Recently installed new plugs originally gapped at 54 as the chilton book suggested ran horrible . So i re gapped plugs to factory setting of 60 running better but there is still a miss in the motor could this possibly be a vaccum problem or am i missing something? It doesnt miss all the time very random. I didnt replace all the boots when i did plugs could this be my problem?

 

I'll take a stab at an answer with another question to the board. How does the knock sense/control work on these engines? I ask because on my motorcycle it is done by sensing the impedance between plug electrode and ground strap. If it's in a known good range everything is OK; if not the computer determines that the engine is pinging and retards timing. Screwing with the gap and/or plug type would affect the impedence measured and could trigger false events that would activate knock control => your intermittant miss. ???

 

The knock sensor on Fords works nothing like the motorcycle one. Factory setting for spark plug gap is between .052 and .056 inch. If yours were gapped at .060, and I'm guessing you checked them as they were removed, they were worn. They started life at the above spec. Most likely .054 which is what we set them to when we change them at work. You could have a bad coil pack, boot, vacuum leak. What engine and how many miles? Let us know and you'll get more pinpointed help.

Robbie

 

This is unlikely to be a spark plug issue. Tell us under what condition your engine misses. Cold, hot, idle, light load, heavy load, constant miss, occasional miss, only after drinking?

 

Its occuring when engine si cold and hot more frequently under heavy acceleration cruising speed is fine. Its a 99 5.4 94,000 running wonderful up until this new plugs i bought were gapped at 60 i gapped them at 54 when i put them in and it ran horrible so i changed them to 60 that helped but it didnt get rid of the miss

 

What type of plugs are you using? I had a similar issue after installing a set of Bosch Plats. I thought it was the coil packs and after replacing all 8 coil packs $$$, the problem was not fixed. Tossed the Bosch and used a set of NGK V-Power (non-plat) and it is fine. Give it a shot. It should only cost you about $12. If that doesn't fix it then you have a bad coil. Buy a new one ($50) and swap it out one by one until the motor runs good.

Anthony

 

I was going to suggest a coil problem also, since I have changed my plugs and know how tricky the whole procedure can be. It might not be a bad coil as much as a coil that is not making good contact. I don't know about the regular Bosch Platinums, but I have the Platinum +4 and don't have any problems. Also, I don't recommend the +4s. I didn't see any kind of power or mileage gain.

 

The plugs I put in are bosch plats. My parts store was out of Autolites and motorcraft so i went with the bosch instead of champions i figured that was a good move guess i was wrong! As far as the coil pack is concerned cylinder 4 was my original problem so i changed the pack that seemed to cure it for a while but now its missing ramdomly with no idiot light on so im stuck?
plugs gapped at 60 im gonna get some motorcrafts or ngks this weekend should i gap different? is there a way to test the coil pack to see if current is good hard to see any arcing 4 inches down ya know? thanks for trying to help out the rookie!

 

Like many have said on this board, it is best to go with OEM...

 

Im slowly figuring this out! VERY GOOD ADVICE OE812

 

My personal experience. I have not tried Bosch Plats in my truck but I tried them on two other cars we own and both ran like sh&t! As soon as I replaced them with NGK's, no problems.

 

The brand of the plug is not the cause, you have to remember new is not always good. Those plugs can have a mfg. problem or a slight crack in one where you cannot see it, they can be easly dammaged in shiping and storage. Can you imagine how many people through that box of plugs around and how many hard hits they took from germany or Japan or even china before you put them in youre truck???? It's a wander any are good.

 

Well the good news is Its been narrowed down to cylinder four the bad news is thats the one I had the most problem getting to any suggestions other than taking the fuel rail off Im sure im missing something easy. Just want to thank everyone for the help. VUK

 

OK new plugs coil packs all tested ok as far as i can tell all are making good contact and i still have a miss im really starting to think its something deeper than a plug problem? Do any of you fellow for fanatics have any suggestions. help please

 

When is the miss? just a slight "miss" at idle? kinda feel the car shaking slightly when in drive, foot on the brake? sometimes a very light version at idle?

is your gas mileage affected?

is your acceleration affected?

How did you come to the conclusion it was cyl 4?

and no, u dont need to remove the fuel rails to get to any of your plugs... i did mine in 45 mins the 2nd time ive ever tried to mess with that motor... and i did it with nothing but 2 socket extensions, a spark plug socket and a ratchet....