Idle question (i know diff. variation of this q have been asked)

[KZGUNS]

Changed out O2 sensors and went back over everything and the issue still persists. Cold start up its fine but once warm and restarted the idle goes up and down for maybe 20 seconds before stabilizing. Not a huge annoyance but something must be off. I'll continue to check over things until i find whats causing it.

 

[General karthief]

You did reset the computer after changing the 02s. Any codes after a drive? Most times mine settles right into a steady idle and sometimes it will hunt up and down for a few seconds,

 

[KZGUNS]

You did reset the computer after changing the 02s. Any codes after a drive? Most times mine settles right into a steady idle and sometimes it will hunt up and down for a few seconds,

I did reset the computer. I still need to get in a drive, it was late and i was tired and hot! maybe it'll work its way out after some relearning. I'll have to time how long it hunts. I may be thinking its 20 sec. or so when its really just a few.

 

[jrichker]

Changed out O2 sensors and went back over everything and the issue still persists. Cold start up its fine but once warm and restarted the idle goes up and down for maybe 20 seconds before stabilizing. Not a huge annoyance but something must be off. I'll continue to check over things until i find whats causing it.

Run the engine until it warms up and then disconnect the IAC and see if it stabilizes out.
If it doesn't, then you have a mechanical problem.
If it does you have an electronic/sensor problem..
If it dies, then the base mechanical base idle is not set correctly.

 

[KZGUNS]

Run the engine until it warms up and then disconnect the IAC and see if it stabilizes out.
If it doesn't, then you have a mechanical problem.
If it does you have an electronic/sensor problem..
If it dies, then the base mechanical base idle is not set correctly.

Do you mean while it’s hunting or shut it off and unplug then restart? What mechanical issues would relate to this? Other than this it runs good and once it stabilizes it idles smooth and steady.
Thanks for all the input!

 

[jrichker]

Do you mean while it’s hunting or shut it off and unplug then restart? What mechanical issues would relate to this? Other than this it runs good and once it stabilizes it idles smooth and steady.
Thanks for all the input!

Try disconnecting the IAC while the engine us surging.

Recheck the ignition timing with a timing light... Too much spark advance causes symptoms similar to you problem.


Setting the timing:

You can forget about anything beyond this point if you don't have access to a timing light. You will never get the timing set right without one.

Note: If you don't have access to a timing light, most of the larger auto parts stores will rent or loan one if you have a credit card or leave a cash deposit.

Paint the mark on the harmonic balancer with paint -choose 10 degrees BTC or 14 degrees BTC or something else if you have NO2 or other power adder. I try to paint TDC red, 10 degrees BTC white and 14 degrees BTC blue.

10 degrees BTC is towards the driver’s side marks.

Note: setting the timing beyond the 10 degree mark will give you a little more low speed acceleration. BUT you will need to run 93 octane to avoid pinging and engine damage. Pinging is very hard to hear at full throttle, so it could be present and you would not hear it.

Simplified diagram of what it looks like. Not all the marks are shown for ease of viewing.

ATC ' ' ' ' ' ' ' ' ' '!' ' ' ' ' ' ' ' ' ' BTC
---------------- > Direction of Rotation as viewed standing in front of the engine.

The ' is 2 degrees.
The ! is TDC
The ' is 10 degrees BTC
Set the timing 5 marks BTC. Or if you prefer, 5 marks towards the driver's side to get 10 degrees.

To get 14 degrees, set it 7 marks BTC. Or if you prefer, 7 marks towards the driver's side to get 14 degrees.

The paint marks you make are your friends if you do it correctly. They are much easier to see that the marks machined into the harmonic balancer hub.

Make sure that you set he timing when the engine is up to operating temperature.

At this point hook up all the wires, get out the timing light. Connect timing light up to battery & #1 spark plug.

Remove the SPOUT connector (do a search if you want a picture of the SPOUT connector) It is the 2 pin rectangular plug on the distributor wiring harness. Only the EFI Mustang engines have a SPOUT. If yours is not EFI, check for a SPOUT: if you don’t find one, skip any instructions regarding the SPOUT
Warning: there are only two places the SPOUT should be when you time the engine. The first place is in your pocket while you are setting the timing and the second is back in the harness when you finish. The little bugger is too easy to lose and too hard to find a replacement.

Start engine, loosen distributor hold down with a 1/2" universal socket. Shine the timing light on the marks and turn the distributor until the mark lines up with the edge of the timing pointer. Tighten down the distributor hold down bolt, Replace the SPOUT connector and you are done.

The HO firing order is 1-3-7-2-6-5-4-8.
Non HO firing order is 1-5-4-2-6-3-7-8

 

[KZGUNS]

Try disconnecting the IAC while the engine us surging.

Recheck the ignition timing with a timing light... Too much spark advance causes symptoms similar to you problem.


Setting the timing:

You can forget about anything beyond this point if you don't have access to a timing light. You will never get the timing set right without one.

Note: If you don't have access to a timing light, most of the larger auto parts stores will rent or loan one if you have a credit card or leave a cash deposit.

Paint the mark on the harmonic balancer with paint -choose 10 degrees BTC or 14 degrees BTC or something else if you have NO2 or other power adder. I try to paint TDC red, 10 degrees BTC white and 14 degrees BTC blue.

10 degrees BTC is towards the driver’s side marks.

Note: setting the timing beyond the 10 degree mark will give you a little more low speed acceleration. BUT you will need to run 93 octane to avoid pinging and engine damage. Pinging is very hard to hear at full throttle, so it could be present and you would not hear it.

Simplified diagram of what it looks like. Not all the marks are shown for ease of viewing.

ATC ' ' ' ' ' ' ' ' ' '!' ' ' ' ' ' ' ' ' ' BTC
---------------- > Direction of Rotation as viewed standing in front of the engine.

The ' is 2 degrees.
The ! is TDC
The ' is 10 degrees BTC
Set the timing 5 marks BTC. Or if you prefer, 5 marks towards the driver's side to get 10 degrees.

To get 14 degrees, set it 7 marks BTC. Or if you prefer, 7 marks towards the driver's side to get 14 degrees.

The paint marks you make are your friends if you do it correctly. They are much easier to see that the marks machined into the harmonic balancer hub.

Make sure that you set he timing when the engine is up to operating temperature.

At this point hook up all the wires, get out the timing light. Connect timing light up to battery & #1 spark plug.

Remove the SPOUT connector (do a search if you want a picture of the SPOUT connector) It is the 2 pin rectangular plug on the distributor wiring harness. Only the EFI Mustang engines have a SPOUT. If yours is not EFI, check for a SPOUT: if you don’t find one, skip any instructions regarding the SPOUT
Warning: there are only two places the SPOUT should be when you time the engine. The first place is in your pocket while you are setting the timing and the second is back in the harness when you finish. The little bugger is too easy to lose and too hard to find a replacement.

Start engine, loosen distributor hold down with a 1/2" universal socket. Shine the timing light on the marks and turn the distributor until the mark lines up with the edge of the timing pointer. Tighten down the distributor hold down bolt, Replace the SPOUT connector and you are done.

The HO firing order is 1-3-7-2-6-5-4-8.
Non HO firing order is 1-5-4-2-6-3-7-8

Thanks, I do run a bit advanced but also only run 93. I will back it off to see if this is causing the issue.

 

[KZGUNS]

Here are my results from last nights work.
I backed the timing down to ~11 Did not change issue
While idle was hunting i unplugged IAC and the idle lowered a little but still hunting, when i plugged it back in it smoothed out right away.
I timed how long it hunts with warm start up and it was 7-12 seconds before settling at 800-850
Firing order is correct but i checked just in case.
I may pull and check gap on plugs, what is the correct gap?

Thanks,
Ken

 

[General karthief]

Around .050/ 050-054 in that area

 

[Blown88GT]

Unless I missed it, what mods, if any, done to engine?

 

[KZGUNS]

Unless I missed it, what mods, if any, done to engine?

Edelbrock intake, 70mm tb and egr spacer and cold air intake with filter in fender.

 

[KZGUNS]

I have driven the mustang to work the last two days and the warm start idle issue seems to be improving.

 

[Blown88GT]

Edelbrock intake, 70mm tb and egr spacer and cold air intake with filter in fender.

These never work right, cold air intake with filter in fender. Too many bends in front of MAF. Put MAF inside fender with filter attached to MAF.

 

[KZGUNS]

These never work right, cold air intake with filter in fender. Too many bends in front of MAF. Put MAF inside fender with filter attached to MAF.

Mines still speed density

 

[jrichker]

A hunting idle with a the IAC disconnected is most likely a mechanical problem.
But or borrow a vacuum gauge - the auto parts store will loan you one if you have a credit card

Vacuum Gauge readings

 

[KZGUNS]

A hunting idle with a the IAC disconnected is most likely a mechanical problem.
But or borrow a vacuum gauge - the auto parts store will loan you one if you have a credit card

Vacuum Gauge readings

I have one so I’ll check it out. I’ll only have maybe 7 seconds of hunting though. Maybe less now as it seems to stabilize quickly now.

 

[KZGUNS]

Ran the vacuum tests and it all checks out. Might pick up a Motorcraft iac. I think I’ll also warm it up shut it down unplug the iac then restart and see how it acts. It has improved so I don’t know.

 

[KZGUNS]

My issue is all but gone, slight 50-100rpm hunt occationally. I'll get a better idea later this week when i can put some miles on it.
Heres what i did, some stuff was just maintenance i was going to do anyway since i have no idea when the previous owner did it.

Checked for vacuum leaks, didn't find any but replaced some lines that looked old and dry
Replaced o2 sensors
plugs and wires, not related to the issue but was doing it anyhow and found old plugs gapped at 35
Installed Motorcraft IAC I thing this was a big improvement from the generic auto parts store one that was on the car.
Reset ecu and base idle, did this a few times as i changed things
Checked manifold vacuum, that tested right on the money
checked fuel psi, 37 psi with reg vac unplugged.

** I have one more question, The previous owner has removed most smog stuff, pump, thermactor, egr... there are some solonoids on the back side of pass. shock tower. Can these all be removed or do they serve another purpose?

Again thanks for all your input and help! I'm pretty good with cars but this is my first fuel injected "classic"

Ken

 

[KZGUNS]

Anyone have an answer for me?

 

[General karthief]

With the smog stuff gone they only take up space. There may be a check engine light issue from the removal and a code stored but will have no effect on performance if removed, I left mine intact so it would not turn on the cel. I still have the egr valve though.