97 Cobra with issues at higher rpm's - Mustang Evolution

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Old 09-27-2013, 04:35 PM   #1
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Question 97 Cobra with issues at higher rpm's

Hey guys, This is my first time posting, I was directed here by a fellow mustang friend. I'm hoping I can get some help/advice.
I have a 97 Cobra that has a stumble/hesitation on the top end. It runs pretty good up until ~5,500+ rpms, and it just seems to stop pulling, rpm's don't want to climb, and the motor sounds significantly different. It doesn't always happen, but probably 80% of the time it does at full throttle. If it's not full throttle, then it seems to go to redline without problem.
I have changed spark plugs, o2 sensors, MAF sensor, checked coils/wire with an adjustable spark gap tester, vacuum test, and did a compression test which a cheap parts store gauge (1 at 185, a few around 195-200, and a couple around 205-210, I can check my sheet to be sure if you want) and I've removed the IMRC's and cleaned them twice! (was throwing p1519 code for a while, not anymore, and didn't notice a change in performance before or after) the only code I am throwing now is p1414 which I think is "Secondary Air Injection System Monitor circuit High Voltage", I believe this is due to the secondary air injection system not being hooked up, but I wouldn't image it would have this kind of effect on the car.
I'm running out of idea's and it's driving me crazy. I'm starting to lean towards a bad tune (I got the car like this, no idea what tune is on it, but I'm sure the ecu isn't stock, no cats and no rear o2's but it doesn't throw a code) Also, any idea's if American Muscle's Bama team can take care of this if it is a tune, or should I get a custom tune from Bob (BobCat) in Park Hills (STL)? It will be a similar price, and I get a handheld from AM (don't currently have one for this car) but I'm concerned they won't be able to fix it, and I'll have to take it in for a custom tune and spend as much money again.
Please let me know if you have any idea's, or if you think of something I overlooked!

Also, for some background, this has been happening since I got the car, (I did a motor swap, put a motor/trans from a wrecked '97 into a '97 cobra body, I made sure to swap the computer as well, so it has the same one that was with the motor) Only mod to the motor that I know of it C&L CAI.
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Old 09-27-2013, 07:53 PM   #2
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Welcome aboard TJ. Should be able to get some good info on here
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Old 09-27-2013, 07:57 PM   #3
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Thanks, I certainly hope so thanks for recommending the site to me. I'll have to get some pictures uploaded of the car. I'll try to get a vid of the issue soon to help explain it.
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Old 09-28-2013, 12:25 PM   #4
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Well hopefully someone chimes in with some info
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Old 09-29-2013, 03:45 AM   #5
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A reputable dyno shop should be able to track it down. Your set up is way beyond my capabilities to trouble shoot. Simple tasks to eliminate would be fuel/spark. Injectors, fuel delivery & coil, wires, plugs. -Thats what comes to mind. Interesting, & I will follow thread. Good luck!
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Old 09-30-2013, 07:17 AM   #6
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It sounds like fuel is cutting off at wot...take it to a tuner...bama might help but best way is a hands on tuner...
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Old 10-01-2013, 04:11 PM   #7
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Thanks for the reply's! I know that was a page-full to read, let me specify a bit more that I forgot.

The car is pretty much stock as far as the engine/drivetrain goes, with the exception of a C&L cold air intake, and a few gauges hooked up.

I have a fuel gauge, boost/vacuum gauge, and a narrowband gauge.

The fuel seems to read fine, and jump's up when I get on it, and the needle doesn't jump around even when the car starts acting up. This is a electronic gauges, and the sensor is in the fuel rail.
The boost/vacuum gauge reads good vacuum, and drops down to 0 when I open the throttle all the way. Unless I have a misunderstanding, that's expected.
The narrowband reads very close to lean, or barely in the lean conditions at pretty much all times. A friend that has watched it while I drove said that when I got up in the rpm's it started reading a little richer, instead of going more lean. I could still have an issue running to lean, but idk how accurate that gauge is.

Leaning heavily towards a tune, just haven't decided which direction to go. I'm thinking about bama for simplicity, and to have a handheld, but I'm sure I'll get better results from a dyno tuner, it would just be more difficult to get the car there. But that's probably what I should do. lol.
Thanks again guys, I'll keep you updated.
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Old 10-02-2013, 09:22 AM   #8
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A dyno tune will put the air/fuel ratio on target throughout rpm range. It's worth the time and effort. Typically cost $500.00. You essentially are paying a modest $100.00 for the custom tunes. A SCT handheld is $379.00. You walk away with your stock tune plus 3 others. I went with a 93 octane performance tune which is perfect for any driving situation & a 87 octane performance tune. Both increase performance, fuel efficiency, ect...
In Virginia, Maryland, & DC area, Excessive Motorsport is the place to be. Scott does the tuning.
Good luck.
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