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Hi all, once again -
My current jetronic investigation has me looking at my air flow meter. Since I've owned the car, I've noticed a very slight hesitation when pressing the throttle, particularly when pressing it hard. I'd always assumed it was a sticky throttle linkage, but now have other thoughts.
I had the hood open this morning and noticed that when I stepped on the accelerator, there was: a very slight and brief hissing sound (like listening to the throat of a carburetor), brief hesitation and the square-ribbed hose convulsing (actually constricting slightly I think). It feels like the flap inside isn't opening enough and the engine is strangling a little. This is kind of in sync with the previous problem of the car spontaneously dying, but restarting with full choke (AAV replacement). I took resistance measurements (from FAQ portion of site) and some seem lower than they should be, but I'm new to the multimeter, so I may be in error. It's always seemed to me that this is a fuel problem tied to an electrical problem. No simple answers with Alfa, right?
Anyway, is there any kind of serviceable stuff inside? It looks like PO removed the plastic cap at some point and resealed it with clear silicone. Just wondering.:001_huh:
The more I think about it, the more this feels like the source of a problem (maybe the source of the problem!?)
Just out of curiosity, could this be an injector issue instead

Thanks in advance, guys!

ps: will try to get a photo of the Italian mistress later today:p
 

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Discussion Starter #3
if it has been siliconed, some PO has been in there......probably to adjust the sweep arm onto a new track. Has the factory tamper proof plug been 'tampered' with also?
see Eric's post here...
http://www.alfabb.com/bb/forums/1055716-post9.html
Wow! You guys are SO awesome! I needed to buy RTV anyway, so this works out well.
Thanks to you and Eric for the great input and I will keep all posted.
 

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Usually, when someone fiddles with the Air Flow Meter (AFM) they make the spring resistance less. 'Back in the day' it was thought that making the flap open further/faster would boost performance. (it didn't & was more likely to cause driveability problems - like you are describing)

That said, when ever there are issues with an L-jet engine the first thing to make sure of is that there are no intake air or vacuum leaks. These are called 'false air' as it is air that does not get measured by the AFM. False air messes up the computer calculations for fuel to be injected. A quick-n-easy test for false air is to remove the oil fill cap while the engine is idling. If the idle does not deteriorate it is likely there is false air. (removing the oil fill cap introduces an air leak - if there is already an air/vacuum leak removing the oil fill cap will not make it worse) Another item to check is that the Oil Vapor Separator is not clogged. A clogged OVS mimics an air leak because it messes with sump scavanging.
 
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Discussion Starter #5
Hi Eric -
Thanks so much for the input. The air flow meter fiddling is actually right there on Greg Gordon's great jetronic site. Will definitely NOT follow that advice.
Tried the oil cap test and the motor definitely lost power...so at least the air tightness of the system is OK.
Am not looking forward to cleaning the oil vapor separator, but know that will need to be my next project.
Thanks for all your great input and insights and I will keep all posted on the dissection of the meter.




Usually, when someone fiddles with the Air Flow Meter (AFM) they make the spring resistance less. 'Back in the day' it was thought that making the flap open further/faster would boost performance. (it didn't & was more likely to cause driveability problems - like you are describing)

That said, when ever there are issues with an L-jet engine the first thing to make sure of is that there are no intake air or vacuum leaks. These are called 'false air' as it is air that does not get measured by the AFM. False air messes up the computer calculations for fuel to be injected. A quick-n-easy test for false air is to remove the oil fill cap while the engine is idling. If the idle does not deteriorate it is likely there is false air. (removing the oil fill cap introduces an air leak - if there is already an air/vacuum leak removing the oil fill cap will not make it worse) Another item to check is that the Oil Vapor Separator is not clogged. A clogged OVS mimics an air leak because it messes with sump scavanging.
 

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I also had a hestitation issue, around 3000 rpm.

I followed that video and didn't see any wear issues.

I also though it was the AFM. Even went so far as to buy another one from a low mileage car.

No change.

I read on other car BB's about hesitation and the O2 sensor.

I saw that mine was spliced in, so I bought a new one, $120 that didn't need any cutting and splicing of wires. It was a direct fit.

10 minute installation and no more hesitation.

My $0.02

Good luck,

Vin
 
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Discussion Starter #7
Hi Vin -
Your post has had my attention for the last 24 hours. I've heard the O2 sensors tend to fail at higher temperatures, and the Spider tends to quit when warm but restarts when allowed to cool a bit (or so it seems). I'd love to just replace all the jetronic sensors, but realistically, this might be the one I really consider.
Am going to try to cut the cap off my air flow meter tonight and see what she has in store. :hammer:

Thanks for the input!

Craig


I read on other car BB's about hesitation and the O2 sensor.

I saw that mine was spliced in, so I bought a new one, $120 that didn't need any cutting and splicing of wires. It was a direct fit.

10 minute installation and no more hesitation.

My $0.02

Good luck,

Vin
 

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Hi Craig,

Did you happen to find the issue?

Hope so.

Vin
 
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Discussion Starter #9
All ok for now

Hi Vin -
Thanks so much for asking.
I opened the air flow meter and 'adjusted' it as much as I felt comfortable with. Put everything back together and it ran much better. Was out the next day and the post that attaches the throttle plate to the throttle linkage FELL OUT! (long story...there's actually a post here about it). Took the two pieces to the local marine metal shop and the guy carefully hammered the post back into place. Put the whole thing back together and between the new relay, new filters, fiddled-with air meter and the tightened-up throttle linkage, she runs like the junior race car she is.
In the bigger picture, the transmission is grindy, the driveshaft's got a wag to it, and I burn a quart ~every 500 miles, but she's one of the best speed limit breakers I've ever owned...so...one project at a time, right?
Thanks again.
 
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