IAC (Idle Air Control) Valve question


MAFoElffen

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Is the static position of the IAC valve normally closed or open? (Can't find this answer in thread search here)

Wondering if I should build a blockoff plate to test a problem I'm having (another thread).

Edit: Never mind found it in the Chilton "Engine Code Manual." Normal is closed. Test voltage when cold should be near battery voltage. Signal is pulsed at 140 for full-open. AFter warmup, 0 volts, 0 pulses. Dependant through the PCM on Info from the Coolant Temperature Sensor, Intake Air Temperature Sensor and the Throttle Position Sensor. Terminals should have resistance betwen them and not be internally grounded to case.

But other noted problems to check before suspecting an IAC were faulty PVC Valve or vacuum leaks. Since these seem to be fine in my case, I made a blank gasket to block it off, installed it after "warmup" to test my situation...
 
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Big Jim M

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Ok the idle system in a carburator compliments the hispeed system and continues to allow the idle fuel at all rpm..
BUT you are saying you have blanked off the iac and it seems to NOT allow either air or fuel after warm-up..
Am I correct in this assumption?
Jim
 

jhammel85

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One way to test it...in a way....is to take it off the intake and turn the key. Have a friend make sure it moves. I did this when I cleaned it out. Not much but its worth a thought.
 

MAFoElffen

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Ok the idle system in a carburator compliments the hispeed system and continues to allow the idle fuel at all rpm..
BUT you are saying you have blanked off the iac and it seems to NOT allow either air or fuel after warm-up..
Am I correct in this assumption?
Jim
Right now I have the MAF unplugged and it starts and runs. If I have the MAF plugged in, it starts, rev's once, then dies. With the MAF plugged in, the codes say the HEGO's are reading lean in both banks - running lean. That's how it seems- lean and starving for fuel. After the above tests, I ruled out the IAC valve and any other vacuum or air leaks... But still have a problem somewhere.
 

masterbrenden

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dirty air flow sensor
 

dopey fudd

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found this thread interesting.

here is what I have been fighting.(copied from another thread)
93 3.0. when the temps drop below 50 degrees, the truck starts right up. runs at around 2500 rpm, then as it starts to drop to regular idle, I get a check engine that flashes 3 times, the idle then drops to around 500 rpm, or dies, of its really cold out. then it spikes back up to 2500, and slowly decreases to standard idle, around 1000 rpm. I have checked the idle air sensor, and replaced the coolant temp switch. cannot pull the code from ecm, due to being a soft code. throttle body is clean, maf is clean ,but will clean to be safe.

I'm at a loss at this point. it did it last year in the fall- winter but stopped. started in the spring, and stopped, all summer long. started again in mid november. its getting worse, to the fact that if it dies now, I need to hold the throttle open to restart.



update, --

with the warmer temps, the truck seemed to be starting easier over the last few days.

Friday---, the iac went out completely. I know this because of last time it went out. the idle stays at where the rpm's were at when I let off of the trottle. and when I disconnected it, they dropped.

yesterday-- so I went to a yard, and pulled 2 of them off of 2 3.0 motors. all had the same part #.

the first one when I put it on loped severly, but continued to run. no check engine.
the 2nd fired right up, had NO issues. so I left it on.

today, I started the truck up. it fired up just fine. when the idle started to lower, it started lopeing severly, and died. I then had to hold the throttle down for it to fire up. it loped until I put my foot on the throttle for around 30 seconds. then it was fine.:dunno::dunno:
 

Tali99

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Did you ever figure out the issue? Searching old threads and had same issue after letting vehicle sit. ran a few time short trips got gas broke down on freeway. Runs rich with maf unplugged dies immediately when plugged in. Bought new one no change
 

oranjvoodoodaddy

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Tali, what brand of replacement MAF as re you using?

Sent from my XT1254 using Tapatalk
 

Tali99

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Tali, what brand of replacement MAF as re you using?

Sent from my XT1254 using Tapatalk
Just saw this my bad. First one was whatever they had at Oreilys. After that was oem from another ranger that had no issues. Still chasing this down on and off. Now I can have it plugged in but dies once it reaches normal temp, but that's not from the new maf
 


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