Won't rev past 1500 RPM... coughs and sputs when given gas
 

I believed the fuel pump to be going out on my 1997 protege so today I replaced it. After doing so I went to crank it and it wouldn't turn over. Once again like it wasn't getting fuel. So I waited and turned the key to the 'on' position and I heard the pump come on and then the car cranked. The RPM's bounced all over the place for a few minutes with it idling very rough and then they went down to 750 and it was still a little rough but a good bit better. When it was idling all over the place, I could rev it up and it was somewhat smooth in doing so. After going back down to 750, I could no longer rev it. I can push the gas pedal to the floor and it will go to about 1500 RPM and cough and sput really bad almost like it wants to shut off, then when I release it, the RPM jumps to about 2000 then it immediately goes back to idling semi rough at 750. Can anyone please help me and let me know what I need to do? I've been working so hard on this car and nothing seems to ever work or go my way

An exhaust restriction will act the same as a fuel pump going out. Create an exhaust leak before the converter and see if it runs better. Maybe remove the front o2 sensor. You can bang on the bottom of a converter and listen for rattling inside also. Clean the MAF and check the intake boot for cracks.

Is there a CEL code coming up?

The only code that it threw was one saying that cylinder 3 was mis-firing. Yesterday it wouldn't crank at all and even though the engine was turning, the fuel pump never would prime. So I checked to see if the spark plugs were firing and none of them were getting any spark. I now think that it may be the crank shaft sensor. Does anyone have any thoughts about this? Thanks

check post "acceleration problem" by charliehorse. his sounds like your problem. He had Mazda dealer check car. read post and good luck

the spark plug problem i would olm the ignition coil or distributor cap whichever you have the fuel pump i have no answer for really it could be an ecu problem (car computer)

would a head gasket be blown or anything to cause that?

if it was a head gasket or a warped head the exhuast would come out white cause there would be anti-freeze and oil burning and thats what color it comes out

Sorry I haven't posted in a while but here is what all I have done... still to no avail. I have checked the timing belt, no teeth are missing. I have tested all the relays involved with fuel and ignition, they all work fine. I tested the crank position sensor, its not that. Tomorrow or wednesday I am testing the mass air flow sensor and the throttle position sensor. If it's not either one of those all that I can think of that it could be is the computer so I'll hit up a local salvage yard and pick one up. In regards to the last post, I never noticed the exhaust having any color to it but if I can get it to crank again I will check

I also forgot to mention that I have also replaced the distributor as well as the cap. Still no spark...