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Discussion Starter #1
Hello again!

I have an 83 Spider and have been trying to figure out an idle problem for over a year. I have posted before, and have tried all of the suggested fixes to no avail. Just recently I noticed something else regarding this problem.

The car runs fine most of the time, but will at some point start dying every time I take my foot off the gas pedal. That will continue for from a few minutes to 1/2 hour and then it will start idling properly again. I recently noticed that when it stalls, it will not start unless I depress the gas pedal slightly, as if it is not getting any gas to the cylinders with the pedal at idle, either when the engine has been running and drops back to idle, or when you are trying to start it. When it is running correctly, it will start without depressing the gas at all, and will idle properly. It seems like a very specific issue, hopefully someone will have a solution.

Thanks,
Dan
 

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Send out your injectors for ultrasonic/solvent cleaning.
Poor spray pattern and/or restricted flow.
That would be my guess if you "did everything" as you put it.
Elio
 

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Make sure the throttle stop screw is correctly adjusted and TPS (Throttle Position Switch) is correctly reading the idle position. The throttle stop screw should never need fiddling with but, since they do get messed with, unscrew it until the stop screw is not touching the throttle stop then turn it in until it just begins to touch. Turn it 1/8 to 1/4 turn more. Use the throttle speed adjuster to set the idle speed to 850-950 rpm. (if the O-ring is old and won't 'adjust' it is easy to replace)

The TPS's mounting holes are slotted to allow it's position to be adjusted (also meaning it can be misadjusted...). The correct adjustment (to be made after adjusting the throttle stop screw as above) tells the computer the throttle is at idle. The computer then follows its pre-programmed idle instructions. If the TPS does not properly indicate idle, the computer fiddles with the fuel injectors. For example, if you are driving and release the throttle to slow down the computer shuts off the fuel injectors (rpm above a certain point & throttle at idle).
 

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Discussion Starter #4
idle problem.

Injectors have all been cleaned, so I don't think that is the problem.

I did check the o ring in the throttle speed adjuster, and it was cracked and a bit dried out. I had difficulty finding a replacement, and was told by a local Alfa mechanic that at our altitude (5280') to just throw it away. Which I did...
That did seem to make the stalling problem happen less often, but idle speed is now about 1200 rpm.

Dan
 

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But Mad North-Northwest
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Not the idle speed adjuster, check the throttle position switch. The electrical switch on the throttle. See the link at the bottom of Eric's post.

Your idle speed is way to high because your mechanic gave you poor advice. That o-ring is like three bucks: try IAP or Centerline.
 

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I did check the o ring in the throttle speed adjuster, and it was cracked and a bit dried out. I had difficulty finding a replacement, and was told by a local Alfa mechanic that at our altitude (5280') to just throw it away. Which I did...
Fish through the trash and find it. That advice is silly or you misunderstood. There is some disagreement about whether the O-ring sold by IAP is the right size or not. What I did was take the old one to the plumbing section at the hardware store and match it up by eye. And, no, I wasn't smart enough to write down the size... Look for a kinda fat one about 5/16" - 3/8" OD & 3/16" - 1/4" ID.
 

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Dan T
Hi, I don't know if the O-ring is the problem in your case, but I just got the O-ring from IAP a few days ago, as I have been slowly working on getting my 73 Spider running good, after probably some neglect by PO. Anyway my 2 cents:

The IAP O-ring is only $2.25, but with shipping, so wait til you order a bunch of other stuff. It measures exactly 1/4" I.D. and 1/2" O.D. But I expected it to be softer rubber and more "squishable" so as to make the I.D. smaller when squeezed down and pinched. But honestly, I can't see how any reasonable amount of pressure would change the I.D. at all.
Also, my old O-ring I removed is hard and had probably been squished for a long time, so its I.D. is set at about 1/8", and it doesn't change no matter what adjustments are made. I have concluded that its best just to buy an assortment of O-rings at Home Depot, Harbor Frieght, or local hardware store, etc. that have different I.D.'s and swap them out, kind of like shims, until you get the I.D. that works best for you.
 

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1966-2013
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told by a local Alfa mechanic that at our altitude (5280') to just throw it away
There's an altitude compensation device in the system to deal with such things. It sits next to the ECU.
Specs for testing its output are in the L-jet diagnostics info as linked out of ghnl's and my signature blocks.



The idle air bypass o~ring has absolutely nothing to do with altitude compensation other than that's the spot where you adjust the idle speed if its low or high.

My 2 cents say to you might wanna find a different mechanic before something really detrimental happens as he apparently doesn't know much about the EFI system which can do so real harm to the engine if frigged around with or experimented on by someone not familar with the requirements and specs needed to make it function properly.
 

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Trained (ex)Professional, , 1953-2018 RIP
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Good call on the altitude, Darren.

The 82-83 cars though had only a high altitude 'jumper' that was to be installed in the harness plug by the ECU for driving at altitudes above 3 or 4k feet (can't remember which). The jumper resulted in a leaner fuel map.
 

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1966-2013
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Well poo, thought it was just the 82's that were that way *sigh*

Query:
Did the jumper have a resistor or other gizmonic in it to alter impendance in some way, or was it just to activate an internal circut in the ECU instead?
(I presume the latter due to the later appearance of the sensor proper and subsequent ECU p# change)
 

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Trained (ex)Professional, , 1953-2018 RIP
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I think the jumper just activated internal circuitry. Easy enough to find out though. Who has a jumper that they can ohm out?
 

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1966-2013
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FWIW, resistance in the actual sensor between sea level and 4000' should be 500-4500 ohms and 2500-6000 ohms over 4000'.
Perhaps if the jumper is internally resisted it would come out simular if it isn't just an ECU circut activator.
 
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