What Causes an Overboost Condition?

[OrionStang]

Thanks Keith, I found the block test on Youtube. Autozone actually lends them out, so Ill go that route. If the cats are bad, Ford will have to cover them under warranty since they are an emissions part(8 year, 80k mile warranty) and the S/C has a CARB number.

If the head gasket is found to be bad, I get to go to war with Ford over a warranty repair. The motor only has 34k miles on it, it has never overheated, and 8.5lbs of boost isn't gonna hurt shit.

[rick1987]

most of the time a blinking CEL means you are dumping raw fuel into the motor.

which would make sence since you are overbosting so the computer is trying to overfuel to keep up with the boost.

So is this a factory stock mustang from ford? or did you add the superchager?

I dont think the BOV would cause this but maybe the wastegate.

I am not very fimilar with Superchargers but I do have a Turbo ford 2.3

I run a stand alone Megasquirt system and I sometimes have a overboost issue that I correct with the throttle. I think it has to do with my Ghetto rigged boost controller.

Random misfires could be caused by the gap on your spark plugs. You may want to try tighening the gap, as when you get into boost the pressure can blow out your spark.

I had this issue for a long time and corrected it by installing the megasquirt and LS2 coil packs which have more spark power goodness!

but before that when I would get into 15-18# of boost I would have a violent misfire and the engine would misfire for a little bit. sounded as if I blew my headgasket. but it would clear. I think what happened is when I got into the boost, It blew my spark out and soaked my plugs with fuel and took a few seconds to un flood them, if that makes sence.

But if your car is not modified and under warrenty, have the dealer check it out.

[OrionStang]

S/C boost way different than turbo. Thanks for the try though.

Overboost is caused by backup somewhere in the exhaust, either a stuck closed exhaust valve (unlikely) or a collapsed/clogged cat.

[OrzechNJ]

im not here to give you any advice just curious what spark plugs u using lol

[rick1987]

Yeah, Im willing to bet the flashing CEL is the raw fuel part tho.

And random misfires could still be plugs. A clogged cat shouldnt make the motor misfire.

I dont know much about clogged cats tho, My little 2.3 has a 3" exhuast from the turbo to the back, no cat, and a hooker aero chamber muffler thats pretty straight through.

Just be carefull with the overboosting. Ive poped 2 headgaskets now. now I run ARP studs so i dont have to keep replacing the head bolts.

[rick1987]

im not here to give you any advice just curious what spark plugs u using lol

dont run platnuim whatever you do!

[OrionStang]

Iridium. A step colder than stock.

And nothing wrong with platinum, especially over copper cheapies.

[OrionStang]

Yeah, Im willing to bet the flashing CEL is the raw fuel part tho.

And random misfires could still be plugs. A clogged cat shouldnt make the motor misfire.

I dont know much about clogged cats tho, My little 2.3 has a 3" exhuast from the turbo to the back, no cat, and a hooker aero chamber muffler thats pretty straight through.

Just be carefull with the overboosting. Ive poped 2 headgaskets now. now I run ARP studs so i dont have to keep replacing the head bolts.

Sorry bro, but you are way off. A clogged cat on a supercharged V8 engine WILL cause random misfire codes. The screws make more boost than the exhaust can get rid off.

You are comparing apples to oranges in regards to your car and mine.

[rick1987]

My bad.

[Broke_Audio_Addict]

Iridium. A step colder than stock.

And nothing wrong with platinum, especially over copper cheapies.

Actually the type of plug you use should be dictated by the car and situation it's going to be in. One type of plug is not better than another they all have their uses. Also platinum plugs do tend to blow out easier in boosted cars because the electrode is way smaller than a conventional style copper plug. This should not apply with the low amount of boost you are tuned for but in a the over boost situation your are having 16 psi could for sure blow out a spark. I know you are using a iridium plugs and I'm not sure if this is true for them so I won't comment on that. I myself had a supercharged thunderbird and always had issues with platinum plugs fouling out after like 3000 miles and misfiring a lot under boost I was told by an old time mechanic to switch to copper plugs and he explained why so I tried it and bam no more problems.