1994 f150 300/6 5 speed

for the last couple months to a year my truck has been slightly sluggish at random times and sometimes would miss horribly on cold start or warm start but then go back to normal, but ive just driven it and not worried about it.

BUT, today i went to pick up my gf and out of no where, it sounded like and exhaust leak and started running amazing. It would actually get up and go and finally for the first time it felt like ALL my power was there, but i knew it couldnt just be an exhaust leak. So, when i got it home, i looked unerneith and the o2 sensor had unscrewed itself from the exhaust and was hangin there, still connected.

Whats with that?? Its running extremely well now with the o2 sensor off but still connected?? Can someone explain this??

Thanks in advance

 

How old is the O2 sensor? More than likely it was giving a false reading to the EEC, and now that it's out of the system the EEC is running in open loop. If I was in that situation, I'd replace the O2 sensor with a new one, clear the memory by disconnecting the battery for awhile, and be on my way.

 

its been on there since i bought it, about 4 years old probably older.

 

replace it, there relatively cheep,let us know how she runs. my truck runs with out it and has some power, but youd be surprised with a good one in there how much better it runs.

 

Okay, so i just remembered that it always came loose and i would always have to tighten it due to the PO crossing the threads. I took it off, fixed the the threads, cleaned it and put it back on with some lock tight. Its now running great and the check engine light doesn't come on.

Could the fact that it was loose cause the truck to misfire and all that previously stated?

Thanks for the replies guys!

 

catching air could give it false readings confusing the computer so anything is possible. as long as the truck is running good dont "fix" it if it aint broke. in other words if its running good now and stays that way dont replace the sensor.

 

^^^ Agreed.

 

Thats always been my logic

I drove it around yesterday for around 20 min to make sure that it still runs good when warmed up, and it does. So ill just let it be unless it starts acting up again.

Loving the fact that i have all my power back! I forgot how peppy these 300/6 were!

Thanks for all the help guys!

 

I was going to comment that your cat could be clogged and the O2 sensor off is what is making it run better (because the exhaust now has a place to flow to in exiting the pipe), but sounds like you got it figured out.

 

Id hope not! i just welded up a new exhaust Y-pipe back and bought a magnaflow high flow cat which was a pretty penny

 

i was with you on that one outdoorfan hahaha congrades on the fix

 

Yes an exhaust leak at the sensor would make the eec think it was running lean and dump a bunch of fuel in. You may see an increase in mpg as well.

 

Yea thats the exact symptoms. Its running great now and it actually gets a noticeable increase in fuel mileage. I just drove 100 miles (50 there, 50 back) to go pick up a part for a buddy and only burned through a little over a quarter tank.

 

Good deal. Enjoy.

 

i get the same feeling all the time. these sixes are pretty zippy around town, even with highway gears. the 5 speed tranny definitely helps though.