dead miss after tune up~

S

shocar4

Registered User
I just installed autolite xp103's (.035 gap) and taylor 8.2mm wire....car runs great at idle and mild acceleration, but the minute that i get on the gas, it cuts out hard.....then goes....then cuts out ...then goes. I checked all my wires and everything is tight and on correctly~ HELP!
 
my wild guess is coil pack, just by having the same condition one time. Mine never threw any misfire codes, only did it on hard acceleration once I got past 3500rpms. Switched my coil pack out and the issue was gone.

chris
 
i have a spare coil pack that i will swap tonight....i tried changing out my DIS last night with no improvement~ thanks for the advice!
 
Assuming you didn't damage a wire, which is possible if using the OEM wires, then it sounds like the porcelain insulator on one of the plugs is cracked. Unfortunately it's hard to see, so you probably need to change all the plugs again. Not that it explains the misfire, but you don't need to gap the plugs that tight unless you are making a lot of boost...suggest .040" next time.

David
 
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Make sure firing order is right too - it will do similar results

PlugandWireLayout.jpg


-Tim
 
What David said. X2. If it was OK b4 the tune up, and this started AFTER the tune up, ALWAYS go back to the last thing you did/messed with. Also like he said, some of the plugs are a beech to get at in these cars. It is REAL easy to twist the socket and crack a plug. I have noticed too, that quality control just ain't what it used to be, could very well have had a bad plug, or wire, right out of the box.

Adam
 
David....now that you mention it i do remember hearing a cracking noise on one of my plugs during install...i checked it with my hand but didnt feel anything....i bet that is my problem!~
 
I'm going to throw this out there - check the DIS module. It sounds similar to what happened on the SHO that I had for a short time. Replaced the DIS and ran great again. May be worth checking into.
 
Melon said:
I'm going to throw this out there - check the DIS module. It sounds similar to what happened on the SHO that I had for a short time. Replaced the DIS and ran great again. May be worth checking into.
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already tried that...no change!~ also just checked firing order ~ all good~~~ when i get home and let the car cool down i will pull the plugs and look for cracks! i think i know when one it is! HOPEFULLY!
 
Switch it back to OE Platinum Plugs or plain old coppers... That WILL solve your problem. The SC will smother the flame front of the small electrode especially under boost. Been running Motorcraft Copper Plugs since the day I got it. Had the same problem when the dork at the auto supply insisted I run IR's. Kenny Duttweiler explained it to me and showed me first hand. All of his high boost motors run copper plugs specifically for the large flame front. The SC Bird only has max pf about 40k of volts. Most modern cars run 60-100K. The only other SLIM possibility is the crank sensor. I have 220k and the OE ignition module. They just don't go bad.
 
re-check your work, make sure the wires are snapped/clipped onto everything correctly.
 
David n wins the prize.....plug #4 had 2 cracks going down the sides....replaced with new one and bammmmmm runs like a scalled dog!!!!! Love this forum....thanks guys
 
shocar4 said:
David n wins the prize.....plug #4 had 2 cracks going down the sides....replaced with new one and bammmmmm runs like a scalled dog!!!!! Love this forum....thanks guys
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Glad you found what plug it was without having to change them all.

BTW, I disagree with the comments about not using IR plugs like the 103 XPs in an SC. I've been using various brands of the iridium plugs with stock ignition components for at least 10 years and never had a problem. I agree that using the copper 103s is fine for most SCs, but I've found the XPs are less likely to foul or misfire under high boost.

David
 
We had issues on the 3.5 EcoBoost with spark blow out, and had to tighten the spark plug gap from .032 to .028-.030. Completely helped it.

Don't know if this the issue, but I thought I would throw that out there.
 
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