Codes 172 and 176

[rkneeshaw]

Truck seems to run ok, but after I drive for about 4 or 5 miles the CEL comes on. I had the codes pulled and its 172 and 176, both banks lean. When I restart the truck the CEL goes away, but always comes back after a few miles. I am getting worse gas mileage than I would expect (about 14mpg hwy). Sounds like a i have an exhaust leak on the drivers side. I've looked for vacuum leaks but I'm not finding any. I've only owned the truck for 2 months and its always had this CEL... early on it had very low power and the MAF was FILTHY. I've since cleaned the MAF and the truck feels like a new machine, regained a lot of power back, but I never did have the codes cleared... could these be old codes maybe? What should I do?

 

[Alex FX4]

you can clear the old codes by unplugging the negative battery lead for a few mins then plug it back in. try that.

 

[rkneeshaw]

It sounds like pulling the negative battery lead will NOT clear the codes according to a lot of online references for the OBD-I system. I found a way to do it in the tech section.

I had the exhaust leak fixed too. No change except the motor doesnt sound like its going to fall on its face.

I was rethinking the vacuum leak thing. When I am driving and put the truck in neutral the RPM's stay at around 2k. When I come to a stop they drop down to a smooth 750 RPM. Is this normal or maybe I do in fact have a vacuum leak? I haven't had the truck long enough to know what is normal and what isn't.....

 

[koda6966]

He doesn't need to clear the codes, he needs to fix the issue. Since he's driving a 94 its OBDI and doesn't get the same testing as OBDII for inspection. Hell, I don't even know if they do those out in Michigan.

 

[basketranger]

imo Vacuum leak. why i believe this to be good, the most recent vehicle to do this to me was a F*cus.

 

[rkneeshaw]

As luck woudl have it, BOTH o2 sensors were bad. Replaced both and no more CEL!