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Discussion Starter · #1 ·
Hey everyone, thanks for looking at this. I've had a fast uneven idle for a while now, have recently replaced all iggnition bits and wires, most hoses, cleaned out the evap canister, checked for leaks and pretty much the whole L-Jet troubleshooting guide.

I just received a new idle adjustment washer from IAP and it seems tiny and thin compared to the old one that I removed, of course, I can tighten it as far as it will go, just like the last one and still the idle would not go below 1200-2300 and would cycle up and down 100-150 rpm.

This is of course exactly what it did before I replaced the washer.

I am going to take a photo right now, since I know how much you all like pictures.

So, I mucked about with the lines and managed to get the idle to drop down to 850 and pretty stable at that by putting a pair of vise-grips on the intake line connected to the idle adjuster. It starts quickly and drives great like this... but obviously not a good long term fix, lol.

But, this can't be the solution, so what is going on?

Is the washer wrong?

Am I missing something?

Am I cursed?

discuss.

BTW, the new one is on the left

 

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1966-2013
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I can tighten it as far as it will go, just like the last one and still the idle would not go below 1200-2300 and would cycle up and down 100-150 rpm.
That's indicative of a false air leak.
For a quick check, take the oil fill cap off while its idling and see if the idle speed noticably changes.
If it does not, you've definitely got a leak.

Other things to look at would be confirming the AAV closes, TPS position and function, the throttle linkage rods, and that no~one has tinkered the butterfly stop screw in the throttle body proper.

That o-ring doesn't look quite right to me either, btw, but your old one may have taken some swell over the years.

EDIT
Is the old one still compliant and flexible, or crisp and hard as stone?
If soft, put it back in before you go rooting around for other things so you're back to baseline persay.
 

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Discussion Starter · #3 ·
yes,, idle falters when oil filler cap is removed. In fact I have tried everything related to 'false air leaks' to no avail.

one thing you mention does resonate, the throttlle butterfly (which i just cleaned last week) seems sticky or something, if i push down on the linkage (at the throttle body, where the return spring is) the idle drops, as if the spring isn't closing it all the way... could it be the linkage?

TPS seems fine, clicks when throttle is slightly opened.

where is the stop screw inside the throttle body? can it be accessed from the air intake hose side?
 

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one thing you mention does resonate, the throttlle butterfly (which i just cleaned last week) seems sticky or something, if i push down on the linkage (at the throttle body, where the return spring is) the idle drops, as if the spring isn't closing it all the way... could it be the linkage?
Quite possibly.
Unhook the linkage rod between the TB and the bellcrank and see what happens.

TPS seems fine, clicks when throttle is slightly opened.
Clicks OK, but does it read continuity on a multimeter when the throttle is fully released?

where is the stop screw inside the throttle body? can it be accessed from the air intake hose side?
It's on the outside of the TB and the external butterfly mechanism arm stuff butts up against it when the pedal is released.
It's literally the only flat tip screwdriver screw on the whole TB barring the hose clamps.

If its exposed, someone has been at it in the past.
If it's got a anti~tamper cover on it (flat plug pushed into the hole like on an untampered AFM) then it likely hasn't been messed with unless someone was meticulous about putting a new plug on it when done.
 

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I also recently ordered that O Ring from IAP and got exactly what you got. The package it came in actually mentioned spica on it... I had to bottom out the adjustment but did manage to get my idle down to just below 1000. For the cost of the O ring it didn't seem worth the hassle of returning it. At some point I'm going to the hardware store and buying something close to see if it'll just work.
 

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Discussion Starter · #7 ·
oh, right... that screw, it's backed all the way out, it was uncovered as you might expect from a 4 owner car going on 23 years, the stuff i found when i bought it could keep you awake at night...

i will check the continuity, and i've been looking for an appropriate washer/grommet but haven't come across one... but to me that new one is never going to close down enough...

i've hadd the old ring in but it's not different with the new one, they both require the adjuster to be bottomed out and neither brings the idle below 1200, it's only by clamping the hose off that i can reduce the airflow enough to lower the idle below 1000, and as i mentioned i have it at 850 solid...

it's got to be related to the washer i am thinking.
 

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That new one does look like the ID is too big. Take your 'old' O-ring to the hardware store and buy a new one of approximately the same size - just eyeball it. They take a set from age & heat and become resistant to compressing/uncompressing once they've been used for a while. Once set, they shouldn't need further fiddling.

Check that the AAV closes when warmed up (I take them off the car and put them in a 150F oven for 15 minutes) and if it does close, check that it actually blocks passage of air in the closed position. (be careful not to burn your lips...) I had an AAV that looked like it was closing fine but when I blew air through it with the vane blocking the passage of light it didn't block air!

The screw on the throttle butterfly should rarely if ever need to touched. Since it is likely your's has been fiddled with, I would disconnect the throttle rod and then unscrew the stop screw (flat blade screw driver) until you are sure it is not holding the throttle open at all. Then slowly screw it in until it just touches the throttle's stop arm and turn it in 1/4 turn more. Re-attach the throttle rod making sure it is not holding the throttle open. The horizontal rod under the plenum is adjustable for length if needed. Then leave it alone.

After adjusting the throttle stop screw check the TPS (Throttle Position Switch). With the engine off, you can hear it click when you just barely open the throttle (by hand) then again when the throttle is nearing wide open. Even better is to test it with an ohm meter to make sure the internal contacts are actually doing what they're supposed to be doing. A properly adjusted TPS is important as it tells the computer the throttle is at the idle position. The computer then uses its preprogrammed idle instructions. If the TPS is misadjusted the computer doesn't use its idle instructions and instead keeps trying to adjust the running mixture.

Once everything else is adjusted (and with the right size O-ring you should easily be able to reduce the idle speed well below 850 rpm) you can consider adjusting the idle by-pass screw. It is another adjustment that shouldn't ever need fiddling but if a PO mis-adjusted it you can improve the idle character by returning it to it proper setting. There are instructions for that in the L-jet page. But everything else first.
 

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Discussion Starter · #9 ·
thanks for the tip, i will get my wife to blow through the aav when it comes out of the oven

just kidding!!!!

thanks for the patience, and yes m car has definitely been 'fiddled with', but we are getting her back to normal, the therapy is expensive but worth it!
 

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I just received a new idle adjustment washer from IAP and it seems tiny and thin compared to the old one that I removed, of course, I can tighten it as far as it will go, just like the last one and still the idle would not go below 1200-2300 and would cycle up and down 100-150 rpm.
Is the washer wrong?
That is very interesting. I was going to order some o-rings from them, but I don't think I will now. That is obviously just a plain old o-ring from a rubber store. No wonder they didn't send me a photo when requested a couple of times. The originals are a specialised thing. There must be an effective solution. Surely someone has the correct ones. They must have been used on other L-Jet engines besides Alfas. What about putting a small adjustable clamp on the hose as an alternative if the vise grip idea works?
 

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Discussion Starter · #11 · (Edited)
while the vise grip works very effectively for the moment it is almost entirely closing off the hose, you'd have a hard time getting a hose clamp tight enough.

In my case I may have some other thing to examine like the TPS but definitely this o-ring is bupkis. and i bought two of them!

I am having a look at my TPS, what are the readings I should be getting? I know it is supposed to click just above idle, i hear nothing closer to wide-open, although the VVT solenoid activates, does it takes it's cue from the throttle switch?

EDIT- Right, I remembered that all this is in the L-Jet diag. I'll be re-reading all of it today.
 

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What about putting a small adjustable clamp on the hose as an alternative if the vise grip idea works?
If one wanted to take a more tedious and time consuming route its completely possible to use a slug of plastic or aluminum that fits inside the hose tightly then get after boring it lengthwise with drills until the right size to achive the desired idle speed was obtained.
(bore it, install it, test it for speed, remove, rinse~n~repeat until its where you wanna be. All while working with a fully warmed up engine of course)

Granted it wouldn't be adjustable in the common sense, but for sure it would never get to the point where idle speed went up beyond X either.

Doing such could allow for the outright elimination of the idle air bypass valve.
 

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while the vise grip works very effectively for the moment it is almost entirely closing off the hose, you'd have a hard time getting a hose clamp tight enough.

In my case I may have some other thing to examine like the TPS but definitely this o-ring is bupkis. and i bought two of them!
I was thinking of a metal ring sort of thing with a small bolt threaded into it that you can tighten against the hose like those wire cable joiners. A fitter and turner could easily make something like that I would think.
 

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Why re-engineer it? The O-ring works fine - just get an O-ring of approximately the right size (the fatter one shown above is about right) and the adjuster will allow you to fine tune its ID to obtain the idle speed desired.

Yes, over time the O-ring will take a set and become non-adjustable. But that is not a big deal for two reasons. 1) once set, the idle adjuster should rarely need fiddling with as the idle speed should remain steady as long as the rest of the system is functioning correctly* & B) if/when you do need to re-set the idle adjuster just buy a new O-ring for $0.99 (don't bother with the expensive mail-order O-ring - buy one at your local hardware store).

* if you notice a change in idle speed then it is more likely there is a fault elsewhere in the L-jet system. Fix that and the idle speed problem is resolved. Don't 'adjust' the idle speed to compensate for a fault.
 

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Why re-engineer it? The O-ring works fine - just get an O-ring of approximately the right size (the fatter one shown above is about right) and the adjuster will allow you to fine tune its ID to obtain the idle speed desired.

Yes, over time the O-ring will take a set and become non-adjustable. But that is not a big deal for two reasons. 1) once set, the idle adjuster should rarely need fiddling with as the idle speed should remain steady as long as the rest of the system is functioning correctly* & B) if/when you do need to re-set the idle adjuster just buy a new O-ring for $0.99 (don't bother with the expensive mail-order O-ring - buy one at your local hardware store).

* if you notice a change in idle speed then it is more likely there is a fault elsewhere in the L-jet system. Fix that and the idle speed problem is resolved. Don't 'adjust' the idle speed to compensate for a fault.
All the O-rings I have seen are too thin and have too large a hole in them. I don't know where I can get thicker ones.
 

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I just went to a local hardware store and browsed the plumbing section and picked an O-ring that was about the same size as the old one.

Try browsing McMaster-Carr - they have a multitude of sizes listed. Maybe if you can find a size that matches a local hardware store or plumbing supply store can get some for you.
 

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try injector seal o-ring

copied and pasted from a year ago.....

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"I just replaced my idle control O-ring. Somewhere on this BB someone stated that the size for a new one is 3mm thick with a 8mm hole for a total of 14mm diameter. I couldn't find any at the local hardware stores. I searched a couple of domestic car dealerships and discovered that Ford sells a kit of injector seals that are very close to that size, but the price was far too high.
So I went home and rummaged through some boxes of old car parts and found some Volvo injectors with the same seal. It fits just right and it works fine."
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still working great a year later
 

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I agree with Eric in fixing the original. If a temp repair was needed an aquarium air valve would work.
 
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