1998 4.6L enigine has two coil packs that run four plugs each. one cylinder is misfiring.how can you test to see if one of those coil pack is bad. also, if the coil is bad, wouldn't all four cylinders being controlled by that coil be misfiring?

 

Not necessarily , with those I would pull the wire and boot one at time while it's running and listen for your idle to jump or fluctuate - try to pinpoint first that way first. If unsuccessful , use the force code procedure.

Good Luck..

 

Each coil pack has two colis, each of which fires two cylinders in a waste-fire configuration.

A coil failure will often take out two cylinders at a time.

Steve

 

is your check engine light on? if it is a code will tell you which one is misfiring.

 

cylinder #3 is misfiring. new plugs, wires and coil have been installed all of which help for a couple of days but the misfire came back. injectors are all good. engine is 4.6l with @ 150k miles. seems to run fine when first cranked up but after @ 5-10 miles of dirving it starts to shudder pretty bad especially under a load like going uphill. any ideas would be appreciated.
thanks

 

Check wiring harness ,Check all wiring in direct relation to #3 - look in service manual proper pin locations, if chasing becomes difficult. check volts, continuity.

Swap coils / components around in order to pinpoint or eliminate possibilities. It's a little trickier now. What brand plugs you running in there?

 

hold the spark plug in ur hand and crank it up. see if that coil is firing its the quickest way to find out..takes less than a milisecond

 

#8 misfire... First I was thinking it was the coil, then I started thinking maybe I have a combination weak fuel pump +#8 misfire code... In the past my truck has thrown misfire codes when there was no detectable misfire whatsoever and that is why I started thinking I possibly have a problem other than ignition. I know I need to be a little more scientific - get an actual fuel pressure reading, etc. but I have limited time and resources available at the moment. Anyway, I have been thinking it's a bad coil again... I wish I had the answer and I'll let you know if I find it first... BTW mine has 90k total mileage with about 10k on new oem plugs and wires...

 

You did replace everything correct - both pacs all wires /plugs. If the integrity isn't in order it will screw with yuh. Its a freakin computer thing.

Sometimes misfires detections don't come at all points of the drive cycle. The come at random certain load points. You can force a light by pushing your motor during a misfire episode - you have to push it hard for accuracy.

It'ds difficult to pinpoint sometimes , i just replace it all because it's cheap on ebay.

 

i had the same problem went threw 2 coils havent went threw anymore because a wise man on this site interduced me to a little thing called diolectric greese.

 

Very wise - if you don't use it , everything is just a big waste of time. I tested with new boots with and without the grease - you can actually see carbon burnouts (spark jump)in the untreated boot lol - did this when I went threw a chitload of misfire problems.. - made me a believer. Truck runs better than ever since doing that last spring.

 

I loaded mine up with it and now when it kicks down hard coming out of the turns it feels like it wants to pull the fricken front wheels up off the ground...

 

LOL , I heard that more than twice now. When all COP's are up to par , power increased. Nahhh, Its makin the same power it came with , you just have to have all the candles lit at the same time to really feel it . I know I gained between 10-15 horse , but I honestly don't know what made the biggest improvement with my trucks motor because I upgraded quite a bit at the same time. New Factory COP'S,Boots(brass/copper config), Harness,Drivers side upstrm O2, New Type 3 19lb injectors(upgrades) K&N Filter, Flowmaster series 50 Muffler only (the shorty , not the SUV) -New plugs as well, Brembo Rotors, Carquest Ceramics. whewwww. I did all that to her before firing up (waiting for the injectors,had time to kill lol)

I couldn't believe all the low end gain - high end around 3400 rpm -freakin hang on!! lol. It's not a racer haha , it's just allot faster then it use to be.

It's going to faster yet around January.