Engine dies when turning wheel to far

[hatecars]

When you unplug the MAF, the PCM looks up the "Load w/ Failed MAF" table, and fuels from it instead. If your truck is bone stock, this is a very accurate table, and the vehicle will run and idle fine. You should also know that MAF failures are not common, and the sensors aren't cheap, and the aftermarket sensors are junk compared to the Ford sensor. Don't buy a MAF, you'll most likely be wasting your money.

You're painting a picture here. You've got both banks lean. The idle surging comes from the lean condition causing the motor to nearly stall. The PCM detects this low rpm, and compensates hard for it, raising the idle via the IAC motor. It overshoots the desired idle rpm, and suddenly the IAC closes and RPM plummets. Then, the whole process repeats. This is the up and down idle speed you're experiencing.

As long as your IAC is clean, and it probably is, this is not your problem. IAC is idle air control motor. It's a solenoid that bolts onto the side of your throttle body.

In searching for a picture of an IAC for you, I ran across this thread that you need to read!

http://www.explorerforum.com/forums/showthread.php?t=217062

First, thanks for you continued help..

I found my IAC, will clean it today..

I read the post your sourced about 4 months ago when my CEL first came on I replaced one of my cracked elbows(car would die and read lights, used a basic elbow for Autozone..) now the CEL light hasn't gone off yet and i am fine at red lights but in park i get the rpm reving thing.

Are there other elbow hoses besides the one i replaced? How many vacuum hoses should I have?

Do you think replacing it with a basic elbow instead of buying the Ford Motorcraft kit is the problem(seemed to work for the past 4 months)

 

[Pontisteve]

Well, nothing fits like OEM parts. But how well an aftermarket rig will work depends on the ingenuity of the rigger. If you want the problem to go away permanently, get the OEM part from Ford and be done.

Your check engine light may not go off for a while on it's own. Once a light is triggered, it takes so many key/drive cycles of the problem not recurring before the PCM will shut the light off. You can shut it off manually using a scan tool by clearing codes. If the problem is fixed, it will stay off.

Instead of looking at any one specific leak, as referenced in the other thread, look in general for ANY WAY air can get into the engine without going thru the MAF sensor. This means any vacuum lines, gaskets, intake tubing rips, tears, loose clamps, etc.

Often an easy way to find a vacuum leak is with your ears. Just listen for that telltale hissing noise and find it. Another way (although with some risk of FIRE!) is to provide a flammable gas (brakleen or propane) under the hood and let this gas leak near any suspected vacuum leaks. If there is a vacuum leak, the flammable gas will get sucked into the motor and burned as a fuel source. That will immediately make your RPMs rise up some. An unlit propane torch can work well for this. UNLIT.

But I must warn you, if you let too much gas out under the hood, and there is any type of spark source (bad plug wire, lit cigarette, etc), it can ignite the gas you've leaked under the hood, which over time may have collected into one large cloud of gas.

This happened to me not too long ago, despite years of experience. I was under a Mustang hood, with a stethoscope in my ears, looking for a ticking noise. My friend was under the hood with a can of brakleen, spraying and looking for a vacuum leak. Over time, he had enough brakleen clouded under the hood that it was dangerous. I was about 10 seconds from finding my tick when the explosion happened. The tick was a spark plug wire that had been left off by friend #3, and it was firing against the exhaust manifold! There was my spark source, and the brakleen was my fuel source. I didn't hear the explosion, because I had the stethoscope in my ears. But I damn sure felt the heat. Burned my nose, some hair and eyebrows. It was no joke... it was just bad enough to not be funny. Thank God, it wasn't worse. So if you go this route, be careful. Let the fumes vent occasionally, and make sure there are no ignition sources.

If you had a previous problem with a vacuum leak, go back and check that leak specifically, with a little brakleen and the engine running. A couple little shots won't hurt anything or risk fire. If it's leaking, the engine will flare when it breathes that brakleen. Suspect aftermarket parts to be problematic first. This is the problem with rigging a fix.... it may work for a while, but not forever. OEM parts generally work for a VERY long time before failing again.

Loose air inlet tubing clamps, or a pinched and folded under intake hose can cause a major air leak around the MAF, so check hose hoses and clamps real good, from the air filter to the throttle body.

 

[hatecars]

I think i have a bad IAC, cleaned it out and it didn't help, but that seems to be the issue, did some scientific work(bang it with a hammer) and it completely failed now.. Now it won't even start, let alone idle back and forth between rpms... Took off the part completely and it didn't effect the engine at all.. will let you know in about an hour..

 

[hatecars]

Replaced IAC everything fixed now. CEL gone...

 

[waskly]

i doubt the lean codes are fixed by the iac, keep an eye on them.

 

[Pontisteve]

I second that. You can try clearing the codes, or disconnecting the battery, and drive it for a while and see what happens.

Rare that an IAC is actually bad. Weird.