My friends 2007 F-150 (4.6l engine)(77,000 miles) was shaking while at idle and the engine light was on. I changed the spark plugs yesterday and it fixed the shaking. We took it for a test drive and everything felt great. When we pulled back into my driveway the RPM's dropped down to about 200 and it stalled. Started it back up and the engine light was back on. We took it back out for another drive and found that every time we came to a stop the RPM's would drop down below 500 and it felt like it could stall. After we would come to a full stop the RPM's would stay constant at 500. After driving it around for a while it only stalled twice when coming to a stop and we probably stopped a hundred times. We took it to Salvo and got an engine scan and it said the #1 o2 sensor bank #1 was below normal.
Tried to diagnose the problem:
While the truck was running I unplugged each spark plug one by one and plugged them back in. Every time the engine would shake just as it did before then go back to normal after it was plugged back in.
I did remove the fuel rail on the passenger side of the engine so I made sure all of the connections were good. Everything seems to be good.
If the spark plugs were misfiring could that cause the o2 sensor to fail? Or should I assume that since the truck never stalled before I changed the plugs that it is something that I did that is causing the low RPM's?
This issue has nothing to do with the plugs, went through the same deal with mine. Pull the throttle body off and clean it with TB cleaner and then do the same to the MAF sensor. Should perk it right up, not sure why but even just a small amount of gunk in the Tb leads to issues
Thanks screw04, it was the TB. After cleaning out the TB and the MAF sensor the truck runs great. The engine light was still on so I had the code checked. It was the O2 sensor. Replaced it and the code went out.
No engine light and the truck runs better than ever!!!
Thanks for all the help!!!