[Haggis13]

The car idles fine after the top-end rebuild, but when it's given gas it just wants to die. Fuel pressure gauge is sitting around 34lbs when the car is running, vacuum line off 39.5-40lbs, but the needle is all over the place when you give it a shot of gas. The fuel pressure spikes when you open the throttle, and then drops off into the 20lb range. Is it supposed to be this way? WTF?

I originally thought the new MAF and injectors were dumping too much gas into the motor, so Steeda burned me some tunes which lowered the fuel delivery rate by 10% and another for 20%. It definitely idles better, and isn't running as rich but I still can't drive it, and I need to drive it 400 km next Monday for it's dyno tune!

ANY pointers or suggestions please!

FYI - new plugs, new cap and rotor, new fuel pump and filter, boost gauge shows the car pulling about 10 in of vacuum at idle. The tune Steeda gave me takes the O2 sensors right out of the equation as well...

Check out the attached video for the exact symptoms:

YouTube - Mustang fuel? Problem diagnosis vid

YouTube - Mustang fuel? Problem diagnosis vid

[fordrarities]

supercharger sounds awesome-i need one of those

back on topic, its definetly a fuel issue, on my dads turbo car it did a similar thing every time we gave it gas. it turned out that we needed to just adjust the FPR, but it seems as if you messed with all this already, so i dunno

[Haggis13]

What's really messing me up is the way the gauge jumps around - shouldn't it be more constant instead of fluctuating up and down when I give it gas?

This is the last thing I need to work out and it's driving me nuts. Anybody else had this issue and been able to fix it?

[1slo5.0]

Originally Posted by Haggis13 The car idles fine after the top-end rebuild, but when it's given gas it just wants to die. Fuel pressure gauge is sitting around 34lbs when the car is running, vacuum line off 39.5-40lbs, but the needle is all over the place when you give it a shot of gas. The fuel pressure spikes when you open the throttle, and then drops off into the 20lb range. Is it supposed to be this way? WTF? I originally thought the new MAF and injectors were dumping too much gas into the motor, so Steeda burned me some tunes which lowered the fuel delivery rate by 10% and another for 20%. It definitely idles better, and isn't running as rich but I still can't drive it, and I need to drive it 400 km next Monday for it's dyno tune! ANY pointers or suggestions please! FYI - new plugs, new cap and rotor, new fuel pump and filter, boost gauge shows the car pulling about 10 in of vacuum at idle. The tune Steeda gave me takes the O2 sensors right out of the equation as well... Check out the attached video for the exact symptoms: YouTube - Mustang fuel? Problem diagnosis vid

The fuel pressure will be all over the place when you give it gas if the vacuum line is hooked up. The pressure changes with vacuum. The higher the vacuum, the lower the fuel pressure.

How does it run with the supercharger belt off?

[Haggis13]

My old man came over and yanked the connector off the MAF, and the car ran perfect. It revved right up to redline with no sputtering or stalling. Plugged it back in - problem returned. We checked all the wiring, and it tested fine, so it must be the sensor. Piece of crap thing has probably been my issue all along.

Ordered a new SCT BA-2600.

At least I've learned about fuel pressure and how it's supposed to flow.

Thanks for the help everybody.

[1slo5.0]

Originally Posted by Haggis13 My old man came over and yanked the connector off the MAF, and the car ran perfect. It revved right up to redline with no sputtering or stalling. Plugged it back in - problem returned. We checked all the wiring, and it tested fine, so it must be the sensor. Piece of crap thing has probably been my issue all along. Ordered a new SCT BA-2600. At least I've learned about fuel pressure and how it's supposed to flow. Thanks for the help everybody.

Do you have a clear picture of the engine compartment so I can see the location of the mass airflow sensor? I had a similar problem on one of my own vehicles years ago. When I unplugged the mass air the car ran great. The problem was the mass air was too close to the supercharger inlet and the turbulence was screwing up the signal.

[Haggis13]

Originally Posted by Darrell Do you have a clear picture of the engine compartment so I can see the location of the mass airflow sensor? I had a similar problem on one of my own vehicles years ago. When I unplugged the mass air the car ran great. The problem was the mass air was too close to the supercharger inlet and the turbulence was screwing up the signal.

Here's some pics - the JLT CAI puts the MAF inside the passenger fenderwell, eliminating it from under the hood entirely.

[1slo5.0]

Originally Posted by Haggis13 Here's some pics - the JLT CAI puts the MAF inside the passenger fenderwell, eliminating it from under the hood entirely. Attachment 17425 Attachment 17426

I think its far enough away to eliminate turbulence as an issue.

[Haggis13]

Originally Posted by Darrell I think its far enough away to eliminate turbulence as an issue.

Yeah - it's one of the few used parts I bought off another Mustang guy. I'll pop the new one in Wednesday when it gets here and if that solves it, I'll tell him he sold me a POS, and that I'd like my money back.

[AdderMk2]

idk... maybe im just not seeing this correctly... but the MAF looks to be backwards...

[1slo5.0]

Originally Posted by AdderMk2 idk... maybe im just not seeing this correctly... but the MAF looks to be backwards...

You might be right.....I think the side with the flange is the air filter side. At least on the two that I have the flange is the air cleaner side.

[AdderMk2]

the flange IS supposed to face the air filter... I bet thats the ENTIRE problem

[Haggis13]

Originally Posted by AdderMk2 the flange IS supposed to face the air filter... I bet thats the ENTIRE problem

I am so f**king blind. The SCT logo has a big arrow under it which I assumed was airflow. It wasn't. Fine print stated the other direction. Flipped it around and BOOM it fired right up!

If you guys are ever in Ottawa, let me know - I'm buying the beers.

[1slo5.0]

Originally Posted by Haggis13 If you guys are ever in Ottawa, let me know - I'm buying the beers.

I'm on my way right now!!!!!!!

Glad you got it fixed.

[1slo5.0]

Good catch AdderMk2. The rest of us scanned right over that in the pictures and missed it.

[Haggis13]

Originally Posted by Darrell I'm on my way right now!!!!!!! Glad you got it fixed.

Me too - 1000% difference! Now the metered air is actually going into the motor. Ha ha! This'll go down as one of the stupidest things I've ever done.

You guys have no idea how happy I am. I would have spent another $300 for nothing.

I've ordered the keg - let's rock!

[1slo5.0]

Originally Posted by Haggis13 Me too - 1000% difference! Now the metered air is actually going into the motor. Ha ha! This'll go down as one of the stupidest things I've ever done. You guys have no idea how happy I am. I would have spent another $300 for nothing. I've ordered the keg - let's rock!

Everybody makes stupid mistakes. If it makes you feel better, I was trimming some of the metal behind the interior plastic in one of my cars once and slammed the sawzall thru the quarter panel.....3 times. There were three distinct sawzall blade tip holes in the driver side rear quarter above the wheel well. It had I'm a moron written all over it.

That shit happens dude, don't sweat it.

[Haggis13]

Originally Posted by Darrell Everybody makes stupid mistakes. If it makes you feel better, I was trimming some of the metal behind the interior plastic in one of my cars once and slammed the sawzall thru the quarter panel.....3 times. There were three distinct sawzall blade tip holes in the driver side rear quarter above the wheel well. It had I'm a moron written all over it. That shit happens dude, don't sweat it.

I'll try not to - I just cracked a beer and laughed at my stupidity.