Car hesitating!

[doodad]

today i took the car out and kinda played around the back roads myself and at first it was fine. now everytime i powershift to 3rd gear, it kinda dies. i mean, it feels like TCS kicks in but not that bad. a little hesitating.

any idea what this could be?

thanks!

Click to read more...

 

[Mth180]

It might be the pprv? Not sure, you'll probably have better luck with one of the more senior members.

 

[wizdawg]

My car has done that since I had it tuned. The tuner said to shift faster, which does correct problem, but I still feel like that was BS solution.

 

[Bob_Kurgan]

im guessing FRPS

 

[doodad]

im guessing FRPS

How can i take care of it Bob?

 

[svtnos]

i believe there is a kit that lethal performance sells to eliminate it

 

[rdsnake]

im guessing FRPS

I was just about to say the same thing

 

[forbanger]

what is an FRPS?

 

[Dragon03]

what is an FRPS?

Fuel Rail Pressure Senor

 

[Nicky Pass]

Thats what mine did!
We have the exact same mods and the same tuner....I say its the PPRV!

You probably don't notice it during the 1-2 shift because its always fast....I noticed my hesitation on the 2-3 shift.

 

[gnxs]

im guessing FRPS

:ditto:

How can i take care of it Bob?

Replace the FRPS.

 

[Nicky Pass]

If the FRPS was bad, why would it only hesitate shifting to 3rd? Does it run fine otherwise? Does it idle good?

I still say PPRV.

 

[doodad]

If the FRPS was bad, why would it only hesitate shifting to 3rd? Does it run fine otherwise? Does it idle good?

I still say PPRV.

the car has been perfect and i always powershift. it used to hesitate but Bob gapped my plugs to 28 and it solved the problem.

i havent powershifted to 2nd due to traction problems and i havent topped out my 3rd gear to shift 4th for a long time on the streets cuz it is too fast. so i don't know if the car would hesistate on 2nd and 4th gear as well. i guess i should try and see.

there is no way i can run good times this way.

where can I find FPRS and is that a big job?

thanks to people who responded my question! I appriciated that!

 

[gnxs]

where can I find FPRS and is that a big job?

thanks to people who responded my question! I appriciated that!

Call a Ford dealer.

Takes about 3 minutes to change.

 

[doodad]

Call a Ford dealer.

Takes about 3 minutes to change.

Awesome! Will do it ASAP!:biggthump

 

[Flyn]

I doubt if it is the FRPS. I've had a FRPS blow before so I've experienced what that feels like first hand. Sounds more like the tune to me. My car also hesitates if I momentarily lift between gears. RWTD has a large thread written on the topic on modularfords.com. There are various suggestions that range from shifting faster to modifying the top hat assembly. Personally, I think that some of the tune settings that are [IMHO] designed to prevent the FRPS from blowing are at least partially causing the hesitation.

If you do replace the FRPS yourself [five minute job], make sure you bleed the fuel pressure off first.

 

[gnxs]

I doubt if it is the FRPS. I've had a FRPS blow before so I've experienced what that feels like first hand. Sounds more like the tune to me. My car also hesitates if I momentarily lift between gears. RWTD has a large thread written on the topic on modularfords.com. There are various suggestions that range from shifting faster to modifying the top hat assembly. Personally, I think that some of the tune settings that are [IMHO] designed to prevent the FRPS from blowing are at least partially causing the hesitation.

If you do replace the FRPS yourself [five minute job], make sure you bleed the fuel pressure off first.

Cliff,

He powershifts and hasn't had this issues before (and hasn't changed anything).

I've learned that these things can blows to different degrees. I blew one 1/2 mile from my house and almost didn't make it home. Had to push the car into the garage. The 2nd one I blew was less severe. Normal driving would be fine, but romping on the car resulted in the fuel cutting in and out at high rpms.

I see what you're saying and you could be right :biggthump, but IMO any regularly driven Cobra should probably carry a spare FRPS anyway. If his turns out to be good, he always has a spare.

Perhaps the best compromise (since he has a few friends with Cobras) would be to try theirs out in his car and see if the problem persists (before spending the money on a new one) since it only takes a few minutes to swap it out.

 

[Marko]

What does PPRV stand for?



Is it true that if you pull the vacuum line off of the frps and gas spills out, it means that its bad?

 

[Nicky Pass]

PPRV = Parallel Pressure Relief Valve

I used to have hesitation between WOT shifts...and the only way to get it to not hesitate was shift really fast and not come off of the gass all of the way.

I had the PPRV deleted and now there is NO hesitation!

 

[Bob_Kurgan]

if it were the PPRV, it would have done it from the beginning... Im pretty confident that its the FRPS... the car was tuned 6 months ago..

 

[doodad]

and the only way to get it to not hesitate was shift really fast and not come off of the gass all of the way.

Nicky, then mine is definetely not PPRV cuz i don't shift slow and it still happens

also flyin high again: I don't think it is my tune cuz the car has been running great. it was fine yesterday morning and i took her outside in the evening and played a little and i relaized this problem. I will replace the FRPS and see if it fixes.

 

[Flyn]

if it were the PPRV, it would have done it from the beginning... Im pretty confident that its the FRPS... the car was tuned 6 months ago..

Larry and Bob,

You guys both know a lot more about our cars' behavior than I do. In my case, there was much more hesitation after my most recent tune [RWTD]. I did switch to 60 lb. injectors so I don't know if they may be a contributing factor.

I understand that FRPS failures can vary from slight problems to complete not running [maybe from the size of the tear in the diaphragm?].

I don't understand why a tune would cause more hesitation and then deleting the PPRV would alleviate this same problem. I [and it seems like a whole bunch of other people] need to be edumucated so we can get rid of the hesitation...

In doodad's case, I would definitely replace the FRPS and see if it makes a difference. It's a relatively cheap part and an easy swap.

 

[doodad]

In doodad's case, I would definitely replace the FRPS and see if it makes a difference. It's a relatively cheap part and an easy swap.

Will do sir! I appriciate the help everyone!!

 

[gnxs]

Larry and Bob,

You guys both know a lot more about our cars' behavior than I do. In my case, there was much more hesitation after my most recent tune [RWTD]. I did switch to 60 lb. injectors so I don't know if they may be a contributing factor.

After getting my most recent RWTD tune, my hesitation is noticeably worse (compared to my previous RWTD mail order tune) and I suspect it's PPRV related (like yours Cliff). I know exactly what you're talking about. :headbang:

I do think Doodad's is FRPS related though.

All of this is good info. :biggthump

 

[Marko]

If you do replace the FRPS yourself [five minute job], make sure you bleed the fuel pressure off first.

How do you bleed the fuel pressure off? Just wondering if I ever need to change my frps.

Thanks.