High idle
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Senior User
Joined: Oct 2010
Posts: 439
Likes: 1
did you have this problem before the intake manifold gasket was replaced? that would be my guess. the IM gasket or the upper plenum gasket. if thet are breached, it will be a vacuum leak and cause high idle. a way you can test for this(not always accurate) is to get some wd40 for carbcleaner and spray around the base of the the manifolds and see if this affects the idle. the fluid will temporarily 'plug' the whole in the gasket if there is one. you can also get a cheap hand pump vacuum gauge from autozone or oreillys and hook it up to where the pcv valve line goes into to upper intake. see if it will hold vacuum. that can eliminate the thought of a vacuum leak if it holds a small about of vacuum for 5 minutes or so. dont pump it up to high.
Thread Starter
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Senior User
Joined: Oct 2010
Posts: 439
Likes: 1
did you have this problem before the intake manifold gasket was replaced? that would be my guess. the IM gasket or the upper plenum gasket. if thet are breached, it will be a vacuum leak and cause high idle. a way you can test for this(not always accurate) is to get some wd40 for carbcleaner and spray around the base of the the manifolds and see if this affects the idle. the fluid will temporarily 'plug' the whole in the gasket if there is one. you can also get a cheap hand pump vacuum gauge from autozone or oreillys and hook it up to where the pcv valve line goes into to upper intake. see if it will hold vacuum. that can eliminate the thought of a vacuum leak if it holds a small about of vacuum for 5 minutes or so. dont pump it up to high.
Fleet Owner
Joined: Oct 2005
Posts: 20,789
Likes: 1,753
From: Kentucky
Code 67: Neutral safety circuit failure or A/C circuit was on during Self-Test.
Even though Ryan's site shows Code 67 as A/C circuit was on during KOER Self-Test, my Ford manual shows it is a KOEO code. Therefore if you had the A/C or Defrost on when running the KOEO tests you would have generated that error.
As I have pointed out before if the engine RPM drops down below normal idle RPM or stalls when the IAC is disconnected you more than likely do not have a vacuum leak.
I am pretty sure I have tossed out the idea you have a sensor causing the problem. I also think I stated the sensor could pass the KOEO/KOER tests but still not output the proper signal at normal operating temperatures. There are a few ways to troubleshoot this, one is disconnect each one then see if the idle RPM comes down or measure the sensor with a meter with the engine cold then once again when it is warmed up. That way you know for sure what you are working with.
If that is inconclusive it may be time to pull out the PCM and inspect it for signs of leaking capacitors and/or burn marks.
Even though Ryan's site shows Code 67 as A/C circuit was on during KOER Self-Test, my Ford manual shows it is a KOEO code. Therefore if you had the A/C or Defrost on when running the KOEO tests you would have generated that error.
As I have pointed out before if the engine RPM drops down below normal idle RPM or stalls when the IAC is disconnected you more than likely do not have a vacuum leak.
I am pretty sure I have tossed out the idea you have a sensor causing the problem. I also think I stated the sensor could pass the KOEO/KOER tests but still not output the proper signal at normal operating temperatures. There are a few ways to troubleshoot this, one is disconnect each one then see if the idle RPM comes down or measure the sensor with a meter with the engine cold then once again when it is warmed up. That way you know for sure what you are working with.
If that is inconclusive it may be time to pull out the PCM and inspect it for signs of leaking capacitors and/or burn marks.
Thread Starter
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Senior User
Joined: Oct 2010
Posts: 439
Likes: 1
Code 67: Neutral safety circuit failure or A/C circuit was on during Self-Test.
Even though Ryan's site shows Code 67 as A/C circuit was on during KOER Self-Test, my Ford manual shows it is a KOEO code. Therefore if you had the A/C or Defrost on when running the KOEO tests you would have generated that error.
As I have pointed out before if the engine RPM drops down below normal idle RPM or stalls when the IAC is disconnected you more than likely do not have a vacuum leak.
I am pretty sure I have tossed out the idea you have a sensor causing the problem. I also think I stated the sensor could pass the KOEO/KOER tests but still not output the proper signal at normal operating temperatures. There are a few ways to troubleshoot this, one is disconnect each one then see if the idle RPM comes down or measure the sensor with a meter with the engine cold then once again when it is warmed up. That way you know for sure what you are working with.
If that is inconclusive it may be time to pull out the PCM and inspect it for signs of leaking capacitors and/or burn marks.
Even though Ryan's site shows Code 67 as A/C circuit was on during KOER Self-Test, my Ford manual shows it is a KOEO code. Therefore if you had the A/C or Defrost on when running the KOEO tests you would have generated that error.
As I have pointed out before if the engine RPM drops down below normal idle RPM or stalls when the IAC is disconnected you more than likely do not have a vacuum leak.
I am pretty sure I have tossed out the idea you have a sensor causing the problem. I also think I stated the sensor could pass the KOEO/KOER tests but still not output the proper signal at normal operating temperatures. There are a few ways to troubleshoot this, one is disconnect each one then see if the idle RPM comes down or measure the sensor with a meter with the engine cold then once again when it is warmed up. That way you know for sure what you are working with.
If that is inconclusive it may be time to pull out the PCM and inspect it for signs of leaking capacitors and/or burn marks.
Fleet Owner
Joined: Oct 2005
Posts: 20,789
Likes: 1,753
From: Kentucky
Just because the other parts you threw at this problem are new does not mean they are good.
You will not have any starting issues related unplugging/plugging in the PCM. Just be careful when you push the connector back on to not bend any pins.
You will not have any starting issues related unplugging/plugging in the PCM. Just be careful when you push the connector back on to not bend any pins.
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Senior User
Joined: Oct 2010
Posts: 439
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I think this will be the last update
I had an emergency gas leak the other day bad out of the rear filler neck tube so gas was squirting everywhere. Being busy with summer classes and work, I let my mechanic fix it and I asked him to look at the idle. He soaked the IAC valve in his parts washer and cleaned it better than I had. After surging to 2000 rpm briefly after the first start, it seems to idle as it should now for the first time in my ownership. I'm calling it done!
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