UPDATE: Rough Running, Then Fine

Maintenance advice to keep your Spider in shape.
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wubie317
Posts: 81
Joined: Mon Mar 03, 2014 3:54 pm
Your car is a: 1977 Fiat Spider
Location: Sonoma, CA

UPDATE: Rough Running, Then Fine

Post by wubie317 »

I think this is quite strange.

The car has been doing the rough-smooth-rough-rough-smooth thing on and off for a while now. On Saturday, I went to the local O'Reilly's for some new wipers. I sometimes buy a bottle of SeaFoam for the placebo pleasure of it, but I noticed that the Ace Hardware down the street had it for $2 less a bottle. $14 a bottle?!?!? Incensed, I was! Near the register, was the Berryman B-12 for only $4..."What the hell," I thought and bought it.

When I got home, I poured it into the tank (didn't start the car or anything) and sat down to work on the old carburetor that had been sitting on my bench. I want to do a thorough rebuild on it (thinking that may be an issue with the rough running), so I ordered all the parts on piercemanifolds.com. Hope to have all the stuff by mid-week, maybe.

Come Monday morning, I started the car and immediately thought, "Golly...that was a quick start, and really smooth." Sure enough, the engine was butter-smooth the whole trip...I mean REALLY smooth, better than it has ever run in the 2 years I've owned her. All week, it has been like a dream and the mileage has gone up to boot.

It's hard to imagine that B-12 just sitting in the tank could have done anything. And I didn't actually touch the Fiat, the carb or anything...opened the hood to look at the throttle assembly, but did nothing. Clearly SOMETHING happened before I started the car 48 hours later. So here's my theory:

St. Lampredi (patron saint of the 1800 DOHC) heard my prayers at the Church of Weber Carbs and worked a miracle. I think we should all dab a bit of 15/40 over our hearts and sip from a cup of espresso in thanks.

Amen.

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Hoping someone has a theory or expert knowledge to help with an intermittent problem.

For the most part, my '77 is a trooper. It's my daily driver and I commute about 200 miles a week. Freeway speeds, stop and go, city driving, you name it, she has to do it.

Yesterday, though, I fired it up after work and she sounded...how to say it...louder than usual. More rumbly than usual. More raspy and buzzy...so much so that the rearview mirror was vibrating. The rev was fine, no missing cylinders that I could tell, no noticeable loss of power or acceleration. It was loud all the way home, and even after stopping for 30min at the grocery store.

This morning, however, she was back to happy. Still throaty and fairly loud, but somehow smoother and less loud in the cockpit. This has happened many times before...I'm quite intimate with my Italian girlfriend, so I know when she's acting strangely. :wink:

One thing I do know is that I have a weak cold choke...so it always has a few stumbles until it warms up. But the weather yesterday was in the 60s and this morning the low 50s, so I don't think the outside temp is the variable. I checked all the plugs the other day, tannish gray, but they only have 1500 miles on them at most. Timing was fine, distributor visually fine (didn't see any cracks in the arms, as has happened before) and points looked ok (single point mod), oil level is fine. Valves were adjusted about 5000 ago.

So what could it be? Is there some part of the tuneup process that I've been missing? Am I just not dialing it in carefully enough? I imagine it could be the carb, but how exactly would that make the detonations seem louder?

Any thoughts?
Last edited by wubie317 on Thu Nov 03, 2016 2:30 pm, edited 2 times in total.
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MikeHynes
Posts: 51
Joined: Fri Sep 17, 2010 5:55 am
Your car is a: 1980 Spider 2000
Location: Central Il.

Re: Rough Running, Then Fine

Post by MikeHynes »

Could be your muffler or resonator giving up the ghost?
PhillySpider
Posts: 325
Joined: Tue Apr 26, 2016 6:51 pm
Your car is a: 1980 Spider 2000
Location: New Hope, PA

Re: UPDATE: Rough Running, Then Fine

Post by PhillySpider »

my 1980 was smooth, then rough, then really rough, then occasionally stalling. I couldn't get her started and popped the hood. Trying to start her I noticed how much vibration the motor has while cranking. Cranking and cranking it finally turned over and was really rough. I kept tapping the throttle and got her to where she'd continue to run and then got out to inspect the engine bay. I wiggled and checked plug wires, cables, etc. When I wiggled the cable at the connector on the air flow sensor on the air box she purred like a kitten! I let go and she was rough. I lifted up a bit and she purred at me again. Hmmm. Now I put some significant pressure and pushed the connector into the housing firmly thinking I might "snap it in" better and she died! I gave it a wiggle and re-started her and again played the wiggle factor for a few minutes going from rough to purring over and over until this dope was satisfied it was definitely the problem.

Solution: I cut the rubber boot around the connector on the cable side and gave each terminal a thorough soaking with contact cleaner. I then used a fine needle nose to push in and "crimp" each terminal and followed with another soaking of the connector on the cable AND the receptacle on the airbox with the contact cleaner. She's been purring at me since, apx 1K miles...YMMV, but i'd give this a try if I were you...
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