Rough Idle (Checked all previous topics!) HELP! HELP! HELP!

[MOscapinski]

I have a 1990 Nissan 240sx. Last year the engine blew so I had a rebuilt one installed by a good mechanic. For the past year I have had a idle problem that has driven me up the wall!!! I've had almost every sensor replaced either because it was bad or I just wanted to make sure that my car would last for a while. In the past year, I've replaced the following: Engine, fuel injectors, MAF, TPS, 2 selenoids, O2 sensor, radiator, hoses, EGR valve, the throttle body has been cleaned, the exhaust system has been replaced (header, cat, pipes and the muffler), rotor, cap, plugs, wires. I think that's all but I'm sure there's more. Anyway, the problem I'm having is that when the car is warmed up, it drives like a champ but when I stop, the idle fluculates up and down for about 4 to 5 times, then it stabilizes, I have checked the ecu for error codes but there are none, I have recently added a Helix throttle body spacer but this has been going on before that. I swtiched out the aic valve with a used one but still no change. Some one suggested to bleed the coolant and I did that too but no change. I have taken my car to 3 mechanics including the Nissan dealer and they cannot figure it out. Any suggestions or advice would be great! Since I replaced the engine last year, I have taken great care of the car. Regular oil changes, maintenance, everything.

[Bwana]

So this was happening before you put the spacer in? And nothing changed when you installed that?

It sounds to me like a throttle body or IAC issue. I assume IAC valve that you put on was a known good unit?

[MOscapinski]

I pulled an IAC valve from the junkyard. I don't know if it was good or not. No error codes came up on the ECU. Doesn't the ECU codes cover that? My problem is not consistant, just for the first 10-15 after I stop. Wouldn't the IAC valve do it all the time? How do I check the IAC valve to make sure it's good?

[Bwana]

Did you read through this thread? These guys seem to have pretty much the same issue you're experiencing. You valve may just need cleaning.