03 Mustang Cobra Problem I need Some Help!

Hey Guys.. A friend of mine has this 03 Mustang Cobra pushing 600 HP Supercharged and all that. this is the problem, car started missfiring so he replaced all 8 plugs and that did no difference ask me for help so I did a smoke test to look for vacuum leaks found none on bank 2 the first 2 cylinders do not fire I checked compression all around 145 psi swapped coils around, nothing! swapped injectors around still nothing. on bank 1 same thing first 2 cyls won't fire. but, If I close the fuel line to bank 1 fuel rail then bank 2 fires all 4 cyl so you would think low fuel pressure right? so do I. but on my scanner it shows that we have 40-42 psi fuel pressure on the rail (sensor is on bank 2 rail). so what gives? I know that his injectors are huge even the rail are huge he's got two fuel pumps one of them from a ford gt he says. I wonder if 40 psi is not enough? maybe it's got pressure but not volume?
Give some ideas please!

 

How have you verified that the cylinders are not firing?

Is it misfiring all of the time, idle, acceleration, cruise?

If the fuel pressure on that system(electronic returnless) remains at 40-42 psi, then it has enough volume because if you use more that you supply, pressure drops. If your scan tool gives you the option, look at the Fuel Pump commanded percentage. If it's above 50%, then the FPDM is commanded 100%, so you might have a supply issue in that case. 75% is the default number sent to the FPDM that shuts it down due to a fault(high current, open circuit, etc) I would make sure you have the correct fuel pressure with a manual gauge to eliminate the Fuel Rail Pressure sensor.

That system has 2 pumps in the tank; why is only one of them a GT pump?

I would also try to do an acceleration run to attempt to read a plug; at 600+ hp, it's also possible the heads have lifted it the tune was a little too aggressive or fuel pressure dropped causing a lean out under load. Coolant would indicate this.

I would pull a coil from a cylinder that is not firing and put a spark tester in it(make sure you ground it) and make sure that you do indeed have spark. Once you have verified spark and fuel, the only thing left is compression and leakdown and valve operation. Spin the engine over with the starter and see if it cranks evenly (with the ignition disabled to prevent it trying to start)

 

It's missing all the time
I Tested the cylinders by unplugging the wire from the coil and also lifting the coil up away from the plug I can see and hear the spark flying in to the valve cover (Ground) and also unplugging the injector

 

Since it's missing all the time, I would check the fuel injector with a mechanics stethoscope to verify mechanical as well as electrical function, then check compression and leakdown next. It's probably the least labor intensive.

If I understand you, you have spark to each cylinder, verified by a spark so on the cylinders that are missing, pull the plugs and see if they are fouled and by what(fuel, coolant, carbon, etc.)

keep in mind that some calibrations disable the injector when a misfire is detected for a certain amount of time to prevent catalyst damage, so you may have to get creative in your diagnosis. Clear any DTC's and then run the engine.

 

I'll look for that option on my scanner what FPDM means? Fuel pressure driver module?

His fuel rails have no schrader valve to hook a manual gauge and his fuel lines are like 5/8 hoses

I'm not sure if only one pump is a GT or both

 

Yes, It's got spark on each cyl I have pulled the plugs that were not firing and they looked wet. now I'm not 100% sure if it's wet with gas or oil like new oil it's clear

If I touch the injector I can feel it clicking

 

Now, Why is that when I close the fuel supply line(Hose) to Bank 1's fuel rail the cylinders that were not firing on bank 2 starts to fire?

 

FPDM= fuel pump driver module. controls current to the fuel pump and is mounted in the trunk. Supply voltage is sent to the pump(s) and the ground is varied based on demand.

unfortunately, you will need to find a way to check fuel pressure, but with a dead miss, I think even if you have a pressure problem, finding the cause of the miss needs to take precedence.

How much of the fuel system has been modified and has this system been run successfully or is this a new build?

 

that's hard to say. that was the reason I was suggesting to manually check fuel pressure. If it has custom rails and lines, where is the Fuel Rail Pressure sensor?

If you have a mini torch, you can try to burn off what is on the plug, oil will smoke, fuel will flame and burn, coolant/water will steam and sizzle.

 

the fuel pressure sensor is on the bank 2 fuel rail between the first and second cyl

 

I don't know how much it was modified other then the lines,rails and injectors
the set up was working fine he has this for a couple of years now. He said it all started when he was sitting in traffic the temp gauge was around 210F and then when the traffic started moving the missfire started

 

Any chance you got a bad tank of gas?

Clamp off the side without the pressure sensor on it while monitoring fuel pressure on the scan tool to see if it rises when the miss on those cylinders goes away. That could indicate a supply problem.

Gold coolant also looks and feels oily to the touch so it may be hard to tell from oil on a spark plug, but it will eventually dry and look chalky while oil will not.

One other option is a chemical block test that uses CO sensitive liquid that changes color if CO is present in the cooling system. Some local parts stores sell them if you don't have one.

 

Going to do that and do the torch test on the plugs. I'll let you know monday what happened.
Thank you very much for now:Handshake you gave me some really important info

 

Anytime.

One thing I thought of, is the lines. Depending on what type of lines you have, they really shouldn't be clamped or pinched off. It can damage the inside liner in the case of the steel braided teflon or harder plastic type. I had mentioned that thinking of the fabric braided softer rubber type but I don't actually know what you have. caps on the fittings would be much better.

Another thought was that if the you have injectors that are leaking significantly, it can bleed off into the ports and flood those cylinders to the point of not firing at all so it might not indicate rich on the scan tool. That could also explain the running with one side blocked. We had a car that ran some sort of race fuel that broke down the inside liner of the fuel lines and all of the pieces ended up in the fuel rails. That car had some very strange symptoms as well and it wouldn't be that hard to run fuel out into a container from the fuel rail to check.

Good Luck!:Handshake

 

Id move the coils and injectors to different cylinders just to see if the misfire moves.