What would be a good indication that you have a bad IAC motor? what type of symtoms would i experience? i have had a few idle issues as of late. My rpm's like to hang around 1500 inbetween shifts or when i put the jeep in neutral to coast to a stop. as my speed is reduced and i am coming near to a full stop, the rpms will dip down to around where they should be. I replaced the TPS sensor, but that was not the problem. could this be a bad IAC? or will a bad IAC cause different problems?
Bad IAC motor??
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What would be a good indication that you have a bad IAC motor? what type of symtoms would i experience? i have had a few idle issues as of late. My rpm's like to hang around 1500 inbetween shifts or when i put the jeep in neutral to coast to a stop. as my speed is reduced and i am coming near to a full stop, the rpms will dip down to around where they should be. I replaced the TPS sensor, but that was not the problem. could this be a bad IAC? or will a bad IAC cause different problems?
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Symptoms would include an irratic idle... somtimes high.... sometimes low... sometimes just right. This is an indication that the plunger on the iac is sticking. Try pulling it out and cleaning it up... see if that helps. Alot of times it is just gunk that has built up on the plunger causing it to stick.
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174 Posts
Did you also clean inside the housing where it sits?
I did. that little black plunger was as good as new looking. Just pushing on it with my finger though, i noticed that it doesn't take much for it to get off track. Meaning that if you push against it on the side, it sometimes will not fall back into place. Now i'm sure these are characteristics off all the plungers and not just mine. Just something i noticed.
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When my IAC was acting up, it just wouldn't run if I didn't have my foot off the gas. It would just stall out at a stoplight ir whenever I took my foot off the gas. I'll tell ya, that was tricky trying to brake to a red-light. Too many pedal's, not enough feet! I was able to clean it up and it hasn't acted up since then.
When my o2 was out the way out, it would idle eratically. I would just try un-plugging the o2 sensor and see if anything changes. Have you checked your codes?
When my o2 was out the way out, it would idle eratically. I would just try un-plugging the o2 sensor and see if anything changes. Have you checked your codes?
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174 Posts
With a bad o2 it will run good cold... but like crap when it warms up.
I kind of already thought about the throttle cable sticking. So i looked at the throttle body with everything off it, and it appears to come to a shut when you go from full throttle to no throttle.. I also think that the way the rpm's like to hang at 1500 and then slowly creap down is too consistant for the throttle cable to be sticking.
the easy test is to take a voltmeter and stick the negative pole into terminal A and then stick the positive into the b terminal. With the ignition on and the throttle closed, you should have a reading of 0 to 0.5 volts. When you open the throttle, the voltage should jump to around 2.0 volts. Check this and see what you get. If you are over 2.0 volts and the throttle is closed, then the motor is bad. If you are 0 volts with the throttle open then you have an open circuit in the harness and you need to find it!
Hope this helps.
Hope this helps.
Thread revival!! Iac testing ?
Does one need to disconnect the IAC harness to perform the above test? If so, how would it produce volts measurable by the meter? If one doesn't connect the harness, how are the terminals?
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Another trick is to slide a business card over the ports in the TB. By opening and closing the ports you can control the air allowed to pass through the TB at idle. Just like the IAC plunger does.
One word of caution. Don`t play with the IAC plunger. I know you want to but don`t. It is "meshed" with the motor and trying to see if it is OK often ends up destroying it.
Factory OEM sensors are by far the best. A few more bucks sometimes but well worth the money.
The IAC harness needs to be connected. You are testing through the IAC and checking the actuator motor itself.
Another trick is to slide a business card over the ports in the TB. By opening and closing the ports you can control the air allowed to pass through the TB at idle. Just like the IAC plunger does.
One word of caution. Don`t play with the IAC plunger. I know you want to but don`t. It is "meshed" with the motor and trying to see if it is OK often ends up destroying it.
Factory OEM sensors are by far the best. A few more bucks sometimes but well worth the money.
How do you make contact with the correct terminals if the harness is plugged in?
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2,626 Posts
It's called "back-probe". Basically you try and stick the end of the meter probe into the backside of the connector, right where the wire is also going in. Sometimes the probe is too fat - so you can stick a sewing pin in there instead, and hook the meter up to the pins.
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What the Iron-Dude said. The wife, sister, GF or Mistress will have a safety pin or a straight pin you can stick through the backside of the connector at the wire/seal junction.
thanks!
which is terminal A and which is B?
It is on the connector side. Small letters
I had some trouble making contact with a thin paper clip, which I cut in two pieces.
Vehicle off- When contact was made, I read 2.2 with throttle closed and 3.7-4.3 with throttle open. these readings fluctuated and I wasn't able to duplicate the numbers and therafter kept gettin 10+ volts whether or not throttle was open. Above readings were with volt meter scale set to "20"
Vehicle off- When contact was made, I read 2.2 with throttle closed and 3.7-4.3 with throttle open. these readings fluctuated and I wasn't able to duplicate the numbers and therafter kept gettin 10+ volts whether or not throttle was open. Above readings were with volt meter scale set to "20"
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