I'm doing an IAC replacement this weekend. Once the new one is installed, is there anything special I need to do? Or do I just turn the key and start her up?
I bought the windstar IACs and they look just like the new one @aero3113 posted - brass pin with spring wrapped around it. They idle too fast - 900 RPM at start up, settles in to around 700 RPM after warming up.
lots of talk about IAC's when the IAC rarely fails on its own.
all that thing does is allow metered air into the TB to allow idle with the blades of the TB closed... that's it. It adjusts throughout it's life and in varying conditions to maintain a steady idle...... it adjusts to what? air flow.... bad air flow.. two causes of bad air flow- dirty filters and dirty TB's.... the IAC drifting that plunger into and out of the hole to maintain a prescribed RPM (or range) becomes difficult when it has to move a lot, and it has to move a lot because it's gummed up, being gummed up disallows the plunger to move within the range expected by it's tiny little motor and they either burn that motor up or the plunger loses it's 'mapping' or calibrated position...
replacing an IAC on a car doesn't happen that much... a matter of fact, it happens most often when someone has taken it off and 'cleaned' it- moving the plunger and losing its 'map'... why is that so? because- cars burn hotter and that heat sinks right up to the TB and varnishes the gummy crap that builds on boats TB's. also, in a car, you're more likely to swap air filters more often.
clean your TB's. it doesn't take a lot of effort. make sure and clean the orifice the IAC occupies inside the TB's throat to make sure gummy crap isn't slowly covering it (which makes the IAC work a lot harder than it should). Clean or swap your air filter/flame arrestor... if you 'really' want to be clever, cut a section of tubing and affix it to your IAC 'breather', remove it's filter, and direct that tube to the air hat/flame arrestor on the filtered side much like your PCV is (but on the inside not the out)...
a little bit of throttle body cleaner goes a long way...
When the IAC fails, is it a gradual fail, or immediate? What I mean is, does it give you any warning before failing?
not really.... it's designed to meter the air and reconcile with the CPS and TPS to achieve a certain RPM. when it starts to wear out there will be momentary struggles to idle... it's a device that does a good job of covering issues until it can't any more- and then that issue becomes apparent all at once... the issue is dirty TB's and/or gummed up IAC ports in the TB, or, dirty IAC filters (that you have to ask yourself 'how did they get so dirty')...
q: how did they get so dirty? oily and trapping crap? a: check your PCV valves, y'all.. take them out and shake them... they should rattle.. if they don't rattle they are stuck... if they are stuck they aren't allowing blow by crank case gasses to enter your air hat, and that has to go somewhere as the pressure pushes past valve cover grommets, and where is there air sucking (an IAC is basically a metered vacuum leak)? straight into that little filter, gumming it up- making the plunger have to open further to allow the same air into the TB as recognized by the CPS and bounced off the TPS- making that plunger work harder... wearing it out faster.
When the IAC fails, is it a gradual fail, or immediate? What I mean is, does it give you any warning before failing?
Mine was immediate. Failed right before I was coming into a harbor. Had very low idle and stalled going in and out of gear. Replaced with OEM and boat works great. (Knock on wood)
2008 280 Express Cruiser, 6.2MPI, B3, Pittsburgh, PA "Blue Ayes" Go Steelers!!!
When the IAC fails, is it a gradual fail, or immediate? What I mean is, does it give you any warning before failing?
Mine was immediate. Failed right before I was coming into a harbor. Had very low idle and stalled going in and out of gear. Replaced with OEM and boat works great. (Knock on wood)
Same here a couple of years ago heading into a lock. Checked today and I do actually have filters there.
fellers, y'all just 'think' it was immediate.. it was a while in the works, and you just didn't realize it. It takes time for it to get to the point it's beyond it's parameters, but it only takes a second for it to finally give up the ghost.
If you add cleaning the TB and area to your ten hour maintenance list you'll be better served than waiting for things to go wrong- simply spray some throttle body cleaner directly into the throat of your TB, making sure to douse it evenly all the way around and the butterflies too, and you'll find a lot of idling and throttle response questions will disappear..... just don't try to start it right after this... wait at least ten minutes or so. If you're 'really' motivated, you can use compressed or canned air to dissipate the solution, too... once the runoff hits the floor (plenum plate) of the intake manifold it can't really do your TB or AIC any harm....
it's also a good time to inspect your air filter/flame arrestor and IAC filter.... and PCV valves. those PCV valves that connect to the air hat/flame arrestor are a good bit of the 'problem' with IAC's gumming up (and TB's becoming nasty).... if possible (it is on mine) have those PCV valves dump into the airhat on the opposite side of the IAC (or as far as you can get them from it).... depending on how much blow by your engine generates, it's beneficial in some applications to install a little catch can with a filter to actually capture the oil and solvent (exhaust gasses) laden blow-by with that can/filter. You just have to dump it every or every other oil change.
Yes, still going strong. I need to replace the filters. Do you know of anyone selling them at a reasonable price? Everyone I see is asking crazy money for them. I bought a pair off of eBay and they were poor quality, way too soft.
Yes, still going strong. I need to replace the filters. Do you know of anyone selling them at a reasonable price? Everyone I see is asking crazy money for them. I bought a pair off of eBay and they were poor quality, way too soft.
For the filters, why not try replacing them with a chunk of a starbrite pad. From memory, I recall the filters being a similar material.
So here’s a fun one. The Delphi IAC idled at 800 rpm. No good. I bought 2 and can’t return them. So with nothing to lose, I ripped the spring off with needle nose pliers. Runs perfect now! 550 rpm without issue.
@aero3113 when I couldn't find a filter I just cut a strip out of a green scrub pad like you use for pots and pans. Folded it over and it worked great.
I have a high pitch whistle coming from my 496's between 1800 and 2300 RPM's. I've changed the filters a couple of times and still the same. Could it be coming from the IAC valves? Any other ideas?
Comments
all that thing does is allow metered air into the TB to allow idle with the blades of the TB closed... that's it. It adjusts throughout it's life and in varying conditions to maintain a steady idle...... it adjusts to what? air flow.... bad air flow.. two causes of bad air flow- dirty filters and dirty TB's.... the IAC drifting that plunger into and out of the hole to maintain a prescribed RPM (or range) becomes difficult when it has to move a lot, and it has to move a lot because it's gummed up, being gummed up disallows the plunger to move within the range expected by it's tiny little motor and they either burn that motor up or the plunger loses it's 'mapping' or calibrated position...
replacing an IAC on a car doesn't happen that much... a matter of fact, it happens most often when someone has taken it off and 'cleaned' it- moving the plunger and losing its 'map'... why is that so? because- cars burn hotter and that heat sinks right up to the TB and varnishes the gummy crap that builds on boats TB's. also, in a car, you're more likely to swap air filters more often.
clean your TB's. it doesn't take a lot of effort. make sure and clean the orifice the IAC occupies inside the TB's throat to make sure gummy crap isn't slowly covering it (which makes the IAC work a lot harder than it should). Clean or swap your air filter/flame arrestor... if you 'really' want to be clever, cut a section of tubing and affix it to your IAC 'breather', remove it's filter, and direct that tube to the air hat/flame arrestor on the filtered side much like your PCV is (but on the inside not the out)...
a little bit of throttle body cleaner goes a long way...
Regards,
Ian
The Third “B”
Secretary, Ravena Coeymans Yacht Club
https://www.rcyachtclub.com/
q: how did they get so dirty? oily and trapping crap?
a: check your PCV valves, y'all.. take them out and shake them... they should rattle.. if they don't rattle they are stuck... if they are stuck they aren't allowing blow by crank case gasses to enter your air hat, and that has to go somewhere as the pressure pushes past valve cover grommets, and where is there air sucking (an IAC is basically a metered vacuum leak)? straight into that little filter, gumming it up- making the plunger have to open further to allow the same air into the TB as recognized by the CPS and bounced off the TPS- making that plunger work harder... wearing it out faster.
Go Steelers!!!
Regards,
Ian
The Third “B”
Secretary, Ravena Coeymans Yacht Club
https://www.rcyachtclub.com/
If you add cleaning the TB and area to your ten hour maintenance list you'll be better served than waiting for things to go wrong- simply spray some throttle body cleaner directly into the throat of your TB, making sure to douse it evenly all the way around and the butterflies too, and you'll find a lot of idling and throttle response questions will disappear..... just don't try to start it right after this... wait at least ten minutes or so. If you're 'really' motivated, you can use compressed or canned air to dissipate the solution, too... once the runoff hits the floor (plenum plate) of the intake manifold it can't really do your TB or AIC any harm....
it's also a good time to inspect your air filter/flame arrestor and IAC filter.... and PCV valves. those PCV valves that connect to the air hat/flame arrestor are a good bit of the 'problem' with IAC's gumming up (and TB's becoming nasty).... if possible (it is on mine) have those PCV valves dump into the airhat on the opposite side of the IAC (or as far as you can get them from it).... depending on how much blow by your engine generates, it's beneficial in some applications to install a little catch can with a filter to actually capture the oil and solvent (exhaust gasses) laden blow-by with that can/filter. You just have to dump it every or every other oil change.
Ray
2006 390
Previous 2000 340