replaced spark plugs, now car runs like ****
 

hey guys,

i replaced the spark plug wires on my 98 mustang GT engine (71K miles, 4.6L) with Plantinum bosh 4+. and the car ran like ****. then i took the bosh spark plugs and replaced them with the motorsport spark plugs, and my car still runns like ****. when i say that my car runs like **** i mean that my car jerks a lot. before the spark plug replacement, my car ran perfect.

do you guys have any suggestions? are my ignition wires busted, or are the plugs bad, or what could be going on?

PS: the jerking is really bad between the idle and 2000 rpm range. in higher rpms i notice significant power loss.


Any advice would be helpfull,

thank you,
avdo

Did you put new wires on too, or just plugs? Check all 8 wires for a good snap when you put them on, or just pick up some Motorsport 9mm's. :D

As far as plugs go, I run champion coppers (forget the model #) at .054, and they're great. No need for platinums on these motors.

The bucking, hesitation and power loss all sound like you are getting bad spark of have a dead cylendar. How'd the plugs you pulled out look? My stock wires were bad, one didn't snap down, and it sucked real bad up on top. I thought it was my fuel pump, but it turned out to be a wire.

I had the same problem. Believe it or not, I had a bad number 7 wire from MSD.

I am 99% sure the problem lies in the wires. Either their seating or quality.

you also might want to double check your gap setting. Make sure its where you want it, and don't let the electrode hit when you slide the plug in.

I bet money you got the wrong wire on the wrong plug:o

Depending on how bad the jerking is you either:

If it's jerking but not to the point where it's about to die
A: Bad plug/wire

If it's jerking and the idle is jumping up and down enough where the car is close to dieing.
B: You put a couple plugs on the wrong cylinders.

im guessing that too, if thats not the case, my second guess is bad wire somewhere.

IMO my recommendation for plugs is Motorcraft AWSF-A22C's they are 1 heat range colder than stock, that helps keep detonation down, if your sc'd or using n2o id go with the AWSF-A12C's thoes are 2 heatranges colder. NA gap around .054 nitrous/sc'd id go .035

THANKS FOR YOU HELP GUYS
 

good news everyone, I fixed it.

it was a bad wire #7 from MSD. surprizingly enought.


I just wanted to thank you guys for you support,
avdo,

weird, both bad wires from MSD were number 7......

would gapping a copper plug @ .060 be a bad idea ive heard alot of people boasting it adds a little power on 4.6s ....would the stock ignition even jump that gap?

It might. Its only .006 bigger than the stock gap. I'm going to mess with the gaps next time I change the plugs. I might start by splitting that diff and go with .057 or there abouts.