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Discussion Starter #1
Problem: Idle is always high. Computer wont store trouble codes.

Hypothesis: Computer is cooked. I suspect that it is in a sort of "limp home" mode. It does not have the ability to store codes or historical engine data needed to set the mixture. I also belive that the EGR system is bypassed in this mode. Needs Replaced.

I ordered a computer yesterday and hopefully it will be here for me to install on the weekend. $45 Shipped!! I will post the results and do a write up on it. Now is your chance to place your bets before the event.
 

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Whats your "high idle"?

My Vulcan idles about 950 when warm, when I disconnect the IAC it idles about 750. Is it just the high idle thats your problem or are there other things that are going a bit wacky, and how is your gas mileage?

Nick Saturday
 

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I dunno I was just trying to be different
 

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Discussion Starter #5
Originally posted by SaturdaysVulcan@Jan 29 2004, 09:39 PM
Whats your "high idle"?

My Vulcan idles about 950 when warm, when I disconnect the IAC it idles about 750. Is it just the high idle thats your problem or are there other things that are going a bit wacky, and how is your gas mileage?

Nick Saturday
computer doesn't store trouble codes. is that whacky enough?

idle is 1000 to 1100. Never tried disconnecting the IAC. when do you do that? hot or cold engine?
 

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I think storing no trouble codes is pretty wacky! I disconnected the connector on the IAC when the engine was fully warmed up, and you should only do it then. If you do it will its cold-warming, up the engine starts to seizure, and the engine idles to low, and computer tries to keep it alive it has to guess on what to do.. ALOT! The car may stall if you do it cold. But warm the rpms should only drop a couple hundred rpms, and still idle somewhat effectively. My Vulcan sometimes does idle that high but I just dont know where to begin to look. Thanks for being the lab-rat!


Nick Saturday
 

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Unplugging the IAC valve AT ANY TIME while at idle should cause the engine to stall EVERY TIME, if your throttle body is properly adjusted and is clean.

With the throttle plate closed, the IAC, under the control of the computer, should be the ONLY source of air into the intake. If the engiine does not stall when the IAC is unplugged, there is still air getting into the engine through one of the following:

1) IAC not fully closed (crud buildup)

2) Throttle plate not fully closed (crud buildup or misadjusted)

3) Air leak in the intake tract (this will cause other, more severe problems).

BTW, if the computer is in FFEM (Limp-to-the-shop mode), it will store a 998 code.

The high idle is probably due to a defective IAC.

Did you run the Ko On Engine Running portion of the codes? That tests the IAC, among many other things.



Steve
 

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Discussion Starter #8
Steve,

I replaced my IAC with a brand new item from ford to try to correct this problem, it did not. I haven't run the test you speak of because I dont know how, do you have a write up on how to do it?

I replaced the computer and the high idle is still there, but it seems maybe 100 rpm lower. I am still corssing my fingers while I drive the car that it gives me a code. My other computer could not store codes so I never got any.
 

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Discussion Starter #9
UPDATE:

Taurus seems to start better with new computer. Also it seems to lower down the idle better at cold start up. The idle is still always a couple hundred rpm high, but the car feels stronger. Old computer was definatly bad. Still no check engine light. I don't know if a slight vacuum leak will cause a trouble code, would that trigger a check engine light or would it be a code I could get with a code reader??

When it warms up I am going to disconnect all the vacuum lines from the intake and see if the idle settles down. This is because I sprayed propane all over the intake to find a leak and couldn't find one, so I am sure that one of the hoses is going to be cracked somewhere that I cant find easily.
 

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Whats the specs on the car year and such?
 

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I voted "other" and here's what I PREDICT :

Car will start better, lower idle at cold start, idle a couple 100 higher, but feel stronger, and you will find possible cracked vac. line.

Ok what'd I win?


j/k....Hope everything works out with bull's new brain.
 
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Originally posted by davesbedroom@Feb 4 2004, 10:18 AM
UPDATE:

Taurus seems to start better with new computer. Also it seems to lower down the idle better at cold start up. The idle is still always a couple hundred rpm high, but the car feels stronger. Old computer was definatly bad. Still no check engine light. I don't know if a slight vacuum leak will cause a trouble code, would that trigger a check engine light or would it be a code I could get with a code reader??

When it warms up I am going to disconnect all the vacuum lines from the intake and see if the idle settles down. This is because I sprayed propane all over the intake to find a leak and couldn't find one, so I am sure that one of the hoses is going to be cracked somewhere that I cant find easily.
A vacuum leak will usually result in the car kicking a lean condition on both banks, I forget the actual code. Subsequently, it will end up misfiring, because additional air is being added after the MAF, and it's not metered. The fuel injectors are working to what the MAF tells them, and the vacuum leak causes a higher (numerically) AF ratio, resulting in a lean condition.

As opposed to propane, which is difficult to detect a leak with on a running car, I prefer some throttle body cleaner spray. If the RPM's increase when it's sprayed on a certain area, you've found your leak.

A sure way to tell if the computer is working is to disconnect the cam position sensor. The car will run, pretty badly, and will kick a code for that.
 

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Discussion Starter #14
I can't make the corralation with the time the problem happend and when I switched to a K&N air filter, but could a K&N air filter have caused this problem. Reason is my mechanic buddy that couldn't fix it, told me that the K&N might have caused the problem and that they see that a lot.
 
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The only way a K&N, or other oiled guaze filter, will negatively affect a car is if it's over-oiled. The oil gets sucked into the MAF, get on the wires, and causes faulty MAF readings. Could this be the case?
 

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Discussion Starter #16
Originally posted by Bob Gervais@Feb 5 2004, 12:18 PM
The only way a K&N, or other oiled guaze filter, will negatively affect a car is if it's over-oiled.  The oil gets sucked into the MAF, get on the wires, and causes faulty MAF readings.  Could this be the case?
Should I zip over to an autoparts store and try to check my codes? Can there be codes that don't turn on the check engine light, but may help me figure out my problem?

Wouldn't that make the check engine light come on? Can I try cleaning the wires?
I found this article on cleaning maf sensors
http://www.bullittarchive.com/Maintenance/maf/
 
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