Misfire or is it

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ramairmustang

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Okay I just had my fuel pump replaced with a 255lb on from scp.com because my car would seem to stop getting fuel under moderate to hard acceleration. It would just stop accelerating for a few seconds then kick back in. I had it checked by Jake Sweeney Chevrolet/Mazda and they said it's the fuel pump. So they replaced it with the one listed above. Got the car back and it's much much better but it will still jerk and lurch a bit under moderate ro hard acceleration but not as bad as it was doing. It does it more in this situation. Say you are going 55mph in 4th gear and you start climbing a hill, you feed into the gas pedal just a bit more to pull the hill but not enough to comand a downshift into 3rd. It will start to jerk untill i either back off the gas or push the button to downshift into 3rd. After performing it downshifts into 3rd everything is fine. But now if im going say 30mph and kick down to 2nd to accelerate it does that same jerky :q:q:q:q. I've replaced the plugs, wire, coil packs, injectors, fuel filter and now the fuel pump. Could this be my Idle Air Control Valve going bad or the Fuel Pressure Regulator? I dont know. I am about to get my body work fixed a very very nice Black Cherry paint job done this summer and would like my car to run good as well. Oh also I was getting about 16.6mpg before the fuel pump was replaced now im getting 20.2mpg.
 
I've cleaned the MAF really good with MAF cleaning spray from autozone about a month ago. I didn't look dirty but cleaned it anyway. No change in the way it looked or performed that I could notice. Where is the TPS located im trying to think if I replaced that already or not I replaced the Camshaft Position Sensor and the Crankshaft Position Sensor. I did have an engine code come up a long time ago for the Idle Air Control but it has not come up sense. Oh and sorry I forgot to mention that I had a code for a no signal to pin1 low speed fuel pump delivery or some stuff like that. That is the code that made them change out my fuel pump.
 
my bet is the crank sensor mine did the same thing, i changed all the stuff you mentioned that's what it was and it was worse because i had already changed it and it was defective get one from ford
 
I would be looking at air flow and fuel flow. You stated you replaced the fuel filter, pump, wires, coil packs, plugs. What about air filter, MAF, or fuel pressure regulator?

Also, have you had a fuel pressure test done? I would want to know if possibly I have a fuel pressure issue do to a combination of things, most mostly a fuel link or air getting into system supply. What you are mentioning when you down shift and when you do it stumbles, it may be due to fuel demand as the RPM's are increased every-time you downshift manually. Which will cause a larger demand for fuel, it would not strike me odd if there was a fuel leak or a possibility of air getting in your supply when this demand is increased like that. May not notice it under normal circumstances but under higher RPM you may.
 
Air Filter is good, MAF have only cleaned and Pressure Regulator have not changed yet that was one of my suspisions.
 
mine did the same thing had me in circles for months it was letting oil get inside and finally started leaking out and when i replaced it the problem stopped. some days it ran fine, i don't mean to say anyone is wrong but i strongly suspect the crank sensor. even the head tech at the Ford dealer said no way that's it he was. wrong
 
The crank sesor is under warrantee so i'll replace it again. But after replaceing it it didn't help anything at all. Sometimes i do have to crank unusally long to start it ie upto 5seconds but that's not that often. Most of the time it's under 3seconds.
 
From what you describe it sounds like a misfire. My bet is spark plug wires. What brand are they? If they are cheap ones I've seen them bad right out of the box. Could be torque converter shudder. I seen 2 or 3 trans that had shudder so bad that when you go to WOT they get even worse. But if that were the case you would feel it often. Also the trans will go to lockup in 2nd gear. If you manually put your trans in second and get at the right rpm the converter will lockup. Anyway you could try starting the car at night, open the hood and wet your wires down and see if you have any arcing. My bet is that they're misfiring down inside the tubes. Do you have any oil inside spark plug tubes?
 
ramairmustang said:
I had it checked by Jake Sweeney Chevrolet/Mazda
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your car is shaking out of disgust from the way you treated it. leaving it with a chevy dealer. you should be a shamed. go out side and polish your car to make it happy again.

have you tried adding anything to the transmission fluid like lucas or whatever your popular brand stuff is to see if it helps make a difference.
 
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