Variable idle and occasional jolting miss

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Nikkum
Posts: 25
Joined: Sat Jun 13, 2015 4:33 am
Your car is a: 1985 pininfarina

Variable idle and occasional jolting miss

Postby Nikkum » Mon Jan 08, 2018 3:59 pm

1985 FI. I thought my lovelly car was now perfect. Set timing at 10. Valve gaps perfect. Plug gaps spot on. Drives fantastic . Good power .best car I've ever driven.
Problem is occasional backfire on starting and fluctuant but smooth idle at around 7 to 800 when cold and really annoying jolting misses . Rare and random.
Where should I start? Is this likely to be timing and should I vacuum gauge it? Could it be air leak in fuel supply? Vacuum leak?
I'm checking everything but does anyone recognise this as a particular problem?
V grateful for pointers!
Nick

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RRoller123
Patron 2020
Patron 2020
Posts: 8179
Joined: Sun Nov 13, 2011 2:04 pm
Your car is a: 1980 FI SPIDER 2000
Location: SAGAMORE BEACH, MA USA

Re: Variable idle and occasional jolting miss

Postby RRoller123 » Mon Jan 08, 2018 5:52 pm

Check connections at the injectors. Have they ever been sent out for cleaning and service? Check the connection at the AFM, and make sure the door swings smoothly without binding. I had the same thing happen last year and it turned out to be a loose spark plug wire. They are easy to check too.
'80 FI Spider 2000
'74 and '79 X1/9 (past)
'75 BMW R75/6
2011 Chevy Malibu (daily driver)
2010 Chevy Silverado 2500HD Ext Cab 4WD/STD BED
2002 Edgewater 175CC 80HP 4-Stroke Yamaha
2003 Jaguar XK8
2003 Jaguar XKR
2021 Jayco 22RB
2019 Bianchi Torino Bicycle


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