Fuel Pressure Regulator?
 

I'm getting frustrated with my fuelie... Tried a different distributor, all my grounds are good, ECM is good, and it still has its miss. I had some computer codes, but fixed those now. I'm wondering, would a bad AFPR cause a lean condition? That's the only thing the computer is telling me is wrong now. Both 02 sensors report a lean condition. If I can't figure this out, I'm seriously considering scrapping the whole fuel injection setup all together.

So if anyone knows how to check a fuel pressure regulator please let me know. I've got a gauge on the rails too, so I can see the readings easily.

What mods do you have? Injectors, fuel pump, etc. What's your fuel pressure set at? Do you have the vacuum line hooked to your AFPR?

Mods in my sig, and my user ride #86.

Vacuum is connected, and I've tried 36 to 48 psi, and no changes, mind you, I don't know what the pressure is like under load, but the fuel does seem to bleed out when I shut the car off after running it. This happens in 15-30 minutes. From say 45 psi down to 20 in 15 minutes or so.

86GT, I don't think that is your problem, I have a brand new Kirban regualor, it takes about 5-10 seconds for it to bleed down to nothing. Every car is different. Hope this helps. Take care.

-Billy

A good FPR should hold the pressure for about 30 minutes or so. If not, there is possibly a small leak in it. ;) Its happened to me before.

Have you checked out your Mass air Sensor? Are you having a problems at idle? Does your FP raise under throttle?

The problem is while driving, it feels sluggish then it'll pop at times. I've narrowed it down to a fuel problem. I had my pump tested yesterday, and its good. It surprised my mechanic (he didn't think it was as high flow as I said, 190lph). I've got another regulator, a Kirban from my brother, and another set of fuel rails, so I'll give that a shot and see. If that doesn't work, then I'm fresh out of ideas. My mass air setup seems to be alright too.

Thanks for the help so far.

Could you E-mail me what you did to fix this problem if you ever figure it out? I am having the same problem with my 95 gt. It chugs a bit at crusing speeds and is gutless from the get go. We replaced plugs, wires, cap, rotor, both O2 sensors, fuel Regulator TPS sensor, fuel filter, cleaned the MAF sensor with electrical cleaner and put some fuel injector cleaner through it. Still runs like crap. Idles very good though now. The codes I am getting are 172 and 176 which is low voltage for O2 sensors and Lean bank 1 and 2.

Thanks,
Stuart

Sorry Billy, but you have a problem. Either your injectors are leaking, you have a slit in the hose after the pump, or a bad regulator. Your pressure shouldn't move down more that 1 psi in 2 minutes. A healthy system will actually have a slight increase in pressure for the first couple minutes after shutting the engine off. You need to figure it out pretty quick.

Take care,
~Chris

Change your PCV valve and the screen underneath it, and your oil and filter. Reset the ECM, and see if the codes come back.

Take care,
~Chris

Changed oil, Filter, PCV valve, cleared codes. Same results and codes.:confused:

Fuel Pressure Regulator?
 

86GT-
If you are getting low voltage readings from your O2 sensors...then you'll probably need to replace them. That's how the sensors work. If the voltage rises or drops below the predetermined O2 settings...then it sends back a low/high (usually low) voltage signal to the EEC-4. How many miles are on your oxygen sensors? Replacing your O2 sensors might be a good step in figuring out your problem.

Stuart-
If your car is feeling sluggish, and none of those things you've replaced or tinkered with have helped...than try pulling out your injectors and getting them cleaned. Or throw in some new ones. My wife used to have a '93 GT (we both had Mustangs for a few years...pretty cool) that got REAL SLOW after some miles started racking up on the motor. I tried everything...plugs, wires, cap, rotor, fuel filter, injector cleaner, etc...nothing helped. I eventually installed my old stock 19lb. injectors (they only had 60,000 miles on them) that I was no longer using (have 24s now), into my wife's Mustang and...walla! Fixed! It felt like a new motor!!

Simi,

The o2 sensors have 3,500 miles on them, they were installed back in May. I've been running MAC 1 5/8" Longtube headers with a 2 1/2" Catalytic H-pipe behind them. Any ideas?


Is there a difference in o2 sensor type from year to year? Say the ones from an 86 to that of an 89? Would the wiring and sensors from an 89 work in my 86? Just a thought...

I'm thinking I'm gonna go to a carb'd setup starting next week, unless I find the problem.

Thanks everyone for all the help, but I'm thinking its time to get some simplicity back.