Fuel Pressure on SS 725

[GT500-2007]

What type of fuel pressure are you seeing at idle with those cars equipped with the 725 KB option? On my 2007 the car typically sits around 50 psi at idle but the other day it jumped to 80 psi with about a quarter tank of gas left. Total miles since conversion about 2000. Wondering if I have an issue with the fuel system.

 

Also, maybe related or unrelated, has anyone experienced any hesitation (or what feels like hesitation) when cruising at a constant speed? Since conversion, when cruising at a constant highway speed I feel as if the car is hesitating. I don't hear the engine misfiring or changing revs but it feels as if the engine is ever so slightly shuddering. As long as I am pushing the accelerator no problems, it's only when cruising at a constant speed. I had the car checked out a few months back and the mechanic didn't find any probelms, The cars not throwing any codes. Any thoughts on what I should look at?

 

Thanks,

 

GT

[Robert M Keefe]

I have also experienced the same issues with both fuel pressure and hesitation at highway speeds.. I however don't let my gas fall below a 1/4 empty and run Shell 93 only.. Does anyone have some sound suggestions.

Thanks

Robert

[INDYSHELBY]

I have had the same problem there is an old post about this issue but Ive never found a good answer my car has run this way from the first road trip thats when its most noticable

[gtt500]

What type of fuel pressure are you seeing at idle with those cars equipped with the 725 KB option? On my 2007 the car typically sits around 50 psi at idle but the other day it jumped to 80 psi with about a quarter tank of gas left. Total miles since conversion about 2000. Wondering if I have an issue with the fuel system.

 

Also, maybe related or unrelated, has anyone experienced any hesitation (or what feels like hesitation) when cruising at a constant speed? Since conversion, when cruising at a constant highway speed I feel as if the car is hesitating. I don't hear the engine misfiring or changing revs but it feels as if the engine is ever so slightly shuddering. As long as I am pushing the accelerator no problems, it's only when cruising at a constant speed. I had the car checked out a few months back and the mechanic didn't find any probelms, The cars not throwing any codes. Any thoughts on what I should look at?

 

Thanks,

 

GT

 

[gtt500]

I do not have any fuel pressures issues but your driveability concern may be caused by air turbelence from your SS hood.I restricted some of my air intake from the hood and it resolved my issues.KB also offers a piece of screen to place in your CAI but I opted not do restrict my intake.

[EUSMCBOB]

FIRST YOU MIGHT CHECK AND SEE IF YOU ARE ONE OF THE MANY THAT SHELBY SCREWED UP AND PUT THE WRONG SPARK PLUGS IN--THEY WON'T NOTIFY YOU OR ACKNOWLEDGE IT SO YOU NEED TO DO IT YOUR SELF. CHECK THE 'TRACTION' THREAD.

 

I HAD SAME EXACT PROBLEM AND I BELIEVE THE KEY WORD HERE IS 'CONSTANT'. WHEN I WAS IN GEAR AND HELD THE THROTTLE EITHER CONSTANT OR VERY VERY GRADUALLY ACCELERATED I WOULD GET ERROR CODES PO104 AND PO171 WHICH ARE LEAN AND MAF. THE CAR WOULD START JERKING UNTIL I HIT THE GAS AND THEN IT WAS FINE. AFTER GETTING THE CODES RESET TWICE AND FINDING NO AIR LEAKS, BAD GAS ETC. I GOT THE SCREEN FIX FROM KB BUT DID NOT USE IT BECAUSE IT SEEMED SO COUNTER PRODUCTIVE TO RESTRICT THE FLOW.

 

I BELIEVE THE PROBLEM OCCURS WHEN YOU HOLD THE THROTTLE CONSTANT AT THE POINT THAT THE BLOWER WANTS TO KICK IN. IT'S A FINE POINT AND THE BLOWER IS GOING ON AND OFF IN QUICK SUCCESSION. AFTER TAPING INTAKE HOLES AND BLOCKING THINGS I FINALLY TOOK IT ALL OFF AND NEVER DRIVE IN THE LOWER GEARS AT A CONSTANT SPEED AND THE PROBLEM DISAPPEARED. IT WAS REALLY JUST IN HOW I WAS DRIVING THE CAR--OR WASN'T.

 

BOB

[hotrodric]

FIRST YOU MIGHT CHECK AND SEE IF YOU ARE ONE OF THE MANY THAT SHELBY SCREWED UP AND PUT THE WRONG SPARK PLUGS IN--THEY WON'T NOTIFY YOU OR ACKNOWLEDGE IT SO YOU NEED TO DO IT YOUR SELF. CHECK THE 'TRACTION' THREAD.

 

I HAD SAME EXACT PROBLEM AND I BELIEVE THE KEY WORD HERE IS 'CONSTANT'. WHEN I WAS IN GEAR AND HELD THE THROTTLE EITHER CONSTANT OR VERY VERY GRADUALLY ACCELERATED I WOULD GET ERROR CODES PO104 AND PO171 WHICH ARE LEAN AND MAF. THE CAR WOULD START JERKING UNTIL I HIT THE GAS AND THEN IT WAS FINE. AFTER GETTING THE CODES RESET TWICE AND FINDING NO AIR LEAKS, BAD GAS ETC. I GOT THE SCREEN FIX FROM KB BUT DID NOT USE IT BECAUSE IT SEEMED SO COUNTER PRODUCTIVE TO RESTRICT THE FLOW.

 

I BELIEVE THE PROBLEM OCCURS WHEN YOU HOLD THE THROTTLE CONSTANT AT THE POINT THAT THE BLOWER WANTS TO KICK IN. IT'S A FINE POINT AND THE BLOWER IS GOING ON AND OFF IN QUICK SUCCESSION. AFTER TAPING INTAKE HOLES AND BLOCKING THINGS I FINALLY TOOK IT ALL OFF AND NEVER DRIVE IN THE LOWER GEARS AT A CONSTANT SPEED AND THE PROBLEM DISAPPEARED. IT WAS REALLY JUST IN HOW I WAS DRIVING THE CAR--OR WASN'T.

 

BOB

 

 

Guys, I think KB has a new MAF housing out now that helps with this issue. It is now standard on the SS upfits. My car also had these symptoms, (except never the error codes) and was down at SA for unrelated reasons, While there they installed the new MAF housing (cast aluminum peice) and it runs better than ever. This may be the solution.

[INDYSHELBY]

Guys, I think KB has a new MAF housing out now that helps with this issue. It is now standard on the SS upfits. My car also had these symptoms, (except never the error codes) and was down at SA for unrelated reasons, While there they installed the new MAF housing (cast aluminum peice) and it runs better than ever. This may be the solution.

 

If that solved the problem and installed at Shelby the rest of us having problems , need to be notified and a replacement sent we all have spent alot of money for our SS upgrade and this is something older SS should have fixed

[MY500SS]

If that solved the problem and installed at Shelby the rest of us having problems , need to be notified and a replacement sent we all have spent alot of money for our SS upgrade and this is something older SS should have fixed

 

[mitch07ss0113]

 

good luck every time i read something on hear somebody has issues with there ss you would think sai would try to make things right for us that spent so much money on these cars its at a point they dont even aswer my emails any more i have two issues with hood and brakes they sent me a new hood but it is not the same hood on my car it is different there is no holes by air intake they told me i dont need them then they put wrong color calipers on now they want to send me used ones because they say mine are used now and hi have been trying to resolve this since i picked it up i dont understand why they sai stand by ther work very frustated

[vipereatr]

You know, my experience with SAI is that they work at being responsive. That's a high compliment in my book. I have had a few issues, and where SAI is the responsible party - they have come through. SAI is much more responsive than any car dealer's service center where I have purchased new cars over the years. If you think SAI sucks, try buying a Chrysler (or Buick or Saturn or Jeep) and take it in with service/warranty issues.

 

So - is there a new MAF housing available or not? Does anyone have a part number or how to buy? If it fixes the air flow issues I'll take one.

[mitch07ss0113]

im still waiting to hear from them its been a long time since i heard about issues i email and call all the time

[GT500-2007]

I didn't really start this post to gripe about the problem. For the most part SAI has been responsive whenever I contacted them directly with what I perceived to be an actual problem with the car. In this case I was trying to get some feedback from other owners to see if anyone else had a similar problem and what they did to resolve it. The hope was to short cut some steps rather than trial and error.

 

As for an update, I had the car out today. I live in South Florida and today was one of those days that you just have to take the car out. Blue skies, temps in the mid 60's and no humidity. Filled the tank with gas and the fuel pressure gauge dropped right back to the typical range I observed previously...lesson here, don't drive the car too much below a 1/4 tank of gas. Not sure what the relationship is between the pressure gauge and the level of fuel in the tank but there appears to be some relationship going on there.

 

As for the hesitation, no sign of it at all. Car ran fine all morning. This is probably the first time I ran the car hard when the temps outside were this low. Only thing I can figure is that there is some form of airflow issue related to air temperature and perhaps humidity (rare to get days in South Florida with humidity below 75%). I have what I believe is the 3rd generation hood (holes drilled in the bottom of the SS hood right above the airbox). Once the temp and humidity come back I'll try to play with the airflow entering into the CAI box and see if that eleviates the problem. I'll repost if I find anything useful. Until then I'll enjoy the cool weather and drive the car...