Car starts, idles, and revs perfect. Under load coming up hills and stuff where you need to give it more throttle, it stutters and "misses" like crazy all the way up to redline. It almost feels like putting it in too high of a gear too soon. I'm not sure what to check next,I hooked it up to my uncles Snap-On scanner though so heres what I know:

*Left and Right Bank O2's: 10-900 mV, Theyre fine
*Fuel Injectors: All have 12.3 V to them, they "sound" fine with a stethoscope at idle
*Fuel Injectors: All Ohm'ed out to the same specs
*All 8 injecters are pulsing with noid lights
*Its getting 45ish LBS fuel pressure, key on, car not running.
*Plugs and Wires are relatively new, and in perfect shape.
*The Opti only has 15,000 Orig. Miles on it (Plus it seems fuel related)
*Coil is fine, Ohm's out perfect
*Nothing is arching
*TPS is working correctly
*BLM's are 128 for both at idle, and stay close through the entire rev range
*MAF is about 8-9grams/sec at idle, goes up smoothely and evenly with RPM
*MAP seems to be fine
*IAT is reading fine
*IS NOT water in fuel cause dry gas did nothing and its getting worse every tankful now
*The computer is not storing any codes other than CAGS...hehehe

~Basically, every single sensor is reading normal, the only abnormal thing is that when its missing bad/stumbling under load or at WOT, the O2's go WAY down to like under 40mV's and stay there until I let off the throttle. Doesnt that mean its leaning out? Which would mean its starving for fuel?

Also, all 8 of the injectors WERE cleaned out professionally and spray a perfect cone shape of fuel. So I dont think this is the problem.

I think its not getting enough fuel cause when you floor it, the O2's pretty much stay under 50mV's. The fuel filter has about 3000 miles on it, BUT the car sat for 9 years with 3/8 of a tank of gas in it. Totalled in 96, rebuilt last year. So I replaced the filter before I even tried to start it. I couldnt siphon the gas out of the tank cause its got something blocking it ???. The O2's are new also, so I know its not them screwing up. Could the fuel filter have clogged back up from having all that build up in the tank breaking loose and stuff?

I dont want to aimlessly throw money away, but it really does seem like its not gettin enough fuel. Enough to start easy, but not enough to feed it under load. Also, it seems like the problem is getting worse, so I thought maybe all the varnish in the tank from sitting 9 years is breaking up and clogging it since I have been running injectors cleaner and stuff through it.

What are symptoms of a bad fuel filter? I dont want to spend 25$ on nothing if I dont have too.

 

Exhaust leak? An exhaust leak actually sucks clean air when the engine is running, causing the O2 sensors to read lean. That will dump extra fuel in the cylinders and cause the car to stumble.

 

Sounds like a secondary ignition [spark] problem (plugs, wires or opti).

 

It's the exact same problem I have right now. I've got the beginnings of a 2nd header leak and I'm thinkin that it's done some damage to one of the plug wires (which are new and installed when I got the hooker shorties 3 months ago). Car runs great till under load in higher gear with throttle 1/2 to WOT, then the sputtering miss...i let off and ease into higher rpm's and all is OK. I'll let you know how things turn out next week when I take it in to get it fixed. It's getting a bit worse as I drive more.

Good luck...if you figure out yours, please post it here and PM me...I'll do the same! Thanks!

mudkat

 

mine was doing that a while back and it was a burned plug wire. ive seen an opti do that once. the optical portion was screwed up (you could shake it and it rattled like a folgers can with rocks in it) and it was causing alternating misses on different cylinders.

id do a plug/wire change, thatll tell if its the opti. it also could be the ignition module, but ive never seen one of those do it on a camaro. my mustang did the same thing when it had a bad module on it. first id try plugs/wires, then the module (its like $40), then the opti. but if the opti is bad in the same way the one i saw was, youll be able to tell by shaking it.

check the fuel pressure first and make sure its not a weak pump. how old is the fuel filter? if over a year put a new one on it.

 

so, youre running NINE year old gas through there? or you ran that through previously? i would have done anything to get that **** out of there besides running it through the fuel system. you say you have 45psi fuel pressure... well my bet is that the pump is gummed up and isnt able to supply the fuel neccessary for the engine to operate under load (ie. going up a hill). youre lucky the pump hasnt seized up completely.

 

sounds like an ignition issue to me as well, check the fuel pressure regulator too as well as the pump and all relays. if you ran varnished fuel through the system then it very well could be clogged somewhere down the fuel circuit. my lt1 misfired before terribly but was due to a burned plug wire.

 

All my misfires have been due to cooked plug wire boots even when they weren't touching anything. However, you are concerned about not enough fuel and the fuel filter so why not just pull it off and check it. It is quick and easy to do and easy/cheap to fix if that is the problem. Should take 5 minutes and you will either eliminate that as the problem or fix it. Simply blowing air through it will tell you real quick if it is bad.

 

It wont let me log onto my username so im using my girl friends but anyways ...


mmmchickenboy ~ No I DID NOT use the 9 year old gas, I disconnected the line at the filter and pumped it all out. But it was still all varnished up inside the tank. I replaced the fuel filter with a new one, but I think its clogged from all the varnish in the tank and lines breaking up. I've been running injector cleaner through it every other tankful or so, and I think it broke up all the **** that varnished up in the tank, and now it clogged the new filter ???

shoebox ~ The plugs and wires are fine, none are the wires are bruend and they only have a couple thousand miles on them. The Opti only has 15,000 origional miles on it so I dont see how that could be bad? Coil is fine, and it almost feels like the car starts to bog down and miss, not just a cylinder or two like if it was the Opti starting to go bad. My uncle rode in it and he thinks its starving for fuel. It feels way underpowered.


IslandZ ~ I've already checked the header gaskets, they are fine. There is no exhaust leaks anywhere. And even if I ease into the throttle, once it reaches a certain point it starts sputtering anyways.

Thanks all

 

just because it only has 15k miles doesn't mean it hasn't corroded or deteriorated inside. i wouldn't rule that out yet.

 

Still though, it was garaged for those 9 years, and it really doesnt feel like a spark related miss. Like, im not saying your wrong, it just doesnt feel like it does when a cylinder is missing, itsm ore like the whole engine is starving for fuel or something and it sucks.

 

does it act this way in neutral? how does it act when you increase the rpms with no load on the engine?

 

In nuetral it revs up perfect to 3500, but I never really rev it up higher than that so I cant say. You can bring the RPMs up smoothly as slow or as fast as you want. With it in gear even, you can bring the RPMs up smoothly as long as you dont go past a certain point. If I stab the trottle, not all the way to the floor, but enough, it takes off. But give it more thottle than at that certain point and it starts to lack power and pull with a bad miss. As soon as it starts to miss bad the O2's begin to get stuck on the lower end of the scale at <100mV. And if its floored they stick at the highest at around 40mV, if not less than 10mV. This is indicating a lean condition though right?At any rate, I think the only reason its not noticable in nuetral is because you dont have to give it as much gas for it to wind out.

In nuetral 25% throttle is probly smacking it off the rev limiter. The problem seems the most noticable at around 50% and higher throttle. I see where your going with things, but I think this might be why i dont notice it in nuetral. Since its more of a fuel demand to wind it out in gear, than in nuetral, it is more noticable ?

What are symptoms of a sticking injector ? Once this storm blows over im going to pull the fuel filter out and try to blow through it from the engine side and see if a buncha **** comes out of it.


Thanks again.

 

I would drop that tank and clean it out. It seems like all evidence indicates that it is fuel starvation likely caused by debris in your tank.

 

... Taking gas tanks out sucks ... But at least this one, if I have to take it out, will be in decent weather. I had to change the fuel pump in my 94 Blazer, and it was literally 10* outside. But I needed it for school the next day so me and my dad were outside from 1130 to 630 trying to get it out, the new one in and then back together ...