[kuskye25]

my 88 gt started running rough a few weeks ago, it runs like crap for a few seconds then clears up, it does this every minute or two and has gotten increasingly worse with time mainly when you get into the throttle some. so i unplugged the tps and it made it stop running rough, replaced tps still does it, unplug new tps and it clears up the rough shit again it just has the normal loss of power from having the tps unplugged but no running like shit then clearing up.

i tried unplugging the iac and starting the car and it wont run without the iac plugged in, ive fully cleaned the iac now and plugged it back in.

ok so i have my tps plugged back in and unplugged the vacuum line to my fuel pressure regulator and it makes my car run properly, so i take it my FPR is bad....

any input is apreciated, sorry for all the backround im just hoping someone has had this issue before and can tell me what to replace next....

[highrider407]

i would look at the injectors, but i use to be a chevy guy, and i'm on my first stang. but it wouldn't hurt to tast them. they have known issues with cold start/ rough idle.

i probly wrong but it couldn't hirt.

[kuskye25]

Originally Posted by highrider407 i would look at the injectors, but i use to be a chevy guy, and i'm on my first stang. but it wouldn't hurt to tast them. they have known issues with cold start/ rough idle. i probly wrong but it couldn't hirt.

most of the time the car runs great though, esp till its warmed up... is this normal for a injector to be bad but most of the time its fine...

sorry i forgot to mention its fine till it warms up. if i leave the fpr unplugged its fine period...

[highrider407]

fuel pressure at the rail

Key On Engine Off 35 - 45 psi
Key On Engine Running 30 - 40 psi

Typical Fuel Pressure Regulator






PURPOSE
The fuel pressure regulator controls fuel pressure supplied to the injectors. The regulator also traps fuel during engine shutdown, thus eliminating the possibility of vapor formation in the fuel line, and provides instant restarts and initial idle speed.

OPERATION
Balancing one side of the diaphragm with manifold vacuum maintains a constant fuel pressure drop across the injectors. Fuel in excess of that used by the engine is bypassed through the regulator and returns to the fuel tank.

CONSTRUCTION
The regulator is a spring loaded diaphragm operated relief valve. One side of the diaphragm senses fuel pressure and the other side is connected to intake manifold vacuum.

[highrider407]

i haven't had the problems with my 87 yet, but i am having many other problems, so i've been doing alot of research on stangs and i'm mentioning issues that i've read on. i wish i know for sure, but just read up on know issues.

[kuskye25]

Originally Posted by highrider407 fuel pressure at the rail Key On Engine Off 35 - 45 psi Key On Engine Running 30 - 40 psi Typical Fuel Pressure Regulator PURPOSE The fuel pressure regulator controls fuel pressure supplied to the injectors. The regulator also traps fuel during engine shutdown, thus eliminating the possibility of vapor formation in the fuel line, and provides instant restarts and initial idle speed. OPERATION Balancing one side of the diaphragm with manifold vacuum maintains a constant fuel pressure drop across the injectors. Fuel in excess of that used by the engine is bypassed through the regulator and returns to the fuel tank. CONSTRUCTION The regulator is a spring loaded diaphragm operated relief valve. One side of the diaphragm senses fuel pressure and the other side is connected to intake manifold vacuum.

im not really sure what you mean by this but do you think it is my fpr

[highrider407]

what your describing fits 84-90 mustand 5.0's but i can't find much on 93.

Hard cold starts, hesitation and stalls on initial start-up or during idle or decel may be caused by sludge in the throttle body and/or idle by-pass valve. Sludge deposits or oil film on the throttle body bore and plate or the idle air by-pass valve may cause one or more of the following conditions.

^ Hard Cold Start

^ Stall On Initial Start-Up

^ Stall During Idle

^ Stall During Decel

^ Rough Idle

^ Rolling Idle

^ Hesitation During Acceleration


ACTION: A new idle air by-pass service kit (F2PZ-9F939-A) is now available for service use to correct sludge contamination concerns of the throttle bore and plate only. It eliminates the need to clean the majority of past model throttle body applications. Cleaning is not required on sludge tolerant throttle body designs released for 1991 and newer model years

[highrider407]

Originally Posted by kuskye25 im not really sure what you mean by this but do you think it is my fpr

it may be, just offering suggestion. i'm a reseach nut. and i'm curious as to what is cuasing your problem.

[kuskye25]

Originally Posted by highrider407 what your describing fits 84-90 mustand 5.0's but i can't find much on 93. Hard cold starts, hesitation and stalls on initial start-up or during idle or decel may be caused by sludge in the throttle body and/or idle by-pass valve. Sludge deposits or oil film on the throttle body bore and plate or the idle air by-pass valve may cause one or more of the following conditions. ^ Hard Cold Start ^ Stall On Initial Start-Up ^ Stall During Idle ^ Stall During Decel ^ Rough Idle ^ Rolling Idle ^ Hesitation During Acceleration ACTION: A new idle air by-pass service kit (F2PZ-9F939-A) is now available for service use to correct sludge contamination concerns of the throttle bore and plate only. It eliminates the need to clean the majority of past model throttle body applications. Cleaning is not required on sludge tolerant throttle body designs released for 1991 and newer model years

no its not hard to start and doesnt stall ever it idles fine and runs like a champ, it just studders sometimes, and idles like shit once warmed up...

[kuskye25]

Originally Posted by highrider407 it may be, just offering suggestion. i'm a reseach nut. and i'm curious as to what is cuasing your problem.

the more i look i think ill replace my fpr and do a base idle reset i think...

[highrider407]

i would check the fuel pressure to make sure it's not that, and then the ohmz reading on the injectors to make sure they all read roughly the same to make sure ones not bad.

[highrider407]

update this thread when you find the problem so i'll know for future needs.

good luck

[kuskye25]

Originally Posted by highrider407 i would check the fuel pressure to make sure it's not that, and then the ohmz reading on the injectors to make sure they all read roughly the same to make sure ones not bad.

i have no resourses and little knowledge in that area, so can i buy something cheap to check the fuel pressure, and what should the injectors be at, thanks

[kuskye25]

Originally Posted by highrider407 update this thread when you find the problem so i'll know for future needs. good luck

yeah im just hoping someone will come along that has had this issue, i know its something basic and simple, if not ill figure it out eventually, all my gt does is collect dust anyway... haha

[highrider407]

not sure about the feul pressure, just repeating what i read. and the resistance on the injectors should be between 11-18 Ohms. whatever they are, they should all be roughly the same number, if one is way off, then you have a bad one.
i'm open to any other suggestions on the problem.

[highrider407]

Originally Posted by kuskye25 yeah im just hoping someone will come along that has had this issue, i know its something basic and simple, if not ill figure it out eventually, all my gt does is collect dust anyway... haha

i agree, i'm sure it's something simple too. i wsh iknew what it is so i could tell ya.

[1slo5.0]

Originally Posted by kuskye25 my 88 gt started running rough a few weeks ago, it runs like crap for a few seconds then clears up, it does this every minute or two and has gotten increasingly worse with time mainly when you get into the throttle some. so i unplugged the tps and it made it stop running rough, replaced tps still does it, unplug new tps and it clears up the rough shit again it just has the normal loss of power from having the tps unplugged but no running like shit then clearing up. i tried unplugging the iac and starting the car and it wont run without the iac plugged in, ive fully cleaned the iac now and plugged it back in. ok so i have my tps plugged back in and unplugged the vacuum line to my fuel pressure regulator and it makes my car run properly, so i take it my FPR is bad.... any input is apreciated, sorry for all the backround im just hoping someone has had this issue before and can tell me what to replace next....

Running better because you unplug a sensor doesn't have anything to do with the sensor being bad. The computer controls everything. When you unplug a sensor the computer things something is wrong and compensates for it which is why the engine then runs different. Your fuel pressure regulator probably isn't bad either. Pulling the vacuum line changes the fuel pressure and also creates a vacuum leak. After you run the car, shut it off and pull the vacuum line off the fuel pressure regulator. Look at it and smell it. Is there any gas in it? If there is, you should be able to see it. If there is gas in the line then the regulator is bad. Typically there will be a hard start problem when the vehicle is warm when you have a bad fuel pressure regulator because the vacuum in the line will suck the fuel out of the regulator and flood the engine after you shut the car off.

Did you check for codes?

[kuskye25]

Originally Posted by Darrell Running better because you unplug a sensor doesn't have anything to do with the sensor being bad. The computer controls everything. When you unplug a sensor the computer things something is wrong and compensates for it which is why the engine then runs different. Your fuel pressure regulator probably isn't bad either. Pulling the vacuum line changes the fuel pressure and also creates a vacuum leak. After you run the car, shut it off and pull the vacuum line off the fuel pressure regulator. Look at it and smell it. Is there any gas in it? If there is, you should be able to see it. If there is gas in the line then the regulator is bad. Typically there will be a hard start problem when the vehicle is warm when you have a bad fuel pressure regulator because the vacuum in the line will suck the fuel out of the regulator and flood the engine after you shut the car off. Did you check for codes?

ok cool thanks darrell, thats the most help ive had yet, no it doesnt smell or look like gas is in the vacuum line, i used a long straw to smell it, i dont have a way to pull codes but will get it done soon.

[flattusmaximus78]

93 hatch has a good how to on pulling up codes for obd1 cars. Do the search my good man.