Someone, anyone help me please!!

[DemonSpeed]

Okay my car has been down for a couple months now. What it is doing is the motor seems to be breaking down randomly, cutting out on me at certain times. It has thrown o2 codes, MAF codes, Random Misfire codes. The MAF has been replaced, the o2's have been replaced, the plugs have been replaced. Seems to be doing fine for a bit, then starts misfiring out of nowhere. The mechanic put a fuel pressure gauge on it and its showing the pressure drop when throttle is applied (Oh yeah the fuel filter has been replaced) and the diagnostic is showing that it is running very rich. I have a predator tune in it but it has been in it for some time now, close to 2 years i think. Does anyone have a clue? Please someone help! I have long tube headers, no cats(deleted), ngk iridium plugs, K&N, Cold Air, and the custom tune I mentioned earlier. Im hoping somebody else has had this prob and overcome it. Thanks in advance everybody.

[2001NBMZ28]

Current codes?

[02z28ls1]

Possible fuel pump-shouldn't drop pressure .Just an educated guess however.

[DemonSpeed]

dont know the actual code numbers right now, but the latest ones were high voltage on sensor 1 and random/multiple misfires. We were thinking fuel pump, but if it was the fuel pump causing low pressure would it be running really rich?

[jimbo98z]

I'm just guessing here, but if the fuel pump is struggling, it could be trying to compensate by holding the injectors open longer, putting more fuel into the engine than necessary, making it run rich.
Also, check your coil packs, you may not be firing on one or more cylinders part of the time.
Just to throw another thing to check out in there, run a top-end cleaner, my buddy's tacoma ran rich as poo before and when we ran that through it went right to where it needed to be. My guess is that there was so much crud on the back of the valves that it just wasn't pulling in enough air.
Hope you get it fixed!

[DemonSpeed]

Man I hope its not the fuel pump. Anyone else have any suggestions? I appreciate all the help.

[~redlinels1~]

Replacing a fuel pump really isnt that bad. Not too expensive either. Scan the car for codes again and write them down so we have a better idea with what we're dealing with.

Maybe its a bad coil. Possibly a bad injector as well. Also, as weird as it sounds, whats the gap on the plugs? Excess gap can make the arc fail.

[DemonSpeed]

I dont have the car at the house right now, ill scan for codes monday when I get it. Aren't fuel pumps like $350+? The gap on the plugs are the factory gap on the NGK iridiums. Also I dont think its a bad injector or a coil because all the cylinders were misfiring. Again I appreciate all the help guys. Keep the suggestions coming though if you have any.

[~redlinels1~]

Never get OEM when you have an excuse to upgrade.
The racetronix plug n' play kit is only $250.

[YoMommasTA]

http://jobberonline.biz/GMFuelPumps.html geter done


did you try cleaning the maf?that k&n could have fouled it causing lots of headaches.

[DemonSpeed]

the MAF is brand new, thanks for the link man thats a bit cheaper

Jimbo98z what is a good top end cleaner?

[jimbo98z]

SeaFoam works in my opinion, but others on here will steer you away from it.

What we did with my friend's tacoma was take off the intake to expose the throttle body, sprayed a good bit of carb and choke cleaner in there, started it up, ran it for a few minutes, then did it over again. And, just like SeaFoam, it will smoke quite a bit, and be a little tough to start. The carb/choke cleaner was just some generic stuff we got from NAPA.

We used some stuff by Slick 50 that you sucked into the intake through a brake booster line at the shop, but I can't find it in any stores. Shame too, because it was really good stuff.

[Sarge]

From the symptoms you described I would suspect two things...
1) Fuel Pressure Regulator has bit the big one.
2) Fuel Leak.

Pressure test your system from the fuel line at the tank back up to the engine at 70lbs....if it doesnt hold dead nut 70lbs your leaking fuel.....

[mo gomez]

you need a new fuel pump i am a pontiac tech for over 6 years and that is the only failed component ive seen a firebird get towed for except for a battery. here is a good inexpensive test to positively condemn the pump;purchase a pressurized can of fuel injector cleaner,the kind with a hose that will thread onto youre fuel rail. now run the vehicle before you use the injector cleaner until the car starts acting up,after the car wont run anymore install the cleaner and see if the car starts and idles,if it does,you need a new pump. this is the method i use to drive cars with failed pumps into the shop. now you can replace youre fuel pump with confidence and stop spending money on any more parts you dont need. good luck.

[Sarge]

You saying a fuel pump is intermittent prior to failure? Thus causing an intermittent but yet consistent fuel pressure issue? (Drops when throttle is applied)....
An easier way to eliminate a fuel pump is check the voltage fluctuation at idle and applied throttle....wouldnt a defective fuel pump show itself during idle as well as when throttle is applied? Why would a defective fuel pump only manifest itself when throttle is applied.... what he describes is a regulator issue...or a fuel starvation issue..the thing that points my attention to the fuel regulator is the codes...I'm always willing to learn like the next guy and am curious of your absolute on this diagnosis....

[mo gomez]

i have seen many gm fuel pumps with enough pressure to start and idle vehicles but not enough fuel volume to do much more than idle; i have never replaced a fuel regulator that was not leaking; and i am not ruling out another possibility that is why i am saying if the vehicle wont start and run after a short period to install a pressurized can of injector cleaner immediately, and if vehicle runs than the pump is the problem. fuel pumps can and will be intermittant just like any other electrical item. i have seen these pumps fail under warranty and on high mileage vehicles dozens of times. but just like you, i feel that anything is possible and i am always learning something new.i just suggesting a very common possibility since i have replaced so many pumps in the past and it repaired the vehicle. i am not trying to knock anybody elses ideas i am just trying to help.

[Sarge]

you need a new fuel pump i am a pontiac tech for over 6 years and that is the only failed component ive seen a firebird get towed for except for a battery.

That absolute statement and pre qualification of expertise is what prompted me to challenge.
No biggie....

[DemonSpeed]

i have seen many gm fuel pumps with enough pressure to start and idle vehicles but not enough fuel volume to do much more than idle...

the car runs fine sometimes though, it will be doing great then misfire for a bit and then clear up for a little while. Sometimes it clears right up, other times I barely make it to where I need to go.

[YoMommasTA]

the car runs fine sometimes though, it will be doing great then misfire for a bit and then clear up for a little while. Sometimes it clears right up, other times I barely make it to where I need to go.

that would be the time to put a fuel gauge on and see what pressure you have.at least you would eliminate something.

[Sarge]

the car runs fine sometimes though, it will be doing great then misfire for a bit and then clear up for a little while. Sometimes it clears right up, other times I barely make it to where I need to go.

Fuel Pressure regulator or fuel leak. Possible you have an intermittant short to your fuel pump.....but folks...if a fuel pump shits the bed...it stays that way...it dont come and go.....