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I have a 91 Mustang, 302, 5-speed, trick flow twisted wedge ported aluminum heads, trick flow stage one cam, vortech supercharger running 9 pounds of boost. I am not too familiar with superchargers but willing to learn all that I can. Here is my problem. I can drive the car easy and it runs perfectly fine. but when I get on it, it starts cutting out (kind of sputtering with a ENORMOUS loss of power)when my boost gauges gets right at the zero mark. It does this EVERY SINGLE TIME. Initially I thought I was not getting enough fuel, so I changed my pump of 95lph to a 255lph. also changed spark plugs and wires. still runs like garbage. when I first had the charger hooked up and then ran, the car would haul a**. Anyone have any suggestions that would help me troubleshoot the problem? Need my power back!! Thanks guys!
 

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You say that the car used to run really well, and now it doesnt, what did you change? Other than that, the next place I would look at is the carb (or fuel injection); not necessarily that you arent getting enough fuel, just that it may not be working properly.

Adam
 

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I am not that familiar with 91 Mustangs. Is that car computer controlled? Is it fuel injected?

I think Adam is correct, it is either a fuel distibution problem or the computer is doing silly things like changing the timing (knock sensor?), maybe a bad oxygen sensor? If it is injected you might want to check your MAF (mass air flow) sensor as well. I am not sure how that work with a blower.

In any case I would park it until you figure it out. If it is going lean and that's what's causing it to run bad, you are risking ruining your engine.

Do you have a boost referenced fuel pressure regulator? If so that would be an area to look into also if it is not increasing the fuel pressure when you start making boost this would cause a lean condition.

If you provide some more information I am sure you will get to the bottom of it.

Royce
 

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Discussion Starter #4
thanks for the replies guys. that is what i thought also...that it is a fuel problem. but the new pump did not solve it. the car is fuel injected. how exactly could i check the MAF?? How could i tell if it was not reacting correctly or not. also if it was something like that, wouldn't i be getting a check engine light error? also you wrote about the fuel pressure regulator. since i have not changed anything else, could it be running less pressure now than before?? or just going bad?
 

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If your fuel pressure regulator is boost referenced. It increases fuel pressure as the boost increases. If the line that goes to the regulator is off or kinked it could cause the problem you are seeing.

Does the car sound the same as before? No hissing? Backfiring? Popping?

As far as the check engine light, are you sure it is even connected?

I suggest you pop the hood and check all vacuum/boost hoses carefully. See if you have a line running to your regulator if so that would be your boost reference, make sure it is not damaged.

Since you went to a different pump, I would think the fuel pressure would have needed to be adjusted as well.

Do you have a fuel pressure gauge? Is it where you can see it while driving? If so watch it to see what it does when the car starts acting up.

If you do a search of MAF (mass air flow sensor), someone posted a simple test to check them. I don't remember the procedure of hand right now.

Royce
 

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Did you install bigger injectors?I have never charged a car,do not know anyone who has,but you may need to go with bigger injectors to compensate the extra fuel demand.
 

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If you did not upgrade injectors and retune the computer, I have to assume the kit is using an FMU. If so that would be were I would start looking. Otherwise, the MAF is a likely candidate. We need DETAILS of the EXACT setup to help.

Chris
 

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Discussion Starter #8
ok guys, it seems i may have mis-stated something. EVERYTHING on the car has been the same for months on the car and it was running perfect. Perfect for months. Then I first noticed the fuel pump began to sound funny when i turned on the car. At that point is when it began to act up. so then I changed the fuel pump. But that did not do it. no the car does not sound the same either. it does when i am cruising, but when i try to get on it it starts popping and then it also sometimes backfires, but it always pops and sputters when i stomp on it. and i know for sure that the check engine light does work, cause one time it did come in but it went out when i eased off the accelerator. and the car does have a FMU. HELPPPPPPPPPPPPPP!!!!!!!
 

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One thing to understand is that an FMU is designed to raise fuel pressure exponentially with boost so that the injectors will flow more fuel than they are designed to flow. For this to work, the fuel pump has to be able to generate enough pressure to make the FMU work since they are pushing close to 100psi in some situations. If it is not working properly, the engine will go lean when it hits boost. If your car is backfiring when you get on it, it sounds to me like it is going very lean. EFI engines act alot differently than carb engines in my experience when something is not right. When I was tuning my turbo/efi setup I had bad lean popping at first untill I got my WBO2 working.

I would check that the FMU boost line is hooked up and is not cracked or something. I would also change the fuel filter to be safe. Be VERY careful with this. EFI fuel sytems are under high pressure. It is a good idea to unhook the fuel pump and crank the car so that the injectors will bleed off any pressure and you will not get an atomized gasoline shower.......can you say fire hazard?

Chris
 

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Discussion Starter #11
ok guys, i will check the fuel lines, fuel filter, maf unit, and also the fmu unit to see if one of these can possibly be the culprit. i will keep you guys updated. thanks
 

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Please Help Me!

Hey guys i just joined this site with the hope that somebody could give me some good advice on my vehicle. I have a 2003 Grand Prix GTP with ALOT of work done to it running about 360rwhp and 430hp at the crank. I have recently been having problems with my supercharger which is a Eaton m90. I installed guages which i i consstantly monitor, typically i run on idle 20 IN/HG of vacuum pressure and i average 9lbs of boost at 6000k RPM. Recently my guage is reading 11 IN/HG Vacuum at idle and about 4-5lbs of boost. I havent noticed any serious performance declines but the readings of this guage is kinda worrisome. I can only figure that it could be a possible leak in the vacuum line? Since what i've heard if its a supercharger bearing i would notice a much bigger decline in performance. PLEASE any suggestions or tips would be much appreciated!!!
Best regards to all,
Steve
 
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