Fuel Pressure Regulator Hose

echostats · 07-22-2008, 10:38 PM

I've done a couple searches and cannot confirm the answer to my question.

I did a basic tune on the car using my AFC and Palm Logger and got it running pretty well. Out of nowhere it began to bog and jerk around 4-55k and it felt a lot like fuel cut. After looking under the hood for a little bit, I noticed that a line had come off of the (stock) fuel pressure regulator. I popped it back on and the car can't even hit boost without jerking and acting like it's hitting fuel cut. It runs noticeably better with the apr line disconnected.

Any ideas?

crimsondragon · 07-22-2008, 11:32 PM

Boost leak test?

echostats · 07-25-2008, 12:36 PM

I am going to do a boost leak test tonight but I really think it's something more than that. The car runs pretty good without the fpr hose connected. With it connected it runs horrible!

echostats · 07-25-2008, 01:00 PM

Also, I forgot to mention that I've got the P0300 CEL (multiple cylinder misfire) a few times in WOT.

delta448 · 07-25-2008, 01:17 PM

Where does that vac line lead to? Are you sure it came off of the FPR?

echostats · 07-25-2008, 01:41 PM

Did I say vac line? I didn't mean to. This is the line I am talking about. The article describes it by saying this, "In this photo, the red vacuum hose on the left of the fuel pressure regulator provides the necessary "signal" so the FPR can adjust for intake pressures."

steve · 07-25-2008, 02:59 PM

That is the reference line for the fuel pressure regulator. People call those hoses, vacuum lines, since on most cars you never have boost.

The hose should run to the Fuel Pressure solenoid on the firewall but some people eliminate it and run the line directly to the intake manifold.

It is required to allow the fuel pressure regulator to track the pressure in the intake manifold. If it doesn't then as the pressure rises the fuel injectors will be pinched off making the car go lean.

echostats · 07-25-2008, 10:23 PM

Quote:

Originally Posted by steve

That is the reference line for the fuel pressure regulator. People call those hoses, vacuum lines, since on most cars you never have boost.

The hose should run to the Fuel Pressure solenoid on the firewall but some people eliminate it and run the line directly to the intake manifold.

It is required to allow the fuel pressure regulator to track the pressure in the intake manifold. If it doesn't then as the pressure rises the fuel injectors will be pinched off making the car go lean.

Steve, thanks for the info. I learned first hand what you mean when you say the car will go lean without that line hooked up.

I changed my plugs today and almost fell over when I seen how white the old plugs were. They look scary lean. I gapped the new NGKs at .28 and popped them in w/o the fpr line hooked up. The car ran great! I hook up the fpr line and the car only runs correctly in lo-throttle. Once I get on the throttle it bogs and jerks around 4-5k.

What should I do next? I appreciate any and all input.

delta448 · 07-25-2008, 10:31 PM

You should keep the "hose" on the FPR and not take it off for any reason for starters. Anything you do to correct the problems you're having will be futile if the FPR has no manifold pressure reference. If I were you I'd disconnect the battery for a few minutes to reset the ecu before the next drive with the FPR "hose" where it should be.

Second thing, I hope that's just a typo and you actually gapped the plugs to 0.028".

echostats · 07-25-2008, 11:02 PM

Quote:

Originally Posted by delta448

You should keep the "hose" on the FPR and not take it off for any reason for starters. Anything you do to correct the problems you're having will be futile if the FPR has no manifold pressure reference. If I were you I'd disconnect the battery for a few minutes to reset the ecu before the next drive with the FPR "hose" where it should be.

Second thing, I hope that's just a typo and you actually gapped the plugs to 0.028".

Yea, I meant .028. I will try disconnecting the battery... maybe I will get lucky. I just checked the new plugs after the first run (just about 20mi around town, nothing rough) and they are crazy white. I am not going to drive it anymore until I figure this out.

turboglenn · 07-26-2008, 01:22 AM

Quote:

Originally Posted by echostats

Steve, thanks for the info. I learned first hand what you mean when you say the car will go lean without that line hooked up.

I changed my plugs today and almost fell over when I seen how white the old plugs were. They look scary lean. I gapped the new NGKs at .28 and popped them in w/o the fpr line hooked up. The car ran great! I hook up the fpr line and the car only runs correctly in lo-throttle. Once I get on the throttle it bogs and jerks around 4-5k.

What should I do next? I appreciate any and all input.

Don't' be too concerned with white plugs on modern cars. When running in closed loop the idea is to get the "perfect burn" leaving behind no unburnt fuel to leave the brown colored residue on the plug electrode or ceramic. (not that you should be looking there for the "real data" anyway) But anyway, it's common for cars with fuel injection to have the plugs come out pretty much white after a decent little light throttle cruise into the neighborhood or to the 7-11... The way you get darker plugs to actually "read" is to run the motor wide open and then kill the ignition at redline and pull off adn pull teh plugs (kill the fuel supply ALSO if possible for the best reading..but don't kill fuel only..that's bad) Don't restart the engine until you pull the plugs, as even the cruise down from speed if the car is running will even mess a plug read up to the point of it being useless if that's the way you're actually tuning or judging your motors AF ratio

Try and borrow a wide band from some one and see what the car is doing with it's fuel when this happens, or just log it and read the factory O2 volts and IDC to get a rough idea.

toojung2die · 07-26-2008, 02:03 AM

Your ECU learned to run with the FPR hose disconnected (as far as it can) and by reconnecting it you screwed up the ECU again. Disconnecting the battery for a few minutes as previously suggested will zero out the ECU to default and you should be running again, assuming nothing else is broken.

echostats · 07-26-2008, 04:54 AM

Quote:

Originally Posted by turboglenn

Don't' be too concerned with white plugs on modern cars. When running in closed loop the idea is to get the "perfect burn" leaving behind no unburnt fuel to leave the brown colored residue on the plug electrode or ceramic. (not that you should be looking there for the "real data" anyway) But anyway, it's common for cars with fuel injection to have the plugs come out pretty much white after a decent little light throttle cruise into the neighborhood or to the 7-11... The way you get darker plugs to actually "read" is to run the motor wide open and then kill the ignition at redline and pull off adn pull teh plugs (kill the fuel supply ALSO if possible for the best reading..but don't kill fuel only..that's bad) Don't restart the engine until you pull the plugs, as even the cruise down from speed if the car is running will even mess a plug read up to the point of it being useless if that's the way you're actually tuning or judging your motors AF ratio

Try and borrow a wide band from some one and see what the car is doing with it's fuel when this happens, or just log it and read the factory O2 volts and IDC to get a rough idea.

Thanks for the advice! I am going to try and buy a wideband within the next week so I can get this thing running correctly. I know that even if disconnecting the battery fixes this problem (which I really hope it does), it still needs a better tune than I've given it with my SAFC2 and Pocketlogger.

echostats · 07-26-2008, 04:54 AM

Quote:

Originally Posted by toojung2die

Your ECU learned to run with the FPR hose disconnected (as far as it can) and by reconnecting it you screwed up the ECU again. Disconnecting the battery for a few minutes as previously suggested will zero out the ECU to default and you should be running again, assuming nothing else is broken.

Makes sense to me! I can't wait to see if it works.

echostats · 07-28-2008, 10:59 AM

Quote:

Originally Posted by delta448

You should keep the "hose" on the FPR and not take it off for any reason for starters. Anything you do to correct the problems you're having will be futile if the FPR has no manifold pressure reference. If I were you I'd disconnect the battery for a few minutes to reset the ecu before the next drive with the FPR "hose" where it should be.

Second thing, I hope that's just a typo and you actually gapped the plugs to 0.028".

I tried disconnecting the battery and the problem remains. Any other thoughts?

steve · 07-28-2008, 11:28 AM

Do you have a fuel pressure gauge?
I see you have a Walbro 255 fuel pump but did I miss the AFPR?
When was your last boost leak test and how long did it hold you max boost pressure?

echostats · 07-28-2008, 11:47 AM

Quote:

Originally Posted by steve

Do you have a fuel pressure gauge?
I see you have a Walbro 255 fuel pump but did I miss the AFPR?
When was your last boost leak test and how long did it hold you max boost pressure?

I do not have a AFPR and I haven't done a boost leak test in awhile. Could that be the cause? Unplugging the FPR hose clearly eliminates the "problem". I know that is NOT the answer but I just don't see how that could lead to a boost leak being the actual cause. I am very willing to be educated though. I don't claim to know what I am talking about.

I just want my car running right again. I am worried about it running to lean... I need to get a wideband and FAST.

steve · 07-28-2008, 01:33 PM

BTW P0300 is multiple cylinder misfire.
The FSM says to check coils, plugs, injectors, O2 sensor, compression, MAF, fuel pressure, timing belt and crank sensor.

delta448 · 07-28-2008, 02:25 PM

I'm wondering if the 255 is overrunning your fpr pretty badly and since the fpr boost/vac reference is off, you're still able to run since boost pressure isn't also raising fuel pressure. If this is true, you'd be running very rich at idle and low rpms. It also explains the problems with 4k+ rpm bogging and jerking, it would probably be very hard to tune that out with the improper fuel pressure. With the tune you did, does your SAFC settings agree with my theory? -Are you removing a lot of airflow at low rpms, and not so much in upper rpms?