IAC Problem?

Look at the IAC, idle air control or sometimes called idle air solenoid. Dont know what engine you have, assuming 4 cyl. Its usually located on the intake manifold directly after the throttle body held on by 2 metric bolts and has 1 electrical plug. Just pull it off the manifold and spray it out with carb cleaner. When they get gunked up they can wreak havoc with the idle.

 

Are you saying that it does not have a check engine light (MIL) or that its not on?

 

whoops now I see the title to the thread, yes id agree with you look at the IAC first, esp on fords.

 

Sea Foam treatment helps my Exploder a lot more than I thought. I usually do it every oil change...should do it more often though. The idle gets rough after a while. The Sea Foam does its job and really helps smooth out the idle and the throttle response. Even the sound of the engine is smoother and not as rough.

 

what the hell is sea foam??

 

Sea Foam

pretty much any autoparts store. 6 bucks a can.

Slowly pour 1/3 can into the brake booster line or any vacuum line. Turn the engine off for 5 minutes then start her up...it cleans out a lot of the carbon build up and crap.

 

How many miles on your Explorer Azn??

 

yeah seafoam is some good stuff.they make a spray too.

i never knew about the vac line trick.exactly how slowly do you pour.how long?

and how long does it run like crap afterwards before its all done?

 

clean the mass air sensor. i did mine some time back cause mine was acting up and it helped.exactly how long do you go between drives.

maybe the pugs are fouled?

 

hmmmm..maybe bad gas.the fact that the engine light hasnt comeon yet has me perplexed.

it could be so many things..

vac hose

cracked plug wire

dirty mass air flow sensor

fuel filter getting clogged?

im suggesting things that have happened to me before and were the probs

does it have a distributor/cap rotor? check those too

 

My Explorer has 147k miles on it.

Pedro..just slowly pour the stuff in because as its sucked into the intake manifold the engine starts to bog...I just drizzle it in there.

After you restart it just run the engine until all the smoke clears out...there'll be A LOT of smoke.

 

the same thing happened to my dodge, i took some carb and choke cleaner, took off the air cleaner, and had my pops rev it up a bit while i sprayed it in the throttle body. it does the trick everytime for me. o and the reason i havent been on for a while is cause my compooper had viruses.

 

I had to completely take off my throttle body and clean off the .25cm of carbon build up with a wire brush and a lot of WD-40. And a toothbrush. After cleaning that crap off my idle was 600rpm higher than before because of the free air flow and idle was a lot smoother too.

 

bad fuel?.....

 

Ranger,

I'm not sure if this is relevant, but here's how I would look at, or dig into this issue. The IAC is the component that does control idle, so I would be concerned with it. But, at closed throttle, it expects a certain amount of air past the throttle blades, and if the bore is dirty, it assumes it isn't, and doesn't compensate for it. So, cleaning the bore and plate is what I would do, first thing. Try to use something that isn't too corrosive on a rag, if you can. Take off the intake boot, open up the plate, and wipe down the bore, and the plate. I try not to introduce any liquid into the IAC itself. Many cars, that is certain death to them. Mitsubishi's for one. Not only can it short the IAC, it will also wipe the ECM. It is open to elements, and putting liquid into a motor is deadly to it. But, I digress.

If you feel the IAC itself is a problem, then take it off, clean the passage, and gently clean the IAC itself. There is a gasket between the throttle-body and IAC, but it usually survives removal.

If all that gives no joy, then we need to look at fuel trims. A scanner that allows data stream is necessary, for sure. Any OBD II scanner will show this. A brief lesson in trims, if I may.

Fuel trims are a window into the fuel delivery on a car with a Mass Air Flow Sensor. (MAF) They work just fine on cars with a Manifold Absolute Pressure Sensor (MAP), but we will concentrate on MAF cars today.

It all starts with the Oxygen Sensor. Though that is the sensor at the end of the combustion process, that is where it all starts, if that makes sense.... Here we go.

Here is a quick overview of the Oxygen Sensor and Fuel Trims. The engine management system has a certain learned value that it uses in different operating conditions of the engine. Idle has one strategy, light acceleration another, as is cruise on the highway, and on and on. Each one of these conditions has a learned value as to how much fuel is injected into the engine. The Oxygen Sensor is the item that tells the Engine Computer what has just happened in the engine in regard to those values. The computer then “adjusts” the fuel to keep it at the perfect 14.7 to 1 mixture that the engine runs the very best at.


So, when the Oxygen Sensor sees that the engine has too much oxygen exiting the engine through the exhaust, it asks the computer for more fuel. This is called Fuel Trim. When Fuel Trims are skewed above a certain value, codes will set. Sometimes it is 18% above normal, other times it my be 25% above normal, or any number the computer sees fit to flag as “too far out of specification”. In other words, based on the rpm, air entering the engine, speed, and other inputs, the Oxygen Sensor is telling the computer that it may need 25% more fuel that it normally uses in these parameters.


In the most simple of terms, the engine is either getting 25% less fuel than it should have, or 25% more air than it should have. The computer sees that, and knows that is far from normal, and turns on the MIL.

So, as Ranger said, a code would most likely set as a result of trims being skewed. But, sometimes trims aren't skewed enough to set a code. Yet. But, drivability concerns still can exist.

I am going to put up some examples, and explain what I see, and y'all can tell me if it makes it clearer to you folks.

Here is a vehicle with a bad MAF sensor. As you can see, it is taking a little fuel away at idle as noted by the negative Short and Long Fuel Trims.



Next, you can see under acceleration that the Fuel Trims follow the engine acceleration. In a positive manner.



These are in a graphical format, and that is really the best way to see trends. What the MAF is doing is under-reporting the air going into the engine, so the PCM is not adding enough fuel. But..... When the O2 sees an excess of oxygen exiting the engine, in other words, running lean, then it tells the computer to add fuel. Hence, it is "trimming" the engine to get it where it needs to be.

Next is a vacuum leak. You can see it is "adding" a ton of fuel in both banks. This is a V-8 Ford, but any engine is the same, just this has 2 banks to look at, not just one as does a 4 cylinder engine.



Here is off idle, where the throttle plates are open, so since they aren't closed, the engine isn't trying to pull fuel from other sources, such as a split vacuum hose, etc.



And here it is after being repaired. You can see where the trims are going opposite and pulling fuel back away after it learned to add fuel from it's previous values.



I have more, but this is enough for now. Of course, I am open to any questions you all may have. But, we need to look at what the PCM sees to get a little window to the workings of it all as far as fuel control goes.

Sorry for the length of this, btw.