Hi guys, I have 97 F150 with the 4.6 V-8. I have a superchip. I was driving to work and all of a sudden the truck jerked like I quickly turned the ignition key off then back on. A check engine light came on. It ran ok after that but the light stayed on. I thought the chip is going bad so I removed it. I had to remove the battery cable to clear the light. With 104,000 miles it was time for a tune up. A friend (mechanic who works out of his truck) did a tuneup. Plugs, wires and 2 sensors. It ran good for 1st day. Then it started raining and the truck started miss firing really bad. I'd pull away from stop sign and it would spit and sputter. Sometimes it ran good, then maybe next light, misfire again. I thought somethings wet. After 3 days of rain, it stopped. It's been 3 days since the rain. It runs better but still missing. I had the mechanic check his work, he didn't see anything wrong. Said better take it to ford. I took truck home, looked underneath and found what look to be 4 oxygen sensors. It looks like I have 2 cat convertors. Each side has a sensor before and after convertor. It appears he change the front sensor on the passager side, and the after sensor on the drivers side. Are the front and after sensors the same? I called parts house they showed only 1 front and 1 after sensors with different part numbers. I am not sure if the tuneup messed up something because the truck stumbled so bad before the tune up. Can you guys help me out? Thanks! Keith

 

If you have an Autozone near you they will pull the codes for free. That is the best way to start. There is also a good chance that the the upstream o2 sensor(closest to engine) that has not been replaced is bad.

I'm sure you will get more replies shortly.

 

The upstream o2 sensors provide the data for the computer that control fuel/air mix. The downstream ones only make sure that the cats and the other sensors are doing their job. Problems with an upstream sensor will cause a feeling like a miss. The other reason a 4.6 would miss is moisture in the spark plug ports, they're 6" deep so it happens. Pulling a battery to clear codes is a bad idea. It comes on for a reason so it reduces guesswork fixing problems on these touchy motors. It could be something small to something big, but if it was OK before the tune up, check :
1. The connections of the wires to the coil and the plug.
2. The quality of the wires, their resistance, and see if they're the right plugs.
3. Tightness of the plugs, especially the tricky ones under the firewall.
4. I would recomend changing the upstream drivers side O2 sensor. Also make sure the new ones are Motorcraft or Bosch, and the factory side of their plug is clean. There is probably more information coming from the new pass. side sensor so it makes the drivers bank run lean.
5. Make sure your superchip is plugged in tightly.
Good luck!

 

If the truck runs worse in the rain then the problem is most likely secondary ignition parts. Coils and plug wires (if you have them) are the culprit.

Try this. Wait until dark. Start your truck and verify missing. Pop the hood and disconnect hood lt. Look every carefully for arcing. If you can't find any use a plant mister to mist the engine (simulated driving in the rain) and recheck.

I'll bet your codes are missfire codes. It will help to have the code info to fix the truck (that is what they are for).

 

Thanks guys for the very good information. I'll check some things out and let you know. Thanks again! Keith

 

Since wires are new, could be your coil packs, they're known to go bad.

 

My 96 Mustang with a 4.6 did this also.. And it ended up being the crank positioning sensor... Just a thought.

 

Kieth..if you suspect coils I have 2 used originals that are still good that I'll let you have for free...I also have a set of new wires (those I'll sell at a discount)..I also have some '97 parts that you might be interested in...plus if you have the Captians chairs in tan I have a set of brand new Saddleman seat covers for "em...sorry if this is a improper post but I'm cleaning out my garage and getting the cash together for some wheels