green/pink wire) and 43 (RH O2 with a dark blue/pink wire). Use the ground next to the computer to ground the voltmeter.

you can also check for vacuum leaks, intake gasket, pvc, etc which can also lead to a lean condition. you can also check lines and observe the the voltage one the O2s.

also did you delete or was the EGR removed and other emission parts?

Spaz

Thanks for the good info skunk. I'll will check all of that. The EGR and everything is all there and stock, I just thought if I needed a bigger TB I would have to get the bigger EGR. My preference is definitely to get it "as stock as possible" and start fresh. I won't get a bigger TB unless it's needed.

skunk21

TB isn't the issue. Sometimes it can has straight forward as bad O2 sensors but many times it can be tricky like wrong O2s, wiring,vacuum leaks like a cracked intake gasket, bad FP reg, vauum lines removed and not plugged, dried and cracked vacuum lines. I have seen people chase this code.

Not to confuse but you would only need to change the egr spacer for a TB change.