87 coupe not running right!! HELP

[1987coupe]

my coupe runs great unless you go more than 3/4 throttle if you go past that it will start bucking and cuts out real bad and when you go back under 3/4 it runs good and pulls hard. I have put a new fuel tank, filter, different dizzy, different tps, different map sensor, changed the regulator, i have changed out the maf, changed the computer, every thing like that, it has stock bottom end with edelbrock heads, e cam, 1.6 rockers, trickflow street intake, 70mm bbk tb with egr delete, a 255 pump, 24lb injecters, bbk mass air calibrated for 24s, it holds 38 to 40 psi of fuel timing is set to 10 with spout out. ANY IDEAS???:confused:

[RIXXX93GT]

You running an aftermarket chip? Maybe a ground issue. Stick a timing light on it and rev it up does it advance, is it erratic? Is this something that started after the mods? When is the last time it ran right?

[sean]

I had a fox do that. My fix was the tps.

[1987coupe]

no chip installed but i have a 4 bank sct for it and i want to set up a app to have it tuned but i want to figure this prob out first so it dont cost me a arm and a leg to figure the prob out. when i rev it with the timing light on it advances.

[1987coupe]

what voltage or ohms should the tps be at closed throttle and wide open throttle? if some one can tell me that ill check that after work tomorrow.

[RIXXX93GT]

voltage with throttle closed, KOEO .98-1.0v

[1987coupe]

i will check that today THANKS!!

[Blackout]

I am also thinking TPS and or Map Sensor. Just a thought though

[Gearhead]

what voltage or ohms should the tps be at closed throttle and wide open throttle? if some one can tell me that ill check that after work tomorrow.

Anywhere from .80 to 1.0 volts at closed throttle and above 4.50 volts at full throttle.

[RIXXX93GT]

Yea probably should watch the sweep on the meter to make sure its steadily rising as the throttle opens.

[MFIELD]

Does sound like a TPS, but isnt that initial timing a little low?

[RIXXX93GT]

Yea with no chip most are running 12-15 initial.

[1987coupe]

i set the tps to .98 volts on the green wire and when i open the throttle all the way it goes to 4.23 volts but when i test the orange wire it starts at around 5 volts and dont move

[1987coupe]

i also changed the fuel pump back to a stock one and when i pull the vac off the stock reg it goes to 40 then drops to about 20 when i rev it hard then back to 40. when it had the gss340 pump it would only drop to about 35 with the vac line off

[JIMS SVT]

Id changed the filter again

[1987coupe]

well i took it down the road and it ran fine ill drive it some more tomorrow and see what happens thanks for all the help so far!!

[1987coupe]

the coupe is running like a champ i dont know if it was the fuel pump or the tps i adjusted it and didnt drive it until after i put the pump in. if i launch it it still has a small hesitation so im going to bump the timing up a little THANKS GUYS !!

[blown96cobra]

I'd say the stumble will go away with some more timing. From what u were describing it sounds like your pump took a shit!

[1987coupe]

well i hate to bring this thread back up but started doing the same thing again. so i bought a new adjustable fpr from work for it and again with the new reg it goes to 40 then drops to about 20 when i rev it hard then back to 40. now it also dont hold fuel pressure after i shut it off, there are no leaks coming from the fuel lines anywhere, regulator or injectors on the outside.

[06V6Andrew]

tony maybe you have a faulty injector when you rev hard. maybe it doesn;t shut off and they stay open. really need to hook an oscilliscope up to it to see what everything is doing.

[1987coupe]

now the bucking dont happen unless it is in lower rpms and it is wot if i floor it above 3000 it wont do it but i can still feel a loss of power at wot but at 3/4 throttle it feels good this makes no sence to me at all.

[1987coupe]

Id changed the filter again

im going to change the filter again tomorrow but it has a new tank and pump sock so i dont see it being clogged

[1987coupe]

also the tps is still showing 4.23 at wot is that too low

[06V6Andrew]

yes wot should be close to 6 volts it is a 6 volt meter. i think between 5.8 and 6 is normal.

[Kevin1989]

my car did kinda what your describing last year, it was my ignition box...

[chris91]

The TPS is not a 6 volt sensor, its 5v. According to this article the minimum voltage at WOT should be no less than 3.21v so you are fine.

http://sbftech.com/index.php/topic,1031.0.html

This is a good read on the TPS too.
http://www.w8ji.com/mustang_throttle_position_sensor.htm

Just a shot in the dark but have you checked the salt and pepper shaker connections? Make sure they are clean and making good connections. They can cause all kinds of trouble.
http://fordfuelinjection.com/index.php?p=85

[1987coupe]

its not the ignition box, i changed the ignition back to stock and have the same issues

[1987coupe]

my concern is the fuel pressure i think at wot it is running lean when im hard on the throttle it drops 20 psi or more and when i free rev it fuel pressure drops not as bad but still drops. i dont think it is electrical unless it has something to do with the feed to the pump

[06V6Andrew]

it is a 5 volt sensor. i found this website out about mustang tps sensors.

http://www.w8ji.com/mustang_throttle_position_sensor.htm

[06V6Andrew]

go to the website i posted above and check out the sentence below the red box. it could explain exactly what is happening to your car.

[1987coupe]

how do i lower the wot voltage and keep the idle voltage the same? right now the voltage difference is around 3.34

[chris91]

Um yeah Andrew I posted that link already bud.

[1987coupe]

thats funny

[06V6Andrew]

i didn't even check...wasn't paying attention to links since there are usually so many below post anyway.

[06V6Andrew]

i don't know about that tone. i justed posted the link...just start replacing everything on the fuel system maybe it will be fixed then..hahaha

[chris91]

You say you replaced the fuel pump with a stock one. Brand new from Ford or from a auto parts chain store? And have you replaced the filter yet? And was the tank you put in brand new? Id pull it and make sure there isnt anything in there clogging shit up.

[1987coupe]

tank was bran new pump was new filter is new there is no way there is a clogging issue im going to check for voltage drop in the supply wires for the pump when i get home

[1987coupe]

i have had the tank out 3 times and every time the tank and the fuel sock still looks new hahahaha lol. its getting to the point of trade off lol

[06V6Andrew]

i can't wait for it to run right and you get the tune on it. It'll run good...FIX IT!!!! If you need help call me.

[chris91]

If you bought the pump at Autozone or the like Id wonder if you might have gotten a bad pump. Just tryin to throw ideas out there for ya. Fuel lines in good shape?

[1987coupe]

jus got done adjusting the tps and timing those are closer to spec now, checked for voltage drop at the pump it actually raised with the charging system like it should, lines are in great shape. the car will run through the gears without bucking or cutting out but it still bucks if i floor it at a lower rpm in any gear except 1st and i still have pressure drop at the guage so im leaning toward the fuel pump again. i think i will go to jegs saturday and buy either a 255lph forced induction pump or spend the extra 30 bucks for the intank 340lph aeromotive pump.

[Racin Jason]

My 86 did that and it ended up being my mass air conversion harness worked its way loose at the pcm.

[1987coupe]

well i think the coupe is fixed again