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Should IACV make noise with ignition on but not running?
#1
Hey, long time lurker first time poster. I have a 2003 frontier XE 2.4 MT that is having troubles after I repaired a split coolant hose. I am a very adept mechanic with 8 years of daily experience on KA24's of all shapes and sizes so I have been driving 240's and now a frontier. TLDR first. I had a coolant line burst under my intake last week and since then, can't get it to idle, especially when warm, and have started getting an IACV code. I have all the details below, but my main questions are these:

-Should a clean and working IACV make noise if I have the ignition ON, not running? I pulled the connector to confirm that was it.
-Should that same IACV not buzz if I power it manually with 12 volts?
-Could a bad iacv have damaged the ecu?
-Can I safely test the IACV circuit with a low wattage test led? (12v side is good, I think the ecu might not be acting right)

I had to remove a lot of parts to replace the line, and ended up changing every coolant hose to get ahead. Once it was back together, I could not get the truck to idle anymore. My first thought was duh... missed a vacuum line (I didn't remove the intake). Well, three days later, still have terrible to stalling idle. Especially once warmed up, it will be fine then suddenly dip and die. What all I have tried so far:
-Replaced all vacuum lines
-cleaned iacv, checked resistance: 10 ohms
-checked IACV operation with 12v direct, got strong clicks and movement
-spring does seem a tiny bit loose but not broken. Piston moves freely.
-tested EGR
-cleaned and tested MAF
-checked vacuum
-checked valve timing chain for skip

I also tested using a vacuum gauge. This was causing the most concern at first because the level is so low it seems like the valve timing is off really bad.  I really want to get some kind of idle so I can set the timing correctly. I considered unplugging IACV and trying to wedge the throttle but not sure that will work. Anyway, off to get some supplies so I can test the wiring harness at the ecu. Any help is appreciated!
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#2
Turned out to be a bad maf and a bad iacv. I will also be flushing my fuel system, short and long fuel trims came back to spec but still way positive, yet a wideband in the second o2 position was showing slightly lean. if the flush does nothing I will swap the fuel pump.

Also, though my truck has been running fine since the day I got it, swapping in the new maf made a huge difference on take-off in first and I feel a lot more mid range torque in second and third. Cleaned the old one several times and it never made a difference. Good shit!
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