Bought a carbureted '79 124 (my 3rd spider) last year and after a few months one day it just started missing horribly, catch a downshift and it ran strong for 30-60 seconds before missing again, let it idol as I coast for 500 yds and it woul;d usually work well long enough to get my speed back up. Managed to limp it most of the way to a mechanic shop (about 8 miles). It was never going to make it to my place. Please realize this isn't the best mechanic but I know him and made it to his shop. He replaced fuel pump, filter, cleaned out the carb bowls and jets (but not a complete carburetor cleaning).
F.Y.I Former owner had swapped the intake and carb to a 1800 setup with the Weber carb and the car runs strong. Electronic ignition.
Car ran good for several months before it all started again. I managed to limp it home where I proceeded to check every wire connection and ground. The distributor was showing uneven rubbing inside the cap. I suspected worn distributor bushings so I replaced the distributor with one from Vicks. Suddenly the car is running good again. A month later it started missing again.
Up until today (my latest attempt at repairs) it had to run at least 20 miles before it started missing.
Since the problem seemed to develop after the car had been running a while I began to suspect the coil (heat and older weak coils don't mix well) so today I installed a coil (Vicks part # 21-2321) and control module (Vicks part # 21-3601). Car starts well but test drive shows a bad backfire under moderate load (I traveled less than a mile).
Any ideas?
missing, now backfiring
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JohnGalt
- Posts: 15
- Joined: Sat Nov 26, 2016 7:06 pm
- Your car is a: 1979 Spider 124
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JohnGalt
- Posts: 15
- Joined: Sat Nov 26, 2016 7:06 pm
- Your car is a: 1979 Spider 124
Re: missing, now backfiring
Update.
First I pulled the new coil and control module and checked for loose wires before trying another test ride. Car was still running poorly and a bit of a backfire through the carburetor. Sounded like the timing was off. The engine was built 10,000 miles back with a new timing belt so I checked the distributor timing.
It seems that the new control module changed the spark timing by about 5 degrees. Not sure how that works but the timing was off. Since the timing marks are messed up on this car I set the timing with a vacuum gauge. It had a rough idol and vacuum was sitting around 17. A bit of a twist on the distributor and the idol smoothed up and vacuum rose to the 20 psi I'm accustomed to seeing on this car.
As I've mentioned before the original engine miss problem usually doesn't occur until the car has run at least 15-20 miles. Car ran great for a 5 mile test ride but I won't take the lady out in it until I've given it a good long run.
First I pulled the new coil and control module and checked for loose wires before trying another test ride. Car was still running poorly and a bit of a backfire through the carburetor. Sounded like the timing was off. The engine was built 10,000 miles back with a new timing belt so I checked the distributor timing.
It seems that the new control module changed the spark timing by about 5 degrees. Not sure how that works but the timing was off. Since the timing marks are messed up on this car I set the timing with a vacuum gauge. It had a rough idol and vacuum was sitting around 17. A bit of a twist on the distributor and the idol smoothed up and vacuum rose to the 20 psi I'm accustomed to seeing on this car.
As I've mentioned before the original engine miss problem usually doesn't occur until the car has run at least 15-20 miles. Car ran great for a 5 mile test ride but I won't take the lady out in it until I've given it a good long run.
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mamsterla
- Posts: 69
- Joined: Sun Nov 26, 2017 10:10 pm
- Your car is a: 1969 Fiat 124 Spider AS
Re: missing, now backfiring
Did you mess with the points and regap them? The fact that changing your timing seemed to even things out makes me think your distributor may not be tight or the advance mechanism might be off. Does it idle well at 10 deg BTC?
Backfiring through the carb can happen with bad timing or with lean conditions. Did you recheck your fuel filter to make sure it was not clogged or see if you can have your carb thoroughly cleaned - perhaps you have a bit of dirt in one of the smaller passages.
Backfiring through the carb can happen with bad timing or with lean conditions. Did you recheck your fuel filter to make sure it was not clogged or see if you can have your carb thoroughly cleaned - perhaps you have a bit of dirt in one of the smaller passages.
1969 Fiat 124 Spider AS0012768
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JohnGalt
- Posts: 15
- Joined: Sat Nov 26, 2016 7:06 pm
- Your car is a: 1979 Spider 124
Re: missing, now backfiring
No points but I didn't mess with the timing.