How can I figure out whats causing Car to redline at 6000rpms??

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I had that problem with my car. Since we had a baby my wife and I mostly use her car. Last week I was in my Cobra and while accerating onto the highway I decided to punch it and bring it up to redline (something I haven't done in a while). At about 6,000 it started to break up. I tried it again, same thing but not as bad. After 4 or 5 times it seems to have cleared up. But I am still going to change the plugs, wires and coils which are all original.
How many miles are on your car? Maybe it is time for plugs.

PS I know that the plugs are supposed to be gook for 100k but that is under ideal conditions and being driven like an old lady.
the cobra has 59k miles....and I'm pretty easy on her(well compared to most of my buddies). I changed the spark plugs, but that just helped the missfire. It still seems to be choking at 6000rpm. I thought maybe fuel was to blame...but I just installed the regulator and to no avail! Maybe its the spark, and I need new wires and or coils too :shrug: ! I'm really tired of the costly guess work, because it's not throwing a check engine light. So I don't really now where to turn. Let me know if you still have problems or anyother ideas.

i know how you feel man. I have tried everything except tearing down the engine. It has been a little over 2 years since this problem decided to rear its ugly head. The frist thing I did was run a scan and it pulled no codes at all. At first everyone said it was my gutted stock MAF. Artifically leaning out which made sense but, when I replaced it with a stock MAF it still did the same thing cutout at high RPM's like I hit my rev-limiter at 6000 instead of 6800. Next it was time to try the ignition. So I changed my plugs, wires and coil packs, and of course it did not fix anything. I did find oil in the plugs I forgot which one but I think it was on the drivers side. Well to make a long story short, next i tried, a adjustable fuel regulator which did not slove anything. Then I cleaned my IMRC's thinking maybe the butterflies were getting stuck, or the controller was crap they were fine opened and closed and were not too gunked up plus the cable looked almost brand new. So my next steps are to check the fuel pump (maybe heading south?), compression and maybe delete the IMRC's and get a chip. It is really strange, it does not cutout all the time either, be it cold day, hot day, with alot of people, with just me or when my car has been driven for more then 30 miles.. it just happens. I want to take a video and show people exactly what the problem is but to find a open stretch of highway in southern Califronia were I can take it to red in the first gears is impossible, legally that is. Have to wait for some track time. I hope someone finds the answer to this problem soon. I started my troubleshooting at "air" then I went to "fuel" now it is more "electrical" ( chip and tune ). I just changed my fuel filter to and it seems almost worse..heh go figure. It is hard to tell exactly what the source of the problem is, sorry for hijacking your post, SWTMUSTANGMAN but maybe we can all work together and find a fix !! please!

yah and I am going to check my seals next Venom 4.6!! Good Idea!! :nice:

"Oil fouled plugs will cause a misfire. Sounds like you have a bad seal somewhere. Check compression"

well i'm gonna try and take it to a buddies uncle who does nothing but mustangs. I figure when we hooked it up it has something to do with
the oil on the spark plug....I didn't see any on the actual electrode or even inside the wire, but that doesn't mean its not in there, or someplace else. Geez this is pissing me off! Anyother comments are appreciated.

does it seem to right when it hits 6,000, just sorta choke, still rev higher, but is extremely underpowered, missing and seem to take forever to rev? If it doesnt, i am 99% sure its your IMRC controller. Mine did the same thing shortly after 60k miles.

To somewhat understand what i'm talking about, check out my dyno graph from when the IMRC was bad.

well I wish my IMRCs were the problem, but seeing how I already deleted them I don't think so. Unless the computers trying to do something with the none pressent IMRCs cause, when I installed the deletes, I left the computer hooked up. I thought, but could be mistaken that your suppost to leave the IMRC computer hooked up to the deletes so that the OBD II doesn't throw a code and or miscalculates something else in compensating for the loss of runner controls?!?!? I hope and think this makes since. Does anyone else with IMRC deletes still have their computer hooked up to it still?? Good idea, never thought that might be a problem.

If you did delete's, You should have had a chip burned for it to turn off the IMRC functions in the EEC. This can cause issues especially if its trying to read the car as if they are there.. but if your loosing power like that on the top end, i doubt its the IMRC's since you dont have the plates there that could possibly be closed in the upper RPMs
took the cobra to Master-Tech Auto, and my buddies uncle scanned her. Well the master-tech scanner said the front 02 sensors are saying the car is running way to rich, and aren't giving proper voltage. So I'm assuming if this is true, then that would explain the reason why the car is ideling funny and throwing a check engine light. The computer is trying to back off the fuel, while my regulator is trying suck in the fuel! Well now I gotta buy some 02 sensors....but I'm still not sure as to why the car is redlining at 6000rpms. Anyone in the south austin area need a mechanic. Try Master-tech auto(512 268-5750). They do custom installations and fabrications. Anyother suggestions are welcome.

I have had the same problem for over a year now with my 01. However mine will still rev to red line but at 5500 to 6200 it will sputter and lose lots of power. Like said earlier it does it if it is hot or cold if people are in car or if I'm in it alone. It does it 95% of the time just sometimes its worse than others. It happened after I installed a denscharger and pulleys. I have went back to the stock air induction and this didn't help. I have had a ford tech look into it. He owns 14 mustangs some cobras some saleens and a roush. He makes sure no one else touches my car and he treats as if it was his own, so I trust him. He tested compression, changed coil packs and spark plugs. Nothing seemed to help. I also changed the fuel filter. I never thought that it might be the o2 sensers. I will talk to my tech and see what he says. Hopefully this is the problem for all of us.
no i haven't. I'd have no idea how to check for that.
What would cause the weak vavle spring?? Before I start ripping off the valve covers, can I get a better discription of what exactly to look for? I wouldn't bet on the weak spring, cause when I hooked it up to the DETERMINATOR scanner, at 6000rpms it says misfire....possibly a computer thing! Also I don't have chip burnt for the IMRC deletes...although it did this before and continued to do it after the deletes were put on! So im kinda at a brick wall untill I have more time to really get into the engine!
Here are some things I found out recently. On the DYNO engine was quiting at 6200, then sometimes 5800. Then a couple pulls to 6500. SO I drove with this limitation just shifting around 5600

7 Days later while practicing a hard launch on the street, she just quit. No fuel pressure at all. Changed the pumps, no difference.Changed the Fuel filter no difference.Found the intake full of fuel, large mess. Also vac hoses..

Problem was the fuel regulator. I think it was slowly cr@apping out for some time now, and it finally just broke.

With the new fuel reg she runs smooth as silk and hard everytime to 6800. Issue is gone.

Not sure it this helps any. Might change that Fuel Reg if all else fails.

Here's what I've changed so far:

-Coil Packs
-Fuel Filter
-Adj Fuel Reg
-Swapped back in stock T/B
-Ran some injector cleaner

I thought I may have fixed it last night after the fuel press regulator, it ran right up to redline smooth as ever during a few runs.. but then on the way back it sputtered once in 2nd on one run, and started to sputter and die at 6000 again on the last stretch.