Help me figure this out... please!

[10thAnnvCobra]

At full throttle my car sputters. It runs just fine otherwise. Throughout the RPM range it seems to run just fine. Under boost it is fine. When on a roll and I mash it to the floor it sputters at the upper RPM with the stock boost gauge pegged. During normal driving, even aggressive driving it runs fine. The sputtering is only when I floor it. I like to do 2nd to 3rd gear pulls and feel the power. Now I feel and hear the sputtering. No more mashing it until I can correct the problem. Fuel? Spark? I just don't know. :??:

Any ideas? All my mods are in my sig. Thanks. :burnout:

 

[rtomlin]

Sounds like you are hitting the rev limiter. What RPM are you doing when the car "sputters"?

Rick

 

[10thAnnvCobra]

Maybe 5,000+ I don't think it is the rev limiter, the sputtering starts to early. Thanks.

 

[redfiresvtsnake]

I'd start by checking the plugs.

 

[Derek@Amazon]

what are the plugs gapped at?

 

[Hissssnsvt]

How long has it been doing this? What are you fuel mods if any?

+1 on starting with checking your plugs but it sounds to me like a fuel delivery issue or maybe a FRPS going bad? Also check all your vaccum lines...

 

[01SVTSnake]

+1 on spark blowout. Get new re-gapped plugs and check the fuel system

 

[1fastredcobra]

How long has it been doing this? What are you fuel mods if any?

+1 on starting with checking your plugs but it sounds to me like a fuel delivery issue or maybe a FRPS going bad? Also check all your vaccum lines...

+1 on the FRPS going bad.

 

[10thAnnvCobra]

I'm running NGK TR6 plugs at .035. I've bought some new ones and plan to put them in. I am doubting it's the plugs because it runs great until WOT. Maybe I'm wrong.

It only started this recently (the past week) my car is a daily driver and I know it well.

I thought of a vacuum line, but everything looks good. I'll have to check again but more carefully.

The fuel system is stock. With my mods it has always kept up before.

Exactly what is the FRPS and where is it (dumb question perhaps, but I don't know). Is there a way to check it?

Here's an idea... would the fuel filter cause this sputtering at WOT? My Cobra has 65,000 miles and the filter has only been replaced once.

Thanks for the replies! :thumbsup:

 

[Derek@Amazon]

change the fuel filter also... its good idea to change it every other oil change in forced induction cars

 

[10thAnnvCobra]

OK a new fuel filter is a good idea then. Thanks! I will replace the plugs and the fuel filter and check the vacuum lines carefully. Any other ideas? Can someone explain the FRPS to me. Thanks again for the replies.

:beer:

 

[Derek@Amazon]

OK a new fuel filter is a good idea then. Thanks! I will replace the plugs and the fuel filter and check the vacuum lines carefully. Any other ideas? Can someone explain the FRPS to me. Thanks again for the replies.

:beer:

frps is fuel rail pressure sensor. its the sensor on the fuel rail, they go bad from time to time.

 

[10thAnnvCobra]

Is there a way to test the FRPS to see if it has gone bad? :shrug:

 

[10thAnnvCobra]

Thanks for the replies so far. Can the FRPS be tested to be sure it it working correctly? Any other ideas? :idea:

 

[RedfireVenom]

My car started sputtering at full throttle. My mass air meter was dirty. I replaced it an all good.

 

[dkscobra2003]

Plugs(old or gap may be too much: blow-out), Coils?:shrug:

 

[Cookieman00x]

Id do the easy things first.... Fuel filter, plugs, clean the MAF.. See if that does anything..

 

[10thAnnvCobra]

OK, I'm trying to debug this problem and now the "service engine soon" light came on. I checked the code with my SCT Xcal2 and it is PO463 FUL LVL S CIR HI IN...? Earlier today (before the service engine light came on) I filled up with gas and the fuel gauge read empty not full. I turned the car off and restarted it and then the gauge read full. Soon after the light came on. What is this code?

As for the sputtering, I am beginning to suspect the FRPS (thanks to some of the earlier replies). I pulled the vacuum line and could not really tell if I smelled gas. I checked my oil and also could not really tell if I smelled gas. If I replace the FRPS can I tell if the diaphram has ruptured? I just changed the oil about 800 miles ago and don't want to do it if I don't have to (7 qts. Mobile 1 and a filter = $).

Are there any special steps to take when replacing the FRPS? I assume I need to bleed off the fuel pressure before removing it. Is that right?

I need more advice from you MACA folks. Thanks. :thumbsup: