95 convertible idle issues stange power surges

[Nubbyless]

Hi i have a 95 mustang vert 5.0 H.O. 5spd idle is erratic sometimes it idles 650 to 700rpm perfectly smooth then randomly starts surging up and down then sometimes it will race up to 2000rpm without touching anything stay there
for 30 seconds or so then fall back down and start surging again then smooths out.

While driving sometimes while driveing at a smooth even speed suddenly it feels like another cylinder or two came on sudden surge of more power then
drops back to normal.

things i have done checked for vacume leaks cant find any unless under the intake havent removed that yet

parts changed all original brand new parts
pcv valve and filter
air temp sensor
coolant temp sensor
iac valve yes mtorcraft
tps
egr and egr sensor
cap rotor plugs wires and coil (tried multiple caps rotor wires)
fuel pressure regulator
fuel filter at tank
driver side 02 sensor

things not changed
fuel pump (pressure seems fine)
ignition module had it tested at pep boys on their computer tested good 12 times in a row
distributor is there any way i can check it
passenger side 02 sensors
is there something else im missing in this list
maf cleaned it though

i did the proper idle setup procedure including letting it idle for 10 to 15 minutes to lear its idle
i hate just throwing parts at it like that but i dont care at this point i just want it to run correctly.

Any ideas

 

[General karthief]

http://forums.stangnet.com/showthread.php?t=698148
The famous surging idle checklist.

 

[Nubbyless]

Thanks been over that list many times as you can see I just replaced most of it and with original Ford parts I haven't pulled the upper intake yet but have the gasket to do that and change vac lines under there also it throws no codes on the read and no cel

 

[General karthief]

Do you get the koeo 11? That means system checked out ok.

 

[Nubbyless]

Yes my scanner shows me code 11 and goes through the self tests of relays fans etc as it should

 

[jozsefsz]

Check and adjust your ignition timing sounds like one reasonable step you don't mention and doesn't require throwing more parts at the problem. Re-check the part in the surging idle checklist about setting your idle. In general, your car should idle (low) with the IAC completely disconnected. You accomplish this through adjustment of the throttle stop-screw and the idle air bleed.

The surging idle checklist is great of course, but it is a little more geared to the Fox setup. This thread contains a more effective procedure for setting the idle in the 94-95 in my opinion which includes using the idle bleed screw which I don't think the Foxes have. https://www.stangnet.com/mustang-forums/threads/where-is-the-iac-air-bleed-screw.609695/

What you're describing sounds like run of the mill surging with a little bit of hanging (revs up a bit when you press in the clutch), along with some bucking at cruise speed. If you don't have major vacuum leaks or other mechanical issues, you can coax away most of the surging with fine tuning the idle settings. Bucking at cruise speed might be helped by checking your timing, I've usually found it's either timing or a fuel problem (running a bit lean) so the only remaining part on your list I'd consider is the passenger o2 which might make a difference. I don't mind suggesting that because depending on how many miles you have, on a 20+ year old car, O2 sensors are really a maintenance item.

If it were my car, I'd check and adjust timing (spout out, 10 degrees btdc), change that passenger O2 if you don't know when (if ever) it's been changed, and then go through the thread I post for the idle adjustment procedure for the 94-95.

 

[Nubbyless]

Hi thanks I did adjust base timing at 10 spout out the passenger o2 was going to be my next try but I finally pulled the upper intake yesterday cleaned it and the throttle body changed the gasket and all the vacuum lines under it
The rubber lines under it were hard as a rock the small line to the fuel vapor cannister was pretty deteriorated I guess from the vapor so I will give it a few days and see how it is now if it does it again I'll try the o2 next