Symptoms of a bad FPR?

[rich3389]

Anyone know what happens when the stock FPR is bad?

On my car I have to add 20% on the afc to zero out fuel trims when car is fully warmed up, but on a cold start the car runs extremely rich and blows out back smoke, and on wam starts, the car runs lean until I drive it a little...

 

[->PrOjEcTGS<-]

Do you still have the fuel pressure solenoid hooked up? It could have gone bad.
What about your Coolant temp sensor? Those are known to do some screwy things when they go bad.
When did you last replace your O2 sensor?
EGR valve could be a culprit also.

You can check your fuel pressure by buying a gauge that taps into the top of the stock fuel filter. By that you should be able to judge if you are getting too much pressure or too little. That will rule out whether or not it's the FPR.

 

[rich3389]

The coolant temp sensors readings look fine via logger, o2 sensor is fairly new, and the fpr solenoid is plugged in but do not have a vacuum line to it. Its beem like that for a year and this problem is fairl recent, I actually hooked it up again and it didn't help at all.

If I zero out the afc it will run good afr's on cold starts, but will run lean when warmed up at idle and will stall out on a warm start.
And the egr is blocked off, there are also no vacuum/boost leaks.

 

[->PrOjEcTGS<-]

I would find a way to check your fuel pressure. It could be the FPR or it could be the Fuel pump itself, clogged fuel filter, etc.

 

[97JDMDC2]

Its saying that its time for a new AFPR.

 

[JusMX141]

The best quick-test for any fuel pressure regulator is to pull the vacuum line and see if fuel squirts out while the engine is running. This would show that the diaphragm inside has a hole in it. If there is no fuel at the vacuum line, listen closely for a change in the engine's idling characteristic. If the engine's idle does not seem to change when the vacuum is taken away, the regulator may be defective.

Normally a faulty fuel pressure regulator will result in a higher-than-normal fuel pressure....especially at idle when the engine's vacuum system would normally draw the regulator open, allowing less pressure at the rail so the engine does not flood itself out while idling.

Our OEM regulators are fairly simple, although they can wear out over years of use. Think of a fuel pressure regulator as a blow off valve for your fuel system....it opens at idle and on vac, closes under normal driving and light boost, and more force is applied to it as the boost level increases.

 

[DSM1G90]

Thx for posting this useful tip for sometimes I also wonder about the condition of my FPR as well...

 

[destrux]

Just had this happen to my modified (OBX adjustable top cap) stock FPR. It was sticking and was keeping the fuel pressure at 54 psi all the time (which is what I have it set to for base pressure). The car was surging during cruise and idling like crap. Under WOT it seemed ok, but was actually running pretty lean. No knock though... maybe because of the water injection. I have a B&M fuel pressure gauge on the fuel filter fitting... which is how I spotted this problem.

 

[blown1]

Not to resurrect and old thread but why are you running such high base fp 54psi? wow

 

[lauj2gdsm]

i was sputtering and missfiring from 2k-3k.. bad.. i did all the usuall like spark plugs, wires, coil, fuel pump and mas change. what a waste of time and money.. it turned out my sx fuel pressure regulator too a crap.. because when i put on my stock fuel regulator. it ran normal.