P0300 random misfire with Roush SC

[Trapper43]

Hi all,

So i have a phase one Roush SC on my 2017 Mustang GT. When I get on it around 4500 to 5k, you can feel the misfire any ideas.

I just picked this vehicle up from the dealer, the owner before me blow the motor up dealer put a new short block in it. Vehicle has 14000 miles, motor around 350 to 400 miles.

It also has cat back exhaust on it. Dealer replaced the old cats with new ones and new 02 sensors.

Also is it normal for this vehicle to run hot, its running about 190 to 210 degrees?

Thanks for any help or suggestions

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[AZ_whippleS550]

make sure they gapped the plugs for boost and make sure they are the right plugs for boost not the stock plugs.

 

[Dominant1]

Properly gap a new set of plugs, if you still throw a 0300 do a crank relearn. I had the same issue and this is what I did and it fixed it to the point where car has never run better then it does now. I have the crank relearn feature on my sct x4 tuner..As far as the temperatures are concerned, if your talking engine temps thats normal if your talking iat’s that’s way to hot.

 

[SSG 5.0]

My car threw that code while on stock plugs. Change to ngk and gapped properly, the code was gone and ran healthier without any hiccups. These guys here knowS what they’re talking about and helped me out.
Good luck and let us know what happen next.

 

[Avispa]

Motrcraft sp522 gapped to .030 says JDM Engineering.

 

[Trapper43]

Thanks guys so I got a chance to pull the plugs today completely wrong part in it. It is just the standard plug from the factory. According to the part number it doesn't match what roush says.

After looking at the plug it look like it is running super lean the plug is rust brown. I will try figure out how to get a picture on here.

 

[AZ_whippleS550]

octane booster can make plugs look brown/orange this is a few thousand miles of boostane.

 

[Dominant1]

Thanks guys so I got a chance to pull the plugs today completely wrong part in it. It is just the standard plug from the factory. According to the part number it doesn't match what roush says.

After looking at the plug it look like it is running super lean the plug is rust brown. I will try figure out how to get a picture on here.

get a set of ngk 6510’s gap them to .25 or .26

 

[ugstang17]

get a set of ngk 6510’s gap them to .25 or .26

Gap at 1/4 inch? That's what .25 is.



OP - Assuming the car is a 91 - 93 octane setup - verify gap is .028" on a stock Roush tune with a heavy drag on the feeler gauge. Also make sure the correct (1 step colder plug) was put in the car which would be the NGK 6510. If not pick up a set and gap to .028". I run 0.026" per my tuner Lund. Doubt relearning the crank trigger has anything to do with this. I've always run .026 - .028 on my 93 octane setups at 10-12 psi boost. On my first two 8 psi setups I ran .030". These were all 2.3L displacement setups. Contact Roush direct if you want FIRST HAND knowledge on what to set them to and WHAT speak plug they spec on their setup.......assuming you are running their stock tune. Gap if anything may need to be closer to .026". This is assuming you are experiencing spark blowout and not another problem.

 

[Stymee]

Looks like Boostane was ran on those plugs
Orange Ash, I won’t run MMT additives in my car

Good ole Shell 93 (Splash of Race gas with no MMT) for me

 

[AZ_whippleS550]

Looks like Boostane was ran on those plugs
Orange Ash, I won’t run MMT additives in my car

Good ole Shell 93 (Splash of Race gas with no MMT) for me

Yeah honestly I don’t really care about the orange stain might cut down the life of the plugs a little but I don’t mind for the safety it provides and boostane is cheaper than race gas and works great as an octane booster. At the track I run straight race gas not boosted pump gas.

 

[Dominant1]

Gap at 1/4 inch? That's what .25 is.



OP - Assuming the car is a 91 - 93 octane setup - verify gap is .028" on a stock Roush tune with a heavy drag on the feeler gauge. Also make sure the correct (1 step colder plug) was put in the car which would be the NGK 6510. If not pick up a set and gap to .028". I run 0.026" per my tuner Lund. Doubt relearning the crank trigger has anything to do with this. I've always run .026 - .028 on my 93 octane setups at 10-12 psi boost. On my first two 8 psi setups I ran .030". These were all 2.3L displacement setups. Contact Roush direct if you want FIRST HAND knowledge on what to set them to and WHAT speak plug they spec on their setup.......assuming you are running their stock tune. Gap if anything may need to be closer to .026". This is assuming you are experiencing spark blowout and not another problem.

My bad lol
Lol .025 or .026.. lol dont think the car will start at 1/4 inch gap.

 

[Trapper43]

This is what my plugs are looking like

 

[Dominant1]

I changed my plugs 4 weeks ago the old ones looked like that also. I use lucas octane booster every tankful. Its normal for them to be red using octane booster..

 

[AZ_whippleS550]

This is what my plugs are looking like

yeah that looks like octane booster staining

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