Tosh

Gentlemen,

I have the just about sweetest running '88GT this side of the '80's decade provided I keep the RPM's above 1500. It is driving me bats. Why? glad you asked?
The motor has been rebuilt to a nice standard. Starting with a .030 overbore. (This was a 56K mile speed density car.)
And including:
1. Y303 heads.
2. CamMotion X2161. Duration-216ยบ,Valve lift-.531. and Comp roller
rockers.
3. MAF conversion, A9L EEC.
4. New fuel pump & press regulator.
5. All engine sensors replaced including O2 pair.
6. Radiator recored.
7. Pro Form' Electric fan.
8. Flowmasters
9. King Cobra clutch.
Am still running 19lb. injectors and a 65mm throttle body with stock 5.0 upper and lower intake setup.
Have set the TPS to read .98 and voltmeter shows a clean linear sweep when the accelerator is depressed.
The IAC voltage is on spec according to my Tech guy. He even substituted (and removed) new one.
The timing is spot on @ 14ยบ BTDC. Distributor and coil are original.
Have not touched any valve settings since the rebuild.
Smoke tested for vacuum leaks....none. The hoses are all new!
This car can idle at 650 when it decides to but gas it and attempt to move forward slowly; like pulling in the drive way or garage or how about cruising thru a parking lot? Fugeddaboudit! It surges and is impossible to move smoothly without constantly feathering the clutch and accelerator.
Approach a stoplight and depress the clutch; surrrrrge up, down, up, down stall.
Gears are stock, very tall 2:73's (I believe) which exacerbates everything I've described.

I know this topic gets flogged to death on the Mustang forums. I have seen the suggestions to drill the throttle plate, rout the IAC ports, install a IAC spacer with trimmer screws etc, etc. Tech guy says the grounds need cleaned up. Have been doing that as best I can, still no change.

Before I start replacing intakes and injectors and throttle bodies and whatever I really want to be sure that I am not overlooking an obvious/simple fix. Is it possible that this car is destined not to idle in its current configuration?

Thanks all, peace on ya.

Tosh

ebk06

maybe the VSS sensor defective or wiring damaged. The MAF and Speed Density cruse control equipped cars will have a vehicle speed sensor on the speedo cable pickup. The purpose of the VSS is to increase the idle speed as the car slows to a stop. If the sensor is defective, you can experience stalling as you slow to a stop.

mattdel

what in the hell are Y303 heads?

Tosh

ebk06, mattdell

Thanks for your replies.

I think I have solved this problem (just this morning) by adjusting the idle return screw to achieve hot idle of (+-) 900 RPM with IAC disconnected. This after disconnecting the battery overnight to clear the computer codes.
This tip came by way of "The Corral" from a "how to" by Darrin Tebbe.

Hey, it worked.

ebk06, quite correct you are about the VSS sensor but not an issue here.

mattdell, Y303 heads are aluminum GT40 heads, a genuine Ford Racing product. Currently out of production, I believe.

Keep on,

Tosh

red95gtconvert

Can't help you with your drivablity issues but for the love of god put some gears in that car

tp65

its ok to discounect the iac?

86 5.0L

I daily drive my 5.0 with the IAC disconnected[8D]

Tosh

Hear you on that red95gtconvert.

Tosh

Sorry tp65 I should have mentioned that I reconnected the IAC after adjusting the throttle stop screw.