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Hi,
Since you are considering the cleanliness and any adjustment check of the throttle body make sure to throughly inspect the accordion hose behind the AMM.
On two different cars, that use the same systems, I had a sudden stalls at a stoplight happen. I traced it down to both having had a small spilt or crack in the accordion hose.
One was a half inch long crack within the bellow volutes and another around the nipple holding a long vacuum hose to the flame trap housing or to the IAC valve. If it rubs up against anything a hole can appear.
I surmised that when the engine shifts while coming to a stop, that is opposite to an acceleration twist, the accordion hose also wiggles each time.
When an opening allows a surge of air to drop into the air stream and it over drives the idle air control system.
The same wiggle under acceleration is covered up with the automatic enrichment from the FPR and the increasing pluse widths on the injectors. It all goes unnoticed until performance or a backfire/sputtering occurs.
A really sudden quantity of plain air mixture gets combined into an "over speed alert to the ECU!
This happens long before any O2 sensor output signal reaches the ECU.
The overspeed reading has priority over all things watched by the ECU. Mainly for safety reasons during a close throttle switch signal. Newer ECU's are intertwined with brake circuits and air bag systems.
The ECU tells the IAC to close right down now and unfortunately it coincides to when the extra air STOPS coming IN!
By then, the engine stalls out and so does it so closely that the CPS sensor signal, that's giving out the RPM signal, of which is holding everything on, stops!
A very slight time difference enables a shudder or a complete stall!
This could be also a dirty lazy/sticking IAC valve or one that is "showing excessive wear" that are both in reality.
A thing to watch for is the startup phase of the upper and lower idle speeds.
The engine should rev up each time upon starting above normal idle speed and then immediately drop down to a fixed idle speed controlled by the computer.
No stepping on the gas pedal when starting should ever be done!
Just turn the key and its all automatically done smoothly on an air tight intake system.
I expect to be able to be standing outside the drivers door and reach into the car and start my cars engines all the way back to 1978 to 1993!
The days of stepping on a choking plate, used around the throttle plates, left a long time ago with Volvos.
The K-jets introduced a whole new way of thinking how to start a car, or any engine for that matter, for me!
How does your car do all of the above?
Phil
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