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*** NOTE: I made this posting to load with pictures for56k dial-up friendly speed.
Does your 3.9L, 5.2L or 5.9L Magnum engine rev up and down during idle (surges) while in park or netural? If so, the problem is a dirty IAC. Here's the process to clean this IAC to keep your engine happy with a nice idle rpm and avoids wasting fuel too.
This DIY maintenance works with 3.9L/239cid, 5.2L/318cidand 5.9L/360cid Mangnum engines found in many of the Dodge Trucks, Full size Vans/Wagons, SUV's and a few Jeeps.
A sample look of a 3.9L, 5.2L or 5.9L magnum engine with the van's dog-house removed.
Here's the jewel of the IAC. Notice the driver on the left mounting screw.
Just remove the connector out of the way.
Rats. [:@] The fuel bridge is in the way to get the second screw off.
OK, I'll use a longer driver socket and a pair of pliers to get the screw loose.
Now, with the flex drive over the bridge, the screw turns quickly. You may use what ever tools you have to get at that screw too.
*** NOTE ***
NEVER move the IAC brass probe more than 1/4" in travel while cleaning or handling. !!?!! Right now the picture shows it all black.
Ah, here's what the IAC looks like. OK, think clean thoughts here.
Up close all dirty ...
My cleaning bench.
A cotton swab and clean rag.
The IAC cleaned up really good.
Ah, but wait, there is more!!! The TB port is dirty too!
One clean IAC port. That's how it's too look. OK, clean thoughts here too.
DO NOTE: Inside of this IAC port hole is an air intake slot. It's very hard to see on the inside on the bottom. This needs to be cleaned very carefully. Avoid breaking the swab head off wiping the crusty bottom slot out. As you look at the picture below, the slot is on the bottom between the entrance hole and the round port in the back.
Alright, just put the IAC back into the hole, drive the screws and plug in the connector!
Hope this helps too!
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On the Gen-2 Ram Vans, this cleaning fixes most of the engine surging and the feeling like the tranny is slipping out of grear while driving down the road. Also, keeping the IAC clean really helps the fuel economy with these vans since the idle speed doesn't rev up and down constantly.
i have a Rochester Quadrajet > where is this IAC located ??
my haynes/chilton don't show me much and mine doesn't look like yours ..
thank you ...
You do not have an IAC on your engine. Only the MAGNUM engines have an IAC. The pre-magnum engines have an ISC actuator instead. ISC = Idle Speed Control. This would be typically found on the Holley carbs. As for the Roch-QJ, I'm not all that familar with that vintage of carb hardware.
If it was really dirty, then the idle surges for the most part. This in turn burns up more fuel while sitting at stop lights or in the parking lot idleing.
DIY How to clean the IAC
