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Discussion Starter · #1 ·
I have a '99 SHO that has been running great until last year when I discovered that I could not go faster than about 105. I know that car did not have a speed limiter because I have driven over 105 many times in the past. Other than this problem the car seemed to be running fine.

More recenlty my check engine light came on and I took the car to the local dealer. They discovered that the butterflies in 2 of my short intake runners where sticking. The problem was fixed by replacing a bad butterfly control module. The dealer thought this may fix the speed limit problem I was having but was not able to test it for liability reasons.

When I got the car back it did have more power. When I had the chance I gave the car a test and floored it. I got the car up to 120. I thought that my problem was solved. That was about 2 weeks ago. Yesterday I tried again and discovered I could not go over 105.

I went back to the dealer and talked to the mechanic about what could be done to fix the problem. The mechanic was not sure what it could be. He did mention that since the Ford Firestone recall, dealers have been reflashing computers whenever a new image was available for the car being repaired. He also said that customers have reported coming in for maintenance or repairs and discovered that their cars now had speed limiters when they previously did not. I wonder if my car was reflashed with a speed limiter.

I would like to know if anyone here has had the same problem I am having and if anyone has heard of this problem before.
 

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Discussion Starter · #3 ·
I can't be a hard speed limiter because I have gone 140+ in the car. This is only a recent problem in the 4 years I have owned the car. If anything it would be a software speed limiter possibly installed by reflashing my computer.

Basically the car acts like it is misfiring at 105. It feels like a speed limiter. You can feel the engine jerking as it hits some upper limit and then shutdowns and then try to start up again only to hit the upper limit again.

As I said in my original post, last week the car hit 120 with no problems, which makes me think it's not a speed limiter, or at least a faulty one.
 

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Here's some info for you. The secondaries are all connected. If two of them are sticking, they all get stuck in that position. And you don't have short and long intake runners, like the V6 Yamaha. The V8 Yamaha has a "tumble port" design, meaning that there are only eight intake runners. Opening the secondaries allows air to reach the second intake valve, but does not open a second set of intake runners.

If the secondary butterfly plates are sticking, it's only a matter of time before you ruin another IMRC control box. At some point, the intake should be disassembled and the butterflies should be soaked in Berryman's B-12 or a similar cleaner. Once they are moving freely, your IMRC control box and cable will have alot less stress on them and won't be in danger of breaking.

It sounds an awful lot like you have a speed limiter now, but I'd fix up the IMRC for good first and see how things go.
 

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I have been having literally the EXACT same problem with my 99 recently. I replaced the fuel filter and checked fuel pressure and everything checked out. I am going to reset the computer and hope that fixes it. If not, then I am getting a chip to fix the problem, as it is most likely ECU-related. I know for a fact the secondaries are working. Kinda hard to miss them with the K&N cone.
 

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Discussion Starter · #6 ·
SixFoFalcon, I did not that. The way the mechanic was talking it sounded like there 2 sets of runners. I guess I misunderstood. I will have to email the mechanic and ask if the problem with the butterflys will persist and ask him to provide more detail on the repair. Hopefully it was fixed right the first time. If the butterflys are not completely fixed and are still sticking depsite the repair this could be the cause of the problem.


99V8SHO, did you recently have the car serviced at the dealer? If so, have you asked them if they reflashed your computer? If I find a fix for this I will post here.

*wonders where I could buy a chip*
 

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Originally posted by skanjo@Jul 17 2004, 02:58 PM
*wonders where I could buy a chip*
Look in our Performance section under EEC tuning. Alberto of American MotorSport has experience with SHOs.
 

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I took my car to my trusted SHO mechanic. He said that there was a tsb issued by Ford for an ECU reflashed for cars built 04/99 and later. Mine never had that. I don't think that has anything to do with it, that may only hinder performance and not do anything about this speed problem. I will reset the ECU today and go for a drive, see if I can get faster than 100-105.
 

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Discussion Starter · #9 ·
I was able to get the car to 110 and then 115 yesterday on 2 occasions. I really don't think is a spee dlimiter problem. Perhaps it still has something to do with the butterflys.
 

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Are you driving in O/D or 3rd? In O/D, the acceleration will slope off dramatically at about 115mph. If you switch off O/D and hold it to 3rd, you can keep on going up to the limiter (144) or faster, if you have the limiters removed. But don't do that. :p
 
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