I installed the Roush S/C this past weekend and on the street it runs like a beast. When I'm cruising on the Autobahn its another story. The first time on the Abahn I took it easy and cruised at 75 mph. After a couple of minutes I got the dreaded blinking check engine light. I checked it with the livewire and got the p0303 fault. It cleared away with no issues. Got back on the Abahn and it came up again around 70. I cleared it and coasted to the house. The next day I tried her out again with a bottle of octane boost and on the street no problems when someone wants taunt me. But back on the Autobahn I got a p0307. The following day I got a p0300 and the light stayed on versus blinking. I'm hearing no detonation, no sounds, nothing. so now I'm worried its getting worse since its involving multiple cylinders. I heard elsewhere I should check my spark plug gap. The roush kit comes with plugs that are one degree colder and are gapped at 45. Roush tells me that they think the plugs are not tightened to torque spec and that the plugs are ultra sensitive when not torqued. Anyone got any ideas?

 

First thing- have you identified what the error codes mean?

 

p0303: Cylinder #3 Misfire Detected

p0307: Cylinder #7 Misfire Detected

p0300: Random/Multiple Cylinder Misfire Detected

Looks like it's probably just the tune that needs some tweaking. It mite be running to lean or rich. Is it pinging? If it is be very careful until you get it right because pinging with a s/c is deadly.

 

I'm tracking the codes. There are no sounds whatsoever that I can detect. Everything seems to run good except for the light. Each time it blinked except for the random/multiple cylinder misfire in which it stayed on until I cleared it. Again, as long as I don't exceed highway speeds all is well. Redlight to redlight at WOT there are no issues.

 

Well, I can tell you from experience that you are going to have to replace all your plugs.

DO NOT EVER USE OCTANE BOOST UNDER ANY CIRCUMSTANCES.

While you say your problem popped up before you put octane boost in, adding the octane boost made it worse, not better.

Change the plugs and you're probably going to be all set.

 

And be sure you follow all the directions for the plugs, gap, torque, and no additives.

 

Even if you can't hear the sounds, it does not mean that detonation is not happening.

As others have said, new plugs, a tune, and no additives should hopefully put you back in business.

 

Autolite HTO plugs for S/C and turbos.. (one heat range colder) Find them on ebay site for around $80-$90 (mustang spark plugs) DO NOT touch the electrodes,do not use less than 91 octane, never use octane boosters!!(learned from experience)

 

The kit comes with HTO plugs. The gap is only adjustable when you have the special tool from Ford. A Roush engineer said he has never seen these plugs with a gap other than 45. He recommend that I install a new set of plugs. He mentioned he had the same problem and drove it for 3000 miles before he changed the plugs. As for the tune, I sent the PCM to Roush as stated in instructions and they reflashed and sent it to me. Do I really need to go through that process again. Doing this stateside is no problem but since I'm in Europe that means the car will have to sit longer.

 

well if you do change the plugs and it acts the same, at least you have a backup set of plugs.............Then you probably have to deal with Roush and the PCM?
When my plugs went bad I never got any codes.NONE. and they were misfiring badly for 1/2 tank of gas/100 miles....

 

I still have yet to get the plugs in the mail so I've been taking it easy on her lately. Yesterday I left a car show and when I started it up the failsafe mode popped up in the messenger center. I coasted back to the garage and pulled out the livewire to get any codes. I came up with p0222. When I turn the switch I can hear the throttle body trying to engage and the motor does turn but dies upon startup. I double checked the cooling and discovered that the coolant was dry in the roush supplied collant tank and a little below the cold fill mark on the factory tank. I topped the tank but now I cant get it to start. The failsafe mode still comes up and the code p0302 is now up and will not clear. I hit the fuel reset switch on the driver side. What else can I do?

 

You could try disconnecting the battery for a few minutes but I wouldn't do much driving on it until you get it figured out and fixed. Was the coolant level full when you did the install? I hope you didn't loose a head gasket. Is there any smoke coming out of the exhaust and have you checked your oil to make sure there's no water in it. If it was full that coolant had to go somewhere.

 

I had a fellow mustang show up and I swapped out the TBs. The car ran like a champ and actually showed a significant amount of more power than before. I guess the TB was an issue from the begining. I let her run for about 10 minutes and no codes or evil messages popped up. Luckily my tuner has a few TBs laying around in his shop that he is going to give me so the time I'm down will be minimized. Of course being free only sweetens the deal. With Race Wars kicking off on the 27th I should have plenty of time to get her up and running, dynoed, and throw on the steeda CAI for a bit more power!

 

That's great, glad it was something simple.