Try pinching it to see if your idle changes.

 

Does black smoke come out of the tail pipe when it finally starts? Does it run rough for a few seconds? I have never heard of anything called a IAB, what does it stand for? Do you mean IAC?

 

sorry, my 91 stang has a IAB (Idle air bypass) but its the same thing as the IAC. No smoke, no rough running. It either goes to 900 rpms and is smooth or it goes to 1500rpm and is smooth. Drops to 600 rpms once warm or it goes to 1500 rpms.

 

Have you tried cleaning your throttle body, or it could be the IAC?

 

I sprayed the TB and the IAC with cleaner... but I think I need to remove the IAC and clean it.

So far I have:

-pulled codes (none)
-replaced cap and rotor
-replaced fuel filter
-cleaned air filter
-cleaned TB and IAC
-checked all plug wires to ensure they were secure
-check PCV (it rattles)

 

ok, I pulled the IAC tonight in the dark and cleaned it...and hit it with a little white lithium grease as well... truck fied up fine (but she was still hot from driving her home from soccer) but I wont know for sure till tomorrow.

 

she started this morning...it took a single try and 12 seconds...but I think part of that might have been left over intake cleaner still in the IAC as I only ran her for 20-30 seconds lsat night after I put her back together. I did notice my idle was lower then where it had been. At lights she was actually down around 600rpms instead of the 750-800rpms so even if it didnt fix my starting issue it will be worth it in saved gas during idle. LOL

 

Wow this ones got me scratching my head ? do you think it could be a combination of two seperate problems ? i mean the hard start could be related to the fuel pump relay not functioning and the system cranks till i think 4lbs of oil pressure is achieved and read off the oil press sensor by the VCM ?
And the idle issue could be due to one of these sensors not functoning correctly the coolant temp senser coolant temp which the vcm compares with the ambient air inlet temp measured by the AIT which also controls timing . then the VCM relays position to the AIC and moves the valve in or out if thats working right . also a vacume leak at the intake manifold or hoses and crankcase vent system or a inlet restriction would cause the iac pintle to compensate.theres no black smoke but the ox senser could be contaminated with silicone and readings would indicate a lean air fuel mix ox check VCM grounds , check all ignition wires reset iac manually im jumping pages so im sorry if all this is a little mixed up i tink for this one you might need a scantool to perform system and engine control tests from what im seeing alot of things play an active roll in this problem and to replace or go thru them all would be a time consuming job ! man i tell ya just to many variables to pin point a single component sorry man

 

I pulled and cleaned the Coolant temp sensor and the Air temp sensor... no change. I may replace the fuel pump relay and see it that makes a difference. The O2 sensors are 6 months old as I had a check engine light back in early April and the O2's were bad. replaced them and all was good till this new issue. I am banging my head on the radiator cover...LOL

 

ok as stupid as this sounds... I checked the tranny..fluid was high (over filed) so I drained some of it... and now she starts right up. I figured it was becuase she was still warm but I was at the soccer field for 2 hours and she started right up, then she sat for an hour at dinner and started right up. Tomorrow morning will be the real test. I will post the results after 2pm (got soccer all morning)