alright so i just installed some shorties with ory and a aeromotive fpr and since then really i started to get this loss of power when at a steady rpm between 15-2000 rpms.

if i am parked and i hold the rpms at about 1900 and do not let off the throttle if will slowly decrease until the engine dies. if i let off the gas or give it gas then everything seems to even out again.. The problem only occurs when the rpms are held constantly at any rpm between 1.5 and 2k.. fuel pressure stays constant until rpms start to decrease, then it drastically jumps up to 50-53 psi right before it dies.

sorry if theirs any confusion, i tried searching for anyone else who has this problem, but didn't come across anything

Jeremy

 

put the stock regulator back on and get your money back.


they are well know for the problem

 

The Aeromotive is known for failing and causing low fuel pressure - while I would also suggest going back to the stock FPR, it doesn't sounds like that's causing his problem.

Fuel pressure is possibly rising due to manifold pressure dropping (telling the FPR that the engine is under load). Could be the new headers wiped out your O2 sensors, giving the computer some bad feedback? Or do you have a bad exhaust leak? Is there a noticeable misfire when the RPM drops?

 

ill swap out the o2s with my old ones(worked when i took them off my stockers) and see if that effects anything. Their are no exhaust leaks anywhere that i am aware off. anyone else had a condition like this?

jeremy

 

There is no reason why intake manifold pressure rising should cause the fuel pressure to rise to 50-53psi, at least not in a normally aspirated engine. If it was set correctly at 43.5psi (no vacuum compensation line connected), it should never exceed 43.5psi (except when you drive at WOT in Death Valley ). The Aeromotive AFPR's have also been known to cause excessive fuel pressure when they fail.

 

Then it's not normal for fuel pressure to fluctuate with manifold pressure in a stock configuration? What's the purpose of the vacuum reference to the stock unit? Both stock and aeromotive units that I've used have used that signal to increase fuel pressure under load (high MAP conditions).

Edit - Maverick, maybe it would help to know what your fuel pressure is set to without the vacuum reference - it jumps to 50-53 from where?

 

Yes... its COMPLETELY NORMAL for fuel rail pressure to vary with intake manifold vacuum (there's no "gauge" pressure in a normally aspirated intake manifold, only the "absolute" pressure which is measured against a theoretical perfect vacuum). That's the whole purpose of the vacuum compensation line to the FPR. It maintains the correct differential pressure, between the rails and the intake manifold. You set the fuel pressure at 43.5psi, with the vacuum line off the FPR. When you reconnect the vacuum line, the vacuum reduces the rail pressure when intake manifold vacuum is high (MAP is low). When you go WOT, the intake manifold vacuum approaches 0 (MAP approaches barometric pressure), and the pressure will rise to 43.5psi.

The fuel injector is an orifice, and the flow rate is a function of the difference between the pressure at the inlet to the injector (rail) and the pressure at the tip of the injector (intake manifold vacuum). Manifold vacuum can reduce rail pressure below 43.5psi, but in a normally aspirated engine, where the intake manifold pressure can never be positive (let's not complicate it with a NASCAR engine design....) the fuel pressure will not rise above 43.5psi (unless you set it higher than that with the vacuum compensation line off).

That's why he should not be seeing 50-53psi at the fuel rail, if he set the pressure correctly to begin with.

 

alright i set it wrong, im an idiot... ill have to adjust it tomorrow and hopefully everything clears up.

Thanks for the help Fred

 

Isn't the adj. regulator only good on a 93', where as 94' and up must also have computer tuning done to compensate for the increase pressure?
Why the adj. regulator? Just curious...

 

Thanks, I understand the system... semantics aside, I guess we agree after all
I guess I should have specified "with respect to atmospheric pressure", I just figured we all knew that gauges normally measure with respect to atmospheric.

 

I had the afr on becuase its was on a car i bought for parts and it had a gauge so i decided "why not throw it on" didnt know the aeromotives had problems.

btw adjusted the fp and now its running a little better. it has a hesitation/jerk when cruising in low gear like its being flooded of air/fuel. it was doing this right after i put on the shorties and removed the cat.. like evilundisguised mentioned earlier could that be caused by a bad o2? Also i didnt hook up the airpump hoses to the new headers i just capped them for now because the stock hoses were a little to short not sure if it matters or not.

 

Were your headers new and coated? The coating can ruin o2 sensors if they are brand new.

 

Are you sure the plugs you put in the AIR connections on the headers are very well sealed? Air leaking at that point will really screw up the O2 sensors and cause it to run rich. So will leaks at the header gaskets. Have you checked the header bolts to make sure they are still tight? Did you verify the header flanges were flat before you installed them? Warped flanges are difficult to seal.

Did you possibly contaminate the O2 sensors when you did the header install? Using excessive anti-sieze or spraying them with penetrating oil to get them loose can ruin them.

 

Another area to check for leaks would be your EGR flange on the passenger's side header (since you mentioned AIR hookups, I'm assuming EGR is also there. The single-bolt flange is a pretty crappy design overall, and can be tough to work with tucked away back there. But like Injuneer said, a leak anywhere prior to or near after the O2 sensors can wreak havoc by pulling outside air in and causing false lean feedback.

Did you swap O2 sensors?
Better yet, do know anyone with any datalogging equipment? That's really the best way to diagnose a problem...

 

just drove my car from Sacramento to Tracy, about an hour drive, and it drove fine. but when i got off the freeway and came to the light the rpms dropped to about 3-400 rpms and almost died.. it leveled out after a few seconds.. soo when i got to my gfs house i checked for exhaust leaks and AIR leaks around the EGR and the caps on the headers..

The car is still hot so i didnt move around the egr to see if it was loose, but i felt no air coming from around it. i checked around where the caps are on the headers and i felt no leaks. but at the base where the piece of of metal hose meets the header i feel air coming out from their. theirs a little screw at the bottom of it i could tighten up to hopefully seal it.. ill look into it more when the car cools down.