I recently changed the spark plugs and wires in my 2000 dodge ram 1500 sport and now my gas mileage is significantly worse(2 mpg). Changed to the Champion Copper Plugs and MSD wires, I have no idea why this would happen. Any thoughts as to why this is happening would really help

 

First things that come to mind...
1) Correct spark plug wire routing and making sure each one is COMPLETELY pushed onto plugs and terminals at both ends
2) Correct spark plug gaps on each plug
3) Correct park plug heat range
4) Any of the new plugs get cracked during install
5) Spark plugs installed tightly
6) Maybe a vacuum line got disconnected while working in there

It may help if you let us know what plugs and wires you were running, as well as the thickness of the new wires, and the specifics on the new plugs. Answers to the list above will also help. This will at least give us a starting point.

 

I tried the Autolites that everyone raves about and ended up with a misfire on #5, poor acceleration, and a drop in mileage. I went back to the original Champions and my truck runs great.

Just some food for thought.

 

I felt the same way about the 3923's or whatever they are. Champions work fine for me.

 

i wonder why some run good with the 3923's, and some donnt? mine runs fine on 'em.

 

As does mine. Mine also ran good on the stock Champions though too. I just wanted the temp range difference of the 3923's.

 

I once too went to a different brand spark plug. Almost instantly the check engine light went on for a misfire in cyl8. Talked to the shop and if you don't get an exact match on spark plugs (resistance, heat, etc) it will cause you problems. be carefull too, the plug wires could be of different resistance.

changed mine back to original equipment and never had a misfire since.

 

I've run autolite, Denso, Bosch, NGK, and Champion.

For me the NGK V-powers have worked the best. Champion Truck plugs were a close second. Autolites ran well for a while and then fouled up after about 1K miles. Densos and Bosch were the worse by far.

I never run platinum plugs and may try NGK iridiums at some point, but I'm so happy with the Standard V power, I don't know if it's worth the cost. If the Iridiums hold up to a MSD ignition, it might be worth it.

 

i am never using bosch plugs again. they dont seem to work in anything except a mower i have(have another mower w/the same motor and it runs like crap on bosch)

 

before blaming the plug design
be absolutely sure
something you did
is not causing a misfire

it is really easy to route the ignition wires
so that they cause 'cross fire'