First off, I was not sure which forum section to put this under, but electrical seemed most likely. Please correct me if there was a more appropriate forum!

My truck is a 1990 F-150 with the 351. I was replacing the spark plugs last night, got it all wrapped up and everything squared away, and after firing the truck up I noticed a ticking noise. It was not there before I replaced the old plugs, and it is not at all loud. I can hardly hear it with the hood closed. It appears to be coming from the driver's side of the engine. It does not misfire when its idling, and it revs smoothly. However, while driving it is noticeably choppy and feels sluggish.

Any thoughts on what it could be? I used dielectric grease on the boots, but I did not replace the plug wires themselves, or the distributor cap. I am probably going to replace the plug wires today though, because the plugs I took out were not in good condition and its been a bit too long since I replaced them last. Its also worth noting this engine is less than years old. This is a frustrating problem because I've replaced the spark plugs on her before, so I'm not quite sure what I did wrong this time.

Help appreciated!

 

I have heard of strange things happening after replacing the plugs, and every time there is a quality control problem with the plug. One thing that comes to mind, the ceramic part on one of the plugs can be loose, and it can be rattling back and forth inside the metal part of the plug, causing a noise.

And check the plug wires like you said. Spark jumping from a wire to ground can make a ticking noise. You should be able to see this if you run the engine at night with the hood open.

 

I did just replace the plug wires with no luck. The ticking noise is still there. I'm considering trying to put one of the old plugs back in on the driver's side, where the noise is coming from, just to see if it is a problem with one of the plugs. Would an incorrect gaping cause this noise? Supposedly these plugs were pre-gapped from the factory, and the one I tested did appear correct.

The only thing I have not replaced is the distributor cap, which I thought didn't look too bad. I'm running out of ideas though. :/

 

If the gap is too wide, the spark will refuse to jump it, and look for another place to jump across.

 

Are you sure they are all tight?