Ford Mustang Forums banner

1 - 13 of 13 Posts

·
Registered
Joined
·
5 Posts
Discussion Starter #1
As the title suggests i have a 1966 Mustang with 1988 5.0 swapped in. I was having this problem where the car would die at idle when i turned the a/c.. typically only after the car was up to temp, before temp it would surge a bit with the a/c on and run alright but wouldn't sputter and die. The past week i have been doing some work to solve the problem, i took off he cold air intake, throttle body, and iac and cleaned them all, this did not help (much). I had noticed that the 5.0's idle was a bit high after the car got up to temp so i put a timing light on it and brought the idle down/timed it the motor sounded way better/relaxed. Now the car will sputter and die even without the a/c on but only after it is up to temp i am thinking this could be related to the a/c problem as well. Though maybe i set the idle/timing incorrectly as i am fairly new to mechanics. Me and my buddy who has been helping me (he knows a bit more than i) think that the problem could lie with the injectors as they are the ones that came with the motor when i got it or possibly a dirty fuel filter,we will be checking those in the next couple days. We also have checked the spark plugs and they are fairly new but are fouled and will need to be replaced, they have a decent bit of gasoline on them. The Mustang has a new Msd fuel pump, new msd coil/distributor cap, and new spark plug wires. I will also be flushing the radiator soon.

When i was cleaning the Throttle body i noticed gasoline on the gasket (pictured) not sure how it got there. it might be oil but i would have to double check. my buddy said it smelled like gas.

Any help or advice would be greatly appreciated
Thanks in advance -Mike

)
1056756
 

·
Registered
Joined
·
383 Posts
Your fuel pressure regulator may have gone out. When the fpr diaphragm breaks internally gas gets sucked into the vacuum line coming off the top of the fpr and vacuum sucks gas straight into the upper intake vacuum tree and saturate's everything with gas. Gaskets, spark plugs, vacuum lines all usually wet with fuel when it happens.
 

·
Registered
Joined
·
5 Posts
Discussion Starter #3 (Edited)
Your fuel pressure regulator may have gone out. When the fpr diaphragm breaks internally gas gets sucked into the vacuum line coming off the top of the fpr and vacuum sucks gas straight into the upper intake vacuum tree and saturate's everything with gas. Gaskets, spark plugs, vacuum lines all usually wet with fuel when it happens.
I will check it out, how would i verify if its bad, with a fuel pressure gauge? do you have any recommendations for brand of a new regulator, or is the typically napa one any good?
Thanks for the help

This any good? might as well upgrade if i have to replace.. unless it will hinder the stock 5.0
 

·
Registered
Joined
·
383 Posts
Start the engine at a cold start and right away before it warms up pull the vacuum hose off the fpr on the backside of the upper intake as its running. Gas will be leaking out or spraying out of the fpr vacuum nipple if the fpr broke internally. If you have a stock engine with no mods and want to keep it mostly stock I'd recommend another stock fpr from napa. If you want to be able to adjust your fuel pressure in the future the Kirban fpr is a good choice but also would need a fuel pressure gauge to go with the Kirban fpr so you can get the fuel pressure set to your applications needs. A fuel pressure gauge would be a good thing to have with stock fpr or aftermarket fpr for diagnosing.
 

·
Registered
Joined
·
22,261 Posts
Like the vid

total lack of understanding of the system, if you have to ease the throttle to maintain idle, then the ECM has no control

Idle speeds in these cars are set in the ECM.

shall the diagnosis start?
 

·
Premium Member
Joined
·
140 Posts
Before you dig in too deep -

Did the A/C previously operate without issues?

When you started the A/C before, did the clutch engage on the compressor and idle increase to accommodate load?

Does the engine try to increase idle when the compressor is turned on, or does it just start to sputter out and die?
 

·
Registered
Joined
·
22,261 Posts
IS the pcv routed like factory?

gas in the throttle body?

also the fact that it dies without a/c being on, is a classic case of a jacked with throttle stop

watch the vid posted, that dude does the same thing, and screws it up everytime,

BTW i do like that guys vids on you tube, i yell at the screen when he doesn’t understand
 

·
Registered
Joined
·
5 Posts
Discussion Starter #9
Start the engine at a cold start and right away before it warms up pull the vacuum hose off the fpr on the backside of the upper intake as its running. Gas will be leaking out or spraying out of the fpr vacuum nipple if the fpr broke internally. If you have a stock engine with no mods and want to keep it mostly stock I'd recommend another stock fpr from napa. If you want to be able to adjust your fuel pressure in the future the Kirban fpr is a good choice but also would need a fuel pressure gauge to go with the Kirban fpr so you can get the fuel pressure set to your applications needs. A fuel pressure gauge would be a good thing to have with stock fpr or aftermarket fpr for diagnosing.
Will check this out, have been busy this week. thanks for the info.
 

·
Registered
Joined
·
5 Posts
Discussion Starter #10
Like the vid

total lack of understanding of the system, if you have to ease the throttle to maintain idle, then the ECM has no control

Idle speeds in these cars are set in the ECM.

shall the diagnosis start?
Yeah i know i dont understand it.. thats why im here asking 😆😆 im still trying to learn about these cars
... i messed with it a bit today and the idle does not go up when i turn on the a/c. after speaking to my dad (he had some of his company guys swap the 5.0 a year ago they usually do big dump isuzu trucks and arent very familiar with old 5.0s) it seems like the wire to the ecu to raise the idle was never installed... they were in a hurry and the ac was not even hooked up when the motor was first swapped... i think that may be my problem. im not sure why it died without the ac on the other day. i think it was because i made the mistake of not disconnecting my iac when i adjusted the idle/timed it but i am not sure. will check the pcv this weekend.
Thanks for the help mr.Indy
 

·
Registered
Joined
·
5 Posts
Discussion Starter #11
Before you dig in too deep -

Did the A/C previously operate without issues?

When you started the A/C before, did the clutch engage on the compressor and idle increase to accommodate load?

Does the engine try to increase idle when the compressor is turned on, or does it just start to sputter out and die?
like i said in my recent response i verified it does not gain rpms when ac is engaged i will need to very the cable to the ecu is connected..
do you know where it should be connected if it is not? i assume to the compressor power switch?
 

·
Registered
Joined
·
22,261 Posts
Yeah i know i dont understand it.. thats why im here asking 😆😆 im still trying to learn about these cars
... i messed with it a bit today and the idle does not go up when i turn on the a/c. after speaking to my dad (he had some of his company guys swap the 5.0 a year ago they usually do big dump isuzu trucks and arent very familiar with old 5.0s) it seems like the wire to the ecu to raise the idle was never installed... they were in a hurry and the ac was not even hooked up when the motor was first swapped... i think that may be my problem. im not sure why it died without the ac on the other day. i think it was because i made the mistake of not disconnecting my iac when i adjusted the idle/timed it but i am not sure. will check the pcv this weekend.
Thanks for the help mr.Indy

just so you are clear.

you cannot adjust the idle mechanically

the idle speed is always changing and is controlled by the ecm

i repeat idle speed is set in the ecm

Idle control is done by computer controlled spark timing, IAC air is for changes in engine load, smooths transitions from part -closed throttle positions, as well as other feed forward/anticipatory functions

when you start playing with the STOP on the throttle body, you will cause surging and stalling

if this is a completely stock engine, you can search for the 'base idle reset procedure' it should get you back to the stock amount of bypass idle airflow
 

·
Registered
Joined
·
22,261 Posts
like i said in my recent response i verified it does not gain rpms when ac is engaged i will need to very the cable to the ecu is connected..
do you know where it should be connected if it is not? i assume to the compressor power switch?

the a/c is controlled by the ecm

there is a WAC relay that the ecm controls

it can delay the cycling of the compressor, or turn in off during WOT

the switch on the hvac control is the request, the output from the ecm is the command
 
1 - 13 of 13 Posts
Top