Hunting/Fluctuating Idle (2)
12-09-2014, 09:17 PM
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Hunting/Fluctuating Idle (2)
Hunting/Fluctuating Idle (2)
I thought somebody might benefit from my recent experience, which is as follows:
On a local trip my 951 refused to accelerate after the left turn stoplight turned green, but it was idling well. I managed to creep to the nearest parking lot, opened the hood, checked hoses for good fitment (especially the one to the TB, which has popped off before) and checked electrical connections to the TB and AFM. All looked good, so the only thing left was some head scratching and closing the hood and try again. Low and behold, this time it worked fine.
Unfortunately the problem re-occurred next morning and fortunately I had some time to guess on the most probable causes, namely stuck AFM door and faulty TB micros witch.
Since the functionality of the micro switch is easy to check audibly, I tried that first and sure enough there was no clicking.
I took the TB off and apart and the micro switch was limp, no internal spring action. I also discovered that the TB to Manifold O-ring had plasticized, so I could actually break it into many small pieces. Fortunately I had another TB (both reconditioned btw, see here) with a new soft O-ring. With a bit of luck maybe this would also solve the annoyance that my idle very often would hunt/fluctuate/oscillate when cold and sometimes creep up to 1200 rpm when hot.
I was lucky on both accounts and now have a 951 with stable idle and great acceleration.
The morals of the story: 1. The TB micro switch can go bad with age and 2. An oscillating idle can be caused by the TB-manifold O-ring having gone stiff (plasticized) and letting unmetered air in at random.
Laust
PS There was a thread with the same title about 18 months ago, which I couldn’t add to since it was closed.
I thought somebody might benefit from my recent experience, which is as follows:
On a local trip my 951 refused to accelerate after the left turn stoplight turned green, but it was idling well. I managed to creep to the nearest parking lot, opened the hood, checked hoses for good fitment (especially the one to the TB, which has popped off before) and checked electrical connections to the TB and AFM. All looked good, so the only thing left was some head scratching and closing the hood and try again. Low and behold, this time it worked fine.
Unfortunately the problem re-occurred next morning and fortunately I had some time to guess on the most probable causes, namely stuck AFM door and faulty TB micros witch.
Since the functionality of the micro switch is easy to check audibly, I tried that first and sure enough there was no clicking.
I took the TB off and apart and the micro switch was limp, no internal spring action. I also discovered that the TB to Manifold O-ring had plasticized, so I could actually break it into many small pieces. Fortunately I had another TB (both reconditioned btw, see here) with a new soft O-ring. With a bit of luck maybe this would also solve the annoyance that my idle very often would hunt/fluctuate/oscillate when cold and sometimes creep up to 1200 rpm when hot.
I was lucky on both accounts and now have a 951 with stable idle and great acceleration.
The morals of the story: 1. The TB micro switch can go bad with age and 2. An oscillating idle can be caused by the TB-manifold O-ring having gone stiff (plasticized) and letting unmetered air in at random.
Laust
PS There was a thread with the same title about 18 months ago, which I couldn’t add to since it was closed.
