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Discussion Starter #1
Hello, my normal idle RPM was about 700-750. It started to bounce down about 50 RPM and then back up when stopped at a light. It was recommended that I clean the IAC. Used throttle/carb cleaner on the IAC until clean and also sprayed in the two holes on the throttle body. Very simple to remove and replace. Also replaced with new gasket. Now, Idle is about 500 RPM and parked idle. Will run for about 2 minutes then stall. I can drive and behaves ok but wants to stall when I stop. Have to brake and apply a little gas. I really didn't touch anything else. Just two bolts on top to remove and then cleaned. Why would this be worse? What am I missing? Did the cleaning uncover another problem/component? should I replace the IAC or is there something I should check? Thanks as always!!!
 

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Hello, my normal idle RPM was about 700-750. It started to bounce down about 50 RPM and then back up when stopped at a light. It was recommended that I clean the IAC. Used throttle/carb cleaner on the IAC until clean and also sprayed in the two holes on the throttle body. Very simple to remove and replace. Also replaced with new gasket. Now, Idle is about 500 RPM and parked idle. Will run for about 2 minutes then stall. I can drive and behaves ok but wants to stall when I stop. Have to brake and apply a little gas. I really didn't touch anything else. Just two bolts on top to remove and then cleaned. Why would this be worse? What am I missing? Did the cleaning uncover another problem/component? should I replace the IAC or is there something I should check? Thanks as always!!!
If yours is Vulcan the IAC should look the pic. I use ammonia and Q tip to clean holding the solenoid up. Dry with hair dryer. Oil the moving slides. Move the piston with a tooth pic to spread the oil and remove excess oil with a Q tip. Carb cleaner likely is not good for sliding bearing surfaces. Need oil.
-chart-
 

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Hello, my normal idle RPM was about 700-750. It started to bounce down about 50 RPM and then back up when stopped at a light. It was recommended that I clean the IAC. Used throttle/carb cleaner on the IAC until clean and also sprayed in the two holes on the throttle body. Very simple to remove and replace. Also replaced with new gasket. Now, Idle is about 500 RPM and parked idle. Will run for about 2 minutes then stall. I can drive and behaves ok but wants to stall when I stop. Have to brake and apply a little gas. I really didn't touch anything else. Just two bolts on top to remove and then cleaned. Why would this be worse? What am I missing? Did the cleaning uncover another problem/component? should I replace the IAC or is there something I should check? Thanks as always!!!
If the IAC is dirty, the prime cause is bad PCV. , or bad air cleaner. Nothing goes through that but filtered air. If the accordion is dry, the PCV is working OK.
-chart-
 

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Discussion Starter #4
Hello and thank you. It is a DOHC 96-99 same IAC all engines. I'll try lubricating. Three months ago I replaced the air filter, PCV and a few cracked vacuum hoses. Also the front upstream O2 sensor. All this cleared codes and was able to pass emission inspection. Two weeks ago back upstream O2 caused a single code. Was idleling rough before the code. Was running fair with a little RPM drop and bounce at stop. 650-700. I cleaned the IAC and ports and now it idles at 500 RPM and stales at stop in a minute or two. Driving is Ok. Thanks again. will let you know if light Q-tip oiling helps. Thanks!!
 

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Discussion Starter #6
I applied a little oil with a qtip RPM went up to 550 and is a little more stable. Held idle in park for 10 minutes. When I accelerate there is a little jump, drops to 400 RPM then settles at 550. Doesn't feel smooth. It looks like a little rubber plunger that appears to have a nick. Thanks!!!
 

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May check directly behind the iac towards the firewall on the backside of the intake/engine and make sure that little black rubber vacuum elbow with the 2 small hard red lines inserted into its bottom is still attached. Every time I sprayed cleaner into the 2 holes below the iac, that elbow blew off when I started the car.
 

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Discussion Starter #8
Thanks Sheila, I do have a clamp on that boot and made sure the hard lines were attached. Stalled four times backing out of the driveway this morning, a little cold 34. Didn't stall at lights but I can tell it was thinking about it. My car 99 DOHC. IAC fit for 96-99 so unfortunately nothing newer. So hoping to find newer replacement for about $11 and junk. Would this be my next try? Thanks!!!!
 

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Thanks Sheila, I do have a clamp on that boot and made sure the hard lines were attached. Stalled four times backing out of the driveway this morning, a little cold 34. Didn't stall at lights but I can tell it was thinking about it. My car 99 DOHC. IAC fit for 96-99 so unfortunately nothing newer. So hoping to find newer replacement for about $11 and junk. Would this be my next try? Thanks!!!!
Low idle speed often stuck PCV valve. Not letting enough air in.
-chart-
 

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Discussion Starter #10
Thanks Chartmaker. I replaced the PCV about a year ago. Is the "rattle" test good enough to test the PCV? worth cleaning?
 

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PCV rattle test is worth little. Best check all passages for blockage and fresh air inlet to the engine. Pop the oil fill cap while idling and the idle speed should remain the same. If it speeds up, the fresh air to the engine crank case is blocked. I had '03 DOHC suddenly went to slow idle. Found water and gunk in the accordion. Proof the PCV is not letting enough air in. In a rush so I bought parts house one and then very fast idle. Cheap junk letting too much air in, idled on the flat road 30mph. Ordered Motorcraft OE and idle now just fine. Idle to high/low indicates some air flow systems are not working right.
-chart-
 

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Discussion Starter #12
Thanks Chartmaker. I'll try the oil cap test to see if RPM changes. PCV is Motorcraft. "Accordian" = the air intake from air filter to Throttle body? Looks clear and clean. About six years ago I was checking out an EGR issue and was cleaning the Throttle body. The C channel was packed with black paste goop. If a JY IAC doesn't fix, maybe I'll give that another look. Thanks!!!!!!
 

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Discussion Starter #13
Hello Chartmaker. I removed the oil cap after car was warmed up and idling about 550 RPM. No change in RPM. How does fresh air enter the crankcase? PCV?
 

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Fresh air on your '99 tec enters through the vent tubes/hoses coming from the the large corrugated intake tube/hose. They run to the tops of of your cam (valve) covers. Dirty air, combustion byproducts, oil, moisture, etc. exit via vacuum through the pcv valve.
 

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Hello Chartmaker. I removed the oil cap after car was warmed up and idling about 550 RPM. No change in RPM. How does fresh air enter the crankcase? PCV?
Some small part of the raw exhaust passes the rings into the crank case. It has nitrogen, carbon dioxide, water, and unburned fuel. Water and unburned fuel make sludge. The PCV draws more volume out than the bypass gasses put in so you have purge air passing with the exhaust stuff. Fresh air needs to be clean and metered. so it is allowed to be drawn off the accordion where it has been filtered and metered by the mass flow meter. Any leak in the fresh air makes for "un-metered" air which makes the PCM have an error in the air flow. The PCV valve is a precision device. I would never use anything but OE parts here.
-chart-
 

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Discussion Starter #16
Understand. Currently one year old PCV. Trying a JY IAC end of day. Thank you for the explanation.
 

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Remove the throttle body and clean the IAC passage in it, and in the intake manifold. If you get fast idle afterwards, do the warm idle relearn procedure.

Warm up, turn off then restart.
Let run for two minutes then hold the brake and shift to Drive. Let run for two minutes.
Whichever way the AC was (on or off) switch it and let run for two minutes.
Shift to Park and let run for two minutes.

The four modes may be done in any order.

If after cleaning the IAC passages and doing the warm idle relearn, you get weird idle behavior when cold but it runs perfectly fine when warm. I have no idea and apparently neither does anyone else, not even Ford.
 

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Discussion Starter #18
Thank you Galane, I'll try the relearn process.
So... he's the update.. Went to JY and had six to choose from. Of course it was the sixth one that had "visually" the best looking option. Overall engine condition etc.. None had a newer replacement. Easy off and $11. at home I gave it a quick Carb Clean spay, dried it out then applied a "little oil with a Q-tip, installed and all good!! In Park idle will settle down to about 750 RPM. I think this one is DONE!!!
.......Now on to the next issues... Firewall O2 bad, and the bigger issue is the front end. Getting inner tire ware. I think Outer tire rod but need to take a closer look. I know the rack and pinion is leaking but I also know that will not be fixed. 20 year old car that is in less than fair condition. I'll save that for another post.
.......Just want to say thank you to all that gave advice. It was much appreciated.
........Also, to those who post a question. Please give feedback on advice. On,e it will help you get a better end result. Two, I'm sure it's also more enjoyable for the experts to be activly engaged. And Three, years from now the back and forth conversation will surely help others. thanks again!!
 
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