After Idling for approximately 20 minutes, being shut off, then restarted my 98 Discovery (90K miles) backfired three times when I tried to drive off. Check engine light was on so I pulled the codes. P1138 (O2 sensor bankAdownstream ofcat high voltage) and P1316 (misfire causing excessive emissions). Any ideas on the cause. I think I may have a leaking injector but not sure. Any help would be appreciated.

Steve

 

I think you are on the right track. Backfire in the exhaust indicates unburned fuel is making its way to the exhaust and then igniting. Would indicate either ignition problem (plug, wire, coil pack), or excess fuel (leaking injector).

While I am not familiar with the 1998 codes, the p1316 would be telling me that it's the number 6 cylinder. Run the engine for a short timeand then pull the number 6 plug and see if it is wet with unburned fuel or if the plug itself is defective in some way (maybe pull them all and have a look see).

If I had to make a guess based on what you have said, I'd guess the 20 minutes of idling fouled a plug. But who knows.

If it's a leaking injector dumping enough fuel into the cylinder to cause a misfire and then backfire, I'd expect the plug to be wet.

Please let us know what you find.

Also, is it running now or was that it and it died?

Good luck,

-Keith

 

Are you still running your orginal O2 sensors? How about plug wires, have they been replaced? What octane gas are you running, have you decarboned the engine in the last 12,000 miles?
With that 1316 code, I would be looking for a vaccumn leak like a hose or even the intake manifold gasket.
Mike

 

Mike, for my own education, why do you think of an intake leak? (would tend to make the engine run a little lean -- but wouldn't the computer "fix" that or at least fix itexcept when it was trying toidle?)

Also, another thought popped into my head -- maybe stuck exhaust valve? What do you think?

 

Send me your ele number and a good time to call, I would be glad to call you and see if we can find your trucks issues.
Mike

 

Still on original O2 sensors as far as I know.
Plugs and wires replaced in June of 06.
Running regular unleaded in the tank. Should I be running a higher octane?
Added a bottle of Lucas injector cleaner to each fill-up in Feb.

I'll check vacuum lines.

Steve