04 Cobra running bad. PLEASE HELP!!!!!!

[modular89]

Hey guys. This is my first post but I have been a member for a while. I am having a big problem with my Cobra and I am at the point of pulling my hair out. The car is an 04 Mystichrome with 26k miles. I am having some driveablitity issues. The cars idles great and I can drive it as long as I do not get into boost. If I am just cruising the car does awesome but as soon as I do any type of tip in or acceleration the car will just backfire and fall on its face. I let out as soon as it does it but it feels like it will die if I did stay in it. It will do this at 1 pound of boost. I am stumped I use to be a Ford mechanic and I am at a loss.

LIST OF MODS:
2.8 kenne bell with low vacuum bypass valve running 25lbs boost
Comp Cam stage 3 cams with beehive springs
ARP head studs
SCT BA3000 MAF
JLT High boost intake
Glenns Performance 1000hp twin walbro pump fuel system
Fore fuel rails
80 lbs Ford inj
Magnafuel fuel regulator set at 42lbs baseline
NGK TR6 gapped at .025
AFCO Heat exchanger
Head cooling mod
Mac longtube headers, x pipe, magnaflow magnapacks
Spec 3+ clutch
Liberty input shaft
UPR tubular k member
Solid axle swap with Baseline Suspension
Strange Struts

Parts replaced since problem began:
MAF
Fuel pumps
fuel regulator
All fuel lines and filter
spark plugs
all ignition coils
TPS sensor
CAM and Crank sensor
Boost bypass valve
Had all exhaust valves and seats replaced
Tried a different shop for tuning

Quick history from when the problem started. The car ran great with just the 2.8 kb. I then added the comp cams and fuel system. I removed the motor and had Marvin Bridge from Bridge Racing degree the cams for me. I towed the car to Kurgan Motorsports where it did awesome on the dyno for 6 pulls. It made 710rwhp and 626ft trq. We backed the car out to test drive and the problem started as soon as we pulled out of the parking lot. He kept the car for a month and was unable to figure it out. I picked up the car and took it to BB&t Racing and they told me my heads were bad so I took the motor back out and had the heads rebuilt but the problem is still there. I am just tired of throwing money away at it. this has been going on since last summer and I need it ready For Bowling Green in October. Any help or advice would be greatly appreciated.

 

[Jimmysidecarr]

Have you or Kurgan data logged the critical parameters during drive cycles?:shrug:

What showed up?

I would at minimum try reducing boost with a pulley & belt change just to see if anything is different.

If nothing has been changed to cause the symptoms then something has failed or malfunctioned.

Or the tune is wrong for the boost level. Which would be very weird since it worked so good on the Dyno unless something was changed.

 

[modular89]

We did datalog while driving and nothing showed up with the short term fuel trims or the A/F ratio. Everything looks fine on the monitor. When I had the heads off I did not see any signs of damage in the pistons or cylinder walls. Is there anyway something could be wrong in the supercharger even though it only has 1k miles on it?????

 

[04cobradude]

i still think there is an electrical gremlin... i was going to call you the other day to see how things were going...

this is exactly what i didnt want to do.. charge you a ton of money to pull the motor apart and get nowhere... when i talked to you last, it sounded promising... if you are worried about something in the blower, just remove the blower belt and go take a drive...

 

[1HUBCAP]

I know this is trivial, but have you checked the plugs? Are they a colder plug than stock? Sounds like it is blowing the spark out, or maybe a bad coil? I can see you have tr6's.. Could they possibly fouled on the dyno? I am sure you checked all of this.. But this would be shit I would overlook myself.. Lol

 

[Jimmysidecarr]

Did your data logs include voltage at WOT @ different rpms?

 

[04cobradude]

guys, i tuned the car... just like i have done with HUNDREDS of 600-900rwhp twin screw cobras..

the thing was FLAWLESS on the dyno making over 700rwhp and no issues with drivability, idle, WOT at 25psi, etc.. when we backed the car off the dyno, the idle seemed to changed.. when we attempted to go for a test drive, ANY load you put on the car would result in backfire... meaning 2000rpm trying to take off.. it shot DUCKS out the exhaust...

as he has stated, he brought the car to BB&T and they diagnosed head issues and charged him to remove them as well as MANY other things... something i didnt want to charge him for since i felt pretty comfortable it wasnt mechanical.. I could have been the bad guy and charged him thousands to remove the heads, give him a line, and put it back together only to have a very pissed off customer..

I have kept in touch with him during this ordeal... i still think there is something ELECTRICAL that is causing issues.. we never removed or reinstalled the motor.. maybe a wire got pinched and over time has worn through?? i dont know..

 

[modular89]

I have taken the plugs back out and replaced them as well as a brand new set of Ford coils, but no change. I have rechecked compression and they are all around within 5 psi around 140.

 

[Jimmysidecarr]

The fact that it ran so good on the dyno leads me to believe any head work done was questionable, unless it was free.

I also think you have some kind of electrical problem. The chassis will twist a fair bit when backed off certain types of dyno ramps and could have dislodged a semi loose ground. I would check every single ground on the car by removing and closely inspecting them. I have heard of grounds that looked good but were corroded underneath when removed.

I would add a couple additional grounds as well.

Power interruptions will produce exhaust back fires, I agree that the electrics on this car need to be looked at.

guys, i tuned the car... just like i have done with HUNDREDS of 600-900rwhp twin screw cobras..

the thing was FLAWLESS on the dyno making over 700rwhp and no issues with drivability, idle, WOT at 25psi, etc.. when we backed the car off the dyno, the idle seemed to changed.. when we attempted to go for a test drive, ANY load you put on the car would result in backfire... meaning 2000rpm trying to take off.. it shot DUCKS out the exhaust...

as he has stated, he brought the car to BB&T and they diagnosed head issues and charged him to remove them as well as MANY other things... something i didnt want to charge him for since i felt pretty comfortable it wasnt mechanical.. I could have been the bad guy and charged him thousands to remove the heads, give him a line, and put it back together only to have a very pissed off customer..

I have kept in touch with him during this ordeal... i still think there is something ELECTRICAL that is causing issues.. we never removed or reinstalled the motor.. maybe a wire got pinched and over time has worn through?? i dont know..

 

[rtvickers]

Make sure you go through all of the connections. Maybe when you guys were unhooking it from the dyno something wiggles loose.

 

[04cobradude]

Make sure you go through all of the connections. Maybe when you guys were unhooking it from the dyno something wiggles loose.

since it has left my shop, it went to BB&T and had the motor removed/head removed... i think if it were something that "wiggled" loose, it would have gotten plugged back in by now..

btw, we dont unplug anything when hooking up to the dyno..

 

[04Cobra85]

since it has left my shop, it went to BB&T and had the motor removed/head removed... i think if it were something that "wiggled" loose, it would have gotten plugged back in by now..

btw, we dont unplug anything when hooking up to the dyno..

you have a pm

 

[Torch04RedSnake]

Check your alternator yet? Seems standard to check but i didnt see it mentioned

 

[04cobradude]

you have a pm

i dont have PM privileges ... just send me an email pls

 

[04cobradude]

Check your alternator yet? Seems standard to check but i didnt see it mentioned

all the logs on and off the dyno show all the sensors, voltages, fuel trims, timing, etc all normal

 

[04Cobra85]

all the logs on and off the dyno show all the sensors, voltages, fuel trims, timing, etc all normal

can you send me the log?

 

[04cobradude]

can you send me the log?

those logs are long gone... this is something that is from over 6months ago

 

[Ironhand]

The only way I can get 140 psi cold cranking compression with 8.5:1 is by having the intake valve close at 55 degrees ABDC.

With:
Comp 106360s at 120 degree Intake Centerline. That is a very retarded cam.
or:
Comp 106460s at 116 degree Intake Centerline. Not as bad but I would expect to see under 114 regardless.

Just an observation.

 

[04cobradude]

The only way I can get 140 psi cold cranking compression with 8.5:1 is by having the intake valve close at 55 degrees ABDC.

With:
Comp 106360s at 120 degree Intake Centerline. That is a very retarded cam.
or:
Comp 106460s at 116 degree Intake Centerline. Not as bad but I would expect to see under 114 regardless.

Just an observation.

i cant comment on any of the above... but i can say that Marvin Bridge degreed the cams in the first time and i would assume that BB&T degreed them in the 2nd time the motor went together... regardless, the issue started after hours on the dyno of flawless driving etc...

 

[04Cobra85]

Its got to be the tune. sounds like to me the load values are off. here is another guy haveing similar problems. if i had a log or the ecu i can take a look at it.

http://www.svtperformance.com/forum...5160-breaking-up-under-hard-acceleration.html