Idle issue when hot

C

Csheets88

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Apr 22, 2024

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Apr 22, 2024

#1

• Apr 22, 2024

• #1

Hello everybody. I have an issue I can't figure out. I have an 89 foxbody with edelbrock heads. F303 cam. Cobra intake. Shorty headers. It'll crank and drive fine. After about 20 minutes of driving and sitting at red-light it will seem like something kicks on and the idle gets super rough. Doesn't seem to affect during driving though, but it will idle bad enough to where it will sometimes die.

 

nickyb

I gotta say i never painted my nuts, Never Ever

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Apr 3, 2009

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nevada

Apr 22, 2024

#2

• Apr 22, 2024

• #2

Could that something that kicks on be an electric fan or is it still stock fan?

 

90sickfox

Wasn't a pretty sight...and I've got big hands

SN Certified Technician

Mar 2, 2015

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#3

• Apr 23, 2024

• #3

Intake air temperature sensor. Seems like it may be your issue....or the coolant temperature sensor. Not the one that looks like a little stud but either the one in the coolant bypass pipe or the one that screws in the intake under the upper intake on drivers side. If the sensors are disconnected or not working it will make the computer think the car is still cold.

 

AeroCoupe

lube between the nut and the face. I know my lubes

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Apr 23, 2024

#4

• Apr 23, 2024

• #4

Even if the CEL (check engine light) is not on there can be codes. This is due to only emissions related codes setting the CEL. I would pull codes first then go from there.

 

C

Csheets88

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Apr 24, 2024

#5

• Apr 24, 2024

• #5

Stock fan. I've pulled codes. Nothing outta the ordinary. Smog stuff, it's been deleted. It has new coolant temp sensor, tps, and aic. I've replaced the thing on the side of the dizzy. (Can't think of the name) And a new msd coil. Cap and rotor are msd as well.

 

mikestang63

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Aug 27, 2012

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Apr 24, 2024

#6

• Apr 24, 2024

• #6

The EEC changes logic at around 170 degrees so I would check the IAT

 

C

Csheets88

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#7

• Apr 24, 2024

• #7

Could this cause an issue with the rpm guage? I have the stock and an auto gage. The stock will bounce around with a blinker on or heat on. But it's not consistent

 

General karthief

wonder how much it would cost to ship you a pair

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#8

• Apr 24, 2024

• #8

Check the ground wire that's bolted to the back of the left (drivers side) head and goes to the fire wall.
Does the alternator charge sufficiently at idle? Needs 13.5 volts or close to at idle.

 

C

Csheets88

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#9

• Apr 24, 2024

• #9

Not completely. It has a newer Motorcraft alternator. Oem

 

C

Csheets88

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#10

• Apr 24, 2024

• #10

With heat and head lights on it will drop it

 

nickyb

I gotta say i never painted my nuts, Never Ever

15 Year Member

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Apr 24, 2024

#11

• Apr 24, 2024

• #11

Time to upgrade to a 3 G alt.

 

General karthief

wonder how much it would cost to ship you a pair

Mod Dude

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#12

• Apr 25, 2024

• #12

Csheets88 said:

Not completely. It has a newer Motorcraft alternator. Oem

Click to expand...

Csheets88 said:

With heat and head lights on it will drop it

Click to expand...

These are not answers that help, the volts will very according to RPMs normally, need to get familiar with diagnostic tools and terms, beg or borrow a volt/olm meter, read voltage at idle, nothing on, and then with blower, lights and wipers on, then say 1800 RPMs, and battery voltage with engine/key off. I have to write things down cause my memory bank is mostly full of useless crap that takes up too much space.
Also need to monitor fuel pressure to see if/what changes when it starts to act up.
We can point you in the right direction, a good start would be a repair manual or better yet an assembly/repair manual by Ford, ebay has some.
Some helpful info can be found in on the tech main page:

Technical Thread/how-to Index

Guys, if "that should be a sticky," then please reply to this thread with the link to your suggestion and why you think it should be added. How to determine if a thread should be included: - Does the topic address a common fox 5.0 owner's needs? / Is it a frequently asked question? / Is it...

stangnet.com

There is some info on the 3g alternator upgrade in there too.

 

J

Jarhead67

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Nov 24, 2018

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Apr 27, 2024

#13

• Apr 27, 2024

• #13

Csheets88 said:

Stock fan. I've pulled codes. Nothing outta the ordinary. Smog stuff, it's been deleted. It has new coolant temp sensor, tps, and aic. I've replaced the thing on the side of the dizzy. (Can't think of the name) And a new msd coil. Cap and rotor are msd as well.

Click to expand...

The thingy on the distributor is the TFI. Did you get the proper one for your car/transmission? Auto car takes a different one than standard.

 

J

Jarhead67

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Nov 24, 2018

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Windsor Locks, Connecticut

Apr 27, 2024

#14

• Apr 27, 2024

• #14

Csheets88 said:

With heat and head lights on it will drop it

Click to expand...

To stop the idle drop when there’s a load (lights or heater blower) get a 130 amp alternator kit.

 

C

Csheets88

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Apr 22, 2024

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May 1, 2024

#15

• May 1, 2024

• #15

AIT didn't correct it.