5.0 idles up and down when warm
 

anyone know why it would be ideling up and down when its warm motor is pretty much stock 88 5.0 i deleted the polution pump cats tabs ect and i left the egr plugged in and plugged the vacuum line off and its non mass air

Re: 5.0 idles up and down when warm
 

Idle surge is fairly common on the SD cars. Make sure your tps is set right, and your IAC is clean. Check your vacuum lines running to the MAP sensor, and other parts of the engine.

Re: 5.0 idles up and down when warm
 

whats is the iac?and how do i set my tps?

Re: 5.0 idles up and down when warm
 

Its more than likely an o2 sensor IMO.

Re: 5.0 idles up and down when warm
 

is there a way test the o2 sensors ?

Re: 5.0 idles up and down when warm
 

It takes a minute or so for the o2 sensors to get to operating temperature. When they get to temperature the ecu then starts collecting data from them, if they are faulty they can cause a serious idle surge especially on a speed density car.

last Summer my car would start up and idle perfect until the O2 sensors warmed up and kicked in, then I had a steady idle surge.

I replaced them both with Bosch O2 sensors costed about a $100.00
and now it idles like a dream.

Re: 5.0 idles up and down when warm
 

Your IAC solenoid is the can shaped item bolted to the throttle body. After the engine warms up, unplug the electrical connector going to it, and see what happens. If the idle smooths out, the IAC needs to be cleaned or replaced.

Have you checked for any codes?

Re: 5.0 idles up and down when warm
 

i havent checked anything im not driving this car right now its not finished yet i just did a complete 88 to 84 conversion but all the drivetrain is in and working and now im having this problem how do i check the codes?

Re: 5.0 idles up and down when warm
 

Actually, I think any Autozone will do it now for free... is your check engine light on?

Re: 5.0 idles up and down when warm
 

the check engine light aint on

Re: 5.0 idles up and down when warm
 

Start with testing the IAC like Pkrwd said. Most of the time a good cleaning with some GOOD carb cleaner fixes them up. If that isn't it, head to the O2 sensors. Just for the record, for some unkown reason, I've had bad luck with aftermarket O2 sensors. It costs a bit more, but I always put Ford O2 sensors back in.

Re: 5.0 idles up and down when warm
 

is there anyway i can test the o2 sensors by unpluging them when the car is running?to if its them or which one it is

Re: 5.0 idles up and down when warm
 

my 89 mass air does this also. doesnt affect the performance at all though