Out of nowhere I have developed a very bad miss which has me completely puzzled. First off, last weekend I took the car on a trip and it drove flawlessly. Took the car out friday night and again the car drove flawlessly. Saturday I noticed the car was real low on gas so I hoped in and went to the gas station to get gas. A couple miles from home I started to get a miss when I would accelerate from a light. I get gas then hop on the highway and when I accelerate hard to merge the car misses terribly (especially at 3,000 rpm). I pull off the highway where the car stalls then struggles to start. I get home and while home the car will not start when warm unless I press in the gas and when I get it started it will die unless I keep the revs up. The car starts when cold but still will not hold the idle for more than 3 seconds unless I keep revving the motor.

First thoughts were clogged fuel filter or injectors. So I went out and replaced the fuel filter and bought some Lucas fuel injector cleaner. Well, no dice and the old filter looked fine. I put in a Racetronix fuel pump kit about 3 months ago and have faith that it has not failed. Then I decide to do some small things like replace the spark plugs, check wires for crossing, and look around for any vacuum leaks. Again no dice. At this point I am thinking coil and/or opti. The car has the original coil and the opti was replaced ~8,000 miles ago/2 years ago with a GM ACDelco unit.

So...I get the volt meter out and do some testing. I checked for voltage of the A and D terminals of the ICM and got readings of 12 volts when results should be 10 or more so that is a go. Then, I tested the B terminal on the ICM while cranking the motor and it's right at 1.7 when it should be between 1 and 4 so that's a go. So looks like the opti is looking good as well as the opti harness, pcm and all the wiring inbetween. Next I tested ohms of the coil and come up with a number than I do not recall (want to say 2.x or 3.x) but is inbetween the two numbers given in my hanes manual so that appears to be alright as well.

So therefore I am completely stumped. I even pulled off a valve cover and checked the rockers to make sure none slipped off any valve tips and they checked out good and there are no irregular noises coming from my engine. Therefore, I am completely stumped and looking to see if anybody might have a suggestion for something that I have not yet thought of, thanks.

 

Maybe O2 sensors. My car acted similar when an O2 went bad out of nowhere. Mine also threw a code though.

 

02's are relatively new. I had issues with them before but they threw a code and I replaced them with some new ACDelcos.

Also to point out that no codes has been thrown which also throws me for a curve ball since I thought OBD2's coded for every little thing.

 

I'm on my 3rd walbro pump now! they never completely died they would run good for a half hour or so and then start dropping pressure causing the car to die and run like **** untill the pump cooled.

 

I;m now thinking it may be that or definetly something else fuel related....I've been doing soem googleing on fuel pressure and whatnot and my car is doing this to a tee...

"When there is not enough fuel pressure, the engine may not start. Or if it does, it may idle roughly and run poorly. Low fuel pressure creates a lean fuel condition that can cause lean misfire, hesitation, rough idle, hesitation and misfire on acceleration."

I'll figure out how the check the fuel pressure and do that tomorrow, really seems theres not enough pressure.

 

Definitely sounds like it could be a fuel related issue.. My feed hose from pump to line rotted away and it would just pump most of the fuel back out into the tank. Acted VERY similar to what you described.

 

Ok so just tested the fuel pressure.....

With the motor running pressure fluctuated a little with a maximum of 20psi.

Definetly is fuel related, probaly either the wiring or fuel pump, any other ideas?
Anybody know how to test the wiring?
I just put a Racetronix pump in the car a couple months ago so if that is bad I will be royaly pissed.

 

Do you hear the pump make any sound when you turn the key on, but not running?

 

Seems like more failures then good workin Walbro pumps.

 

Nope no noise.

 

i had this problem.. cycle your key(off and on) go to the F/P test fitting and bleed out the air... then spray starting fluid in throttle body.. then fire it up... fixed my problem... when you run a car low on fuel you get air pockets.. and its hard to get em out of the lines until you bleed it..

 

Somethin is definately up with the fuel pump then, you should hear it cycle for 2-3 seconds when yout turn the key to the on position. Did you do a rewire? Maybe check all the connections and grounds before pulling the pump. Check the pump relay. As stated above, spray starting fluid in the tb when it does not want to run. If it fires up, its definately the pump or fuel related.