2001 SVT Cobra Low Fuel Pressure 28lbs

[01CobraFlow]

I recently brought my car to a mechanic to have my acceleration studder taken care of. When i'm on the accelerator on third and fourth gear it studder's before taking all the way off. I definitely noticed a lack in power, so my mechanic looked into it for me. 28lbs for a fuel pressure rating is definitely kind of low, anyone have any ideas what it could be? I just had an oil change / fuel filter and oil filter change a couple months back. I had a small oil leak which was taken care of of this week, along with putting in a new gasket. My mechanic also told me I have a small antifreeze leak which should be fixed after this o-ring gets put in. My mechanic thinks it might need a new fuel pump, any ideas?

 

[procharged420]

Hey sorry to hear about your issues. My first question is how did your mechanic measure the fuel pressure?

At idle, target fuel pressure is around 40psi differential (i.e. measured with a scan tool). However, if you measure using a fuel pressure gauge on the schrader valve you will measure around 30psi assuming that the car is making around 20" Hg manifold vacuum at idle (20" Hg at 60F ~ 9.8psi).

If he used a schrader valve your pressure isn't far off and I would check your FRPS or MAF first.

Also for kicks check that fuel filter out to be safe. If your not shuddering in 1st and 2nd I wouldn't jump to the fuel pump right away...

 

[01CobraFlow]

Thanks! I will let my mechanic know anything else to be looking at? He used a fuel pressure gauge to measure it.

 

[Brutal Metal]

my fuel rail reading on the auto meter gauge is about 10 psi lower than actual with 21 vacuum. I bet your mechanic went right off the rail so pressure isn't your issue..

 

[Black*Death]

Seems many Cobras have a stutter when accelerating. Many things can cause it. Mine was due to a bad IAC valve and leaking EGR valve.

Basically had a vacuum leak...

 

[01yellercobra]

When was the last time the plugs were changed?

 

[shurur]

I'm getting the same thing..usually on hwy....stutter on accell..more like bog on down shift accell.

Changed the plugs.
Fuel filter is next.

Research points to egr, dpfe and vac tubes...but tired FP is also suspect as well.

But no code is showing yet.

I also get a high pitch whine or whistle off the line in first. Do you hear that on yours as well??

 

[01CobraFlow]

A little but it's most likely from my 4.10 gears, I've heard they make a whine sound kind of like a supercharger. Everyone always thinks my cobra's supercharged. The stutter doesn't happen in 1st gear, I pull hard on first into second which is about 85% good, third and 4th i notice that it stutters more often. The thing about the stutter is that it'll stutter then it'll pull through afterwards. It's not a permanent stutter it will move past that but I definitely feel like it makes my car lack on power.

 

[shurur]

A little but it's most likely from my 4.10 gears, I've heard they make a whine sound kind of like a supercharger. Everyone always thinks my cobra's supercharged. The stutter doesn't happen in 1st gear, I pull hard on first into second which is about 85% good, third and 4th i notice that it stutters more often. The thing about the stutter is that it'll stutter then it'll pull through afterwards. It's not a permanent stutter it will move past that but I definitely feel like it makes my car lack on power.

Sounds like my same problem.
After fuel filter, I'm looking at egr, dpfe and the
rubber vacuum tubes. I still think the whistle or whine is a clue.

Others threads are saying cats could be partially clogged..others say O2 sensors....

No code is being thrown yet.....but behavior is consistent at least.

OK..I'm gonna lurk on this thread, unless I fix it.

Good luck.

 

[01CobraFlow]

Thanks Man, I already changed the fuel filter as well. I also did notice when it's stuttering the exhaust sounds really muffled and distorted. You can hear and feel the stutter, is anyone else able to hear the distortion in their exhaust.

 

[01yellercobra]

FWIW, when my cats went they didn't cause any kind of stutter. The car just felt down on power. About the time I was trying to figure out what was going on my car got really loud and all the power came back. Pulled the cats off and they were completely gutted.

 

[shurur]

Recent development today:

I am finally throwing a code: P0153: O2 ckt bank 2
Though I don't know what it means yet.

I'm not sure how this might relate to OP and do not want to jack this thread.
I just thought I should share this recent development.

OP...I hope you throw a code soon too!!

 

[01CobraFlow]

So, I got my cobra back from the mechanic yesterday and they've managed to fix most of the stutter. It rides really clean now, it still stutters but only in the 5500 rpms and up. They said my spark plugs were going bad, so they replaced them with oem spark plugs. He told me that he thinks my car needs to be dyno tuned, he thinks it might be able to fix the rest of the stutter. It definitely has picked up some power from the plugs, even though it still stutters a little at those high RPM's it still has a really nice pull.
On another note though, today I was driving around and I noticed my car was kind of acting up. It wasn't stuttering but instead the car was randomly bogging and at random times, I really think it might have something to do with my MAF. The reason I think so is because in my previous cobra I installed my CAI by myself and I didnt have the MAF tightened enough so it came loose one day and my car was doing the same exact thing. The problem is that the MAF is placed really weird on the CAI I have on my new cobra, it runs into the fender. I don't think it has been maintained in some time. It might need to have some cleaning done to it, which could also help fix the rest of the stutter.