5.2 in 98 Ram truck-wierd air sucking intermitently

My sons Ram truck has a strange intermitent suction of air , through the throttle body (so it appears), the rpms drop and it runs rough ,trying to stall. It will do this and then for no reason ,just straighten itself out and idle fine. We checked IAC ,PCV ,intake bolts ,throttle body bolts ,and all vaccume connections. The fuel pump shows a steady 50 lbs.
I remember reading something here about the bottom of the "beer barrel" intakes having a steel plate rivited on.....Where they coming loose and creating air leaks?
I't's driving us crazy!!!

That's the idle air control valve opening up for some reason, probably a code is being thrown. Don't force that valve open or closed as they are easy to break. Does he have a check engine light on? I had the same symptom when my TPS was wired backwards and I had no ground to my O2 sensor.

The plate on the bottom of the intake is bolted on, and is infamous for leaking. It sucks oil into the intake and will cause increased oil consumption that increases over time. With a flashlight, you might be able to see oil streaks on it by looking down a wide open throttle body. Engine off of course... Hughes and several others make a complete kit to upgrade the seal. Be careful over-torqueing the intake bolts!

There are some knowledgeable trouble shooters on this board that may chime in.

yup. IAC.

I would start by giving the truck a tune up. new plugs, wires, cap, rotor, and clean/replace sensors, clean the TB and IAC port, etc.

then, reset the computer (unplug battery overnight)

the IAC function is a learned aspect in the computer programming. the computer learns/remembers what settings the IAC needs in various conditions to keep the engine running at the target idle speed. If these conditions begin changing, the computer doesn't know what to do and freaks out.

now, some noise is to be expected, did you guys recently change air filter/intake systems? you may be hearing it more now because of such a change.


if your belly pan gasket is blown/leaking, you won't hear it. but you will have excessive oil consumption and pinging under WOT from the oil getting sucked through the intake. it's bolted on, not riveted, and many have found that the OEM/factory bolts are too long for the tapped holes, and don't allow you to fully tighten down the plate. washers stacked on the bolts eliminate this problem.

Thanks for the reply's. I suspected the IAC too.

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Thanks for the reply's. I suspected the IAC too.

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Change the O2 sensors. Just had a 97 4x4 in the shop with the same issue. A minute into cold start up as soon as close loop occured it would start to drop the idle and run rough and the IAC would try to compensate it. After the engine warmed up it would smooth back out. The only thing that occurred abnormal on the scan tool was O2 function. You could see the O2's slow down and stop at times. I have a 97 that I tested along side this one and mine worked perfectly. I changed the O2's and problem went away. Also there was no codes during this problem. A friend of mine who was a chrysler tech for years told me also that that was the problem. The O2 heater in one of the O2s had quit working. These are to be changed on a certain mile interval but people never do mainly because they are unaware that it needs to be done.