SPICA Flat Spot Just Off Idle - Page 2 - Alfa Romeo Bulletin Board & Forums
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post #16 of 23 (permalink) Old 01-19-2017, 08:42 PM
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The odd part is that it doesn't happen as the car is warming up, only once it has reached operating temp...
That would seem to suggest that at temperature you are running lean at tip in. If the bell crank stops are set properly I would be looking for vacuum leaks. Check that the butterflies are completely closed at idle.
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post #17 of 23 (permalink) Old 01-19-2017, 09:44 PM
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My Berlina has a similar pause on tip in, and also it isn't as noticeable on warmup. I have a wideband so I can see it go a bit leaner then come back. Which makes sense to me, as you're opening the throttle I assumed you're getting more air faster than the fuel can catch up.

Other than that mine runs great, starts in cold weather, runs pretty close to 14:1 on the freeway, gets good mileage. One of these days I'll get the factory bellcrank tool and go back through and double check everything again.

I'm happy to post a video of the wideband if I get a chance.

Ian

Ian Lomax - Current: 1973 Berlina, 1987 Milano Platinum "racecar"
Past: 71, 74 Spiders, 2x 74 Berlina, 74 GTV, 76 Alfetta GT, 88 Milano 3.0, 164LS
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post #18 of 23 (permalink) Old 01-22-2017, 07:35 PM Thread Starter
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Success!

Roadtrip was kind enough to send the factory bellcrank tool to me and I was not surprised to find that the stops were quite a ways off. Adjusted everything using the tool, took the car for a short drive today and am happy to report all appears to be well. Time and weather didn't permit a long test drive but I did get it up to operating temp and went through several stop/start cycles and it pulled cleanly each time.

Many thanks to all, I still want to set the mixture using the wideband (and I'd love to see your video archeologist) but I am a quite happy with where it's at as is.

Cheers
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Greg East
Loveland, CO USA
'74 Alfa Romeo Spider
'87 Porsche 944 turbo
'93 BMW 740i
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post #19 of 23 (permalink) Old 01-22-2017, 07:57 PM
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Glad to hear of the success.

To reinterate again, the throttle stop screws (idle and wide-open screws) are set in a particular place according to the factory tool. The idle stop screw DOES NOT control the idle speed like it's nomenclature might suggest. Idle speed technically is controlled by the amount of air admitted through the idle air system (which is notoriously poorly adjustable). If you're getting a 600-900 rpm idle, that's within spec. These stop screws are set with the factory jig and then NOT TOUCHED AGAIN.

John Stewart
74 Spider
91 164S

Last edited by Roadtrip; 01-23-2017 at 06:43 AM.
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post #20 of 23 (permalink) Old 01-22-2017, 09:13 PM Thread Starter
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When I got my Spider the TA was dead. I suspect most, if not all, of the adjustments I've had to make, from pump gap, to mixture to CSS and now bellcrank stops, were the result of someone trying to compensate (badly) for an inoperable TA.

Greg East
Loveland, CO USA
'74 Alfa Romeo Spider
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post #21 of 23 (permalink) Old 01-23-2017, 06:44 AM
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It is amazing how pathetically out of adjustment the Spica system can be and still actually run.

John Stewart
74 Spider
91 164S
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post #22 of 23 (permalink) Old 01-23-2017, 10:43 AM
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Quote:
Originally Posted by gregeast View Post
When I got my Spider the TA was dead. I suspect most, if not all, of the adjustments I've had to make, from pump gap, to mixture to CSS and now bellcrank stops, were the result of someone trying to compensate (badly) for an inoperable TA.
This was very common in the past. Interestingly since SPICA was so critical to US emissions regulations the factory's policy was to try keep all of the technical information on it out of the hands of the end user hoping it would deter them from messing with any of the settings. It didn't. Nowadays all of that information is available so slowly but surely the out of whack ones are getting set right and that now includes yours.

Good job.

Paul - 1972 Spider - (2)1991 164S's - 1983 308 - 2001 Discovery - 1997 F350
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post #23 of 23 (permalink) Old 01-30-2017, 02:25 PM Thread Starter
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Just wanted to close out on this and to thank everyone again for all the input.

The weather in Colorado cooperated this weekend so I got to take the Spider (top down!) for an extended drive and am thrilled to report that it has never run better. No flat spot, much more eager to rev, smoother throughout the rev range.

If you haven't borrowed the magic tool to properly set your bellcrank relay I highly recommend it!

Greg East
Loveland, CO USA
'74 Alfa Romeo Spider
'87 Porsche 944 turbo
'93 BMW 740i
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