I have a 97 F-150. Has about 206,000 miles on it. Check engine light just came on and had the codes run at Advance. Gave me 1538 which is IAC? I have no problem with my idle. Any ideas?

Thanks, Mark

 

take it off and check it for cleanlyness and that it works, make sure the ports are not clogged. spay some cleaner in there to clean the carbon off then try again. if it comes on again then change it I don't think they cost to much, anybody know the cost and can it be bought as a after market?

Lance

 

Hi Lance,

Thanks for the suggestions. I checked on the price and it is around $65 at Advance. Not all that much. Just was wondering why the idle would not be noticably bad if the part was not operating correctly. I guess that the sensors must be touchy. I'll try cleaning it and see how it does.

Mark

 

The cpu may be catching it before it does cause you idle problems?

Lance

 

Lance, I purchased a new after market part and installed. The light still ccame back on I am going to take it to another store in case the codes were read incorrectly the first time. I must say that it at least seems to run a little better, but the light keeps shining!! Of course, you know it had to come on 10 days before emissions were due. :P Mark

 

Did you reset the CPU? Or go in and erasse the codes stored in the cpu? I do either of them and then check to see what happens. If you don't have a scanner to clear the codes then disconnect the neg cable for 15 min then reinstall.

Lance

 

Hi just went to AZ to have them check and got the same results. The used the Code Reader to erase the codes. The light was back on within a short period of time. Do you know if there is anything else that might give the same fault code? Or possibly a defective part maybe? Hate to spend another $60+ to find out. If the code is very specific to the part, I will take it off and take back. Would this make sense?

 

OK my Chiltons shop Manual says that the code 1538 is a Intake manifold runnercontrol (IMRC) Malfunction (Bank One stuck open). If they allow you to return the part Go ahead. let me do alittle reserch to try to figure it out.

any help outthere.

Lance

 

The best I can find is there is a control or actuator, (Intake Manifold Runner Control) it is located on the manifold but I can't even find a pic of it. So If you can find it or what it looks like it is probaly your problem (stuck Open) My 2000 does not have it so any help out there as to what it looks like?

Lance

 

here is what I found:
P1538 Intake Manifold Runner Control Open (Bank 1)
Intake Manifold Runner Control Open (Bank 2)
The long and short intake manifold runners are part of the intake system. The Intake Manifold Runner Controls (IMRC) open and close a valve depending on driving conditions. Misrouted cables, a damaged IMRC housing or springs, binding or disconnected lever/shaft or seized gears can cause this code to be set. Bank 1 refers to the bank of cylinders containing Cylinder #1.
Bank 2 refers to the bank of cylinders opposite Cylinder #1.

hope it helps

Lance

 

OK Lance, I had seen some posts about that, but the codes in that case were 1537 and 1538. I will say that on the low end it does not have near the get up and go as it does on the upper end. It is my understanding that bank one is up to 3000 RPM when bank two takes over. This would make more sense based on what I am experiencing when driving; although, I do not recall this being a new phenomenom.

 

It sounds like the IMRC on one of your banks is stuck open. The IMRC should be open at higher engine speeds >2000RPM to allow air straight access to the manifold and cylinders. At low speeds the runner is closed and creates a tumbling effect of the air for better combustion at low speeds. I believe the IMRC is electrically actuated on the 4.6L, probably not vaccum. Check connections etc...

 

Well, I searched the forum and there seems to be no good (consistent) answer to the problem. There is a picture, but no location in the Haynes manual which I know blows. The manual suggests taking it to a dealer to get ripped off. Any suggestions on how to test the banks before removing the intake plenum, etc?

Based on the photo, they are vacuum operated. I looked under the hood, and can not tell where the vacuum hoses come out. I think maybe they are in the front? Or, possibly, I have to remove the intake plenum before I can even see them. Ugh. Based on a number of photos in the manual, I believe they are in the back. The photo of the fuel rail (plenum off) clearly shows them. Thanks again. Mark

 

AH HA!!! I went to the Ford dealership and talked to the parts guys -- who are great and a fount of knowledge. They said that the little plastic bushings that hold the arms in the holes are known to break. I managed to reach behind one of the IMRC actuators, and the rod just flopped around -- not good. I picked up a couple of the bushings figuring on replacing both while I had the intake plenum off. Good thing as they were both out (bad).

The job is not that terrible once the plenum is off -- I used a little medical clamp with a curved tip to line the bushings up square so I could push them into place. If the bushing is at a slight angle, one of the tips will hang on on the edge of the hole (which by the way is square) The rod end, once lined up, pushed easily into place. I ran in the driveway for a short time. Turned off and ran again and no light as yet. I plan to take it for a spin soon. Needless to say, they were both bad whether the light comes on again or not.

I took some photos of the rod out of the hole (no bushing) and the bushing replaced with the rod in place. Also a photo of the location with the intake plenum off. Not the best, but I think show what needs to be shown. They are jpegs, but I have no idea how to post them. So if someone knows how to post, or would like to take a look at them, let me know, and I can email them anyway.

Thanks for all your help, Mark

 

Engine light stayed out -- emissions here we come. I think it actually ran better at midrange (acceleration) when it was broken -- DOH! No real noticable difference at lower RPMs. If not for the stupid light and emissions -- disconnect them?