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

[crfrider16]

Like Ironhand said, the flatline fuel pressure is a big deal. As boost builds, fuel pressure must as well, or you will instantly start going lean, hence the popping and backfiring. What does your A/F look like when it starts to run bad?

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[utfan98]

I was going to say it seems like a boost/vacuum/fuel issue, not electrical or mechanically in the engine.

 

[04cobradude]

considering that i made over 700rwhp with his car and his fuel pressure rose on the dyno, i dont think that is/was the issue... now, if a pump failed (which was something we discussed at the time), then that may be an issue

 

[04cobradude]

"Power ratings are for naturally aspirated engines running gasoline."


I would double check the reference line and make sure all routing to the regulator is correct and fix that problem.

the regulator he has works great on power adder cars

 

[Ironhand]

the regulator he has works great on power adder cars

I never said it didn't. I just posted what Magnafuel posted about the horsepower rating.

 

[04cobradude]

I never said it didn't. I just posted what Magnafuel posted about the horsepower rating.

never implied you said it didnt... just stating that the regulator is not an issue.. again, it was fine for the entire tuning session

 

[Ironhand]

never implied you said it didnt... just stating that the regulator is not an issue.. again, it was fine for the entire tuning session

He said that the fuel pressure wasn't rising with boost. I can only think of 3 thinks to cause that, reference line popped off, bad regulator, or maybe a pump problem. The fact that you couldn't figure it out is odd and I'm positive its not in the tune.

Im curious if you guys tried backing the boost down and driving it on the street to see if the problem persisted?

 

[04cobradude]

He said that the fuel pressure wasn't rising with boost. I can only think of 3 thinks to cause that, reference line popped off, bad regulator, or maybe a pump problem. The fact that you couldn't figure it out is odd and I'm positive its not in the tune.

Im curious if you guys tried backing the boost down and driving it on the street to see if the problem persisted?

it wouldnt even drive in vacuum... you couldnt accelerate at all.. popped and backfired when you put a load on it

 

[modular89]

I have redone all the vacuum/boost lines. I bought a billet fox body vacuum block and rerouted everything. I am gonna borrow a friends A1000 pump tomorrow and see if that makes a difference.

 

[horspla2000]

Consider PCM issue. Also, I know it was mentioned above that PIDS and values "look ok" but compare mechanical fuel pressure to FRP value and ensure it does look good. Possible MAF issue?? (reading incorrectly just in that one little flow value) Its gotta be something small thats being overlooked. Interesting.......

 

[horspla2000]

At light load low RPM (assuming it idles ok and starts ok etc) I don't see plugs being the issue. Anythings possible, but.....

 

[modular89]

Well I put on an Aeromotive Pro Series fuel pump and it didn't change anything. I don't know where else to go with the car. It seems like I'm never gonna figure this thing out.

 

[04cobradude]

Consider PCM issue. Also, I know it was mentioned above that PIDS and values "look ok" but compare mechanical fuel pressure to FRP value and ensure it does look good. Possible MAF issue?? (reading incorrectly just in that one little flow value) Its gotta be something small thats being overlooked. Interesting.......

i swapped the PCM as was stated earlier in this thread... plugs were also changed..

 

[Zacharyx]

So leaking pump and bad alternator, did you ever get a chance to try and merge the lines from the rails before the regulator?

 

[2002BLGT]

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..

Just went thru this same thing but on a 88 fox other than it came in with similar crap going on , that had been hacked up by 15 different shops , numerous PCMs , chips , MAFs , injectors etc.

I found rust in the EEC relay , and ignition switch was separating , replaced fuel pump relay just for sh*ts and giggles , and still same thing , ordered a used 89 wiring harness from MPS autosalvage after the relays and BAM fixed it

 

[Zacharyx]

as i stated, i have tried so many things it's not even funny...

between bart and me, we have over 40yrs experience with mustangs... and then throw BB&T into the mix... thats alot of experience troubleshooting... hence, why i believe there is an electrical gremlin

Did the car have a pulsing in the lines between the regulator and and fuel rails while you had it on the dyno??

 

[sprstr1000]

Do you have adjustable cam gears?( maybe only degreed the first amd only marked the second time) maybe they backed them selves off. Thats if you have them?
Does sound electrical though

 

[sprstr1000]

Well I put on an Aeromotive Pro Series fuel pump and it didn't change anything. I don't know where else to go with the car. It seems like I'm never gonna figure this thing out.

Keep your chin up!!
It will work out eventually

 

[modular89]

It has the factory cam gears. The problem is so consistent. That's what bothers me because it has to be something broken. Most electrical problems are hit and miss

 

[modular89]

Just an update. I will be taking it to Dynospeed Racing here in Memphis for a tuning session to see if they can get this problem sorted out. Keep you fingers crossed for me!!!!!!!!