IAC Over Speed Error P1506
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Elder User
Joined: Apr 2004
Posts: 866
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From: North Carolina
IAC Over Speed Error P1506
About 3 days ago I noticed my engine RPM was around 250 higher than usual. Usually my truck idles around 550-600 rpm (I know this is low).
Anyway, yesterday it threw the P1506 "IAC over Speed Error" Code. It is idling very rough, shifting weird, but does crank up fine.
My truck is now at 93,000 miles and I just cleaned the IAC at 87,000 miles due to the common no start condition. I guess I am going to get a new IAC now since another code came up.
Well, my question is it came up with two other codes also:
Do you guys think I should get a new IAC or try to clean it again?
Thanks so much.
Anyway, yesterday it threw the P1506 "IAC over Speed Error" Code. It is idling very rough, shifting weird, but does crank up fine.
My truck is now at 93,000 miles and I just cleaned the IAC at 87,000 miles due to the common no start condition. I guess I am going to get a new IAC now since another code came up.
Well, my question is it came up with two other codes also:
• P0171 - System too Lean, Bank No. 1
• P0174 - System too Lean, Bank No. 2
Do you think the P1506 (IAC Code) made the O2 Sensor codes show up or is it really the O2 Sensors? I just changed my two upstream O2 Sensors around 90,000 miles.• P0174 - System too Lean, Bank No. 2
Do you guys think I should get a new IAC or try to clean it again?
Thanks so much.
Senior User
Joined: Mar 2004
Posts: 224
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From: Central Ohio
Neither. A vacuum leak is causing both. Once in closed loop where the O2 sensors adjust the mixture based on the exhaust, a vacuum leak is just like a wider open throttle. It lets in more air, the computer playing off the leaner exhaust adds correspondingly more fuel so it runs smoothly, just faster. Although the computer commanded more fuel, it realized that it had to add much more fuel than the amount based on the amount of air going through the MAF. Since it had to add more fuel, it concludes the engine is lean. Since the IAC closes but the engine RPMs are still up (because of the vacuum leak) it sets to IAC failure to control code.
Use a length of fuel hose to your ear to listen for the leak. Especially check for rotted hoses on the PCV, at an elbow behind the throttle body.
Use a length of fuel hose to your ear to listen for the leak. Especially check for rotted hoses on the PCV, at an elbow behind the throttle body.
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Elder User
Joined: Apr 2004
Posts: 866
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From: North Carolina
Thanks for your response cantrma.
I guess I will check for vacuum leaks then. I mean that could be the problem but I am going to go ahead and get a new IAC. Just to get that out of the way.
I guess I will check for vacuum leaks then. I mean that could be the problem but I am going to go ahead and get a new IAC. Just to get that out of the way.
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Elder User
Joined: Apr 2004
Posts: 866
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From: North Carolina
ok guys it is a vacuum leak. The back 90 degree hose fitting that comes from the PCV valve and connects to the back of the intake.
I went ahead and bought a new IAC for $78.50. I am going to go ahead and install the IAC and get a new hose fitting in the morning.
IF YOU ARE HAVING PROBLEMS WITH THE TRUCK IDILING, CHECK THAT HOSE!
I went ahead and bought a new IAC for $78.50. I am going to go ahead and install the IAC and get a new hose fitting in the morning.
IF YOU ARE HAVING PROBLEMS WITH THE TRUCK IDILING, CHECK THAT HOSE!
Senior User
Joined: Dec 2003
Posts: 205
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From: Arlington, Texas
hmmm...I'll look over the hoses to see if this is my problem too. You don't happen to have the 5.4 and could yield any tips on removing the IAC do you? Also, I noticed you said you changed out your O2 sensors. Do you know the recommendations for how often these are to be changed?
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Elder User
Joined: Apr 2004
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From: North Carolina
Yes, I have a 5.4L as you can see in my signature.
You can get to the IAC without removing the throttle body or intake manifold spacer. The IAC is mounted on with two 8mm bolts. It is easy to get to with a 1/4 drive and a universal joint. It might not look like you can get to it but you can.
I wouldn't change the O2 sensors until you start having problems. Actually the upstream (closer to the engine) O2 sensors are the ones that only need to be changed most of the time. The downstream (towards the tail pipe or muffler) O2 sensors never give a lot of trouble. We do have four 02 sensors in all.
You can get to the IAC without removing the throttle body or intake manifold spacer. The IAC is mounted on with two 8mm bolts. It is easy to get to with a 1/4 drive and a universal joint. It might not look like you can get to it but you can.
I wouldn't change the O2 sensors until you start having problems. Actually the upstream (closer to the engine) O2 sensors are the ones that only need to be changed most of the time. The downstream (towards the tail pipe or muffler) O2 sensors never give a lot of trouble. We do have four 02 sensors in all.
Senior User
Joined: Dec 2003
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From: Arlington, Texas
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Elder User
Joined: Apr 2004
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From: North Carolina
ok guys everything is fixed now. Truck runs great!
I installed a new IAC and the PCV valve hoses (They all come together).
I installed a new IAC and the PCV valve hoses (They all come together).
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New User
Joined: Apr 2013
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I get a P1506 code,and can hear possibly a vacuum sound comeing from behind and to the left of the insturment cluster, that will change if the throttle is opened wide and quick. What is behind there??
Lead Driver
Joined: Sep 2006
Posts: 7,907
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Sand,
while you have a 97, it is an older push rod motor and is not equipped with all the same system.
I would say if you look up the 320 code, it would suggest what your issue is.
There is no 320 code for the rest of the engine families being discussed in this thread.
I don't feel a vacuum leak is your issue either.
The 1506 code is the same because it is the same type part on both engine families so the code description will be the same, in this case but not for code 320.
Good luck.
while you have a 97, it is an older push rod motor and is not equipped with all the same system.
I would say if you look up the 320 code, it would suggest what your issue is.
There is no 320 code for the rest of the engine families being discussed in this thread.
I don't feel a vacuum leak is your issue either.
The 1506 code is the same because it is the same type part on both engine families so the code description will be the same, in this case but not for code 320.
Good luck.
New User
Joined: Mar 2018
Posts: 2
Likes: 0
Idle
I have a 2000 Ford Ranger 2.5 Rough idle Every time I Bring RPMs up high then let off it idles down real low and dies what could be the problem I have already changed just about every sensor on motor And took throttlebody a part and cleaned