 Big backfire, Diagnosis? |
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| Trevorg7 |
 Jan 18 2006, 12:16 PM
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#1
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Senior Member  Group: Members Posts: 1,242 Joined: 7-December 04 From: Highland Village, TX Member No.: 3,241 Region Association: Southwest Region  |
72 1.7 dual Weber 34 icts
Car was warm, in stop and go traffic. 3rd gear, 2100 rpm, 25-30 mph and the car seemed to lose power (no throttle response) for about 2-3 seconds and then boom! A large backfire with billowing black smoke. Car has begun to buck a little at lower rpms and speeds in the past 1000 miles. Plugs pulled 500 mph and are fine (gap, etc), solid state ignition. Thoughts on where to start? Thanks T |
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| r_towle |
Jan 18 2006, 12:42 PM
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#2
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Custom Member Group: Members Posts: 24,574 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States 
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take out the jets and clean them.
Sounds like some crap in the jets... Lets say your idle jet is plugged, you would get no fuel at idle, and none till you transition to the main jet,,,which would shoot alot of fuel in based on the position of the throttle... so then pow, you get a backfire... you need to clean your jets, then changed your fuel filter. Rich |
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| JWest |
Jan 18 2006, 01:04 PM
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#3
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Senior Member Group: Members Posts: 1,662 Joined: 6-January 03 From: Fort Worth, TX Member No.: 97 Region Association: None
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The problem is that 914s are limited to about 0.6 Mach at sea level. You were going about 0.66 Mach (assuming it was a near standard day), and created a local shock at the back of the targa bar which disrupted the airflow into the carbs. This is yet another reason you should have fuel injection, as it is typically good to 0.89 Mach (678 mph). (IMG:http://www.914world.com/bbs2/html/emoticons/happy11.gif) Actually, it sounds to me like you have an ignition issue, as you were still dumping in fuel but not firing it, then lit it all off at once (lots of black smoke) when the ignition came back. Throw some points back in for a test. |
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| joea9146 |
Jan 18 2006, 03:06 PM
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#4
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Senior Member Group: Members Posts: 663 Joined: 10-February 03 From: Denver, NC Member No.: 283 Region Association: None |
I Agree I Think u have some type of Ignition problem. |
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| 914Jr. |
 Jan 21 2006, 06:47 AM
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#5
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Newbie Group: Members Posts: 32 Joined: 15-January 06 From: Atlanta Member No.: 5,422 |
Check timing.
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| DNHunt |
Jan 21 2006, 09:18 AM
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#6
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914 Wizard? No way. I got too much to learn. Group: Members Posts: 4,099 Joined: 21-April 03 From: Gig Harbor, WA Member No.: 598 |
Bet the ricers would approve, nice long flame out the exhaust.
(IMG:http://www.914world.com/bbs2/html/emoticons/blowup.gif) Dave |
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| lotus_65 |
Jan 21 2006, 10:01 AM
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#7
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Senior Member Group: Members Posts: 1,608 Joined: 21-March 05 From: minneapolis, mn Member No.: 3,795 Region Association: Northstar Region |
that happened to me once, what kind of damage does that cause?
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