Fuel Pressure Regulator Hose

[echostats]

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]

Boost leak test?

 

[echostats]

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]

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

 

[delta448]

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

 

[echostats]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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?

 

[aero_sallee]

I would definitely check for boost leaks. What are your settings on your SAFC? It is possible you were adding fuel on the SAFC to compensate for the FPR not adding fuel pressure. Now that it is, if both the fuel from the SAFC adding and FPR also, it may be running rich enough under boost to bog like you are describing. The boost leak could also be causing the same situation.

Whatever you do, make sure that vacuum line is secure on the FPR and don't run without it. I had mine pop off under 17psi and it blew the head gasket before I could even let off the throttle.

 

[echostats]

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?

Since I noticed the fpr line was disconnected, I have played with the SAFC quite a bit. The Hi-Throttle was set around -13 to -15%. I have since (mainly because I am concerned about the white spark plugs) set it to -10% across the hi-throttle board. Needless to say, I am not driving the car at all so this doesn't really matter at this point.

I tuned the lo-throttle with my PocketLogger. I have since added a couple percent of fuel to that map too (because of the white spark plug concern).

I realized tonight that it doesn't really feel like it's bogging at 4k but more like 10lb of boost. I know it is a fuel issue so this just throws more confusion into the mix.

 

[echostats]

I would definitely check for boost leaks. What are your settings on your SAFC? It is possible you were adding fuel on the SAFC to compensate for the FPR not adding fuel pressure. Now that it is, if both the fuel from the SAFC adding and FPR also, it may be running rich enough under boost to bog like you are describing. The boost leak could also be causing the same situation.

Whatever you do, make sure that vacuum line is secure on the turbo and don't run without it. I had mine pop off under 17psi and it blew the head gasket before I could even let off the throttle.

I just ordered a boost leak tester from boostpro.net. I was going to make my own but the parts were adding up to about what their really nice one costs. Hopefully I will have it soon.

Yes, I absolutely was tuning it incorrectly because of that fpr hose being disconnected. Now that it is connected, everything seems messed up but everything I do on the SAFC doesn't make a difference. I am starting to think it may be combination between a fuel problem and maybe a boost leak of some kind. It seems to bog at 10lbs but this problem DID NOT EXIST WHATSOEVER when the fpr hose was disconnected.

I am not sure what you mean about the vacuum line on the turbo. I haven't mentioned that. Are you saying that I should double check to see if it's still connected?

My car ran great before I found that fpr hose. I wonder if buying an upgraded regulator would fix the problem. Possible?

 

[aero_sallee]

I just ordered a boost leak tester from boostpro.net. I was going to make my own but the parts were adding up to about what their really nice one costs. Hopefully I will have it soon.

Yes, I absolutely was tuning it incorrectly because of that fpr hose being disconnected. Now that it is connected, everything seems messed up but everything I do on the SAFC doesn't make a difference. I am starting to think it may be combination between a fuel problem and maybe a boost leak of some kind. It seems to bog at 10lbs but this problem DID NOT EXIST WHATSOEVER when the fpr hose was disconnected.

I am not sure what you mean about the vacuum line on the turbo. I haven't mentioned that. Are you saying that I should double check to see if it's still connected?

My car ran great before I found that fpr hose. I wonder if buying an upgraded regulator would fix the problem. Possible?

Sorry turbo was a typo, I was tired last night.

I meant FPR, I fixed it in my first post.

Since you have a 255 pump a AFPR would definitely help with tuning issues since you are likely overrunning the stock FPR.

 

[echostats]

Sorry turbo was a typo, I was tired last night.

I meant FPR, I fixed it in my first post.

I know how that is! I am not sure how the line came off in the first place but I would have never noticed if my car didn't all of a sudden start running horrible. I wish that I could say that was the cause of the CEL and the way the car was running but it's when I plug it back IN that it starts running bad.

I just can't wait to get that boost leak test done so I can rule that out once and for all. I really don't think it's a boost leak but at the same time, I hope it is.

Because of this mess (and because I just want my car to run right), I plan to take the car to Buschur for a dyno tune. I have some things I want to get done first: fix any boost leaks, install the Fireball ignition I've had laying around and now that you've mentioned it... install an AFPR. Of course, if any of those 3 things fix the issue I am having, the trip to Buschur will be delayed but I am pretty dead set on going there eventually.