P0300 random misfire with Roush SC

[ugstang17]

This is what my plugs are looking like

That tells a different story. As mentioned octane booster has been present in the fuel mix. Is that your doing? Or is that how the plugs look after pulling them the first time? Are you currently running octane booster? Are you sure the car is on the Roush default tune? Often times a previous owner will keep the tuner device and sell the car. So you need to know if the car was retuned or if the previous tuner just ran octane booster in the car.

Before you can resolve the issue the unknowns need to be answered. The dealer should know the name of the name of the person (hopefully if not taken in on auction). Otherwise your next recourse of action is to verify that the Roush package is original - meaning no upgrades to the package such as TB, FI's, pulley, etc. Once you have verified that the ROUSH package is in tact you can -- for a price -- contact a Roush dealer who can assist you with getting the correct Roush tune back in the car. This will verify the correct tune giving you cloture to that and then begin chasinghte problem further if the problem continues. Just regapping the plugs without proper 411 will not resolve much IMHO.

Should you find that there are mods such as a larger TB, upgraded FI's, smaller pulley -- you will need to get the car retuned for those modifications..........assuming you cannot find out if the car was retuned and to what level.

I bought a modified 17. I verified the cars tune and the modification list before purchasing. I made the dealer provide me the flash tuner that the car was flashed to from the original owner in the closing. I will not buy a car that does not have paperwork on modifications and the original flash device if it has been retuned.

Once all of this has been resolved and you know what you actually have it may be as simple as running the octane booster in the fuel OR retuning. Should everything be factory ROUSH including the tune and you have this verified, then replace the plugs and gap to 0.026 - 0.028" as mentioned.

Helps save time and eliminate guessing when you provide CORRECT, ACCURATE, AND COMPLETE 411.

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[Trapper43]

That tells a different story. As mentioned octane booster has been present in the fuel mix. Is that your doing? Or is that how the plugs look after pulling them the first time? Are you currently running octane booster? Are you sure the car is on the Roush default tune? Often times a previous owner will keep the tuner device and sell the car. So you need to know if the car was retuned or if the previous tuner just ran octane booster in the car.

Before you can resolve the issue the unknowns need to be answered. The dealer should know the name of the name of the person (hopefully if not taken in on auction). Otherwise your next recourse of action is to verify that the Roush package is original - meaning no upgrades to the package such as TB, FI's, pulley, etc. Once you have verified that the ROUSH package is in tact you can -- for a price -- contact a Roush dealer who can assist you with getting the correct Roush tune back in the car. This will verify the correct tune giving you cloture to that and then begin chasinghte problem further if the problem continues. Just regapping the plugs without proper 411 will not resolve much IMHO.

Should you find that there are mods such as a larger TB, upgraded FI's, smaller pulley -- you will need to get the car retuned for those modifications..........assuming you cannot find out if the car was retuned and to what level.

I bought a modified 17. I verified the cars tune and the modification list before purchasing. I made the dealer provide me the flash tuner that the car was flashed to from the original owner in the closing. I will not buy a car that does not have paperwork on modifications and the original flash device if it has been retuned.

Once all of this has been resolved and you know what you actually have it may be as simple as running the octane booster in the fuel OR retuning. Should everything be factory ROUSH including the tune and you have this verified, then replace the plugs and gap to 0.026 - 0.028" as mentioned.

Helps save time and eliminate guessing when you provide CORRECT, ACCURATE, AND COMPLETE 411.

So quick background on the vehicle it was turn into the dealer from the original owner a upper 60s to 70yr old man, the kit was installed by another dealership when he bought it back in 2017 which lucky for me, my buddy works at that dealership and knows the guy that did it he takes picture of every vehicle he does.

But that been said at some point during the guy owning the vehicle, he had a aftermarket tune put on that vehicle along with other modifications shortthrow shiftier, Cat back exhaust, steeda subframe supports, lowered, JLT3.0 canister and after market radiator. The pulley is the correct pulley for the phase one along with the fuel injectors. I know the tune was replaced with the Roush tune for Phase one, do to the fact the guy cracked piston #4 and the dealership I purchased it from put a new motor in the vehicle. I have all the paperwork showing that it was replace, what i think what happened was when they got the new motor they just never switched the plugs out for the high performance once.

Yes i had ran one tank of octane boost thru the vehicle to see if that would help which it didn't change anything, So today I will go purchase the correct plugs for the vehicle.

 

[AZ_whippleS550]

So quick background on the vehicle it was turn into the dealer from the original owner a upper 60s to 70yr old man, the kit was installed by another dealership when he bought it back in 2017 which lucky for me, my buddy works at that dealership and knows the guy that did it he takes picture of every vehicle he does.

But that been said at some point during the guy owning the vehicle, he had a aftermarket tune put on that vehicle along with other modifications shortthrow shiftier, Cat back exhaust, steeda subframe supports, lowered, JLT3.0 canister and after market radiator. The pulley is the correct pulley for the phase one along with the fuel injectors. I know the tune was replaced with the Roush tune for Phase one, do to the fact the guy cracked piston #4 and the dealership I purchased it from put a new motor in the vehicle. I have all the paperwork showing that it was replace, what i think what happened was when they got the new motor they just never switched the plugs out for the high performance once.

Yes i had ran one tank of octane boost thru the vehicle to see if that would help which it didn't change anything, So today I will go purchase the correct plugs for the vehicle.

so the brown orange tint is from the octane booster its mostly harmless aside from possibly making the plugs last a shorter amount of time. but plugs are cheaper than engines so fine by me.

 

[Trapper43]

so the brown orange tint is from the octane booster its mostly harmless aside from possibly making the plugs last a shorter amount of time. but plugs are cheaper than engines so fine by me.

Thanks for your help man, this is my first Mustang with a blower on it so I have some stuff to learn about it.

 

[AZ_whippleS550]

Thanks for your help man, this is my first Mustang with a blower on it so I have some stuff to learn about it.

No problem happy to help.

 

[ugstang17]

So quick background on the vehicle it was turn into the dealer from the original owner a upper 60s to 70yr old man, the kit was installed by another dealership when he bought it back in 2017 which lucky for me, my buddy works at that dealership and knows the guy that did it he takes picture of every vehicle he does.

But that been said at some point during the guy owning the vehicle, he had a aftermarket tune put on that vehicle along with other modifications shortthrow shiftier, Cat back exhaust, steeda subframe supports, lowered, JLT3.0 canister and after market radiator. The pulley is the correct pulley for the phase one along with the fuel injectors. I know the tune was replaced with the Roush tune for Phase one, do to the fact the guy cracked piston #4 and the dealership I purchased it from put a new motor in the vehicle. I have all the paperwork showing that it was replace, what i think what happened was when they got the new motor they just never switched the plugs out for the high performance once.

Yes i had ran one tank of octane boost thru the vehicle to see if that would help which it didn't change anything, So today I will go purchase the correct plugs for the vehicle.

Bingo. FYI if the tune is a mail order and not a Lund, VMP, or PBD tune I would recommend going one of those routes. Never had any issues with these three guys and I have used all three at one time or another. The car will have the power it is supposed to with one of these tuners behind the scenes compared to the Roush tune which is very conservative and overly protective.

Yes replace the plugs one step colder and regap to 0.026 - 0.028". Lund has me gapping my current 93 setup at .026". PBD preferred 0.028" with their tune on the same setup. Keep it on 93. The octane booster is good only for the purposes of asurring the tuner that good fuel is in the tank when tuning in the event false knock rears its ugly head. First thing they like to blame is fuel. If you are ahead of the game this eliminates that and takes time out of the tuning process. I run 93 with a boost-a-pump on an 80mm pulley (2300 TVS unit not a 2650) and never pulls timing on SHELL SU2000 premium.

Last your engine cylinder temp is fine btw. Don't confuse that with engine coolant temp (ECT) which is not on the display but can be seen on a datalogger.

 

[Trapper43]

Swapped the plugs last night fixed the Gap on everything .028. Holy crap what a difference in the vehicle after that, she is running much better and has the power it should have.

I will have to checkout those tunes, to replace the roush one.

Thanks again everyone for the help

 

[ugstang17]

Good to hear. Always nice when a person provides feedback after asking for help. two thumbs up to ya.

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