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2007 Mustang won't go over 3800 RPM

I bought a gorgeous red 4.0L V-6 Mustang very cheap last week because it needed a clutch. I would not even pull the car. Little did I know that the clutch kit, including the slave cylinder and flywheel, was over $600. (But that’s another story.)

The car runs now, but will not go over 3800 RPM in any gear. It had NINE codes, which they cleared. I was told that they primarily pointed to the MAF sensor. I cleaned it with the recommended aerosol. I have driven it 20 miles, and the MIL has not returned, but the little wrench symbol has. The Manual says to take it to the dealer (of course). The car seems to run fairly well, with the exception of the low rev limit. It is a “fly by wire” set up, with electronic throttle.

The cleared codes were P0102, P0113, P0135, P0141, P0155, P0161, P0403, P0443, and P0446. They actually repeated on Autozone’s scanner. (My six year old Actron won’t link to this car for some reason. May be getting old like me)

Will the wrench symbol squawk a code too? I can take it back for a re-read.

What are your ideas on this situation?

Maybe the rev limiter function doesn’t know when the car is in gear. Does the clutch switch function as the “in gear” indicator?

@Rod Knox The clutch has to be pushed in to engage the starter. Is that what you mean?

All of the codes except P0113 came back when I started it this morning. It started with difficulty, acting like it was out of time. I stopped at AZ on my way to work this AM.

Guesswork can be far more expensive than taking it to a Dealer. It could be several things…A plugged fuel filter or exhaust system come to mind…

Check the fuses in the bussed electrical center (under hood fuse box?), fuse #47 supplies power to the MAF and oxygen sensor heaters. You may have pinched a wire near the transmission/bell housing.

When the engine controler detects an active fault some ECU’s lower the rev limiter.

i agree with nevada

My initial thought on this is that there is a loose connection or a connection that is unplugged and it is probably either at or very close to the computer. It is hard to imagine that all those parts failed at once. Maybe you had to unplug a wire bundle when you dropped the transmission and forgot about it, or had to tug on a bundle to get around it and it pulled loose at the computer.

After looking up all those codes and reading Nevada’s post I would say his diagnosis looks promising.

@Nevada_545 and all: You absolutey nailed the fuse. Now all I need to do is figure out why it’s blowing.


More later


I don’t see anything out of whack from the top or bottom. The #47 fuse blows as soon as soon as I start it, so it must be a dead short. I don’t think my local library has any factory manuals for anything this new. Can I find a wiring diagram online without paying a hefty fee?

Try They can be a good resource for about 20$. I hate them now but that is only because they spammed me for four years when I left them 7 years ago.

Were you able to see/reach the top of the bell housing? Fuse #47 powers all four oxygen sensor heaters, EGR and MAF. Also the brake pedal position switch and evap canister.

The paper version is a bit pricy but you might consider a Helms manual. These are used by Ford dealers but are worth their weight in gold when it comes to electrics. They have schematics that are laid out well (flow charts) with all connnectors being numbered and locations shown for those connectors.
This could allow one to unplug connectors until the fuse blowing stops and narrow the section of harness down where the short exists.

I think(?) the paper version is about 75 dollars with the on-line version being cheaper but it’s a good investment if you’re going to keep the car for a while. I’ve got several of their publications and they’re invaluable.

@Nevada Please excuse my ignorance of these new fangled cars. Is there a brake pedal position switch other than the brake light switch? If so, what is its function?

The brake pedal position switch is for the engine controler. The switch is mounted above the stop light switch. Some manufactures combined this into one switch, two contacts and four wires. The stop light circuit carries a load so it is kept seperate from the PCM circuit for reliability reasons.

This not an area I would expect to find a short.

@Nevada_545: My inspection mirror was cracked into a multivisioned picture of dubious worth. I finally broke down and bought another. Lo and behold, there on the very top of the transmission where I could not see, or feel very well, the wire for one of the O2 sensors disappears between the engine and the bell housing, and comes back out on the other side. You had it right, right from the start.

Thank you so much for your help. I’ll pull the tranny away and check for wire damage on Monday. RIght now I need to tend to some other business.

Thank you, thank you, thank you.

You’re welcome.

As Detective Columbo used to say, “One more thing”.

Since the car was in “limp” mode, the A/C and cruise didn’t work. I was not aware that limp mode would render those systems inop. I had checked their fuses, and found them to be OK. Now that all the codes are gone and the MIL is off, the A/C and cruise work perfectly. I guess that’s so car owners will get their cars fixed ASAP. Not a bad idea. Unfortunately most car owners don’t take advantage of this website. If they only knew…

Thanks again guys.

Our Windstar went through a similar thing, new plenum orings to the tune of $500. The dealer claimed they could read codes others could not, just a thought.