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Re: 97 9000 Aero backfire & check engine light Posted by Ari [Email] (#2847) [Profile/Gallery] (more from Ari) on Sun, 12 Jul 2009 06:41:16 In Reply to: 97 9000 Aero backfire & check engine light, repoSAAB, Sat, 11 Jul 2009 07:36:30 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Backfire occurs when unburned fuel finds air in the exhaust system. Did the backfire occur when you backed off the gas, or were just cruising along?
First, pull the spark plugs. Of course, check the gap. Do the plugs look black, like the engine is running rich? Any one plug look different than the rest? Crawl under the car and inspect the exhaust. The middle resonator is famous for developing holes, especially where the front pipe enters the box. Check for holes anywhere (that can let in air).
I'd ignore the fuel issue. Good fuel is good fuel. The only way to get unburned fuel into the exhaust is to have a misfire, so either the plug doesn't fire, or you've got so much fuel that only part of it burns (running very rich, stuck injector, etc.) So that can be ignition or it can be a fuel issue. Once the raw fuel gets to the exhaust, it is bound to find something hot and some oxygen. That raw fuel will quickly destroy the catalytic converter.
So start at the engine, and look at the plugs. Running rich?
posted by 75.11.4...
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