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Discussion Starter #1
On cold starts, the idle on my '88 T16 swings from around 1200rpm to nearly stalling -- after a few minutes it's great and the car hauls. I don't believe I have a vacuum leak; I've gone over a lot of the lines (and have replaced a few as well). Any ideas?

-Ian
 

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When you say the idle "swings," do you mean it oscillates repeatedly until the car warms up?First thing I would do, regardless, is remove the AIC valve and flush it out with WD-40; see if this helps!
 

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I had this exact same problem. here is what I found:

Bad AMM. My original one was questionable (surging issues) so I bought one off ebay to replace it with. After installing it, the car began to act just like you are describing. after about a minute it would stop and be fine. I put the old one back in and it's been fine ever since! go figure.
The check engine light would illuminate with the bad one from ebay repeatedly. since the old one's been back in, it's been fine.
 

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Discussion Starter #4
By "swings" I mean like runs up to 1200-1500 and then drops back down to nearly stalling within about 2 or 3 seconds, then back up, and down, etc.

I guess tonight I'll clean out the AIC valve and try reseating the AMM plug.

Thanks for the suggestions!

-Ian
 

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With the engine running spray carb cleaner on the seals where the T pieces go into the throttle body as well as on the hoses and connectors themselves. Where the idle changes when you spray it, that's where the leak is. You can also spray carb cleaner through the AIC to clean it out, rinsing with WD40.
 

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Discussion Starter #6
Jezzadee said:
With the engine running spray carb cleaner on the seals where the T pieces go into the throttle body as well as on the hoses and connectors themselves. Where the idle changes when you spray it, that's where the leak is.
I tried that trick and didn't find anything. I'm pretty sure there's no vacuum leak.
 

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drcoopster said:
By "swings" I mean like runs up to 1200-1500 and then drops back down to nearly stalling within about 2 or 3 seconds, then back up, and down, etc.

I guess tonight I'll clean out the AIC valve and try reseating the AMM plug.

Thanks for the suggestions!

-Ian
yup mine did exactly that. I tried cleaning the AIC to no avail. it seemed to work without a problem.
the fact that its only doing this when its cold leads me to believe its the AMM. this just sounds exactly like my problem. Once I put my older unit back in, it stopped the idle crazy-ness. I think if its the AIC it would do it when it was warm too.
I found one on ebay for 10 and one for 20 bucks. the place I got mine said I could send it back for replacement for a good one so that's what i'm going to do.
 

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Hi there,

When my '86 suffered this prob, the throttle switch was suspect. Reset the alignment of the switch at idle position, problem never came back.

Good Luck.
 

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Discussion Starter #11
I installed a new clutch last night and managed to forget to plug in the AMM. Lo and behold, it idled okay (of course with the addition of a check engine light). When I plugged it back in, the idle went back to its erratic usual behavior.
 

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drcoopster said:
I installed a new clutch last night and managed to forget to plug in the AMM. Lo and behold, it idled okay (of course with the addition of a check engine light). When I plugged it back in, the idle went back to its erratic usual behavior.
ha thats funny. When I unplugged mine to see if it would help the car just up and stalled. no decrease in rpms, just an abrupt cut out.
 

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same problem

Hey I'm having the same sort of problem on an '87 900 non turbo 8-valve, which doesn't have an Air mass meter... also every time the idle drops there's a click sound like a relay or something.
Anyone have any suggestions?

oh also... in correlation with the clicking sound, the fan on the passenger side turns on or off when the idle goes back to normal.
 

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drcoopster said:
I installed a new clutch last night and managed to forget to plug in the AMM. Lo and behold, it idled okay (of course with the addition of a check engine light). When I plugged it back in, the idle went back to its erratic usual behavior.
When the AMM is unplugged, the ECU goes into limp home mode and in that state, only the basic functions are performed. The air/fuel ratio is fixed to a safe preset and the ECU simply fires the fuel at the given trigger point from the ignition/distributor. The idle now just sits at the rpm that equates to the amount of air passing through the throttle body when closed.
All other automatic features such as idle control, are canceled until the system is complete again.
The AMM may be suspect but I tend to think otherwise.

Good Luck
 

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drcoopster said:
By "swings" I mean like runs up to 1200-1500 and then drops back down to nearly stalling within about 2 or 3 seconds, then back up, and down, etc.
This oscillation is the problem I had with our 1990 900S. If flushing out the AIC valve doesn't help, I would conclude that, as was the case with our car, the AIC is bad and needs to be replaced:eek:

These are expensive, but rarely go bad; try one from a junkyard, if they'll guarantee you another one (or a refund) if it, too, is no good.
 
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