1971 1750 Spider “hunting” at idle - Alfa Romeo Bulletin Board & Forums
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post #1 of 8 (permalink) Old 08-12-2018, 06:50 PM Thread Starter
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1971 1750 Spider “hunting” at idle

Hello All,

Been away for some time, but now back into the thick of it. A few months back my Mom passed away and she left to me her 1971 1750 Spider. I am not unfamiliar with this vehicle hence my sign on name... she had this car since new and Ive known it my whole life. It was also the first Alfa I ever drove or worked on when I was a teenager; it also started me with the sickness which ultimately led to my Quadrifoglio, GTV6 (long ago sold) and 164S (which just went to Alfa heaven).

In any case, I moved away from my home state of PA, and when I did, the car sat for some 11 years in a dry garage... but wasnt touched.

After receiving ownership of the car, I drained the fuel tank, replaced the rubber fuel lines, had a mechanic service the SPICA pump (de-gunk it and change out the oil filter), changed air filters, new brake master, new clutch master/slave, new rubber on all four corners, oil change and lube, new fuel filters and rear section fuel pump, rebuilt starter etc....

Car starts and “runs”. Can drive the stink out of it.... but at idle it comes close to stalling with every full cycle of revolution. Its not misfiring, its not blowing smoke, it accelerates just fine.... but at a stop, it surges from 200 rpm -800 rpm and running cold or hot doesnt seem to matter.

Fuel pressure seems good, adjusting the idle air screw doesnt seem to help. Thermo switch on pump is set for normal weather...Not sure what else to try

Any suggestions are welcome.

Best Wishes
ML.
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post #2 of 8 (permalink) Old 08-12-2018, 07:24 PM
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Quote:
Originally Posted by AlfaRomeo1750 View Post
Hello All,

Been away for some time, but now back into the thick of it. A few months back my Mom passed away and she left to me her 1971 1750 Spider. I am not unfamiliar with this vehicle hence my sign on name... she had this car since new and Ive known it my whole life. It was also the first Alfa I ever drove or worked on when I was a teenager; it also started me with the sickness which ultimately led to my Quadrifoglio, GTV6 (long ago sold) and 164S (which just went to Alfa heaven).

In any case, I moved away from my home state of PA, and when I did, the car sat for some 11 years in a dry garage... but wasnt touched.

After receiving ownership of the car, I drained the fuel tank, replaced the rubber fuel lines, had a mechanic service the SPICA pump (de-gunk it and change out the oil filter), changed air filters, new brake master, new clutch master/slave, new rubber on all four corners, oil change and lube, new fuel filters and rear section fuel pump, rebuilt starter etc....

Car starts and “runs”. Can drive the stink out of it.... but at idle it comes close to stalling with every full cycle of revolution. Its not misfiring, its not blowing smoke, it accelerates just fine.... but at a stop, it surges from 200 rpm -800 rpm and running cold or hot doesnt seem to matter.

Fuel pressure seems good, adjusting the idle air screw doesnt seem to help. Thermo switch on pump is set for normal weather...Not sure what else to try

Any suggestions are welcome.

Best Wishes
ML.
Check the Spica timing to make sure it is aligned properly. Had a belt that stretched, jump around on the pulley, and although the car would start it would run poorly until up to speed.

Last edited by 6alfas; 08-13-2018 at 12:56 PM.
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post #3 of 8 (permalink) Old 08-12-2018, 07:25 PM
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given the age of your car and the fact that it sat, I'd be looking for a vacuum leak first. As your car accelerates, it build vacuum so you don't experience drivability issues.

I can't speak to SPiCA and idle as I'm not familiar with the system or its components.
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[FONT="Microsoft Sans Serif"]Don - 1984 Spider Veloce[/FONT]
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post #4 of 8 (permalink) Old 08-13-2018, 12:53 PM
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Sounds like a problem with a lean fuel-air ratio.


I would try and do the basic Spica setup also, there's a pdf on the site somewhere. A vacuum leak could be the culprit, agreed.

Tad
Alabama

'59 Sprint
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post #5 of 8 (permalink) Old 08-13-2018, 03:29 PM
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Pull the idle air adjuster nipple all the way out and make sure the manifold passage is clear and that th old o-ring isn’t blocking it. Sounds like your idle air is choked off. I assume if you crack the throttles it smooths out?

Paul - 1972 Spider - (2)1991 164S's - 1983 308 - 2001 Discovery - 1997 F350
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post #6 of 8 (permalink) Old 09-21-2018, 03:42 PM Thread Starter
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Good afternoon All,

Im sorry its been a month since I wrote this post... unfortunately this afternoon was the first opportunity Ive had since then to mess with the car...

In any case, Ive got the idle smoothed out, the issue was multifactorial.

When the car was first revived from storage, My Dad had it sent to his local “ford” mechanic down the road from his house with whom he was friends (despite my suggestion of an Alfa shop in Philadelphia Id dealt with in the past). This mechanic flushed the fuel system and cleaned the old gas from the SPICA...but he disturbed a few other things along the way I was not aware of.....

Intake air hoses to the idle air manifold were dry rotted and had holes in them on the back side closest to the cylinder head, Someone had messed with the throttle linkage control rod... was way out of spec. Spark plugs were all out of gap and fouled... plus they were cheap.... so .... who knows why they pulled the bosch platinums off there I had on the car when it rolled into storage... oh... and the distributor cap was not on snugly... nor were the wires on in the correct firing order.

All those small issues addressed.... car is purring like a big jungle cat. I am very pleased.... now to address some of the other issues.... but... at least its running smoothly (for the moment).

Thanks again for the suggestions!!

M.L.

Last edited by AlfaRomeo1750; 09-22-2018 at 06:43 AM.
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post #7 of 8 (permalink) Old 09-21-2018, 09:20 PM
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You've got to be impressed that it ran at all...
Alfas unreliable? Bah humbug!
The car obviously wants to live. It's a keeper.
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post #8 of 8 (permalink) Old 09-22-2018, 06:23 AM Thread Starter
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Yes a keeper for sure... and yes... Im quite impressed it ran at all... although im baffled HOW the mechanic thought it was running right when he called my Dad to come get it... or that my Dad (knowing what it was supposed to run like) drove it a few times before loading it on the car carrier.... I can only guess he was just elated it was running.... and figured id sort out the rest...

I feel like a bit of a dope though for not double checking the simple stuff first before posting... you know... make sure the spark plug wires were on in the correct order... etc.... I did all these other big things that i knew would have to be done after the car sat for 11 years.... but ... duh.... fuel/air/spark hadnt initially crossed my mind because never in a million years would I have thought someone would start pulling wires off.... but I guess the mechanic did when he de-gunked the SPICA....

This car has been in my family since new, It was my Mom’s before my folks were married... There are photos of me in it as a little kid, photos of me rebuilding it when I was 17- 22 years old and photos still of me and the family driving it until I was in my late 20’s....So now that my Mom has passed away.... its even more important to me that “her Alfa” stay in tip top shape.... as I want to make new memories with that car.... not only for me.... but with my Wife and Son so that when he grows up.... he can know a little bit about his grandmother and hopefully have the same affection for the car remembering the two of us working on it together as I have thinking of my Mom.

So .... this car is not and never will be for sale lol.
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Last edited by AlfaRomeo1750; 09-22-2018 at 07:01 AM.
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