Hunting idle

Got a 1995 wagon with 3.0 V-6, 60,000 miles. Seems that after it warms up it starts this idle hunting thing. Almost stalls then rpm's go up, then almost stalls and continues like that. Sometimes when after shutting it off, it will start and then stall. Then after starting again it will hunt. Always starts right back up. I took it to the shop and they changed the EGR sensor because of a code they got out of the computer but it still does not idle correctly. It is going back to the shop to get the codes cleared and we start all over again.

I don't have a code reader so not sure of the code numbers. I did several searches on this forum and found that it could be EGR valve or IAC valve causing some of these problems. I checked the vacuum hoses and could not find any leaks. Also, while the car is idling (just barely) I disconnected one of the small vacuum lines on the intake manifold and the car would idle smooth with a vacuum leak.

I was gonna remove the IAC and give it a cleaning. Any way to test this valve to see if it is opening?

Other thoughts?

Great site! TIA!

Welcome to the forum!

Is your 3.0l V-6 the 12V (Vulcan), 24V (Duratech) or 24V (SHO)? If the Duratech or SHO, you will want to make sure the vacuum secondaries are closing properly.

When I come across a hunting idle issue, the first thing I suggest is to use a bottle of fuel injector cleaner with the fuel. That's solved the issue many times. Also try turning on the A/C. If the idle speed changes, your IAC is probably working fine.

Do you have a K&N or other oiled air filter? If so, you may have a contaminated Mass Air Flow (MAF) sensor contributing to the idle issue. The MAF can be cleaned if you have a very steady hand, some electrical parts cleaner, and a chamois tipped swab.

-Rod

The engine is a 12 valve. I've already tried the fuel injector cleaner route. That did not help. No K&N, just typical paper element in stock air box.

I will turn the A/C on and see what happens.

I have a spare stock MAF from a 94 5.0 mustang. Are they interchangable?

I'm not sure about interchangeability of the MAF sensors.

Do you have access to a scan tool that would be able to display the datastream? It would be interesting to monitor the lean and rich readings of the oxygen sensors. Maybe your O2 sensors are slow to respond so the car leans, then richens the mixture causing the hunting idle. Your mileage would be right about the normal change interval for oxygen sensors....

-Rod

I don't have access to a scan tool. The car is going back on tuesday for more diagnostic. I'll keep ya posted.

Welcome to the forum!

Is your 3.0l V-6 the 12V (Vulcan), 24V (Duratech) or 24V (SHO)? If the Duratech or SHO, you will want to make sure the vacuum secondaries are closing properly.
He said 95 Wagon :-p

That would make is 3.0 Vulcan :-p

Update, car is running good after replacing the MAF sensor. Also cleaned the IAC solenoid but not sure that had anything to do with it. All is well for now.

Thanks

Glad to hear it!

Thanks for posting an update with your solution.

-Rod