Need Help ! ! ! !
#1
10-29-2007, 09:09 PM
Need Help ! ! ! !
I have a 1993 F150 single cab 5liter v8 302 and whenever i start it and put it into drive it will do like 15-20mph without me even putting my foot on the gas pedal. It doesnt do this if the truck is warmed up though. If you let it sit there and warm up for a while before putting it into drive. PLEASE HELP ME WITH THIS!!!!!
#2
10-29-2007, 09:18 PM
Senior Member
#3
10-29-2007, 09:19 PM
Cold starts normally go to high idle then come down as the motor warms and the OX sensor takes control of the fuel.
We all can get into a pulling condition if we start the motor and go right into gear. That's one thing the brake is for.
If the idle stays high for too long, you may have an IAC sticking until some motor heat frees it up. If so it cleaning time.
What's your condition?
We all can get into a pulling condition if we start the motor and go right into gear. That's one thing the brake is for.
If the idle stays high for too long, you may have an IAC sticking until some motor heat frees it up. If so it cleaning time.
What's your condition?
#4
10-31-2007, 04:51 PM
Well if I turn the truck on and let it sit there for 3 minutes or so it doesn’t do it but most of the time I don’t want to sit there in a parking lot and wait for it to warm up. It wouldnt be such a big deal if when i put it in drive it didnt do 20mph without me even touching the gas pedal.
#5
10-31-2007, 11:59 PM
Let me explain something to you. A cold start requires more fuel and more air to have the ability to cold start and drive away.
The coolant temp sensor and air temp sensor set the main fuel and air levels to make this happen. These sensors are looked at the instant you turn the key on, before cranking, for determination of conditions the motor has to deal with. It's the only way it knows by reading these senors since it can't feel like we can.
High idle is mainly a function of how much air is allowed into the motor and not so much on the amount of fuel.
These sensors won't give up there control until the OX sensors have come up to their operating temperature of close to 600 degrees. This in it'self takes some time, especilly if the air injection operation is not healthy.
That's the way the systems have been designed since the first port EFI in 1985 and earlier with CFI and all the way back to carb days with fast idle cams on the carbs where the driver had to tap the pedal to get the carb to set the fast idle cam and release the choke to close.
Without this kind of operation you would complain you HAVE to set there until it warms enough to drive away, without stalling.
Naturally the idle will be high with the extra air and fuel.
If you think you have a fault above and beyond that, it's a possibilty.
Test the sensors resistances, clean the throttle body, Check for a leak allowing extra air boosting the cold idle higher than it needs to be, reboot the PCM/EEC and see if it makes a difference after some relearn time.
Unless there are codes stored, it's crap shoot finding any hard faults.
The trucks of the 80s and early 90s had a tendency to high idle after some age.
There's not much more to discribe on how the operation works.
Good luck and put the check in the mail.
The coolant temp sensor and air temp sensor set the main fuel and air levels to make this happen. These sensors are looked at the instant you turn the key on, before cranking, for determination of conditions the motor has to deal with. It's the only way it knows by reading these senors since it can't feel like we can.
High idle is mainly a function of how much air is allowed into the motor and not so much on the amount of fuel.
These sensors won't give up there control until the OX sensors have come up to their operating temperature of close to 600 degrees. This in it'self takes some time, especilly if the air injection operation is not healthy.
That's the way the systems have been designed since the first port EFI in 1985 and earlier with CFI and all the way back to carb days with fast idle cams on the carbs where the driver had to tap the pedal to get the carb to set the fast idle cam and release the choke to close.
Without this kind of operation you would complain you HAVE to set there until it warms enough to drive away, without stalling.
Naturally the idle will be high with the extra air and fuel.
If you think you have a fault above and beyond that, it's a possibilty.
Test the sensors resistances, clean the throttle body, Check for a leak allowing extra air boosting the cold idle higher than it needs to be, reboot the PCM/EEC and see if it makes a difference after some relearn time.
Unless there are codes stored, it's crap shoot finding any hard faults.
The trucks of the 80s and early 90s had a tendency to high idle after some age.
There's not much more to discribe on how the operation works.
Good luck and put the check in the mail.