Car falls flat above 1500rpm, sounds like fpr?

[kumba]

Firstly the car is a 95 ATX with 91K-mi.

I did the 96+ upgrade today, and changed the fuel filter. The old filter must have been the original one because it was rusted and blended in perfectly with the rest of the under-body rust. Took me two passes around the car before I finally found it. Definitely one of my problems. When I poured the fuel out backwards (poured out the inlet side) I got all kinds of nice brown rust come out as well.

But now I have a new issue. It seems like the FPR is stuck partially open. I can start the car, and drive it up to about 1500-2000 rpms before it starts falling flat. This is definitely a fuel related issue, not knock or a miss. The car idles good, doesn't miss, I get no pops or bucks or jerks when trying to accel, it just goes flat.

I turned the car off and let it set for 10 mins. I then hooked up my fuel pressure gauge and had about 20-psi at the schrader valve on the rail. When I start the car and let it idle I have about 30-psi without fluctuation. By just revving the engine without load the fuel pressure will drop down to 20-psi or lower and then come back up once it's at idle. I tried knocking the fuel pressure regulator with the handle of a screwdriver but it didn't do anything. If I pull the vacuum line on the fuel pressure regulator the needle comes up quickly to around 35-38-psi and stays there. Engine idle also smoothed out nicely as a side note. From what I read in other threads that is a good pressure for the pump to push, and it holding 20-psi when off means it's not a bad check valve in the pump (I hope!).

SO, the big question is, Is the FPR my issue? Or should I check and look at other things too?

As always, any help is appreciated. Eventually I'll just do like everyone else on here and buy a second SHO. That way I always have one to drive and one to wrench on.

 

[SuperHO]

you're likely knocking on the right door. it's a good, inexpensive place to start, anyway. i'd suggest investing in some crow's foot wrenches to get the thing off, though.

 

[kumba]

Inexpensive? The damn thing is $125 at napa. Autozone and Advance are $80 and $70 respectively. Only good thing is it's easy to get to.

Glad I found my crows feet the other day.

 

[HotRodKid]

is thsi car by chance new to you ?

if the fuel filter was full of rust, the tank is probably rusted horribly on the inside, so the fuel pump sock will also be full of trash. If thats full of trash, your fuel pump isnt getting the supply it needs.

if your FPR was stuck open it wouldn't hold pressure AT ALL after the car was shut off. Not for 30 seconds, and definitely not for 10 minutes.

 

[kumba]

It's about a year old to me. Prior to replacing the fuel filter today it ran seemingly fine and pulled nice and hard up to the rev limiter.

If I pull the FPR vacuum hose off so it's at 38-psi just to see if the problems go away during a drive around the block, will that hurt anything?

Just looking to rule out other things, not make a band-aid.

 

[kumba]

Since this all started when I replaced the rusty crusty presumably bad fuel filter with a brand new one, I'm going to pull the new one back off and see if I can blow through it. Maybe I did something incredibly stupid like putting it on backwards, or maybe it's bad, who knows. It's easy enough to check and cheap enough that I don't care if it's bad. Gives me something do to before I start throwing parts at the problem.

As a side note, I pulled the vacuum hose off the FPR, got 40-psi at the regulator, but I couldn't even power-brake the car without it stumbling. So much for that idea.

 

[VortecGT]

is the fuel filter on backwards?

 

[kumba]

Well, I will file this one under my "weird ford crap" file. Anyways, here is what I did:

1) Beat bottom of gas tank like it owed me money, car still ran like crap. So not a stuck checkball.
2) Bit the bullet and took the fuel filter off. It was on the right way, blew through fine. Put it back on. Car now runs fine.

The only thing that looked funny about the filter is that it was pushed all the way back in the mount to the point that the rear hose was kind of stiff and not moving freely on the ******. When I put it back on I made sure both hoses would move freely with the filter in place. Maybe I had a piece of garbage in there or something. Who knows.

I'm going to let it sit for 30 minutes and then see if it still fires up and has power. Maybe I just got lucky. If it still does then I guess I'll go for a nice 80mph stroll down the interstate and see what happens.

 

[SuperchargedSHOguy]

Make sure you don't have a kink in the line or have a slight leak in it near the attaching points to the fuel filter. You may want to dump the tank and have it cleaned if there was rust looking particles coming out of the fuel filter. Fuel pump screen probably has that crap all over it too.

 

[kumba]

I am guessing the line was partially kinked from where it was shoved back in the bracket. The fuel fittings were bone dry when I went to pull it out, so no leaks there. A high-speed-driven-like-it-was-stolen cruise down the interstate went flawlessly. The engine does seem to start easier with the new filter and has slightly less vibration at idle.

I guess I will make plans to pick up a fuel pump and drop the tank when it's nearly empty. The good part is it doesn't look like I have to drop the exhaust to get it out, just jack the car way up for clearance.

It seems like the more I fix stuff, the more other stuff starts to break on this car. I guess at some point I'll run out of things to fix and have to start breaking stuff in places I've already been.

 

[moobypets]

yeah i would definatly open the tank and clean it asap

the pump on those car are not that strong lol so i tneed all the help you can get

maybe do the hole in the floor mod to have acess to the gaz tank then you could suck and wash till clean and new and maybe even replace the small filter on the pump itself

oh and never use a shop vac

 

[SuperchargedSHOguy]

Yeah, they didn't put in the higher flow pumps in those ATX cars. Again if there were rust particles coming out of the filter and line you will want to have the tank cleaned as well as pulling the intake and fuel rails because there will most likely be some particles on the screens to the fuel injectors. We just had to do this to a 2001 Ford Mustang last weekend that was having low idle issues.