I changed the plugs in my 98 4.6 expy this last weekend. It has been running fine until this morning. It was running rough, and the check engine light came on. I also replaced the IAC at the same time. Any thoughts?

Thanks

 

Have your pcm scanned for the thrown codes. I'd bet you have a misfire at one or more of the cylinders....probably a bad coil pack, boot or improperly re-installed boot.

 

As it's a 1998 4.6, it uses two coils, each powering four plugs. The 4.6 didn't go to coil-on-plug until 2000. That said, what brand of plugs did you use? Tritons are a bit finicky about plugs, with more than a few people on this board having issues with non-Motorcraft plugs. Did you reuse the old spark plug wires? They may have been borderline before you pulled them off the old plugs.

 

You may have gotten plug wires crossed up or didnt put an injector lead on. Two things I personally done in the past. Just make sure everything is connected and to the proper place. Get it scanned for codes, that will probably point to which cylinder is having the problem

 

I had a similar problem when I changed the plugs on my 97, 4.6. The wires were original and after being on so long, they were seized on the end of the plug, so when I removed the wire, something broke, and then I didnt get a tight fit and after a short time, it ran rough, check engine light came on. Scanned for codes and said problem with #3. Kept snugging plug wire back on, but after a couple of times of same problem bought the new wires and problem solved. Worth checking.

 

I reused the original plug wires and use Motorcraft plugs. The truck is running fine now, but with the check engine light. I will get to Autozone this weekend to get the scan codes. I am leaning towards the plug wires, because they were hard to get off. I also have to look at the PCV hose. When I changed the plugs, I did it one at a time. No chance of messing that up (I have done that before what a headach). Thanks for all the input. On another note, it seems to me that the ac compreesor is running all the time. I get water dripping from the front and rear whenever the controls are on. Any suggestions?

Thanks
Dean

 

Is it hot and humid where you are? It is not unusual for a compressor to work continuously under extreme conditions although ideally it should cycle on and off. The drips are normal if you have dual ac.

 

You may have cracked a plug as well. The same thing was happening to me. I just gave it one too many turns. I replaced the plug and the light went off.