I have a 99 EX, V6 Coupe 120K, Auto with a bad idle. It drops too low and sometimes kills at stop signs. It has no problem when stone cold but starts having issues at operating temp especially when lugging in freeway rush hour stop and go.


I suspect that the msifires occurs when the idle goes too low triggering the codes. It runs perfect when the throttle is open.

Here is what I have done

Valve adjustment 10k ago
Removed upper plenum and cleaned and drilled out the port that clogs
Cleaned the egr valve and passage
Checked the idle control valve by unplugging it (it works)
New plugs, wires, cap, rotor, air filter, throttle body gasket
Two Seafoam Treatments

Anyone got any ideas?

 

What is the base idle at?

 

As you may have seen I have made a half dozen posts regarding an up until now unsolvable rough idle problem on a 99 Accord EX V6. I cleaned the mainfold port, EGR valve & ports, new plugs, wires, cap, rotor, and just about everything else.

I noticed that when I removed the throttle body that no coolant came out of the IAT lines. I checked thle recovery tank and it was a little low but not to the point where it was a concern. I removed the radiator cap with the motor running and I was able to add 2/3 of a gallon!! I let the motor get to temp with the cap off and it burped huge air bubbles. I couldnt find a bleeder screw anywhere so I just burped it by squeezing the upper hose.

For some reason these cars have a coolant line running to the IAT valve. I am thinking the purpose is to warm the sensor so when at temp it restiricts air flow to reflect a leaner idle mixture when hot versus richer a t start up.

My logic is if there is air in the system not enough coolant flows to sensor to make it effective?

Any ideas on this?

 

Yes, there's supposed to be coolant flowing there to warm up the FITV and IACV.

Air pockets in the cooling system are well-known to confuse the idle-control system.