My LB9 idle cycles once the car warmes up,you can feel this at speed as well(slight tugging). The ECM,EGR,IAC,O2 and TPS all check out. The airpump however has begun to make noises and is diffuclt to spin by hand.When the o2 sensor is disconnected the car seems to run better.Could an eratic air pump cause the o2 sensor to become confused thus causing the engine to cycle (close loop to open loop)

------------------
1990 Iroc convertible,305 tpi,Black with black leather interior,lowered,Taylor 8mm wires,K&N's

 

Is the A/C or defrost on while its doing this??

------------------
ASE Mechanic/Machinist/Smog Tech

1999 NBM Trans Am
1986 Chevy 3/4 ton pick up
1981 corvette
1995 Kawi ZX6R
and 2 POS commuters...

R.I.P. #3
"He can see air"

 

No, the ac and defrost are off.

 

I can't see the air pump causing the idle surge.

I would check for any vac. leaks first, do you have access to a DVOM or a scanner so you can see what the ECM, O2 voltage, etc. are all really doing??

------------------
ASE Mechanic/Machinist/Smog Tech

1999 NBM Trans Am
1986 Chevy 3/4 ton pick up
1981 corvette
1995 Kawi ZX6R
and 2 POS commuters...

R.I.P. #3
"He can see air"

 

I might have acess, but it was just on a scanner last Thursday and the mechanic didn't find anything. I plugged the line going to the egr valve and drove around for a while. This eliminated the engine tugging at speed but the car idles rough . Since the EGR is new might the EGR solenoid be the problem? I replaced the weather pack connector for the IAC because the old one was cracked. I'm wondering if the actual connection to the harness is working. How can you test the connector to see if it is working properly?maybe my problem is a combination of a couple of things?

------------------
1990 Iroc convertible,305 tpi,Black with black leather interior,lowered,Taylor 8mm wires,K&N's

 

I would change that solenoid because you are having the same problem I am and once I diconnected the solenoid the problem left so I will be replacing it this weekend.