Could SHOnut FPR cure low RPM studdering & bogging?

[morebhp]

I've been reading older threads about FPRs in searches and many people with the SHOnut FPR commented that their low range bogging was gone and that the car ran much better.

Can anyone elaborate on this? I have a low RPM power loss that WILL NOT go away. I've reaplased EVERYTHING (MAF, ETC, HEGO, ACT, CPS...) except for fuel-related items (orig FP and FPR).

All sensors except the MAP basically have been replaced as well as 2 new sets of plugs and wires.

If you have experience with this FPR, please shoot me a few comments on your results after installing. I'm hoping this may solve my elusive low RPM power loss problem.

Thanks!!

 

[shopartsnw]

One last thing to check.

Are your secondaries opening properly, or are they stuck open? That will cause a low end bog/stumble also.

Mike

 

[SASHO91]

Have you pulled any codes?

While Josh's FPR is a nice unit, its not needed for a stock-ish sho. The stock unit is really a nice piece, it just cant handle the flow of the larger pumps.

I'd check fuel pressure. Have you changed your Fuel Filter?

 

[F-22 Raptor SHO]

I've been reading older threads about FPRs in searches and many people with the SHOnut FPR commented that their low range bogging was gone and that the car ran much better.

Can anyone elaborate on this? I have a low RPM power loss that WILL NOT go away. I've reaplased EVERYTHING (MAF, ETC, HEGO, ACT, CPS...) except for fuel-related items (orig FP and FPR).

All sensors except the MAP basically have been replaced as well as 2 new sets of plugs and wires.

If you have experience with this FPR, please shoot me a few comments on your results after installing. I'm hoping this may solve my elusive low RPM power loss problem.

Thanks!!

I'm right with you in your quest and have been following your posts. "Hi my name is mike and I have bogging issues".....HI MIKE. Ok I have a hesitation between 3 and 4k and it doesnt pull as hard as it should (even for being in the mountains I'm in). The car is worse when its cold. Not as bad when warm.No codes, so I'm left to check those things that dont toss codes.

Here is what I did this weekend just to cover my bases.

cleaned my air filter (snorkel was dirty)

replaced my fuel filter. Yea it was dirty, and I didnt know how long the PO had it in.

NO change.

So I took my intake off again (I just recently swapped my nice one to this car). Checked all the connections and couplers visually. Trimmed some of them (I have the silicone couplers and they were a bit fat). Checked all the hose clamps...ya know the original clamps work better than the after market ones IMO. The grab nice and round vs the aftermarket ones seem ovular.

MAF is good (swapped wifes over to be sure).

Plugs appear ok, they have white electrodes (wifes are cocoa brown). This leads me to believe I might not be getting the fuel I should be as white means lean no?

I am picking up a Fuel pressure gauge as my tire gauge option I tout so often to check FP doesnt quite reach the schrader valve in the rail. I dont want to change the FP or FR unless I know that is what is wrong.

Likewise, unless I can say my injectors are bad, I dont want to tackle that job either. I do hear one clicking loudly on occasion.

Clogged cat? who knows.

I will check the FP issue first. Thing is, no other FP type issue seem to be happening.

 

[morebhp]

Thanks Mike, you are right about where I am with the exception of taking off the intake. I'm afraid of causing more problems that I already have. I only have 62K miles and thus far have had no reason to remove the intake.

To answer a few questions from others, I have checked codes countless times but nothing has ever indicated what this may be. I have had codes in the past but those issues were resolved with a new TPS, CPS and other diagnosable failures. I can check codes any day and get nothing. What I'm saying is... if I took my car in to the dealership, they'd return it and say there's nothing wrong. --In fact, I did that several years ago when this problem started happening around 10K miles. If there are no codes, they are clueless.

My secondaries are opening at 4200 and staying tightly closed otherwise, I verified that last weekend.

I too need to get a fuel pressure guage and ckeck the pressure. I'm not expecting to find a problem but you never know. I'm just so sick of chasing this problem I sometimes feel like selling the $#&*@ car and getting a used Civic. :cuss:

 

[Devin]

Ha, that's funny.

I think you really need to check the fuel pressure at the rail. That could answer your question already.

Does your car have a hard time starting when it is hot (as in the car, not the weather)?

 

[Mr Anonymous]

As suggested already, unless the problems you're having are fuel pressure-related, a new FPR (whether it be stock or aftermarket) won't cure the issue.

 

[morebhp]

Right, that's understood. I didn't intend for my question to imply there's magic in the SHOnut FPR. I'm just fishing for wether or not a faulty FPR could indeed be the cause of that sort of drivability problem.

It seems that checking the fuel pressure while my car is idling will only tell me part of the story. Could varying load conditions I.E. varying vacuum conditions alter the pressure at times when it cannot be measured? I don't know... these are questions I'm attempting to answer.

This is a problem I've been chasing for a long time and I've had to resort to asking specific (albeit seemingly odd) questions in order to try to deduce what could still be an area I haven't ruled out as a cause.

 

[thecrew2999]

just to add there is no map on maf cars sometimes but 99 % of the time no

 

[hawkeye18]

Umm, seriously, change the fuel pump. Both of my cars had low RPM bogging issues, it was a weak fuel pump both times. Fuel pumps are a notorious failure item on this car. I would say the ratio of fuel pump failures to FPR failures are about 80:1. FPRs simply don't go bad. I won't say ever, but pretty close.

go to http://www.shophoenixproject.com to see a great write-up of how to replace your fuel pump.

 

[F-22 Raptor SHO]

Ok, here is my fuel pressure test results:

Test Car: My 91 with bogging issues (more when cold, less when warm but doesnt pull as hard as it could.

Control Car: My wifes 95 that I put a brand new walbro 155 unit into about 2 years ago due to a much worse fuel pump problem: random dying due to an overheating pump.

RESULTS

Key on engine off:

Test Car: 40 psi
Control Car: 40 psi

Key on Engine Idle:

Test Car: 34 psi
Control car: 36-37 psi

Key on Engine with partial throttle application:

Test Car: To 40 psi intially, but it backs down to 35 psi so long as I am only raising the idle slowly without backing off.

Control car: To 40 psi and seems to stay at 40 till I back it off (I say seems to as the Wifes car is an ATX and the car's 4k safety cut out activates. That and its 9:30 at night and I'm out front revving the poopy out of my cars waking up the neighbors and stuff.

WOT:

Test car: Hits 40 and seems to back down a bit
Control car: Hits 40 and stays 40 till cuttout.


These test conditions are at idle no load. Unless I can get somone to ride on the hood, I will have to assume the car misbehaves more under acceleration.

Hate to do it unless I have more symptoms, but it seems I'm going to have to do the Fuel pump just to eliminate that as a suspect. I'm in the mountains so my pump is over taxed anyways as most folks in this town have burnt through a pump or two in their fleet.

Trap door and 80 bucks will be what I have to take on next.

 

[thecrew2999]

pump symptom would be a whine from the pump is almost always meaning the pump is gonna die on ya.

also check the injectors out. make sure they are clean and operational.

another thing to check is the IAC, trust me it causes the symptoms you describe

 

[morebhp]

Thanks Michael, that's helpful for me to have something to compare my numbers to. So, correct me if I'm wrong but, according to those numbers everything seems to be within spec right? Hopefully today I can peel away from work and get a pressure guage.

Something I'd forgotten about but was remined today because it happened on the way to work. About every two weeks, after sitting at a light and idling for 3-4 minutes, I get a backfire through the intake when I first blip the throttle to begin rolling. It's not a bad backfire, just a pop. And then that's it. The car drives fine.... well, except for the sputtering between 2-4K as I accelerate. I'm hoping this is linked to the sputtering.

Okay guys. Again, knowing that my MAS, TPS, plugs, wires, HEGOs, ACT, ETC, fuel filter have all recently been replaced or proven good...

What causes an occasional intake backfire? Certainly there can't be too many possiblities. I sure hope this is a big clue.

 

[F-22 Raptor SHO]

Thanks Michael, that's helpful for me to have something to compare my numbers to. So, correct me if I'm wrong but, according to those numbers everything seems to be within spec right? Hopefully today I can peel away from work and get a pressure guage.

Something I'd forgotten about but was remined today because it happened on the way to work. About every two weeks, after sitting at a light and idling for 3-4 minutes, I get a backfire through the intake when I first blip the throttle to begin rolling. It's not a bad backfire, just a pop. And then that's it. The car drives fine.... well, except for the sputtering between 2-4K as I accelerate. I'm hoping this is linked to the sputtering.

Okay guys. Again, knowing that my MAS, TPS, plugs, wires, HEGOs, ACT, ETC, fuel filter have all recently been replaced or proven good...

What causes an occasional intake backfire? Certainly there can't be too many possiblities. I sure hope this is a big clue.

My SHO brutha from another *****: I was monkeying around on Saturday checking idle, and blipping the throttle. Car was nice and warm. I for the first time ever got a pop thru the intake (loud muffled cough is what it sounded like). Didn't know the cause, and it prompted me to remove the whole intake as mentioned above. Plug wires were all correct. I didn't ever hear it again, but it has me baffled.

Yes, the numbers on the pressure seem all in spec. I bought a pump anyways and will eventually replace it as uel pumps just go bad up at 7000 feet. They have to work pretty hard to move fuel due to the reduced atmospheric pressure. I dont think that is my problem, as of yet, but it is one possibility.

My IAC is less than 2 years old. I will likely clean it out just to make sure, but my idle is fine.

A bit of a warning in that because I swapped over so many performance parts from my old car to my new car and had to remove some California emissions stuff (new computer, plugged up my exhaust ********* for the smog pump), I'm still thinking I did something to the car rather than a part went bad. Though I've checked everything I touched.

 

[morebhp]

I searched "intake backfire" and found a few replies that suggested this could be caused by low fuel pressure. But, I guess in your case, we've already ruled that out.

Grr! I hate these pesky little problems!

 

[morebhp]

Michael... Your test guage... Is it just any-old fuel pressure guage from a local parts store? Does it connect easily to the shrader valve on the fuel rail?

 

[F-22 Raptor SHO]

Michael... Your test guage... Is it just any-old fuel pressure guage from a local parts store? Does it connect easily to the shrader valve on the fuel rail?

checker auto special 40 bucks and it fits all cars schrader valve or not. It had an adaptor for the schrader valve that fit perfectly.

 

[hawkeye18]

Just make sure you take that adapter back off when you're done! I forgot to once and caused one **** of a fuel fire in the engine compartment cos it stuck open... I didn't notice it until mile 8 of my 10 mile trip... good thing I had a fire extinguisher handy!

 

[F-22 Raptor SHO]

Update: Ok, so I replaced my Plugs just to eliminate one more thing: nope didnt help. The swapped out my wifes TPS just to check as well. Dangit, didnt help either.

Fuel Pump is on order and should be here soon.

Im hoping its just bad gas. I drive a mere 10 miles a day, so its taking a while to get this tank down. If its not either of these, the Y-pipe will come off and I will look inside.

 

[F-22 Raptor SHO]

morebhp: one other thing that neither you nor I have replaced is the CTS (the coolant temperature sensor). It is located to the left of of the Theromostat. Just follow the upper radiator hose to the block and it is the only senosr you see there. My temp gauge seems to read high when I'm warmed up...in fact the fan doesnt kick on till the gauge is an the O or the R. this with a new radiator and clean fluid and water pump. My thoughts on this are if the temp sending unit is somehow out of wack and reading high, the car will sense that the temperature of the motor is higher than it should be and adjust fuel/air accordingly based on the signal it receives from the coolant temp sender. I may be totally off base here and woudnt mind hearing SDPATT or dooley chime in on this.