924Board.org

[Boogieman28]

So a couple days ago i noticed my car have a hesitation when revving it up. It also has loud backfires out the exhaust randomly when idling but constant when rev down. So i took a spark tester and they all worked the coil seemed to cut out or dim with it revving up.

So i started the car one morning let it warm up still backfiring it sound like a spark problem backfire it a loud bang. All the timing marks are lined up and its running. So i cut the car off and went to school came home with a new rotary button and i was gonna start the car before i change anything and it doesn't fire which is weird since its been starting every time so i checked spark leaving the coil and nothing i have power on the positive side of the coil but no spark leaving.
i went and bought a new coil and its still doing the same thing. My next step is replace the ignition box on the fender and see if it does anything different. i was posting here to see if anyone has any ideas on sudden lack of spark leaving the coil.

[Paul]

Possible causes:

Wiring/connection to coil

Wiring/connection to distributor

Wiring/connection to ignition module

Ignition switch

Distributor

Ignition module
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White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

[Boogieman28]

Got a little update i went out there the next day and tried it and i have spark and it cranked up and ran. I still think the spark is breaking up when revving up the backfires are happening the same it doesn't backfire when the engine is cool which makes me think it might be a carb issues it has regular gas in it i was thinking that might be an issue but the car has been running of it its whole life which i plan to swap to premium when i drive it. Im running out of ideas ive synced the carbs the whole ignition system is new from the coil to the sparkplugs it gets good power o the coil and its a new coil. it just seems like the spark from the coil breaks up sometimes when revving and on deceleration

[Ozzie]

similar issue- rotor button was wrong resistance
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Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

[Boogieman28]

Well I got home yesterday and decided to swap distributors since I had one laying around and it gave me spark. So I cranked it up and it ran it still backfired a lot under deceleration I’m thinking it’s more of a carb issue of a ground issue but the spark is nice and strong. Got an extra fuel pump I’m gonna try and see if it changes anything. It runs great when you start it up and take the choke up but when it warms up it backfires out the exhaust a good bit.