I recently bought a 2009 mustang gt 45th anniversary. When I bought it had a generic brand cold air intake. I couldn't find a filter to replace the dirty beat up one that was in it so I decided to put the factory air box back in. After reconnecting the battery and buttoning everything back up I took it for a drive. Almost emediatly it put it into limp mode. So I pulled over and disconnected the battery and reconnected it and ended up with the same result. So I put the cold air back in and now it runs fine. It's mind boggling and I have no idea what to do other than buy another intake which I plan on doing anyways I just don't have the cash right now for the one I want, any input would be helpful.

 

I'd bet it also has a tune for the CAI that the original owner didn't tell you about. So the engine is expecting more air, but the stock air box isn't supplying enough.

 

Yeah I've considered this and it is a little faster when running with other mustangs same year model. It does have BBK pipe from headers back but I would only expect 15-20 hp in it's current set up with out a tune

 

If it's got a full exhaust and a CAI, I'd almost guarantee it's been tuned. You should've made him return the car back to stock, or lower the selling price to allow for money that you'll have to spend. You can take the car to a dealership, and they can tell you if it's been tuned and can put it back to stock for you. But given the exhaust and intake, it'll probably still give you a CEL unless you wanna buy the parts to return it to stock. Otherwise you'll probably have to buy a tuning device and get it tuned for the mods.

 

That's what I figured I would have to do, I've already got a factory airbox but none of the exhaust components. But I did buy it from a dealership and may be able to get them to do it. I do have another question though, does anybody know the top speed in third gear for the 2009 gt's? Cause I've ran it around 110 at somewhere about 6300 rpms. I'm asking cause I've never owned or seen a car that hasn't been geared and been able to do that.

 

Idea 1:
Try to properly clean old air filter.Put intake and filter back on.
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Idea 2:
Go somewhere local that sells K&N filters (they have a lot of dealers) or similar if you can find one. Select a filter that fits the end of the intake and put everything back on.
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The bottom line here is that for now you are stuck with that particular intake because of your tune. Get a filter on the end and put it back on.

 

The stock 3.31 rear end should do that.
3.55s would be closer to 6500rpm.

 

I haven't done the math, but I'm sure it should do 110 mph in 3rd.

 

I did go by all the auto parts stores in town and none of them carry a filter with the pipe end large enough, I havnt measured it but it's probably 5 or 6 inches I tried a ford racing filter but the inlet doesn't match up. I guess I'll have to Ty and clean it. I just don't know how to tell if its an oiled filter or dry filter. The thing is pretty filthy, I appreciate the help guys.

 

Can you post a picture of the intake and filter?
Maybe we can tell what it is.

 

Yeah as soon as I'm done with this pt test I'll get that up here