Thread: 97 GTP Misfire

last night on the way home from work my SEL came on on the highway. it still drove fine so i didnt pay much mind. checked it out when i got home it was a p0303. i noticed a slight miss so this morning i did the plugs and wires. the plugs were white so i assumed it was running lean, but the fuel pump was just done so i just figured thats what it was from. started it up and its misfiring 10x's worse. SEL flashing and its throwing p0300. i seafoamed the car this morning and it ran smooth while i was running it through which makes me think its fuel related. im leaning towards the fuel pump being bad. i just got the car so i dont really know much about it, but the guy i got the car from put a cheap fuel pump in it. so im wondering if its not pushing enough volume. also i just filled the tank with regular. but i dont think not using premuim would make it miss. any help would be appreciated

this might be caused by running regular because the car is probably adjusted for running premium unless the guy you bought it from used regular and then you may have a problem with the fuel pump but if he ran premium i would think that the fuel is detonating before the piston reaches the top of its stroke. how does it run after the sea foam?

runs the same. still missing. ive never seen a car miss because of regular fuel though. and i highly doubt he ran premium. the car doesnt seem to have been taken care of

how many miles are on the car?

Originally Posted by 2000 Black 2dr

how many miles are on the car?

150k

Originally Posted by Zef_66

My bet would be that he ran regular and somewhere along the lines chipped a piston because of it.

Were any of the spark plugs smashed when you took them out?

no. and it was running great up til this morning. plus the cyl3 miss is gone. now its missing across the board. i think its gotta be the pump at this point. i had to take the pump assembly apart and clean it to get it running when i bought it. i took the screen off the pump itself cause it was clogged, and because there is one on the bottom of the assembly. i think im just gonna break down and buy a pump. i figured i would need to do it eventually anyway. i wad just hoping maybe there was a common problem i didnt know about.

it could also be a vacuum leak but you may still be right with the fuel pump because it could also be caused by low pressure. if you do get a pump let us know if it fixes the problem. before you buy the pump i would just look over the engine bay at the vacuum lines to make sure that they are not cracked or broke.

i found 1 broken vac line going from the TB to the MAP sensor? i think. i didnt have much time to play with it today

i would fix that first no matter where it goes.