Modded Mustang Forums banner
1 - 18 of 18 Posts

·
Registered
Joined
·
34 Posts
Discussion Starter · #1 ·
hey everyone, i own a 2000 mustang gt, just dropped a brand new long block into it 600 miles ago. Ive been having this problem ever since ive owned the car, old motor, and new... It idles great, runs great, does everything right when its cold, then the minute it warms up you cant give it any gas without it giving out and basically stopping the car. ive got a brand new wiring harness, i switched out my injectors for some used 04 ones, changed all the spark plugs, and still no results. I checked my idle fuel pressure and its in spec. Basically what happens is once it warms up you can nail the gas pedal and it will throw you back in your seat until about 2500 to 3000 rpm then you fly forward as the car just cuts out. anyone have any ideas?
 

·
Registered
Joined
·
34 Posts
Discussion Starter · #7 ·
ya, when i say it stops, i mean like, it loses ALL power in a nasty shuddering, fuel starving kind of way, but it dosent completly turn off. I noticed on a scan tool that one of the oxygen sensors voltage is way off compared to the others, and i also havent checked fuel pressure when it actually happens, There isnt a specific rpm but its usually right around 2500,3500 in the lower gears, but if i put it in 5th and try to step on it at say around 50 mph and 1500 rpms, it studders so badly, no pick up and once again this only happens when car is warm, runs like a top when its cold
 

·
Registered
Joined
·
16,245 Posts
you dont happen to have your old shortblock do you? Id love to give you a few bucks for it.
 

·
Registered
Joined
·
16,245 Posts
when my 95 model GT did this EXACT same thing, i got a new MAF from the dealership and it cured it. Mine acted the same way and it would just act like it was bout to die at about 2800rpms or so. Had to keep it in low rpms just to make it around. Ordered brand new maf and it completely went away. Just a thought. So, you still got that shortblock? LOL
 

·
Registered
Joined
·
257 Posts
ya, when i say it stops, i mean like, it loses ALL power in a nasty shuddering, fuel starving kind of way, but it dosent completly turn off. I noticed on a scan tool that one of the oxygen sensors voltage is way off compared to the others, and i also havent checked fuel pressure when it actually happens, There isnt a specific rpm but its usually right around 2500,3500 in the lower gears, but if i put it in 5th and try to step on it at say around 50 mph and 1500 rpms, it studders so badly, no pick up and once again this only happens when car is warm, runs like a top when its cold
what happens when you mash the gas while its just sitting or in neutral??...does it only happen under a load?
 

·
Registered
Joined
·
16,245 Posts
good question ^
 

·
Registered
Joined
·
16,245 Posts
my 95 did it regardless of being in neutral or in gear.
 

·
Registered
Joined
·
34 Posts
Discussion Starter · #13 ·
haah sorry dude ide love to give it to ya but the machine shop i got my new motor from took the old one for a core charge, and it does it in neutral too, it wont rev all the way up when its warm, but when its cold it does, its just way worse under a load, this problem happend in both motors
 

·
Registered
Joined
·
16,245 Posts
happened with both motors..... well that tells you that my suspicion of the maf is still a thought! Unplug the maf and see what happens maybe?
 

·
Registered
Joined
·
257 Posts
happened with both motors..... well that tells you that my suspicion of the maf is still a thought! Unplug the maf and see what happens maybe?
good call, thats also what made me think fuel pump because you didnt replace that with the new engine buuuuut...if its doing it in neutral to i would guess its electrical, you said you replaced the wiring harness so i would def agree with baker and check maf.
 

·
Registered
Joined
·
34 Posts
Discussion Starter · #18 ·
figured it out everyone, it is the fuel pump, it can supply enough pressure to let the car idle and slightly accelerate, but not enough to really drive the car. used a fuel pressure test inbetween the fuel filter and tank, only 25 psi and dosent change if you block off the flow or not.
 
1 - 18 of 18 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top