After driving several hours I have started to pick up the check engine light on my 95 EB. Sometimes it goes on and off but I also have seen it in for 2 hours continuous.

I pulled the codes and found 172 and 176 for lean right and left sides. Took the vehicle on next trip and the check engine came on again and this time I noticed fuel economy and power drop. I suspect the computer is trying to compensate for lean by riching up the mixture (too much).

Since I doubt that both O2 sensors simultaneously are going bad, what common component can lead to this condition?

 

Any additional air in the intake or exhaust system will cause a false lean reading by the o2 sensors. A vacuum leak can do it, or a malfunction in the thermactor causing fresh air into the exhaust at the wrong time.
Since you didn't get a thermactor error code, it's most likely a vacuum leak.

Also, though unlikely, it could be your o2 sensors. How many miles, and has any maintenance work been done lately which could have allowed something to damage your o2 sensors?




Winford

 

Thanks for the reply Windfordr.

It just rolled 70,000 miles. On a previous trip, the torque converter was repeatedly unlocking and locking. Dealer in Arkansas found the Throttle Position Sensor failing and took care of the O/D flashing and check engine light. No other engine work to speak of.

On the return trip from Arkansas is when the lean condition developed.

On our latest trip, the check engine came on 8 hours from home. It reset after stopping for a short while. On another leg of our trip, the check engine came on 6 hours into a run.

I'll go pull the codes again and make sure the thermactor is not showing up.