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My 91 legacy fwd MT has been randomly stalling. Especially after getting off the highway when i coast the rpms will drop and then keep going till it stalls out. If i pop the car back in gear i am fine. I can tell when it is about to stall becasue the rpm needle drops about 3 times faster than when it wont. I read on an OLD OLD board about some one who checked just about everything imaginable and finnally came to the conclusion that it might be the fuel pressure regulator but the post was never finished and i never got a definite answer.
http://pub110.ezboard.com/fultimatesuba ... D=68.topic
If anyone knows more about this , or knows an easier way to clean it help me out.

The easiest (for you) way to clean it would be to get a Motorvac treatment, but that's a bit pricey. A less effective but cheaper way to give your fuel system a minor cleaning is to use one of those in-tank cleaners like Chevron's Techron injector cleaner or Sea Foam.

I forget, did you try doing a tuneup and replacing all the filters and stuff?

It could be a fuel pump issue, too. I've heard of a lot more fuel pumps going bad than FPRs dying.

yeah i did a tuneup, replaced plugs, wires, pcv , fuel filter, recently replaced knock sensor and cleaned the MAF. I was told by a friend that i can get an aftermarket fuel regulator and rerun the fuel lines and attach it to the firewall... Im not sure how much an oem regulator is but the ones i saw were about 120 for this car and i was told an aftermarket one would be cheaper. And fuel pump i would guess is quite expensive too If this helps at all.. when the car is about to stall i can hit the gas a few times and balance it out or throw it back into gear.

Like I said, I haven't really heard of FPRs failing often, so you might want to just buy a used FPR and see if it resolves the problem.

To use an aftermarket FPR you'd need some kind of adapter for the rail; I'd doubt you'd end up saving money in the end.

I have a stock Legacy FPR you could have cheap if you want it; I was going to try converting it into an RRFPR but making your car run right is a nobler cause.

You can buy lightly used fuel pumps (stock or Walbro) pretty cheap on NASIOC. I've seen stock WRX pumps sold for around $30 or $35.

Have you tried looking for vacuum leaks? What about cleaning the IAC valve?

No i havent tried vaccum leaks but i also dont have the tools to do that myself, i will look into cleaning the iac. Those prices sound good on the pump. If you can that fpr would be great if you can pm me with a price. ALso if you have a link to the fuel pump please pm that too , i would take your word on which one would be best for the car.
I wish the problem was constant.. its the randomness that bothers me the most and trying to recreated the situation.

Konrad

You can look for a vacuum leak using a can of starting fluid. Do a search for "starting fluid vacuum leak" or something along those lines for an explanation.

You may have to look for a week or so to catch a good deal in the NASIOC Private For Sale classifieds. I'll PM you about the FPR.

The randomness is weird for sure. After doing all the other repairs did you reset the ECU? Sometimes when something's wrong the ECU tries to learn around it and then when the problem is fixed it's learned all the wrong things.

yes after each i reset the ecu but disconnecting the neg and holding the brake pedal. could it be a weak alternator? i know when i throw my lights on i get a dip in rpm but i get the stalling regardless.

It's hard for me to imagine the alternator causing it to stall; the engine can actually run for short periods of time without the alternator. If you want to test that you can just disconnect the four-pin connector from the alternator and see if the engine idles.

I still have a similar problem to you. My car never gets to stalling, but it does stumble. I think it happens most often when I've been driving hard or on the freeway and I'll stop at the light and it may be in gear with the clutch in or in neutral. I'll be sitting there idling and it will feel like the car is barely able to stay running. It will kinda shake a bit as the car acts like it is misfiring and the stumbling. It never dies, at least it hasn't yet.

I've changed the fuel filter, plugs, wires, coil pack (Thanks for the Diamond Matt), I've cleaned my grounds, and even changed to a four wire 02 sensor. (which I've currently gone back to the 3 wire one since I didn't wire it well enough. I'll have to swap it back in later). The only thing I can do at this point is change my battery/alternator and go over my vacuum lines again. The fuel pump is another issue I'm wondering about. The car runs fine otherwise. I just wonder if somehow the fuel pump at idle just isn't delivering the fuel well enough. Maybe Throttle Position Sensor??? I'm really scratching my head like you.

This should probably be moved to the engine section.

yea hi wondered why the hell i posted it here to beguin with.. see my problem started liek yours it would just dip.. and as you said mostly after freeway driving like comming off exit ramp to a stop. My mom said when she had the car aparently one of the wires going to the starter was frayed and a mechanic taped it up but i was unable to locate such a wire.
Thing is liek i said if i give it a little gas a few times i can stableze it... and strangely enough when the car is still cold it rarely happens ( if ever) but i have to put in more driving time and acctually pay attention. This made me belive it was a sensor that was setting off the check engine light but after fixing all those the problem is still here. the fuel pressure regulator makes sort of sense, i was told at work that if it gets stuck open it could be flooding the cylinders, and when i hit the accelerator that excess is burned off. I will replace the regulator thanks to vrg3 i will see what what happens.

Konrad

well like vrg, I kinda doubt that is it. But hey, I'm open for anything right now. Let me know how it works out. I haven't exhausted my options but I'm coming close.

-Ryan

you don't need an adaptor for the fuel rails, just run both, if you go to a rising rate fpr it will bleed off upon deceleration, i know, i have one, in fact i'll be soon modding my rails to 2 left hand side rails with fpr on them as well as my rising rate fpr.

If you suspect your stock FPR is clogged, then it wouldn't necessarily fix the problem to leave it in place and install the aftermarket one after it; it won't be able to reduce fuel pressure, right?

would a stronger than stock pump hurt the car or put unnecessary pressure on the regulator? i see tons of walbro and wrx pumps for cheaper than replacements specific to the car.

several guys here have the walbrow 255 lph pump. When I thought mine was dead they told me to get that one for 100 bucks. It ended up being an electrical connection under my rear seat that kept my pump from getting power.

OMG, I'm glad someone else has been having this problem! Well, I'm not really glad, per se, but reassured rather...
I've been having the exact same problem with my n/a. Like you guys, I've changed plug wires, plugs, fuel filter, cleaned my grounds, I Sea Foamed my car twice (once through the vacum lines and just recently, I added about a pint to the crankcase oil), run a bottle of Chevron (Techron) through the gas tank every 1000 miles or so, and still it wants to do the dipping RPM dance every now and then.
I hope I don't have to replace my knock sensor or worse, but this is has been a mystery I've been trying to unravel for awhile.

this is a true fact about the wiring under the back seat, it has happend to me many times, if you cheked everything and all is good, check your pistons maybe you blown one. my car was all fine checked everything and did a compresson test and sure a nuff it was a blown piston.

my knock sensor made the engine light go off but it seemed to have on effect at all when i replaced it, all it did was turn the light off. It was not much though i belive i picked up an oem for 35.