# Back fire problem **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [July 8, 2008, 5:02pm UTC](https://community.cartalk.com/t/back-fire-problem/16411 "2008-07-08T17:02:58Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![hcolonna](https://avatars.discourse-cdn.com/v4/letter/h/b3f665/32.png) [@hcolonna](https://community.cartalk.com/u/hcolonna)\ **Post date:** [July 8, 2008, 5:02pm UTC](https://community.cartalk.com/t/back-fire-problem/16411/1 "2008-07-08T17:02:58Z")
I have a 97 Jeep wrangler with a 4.0 engine, I had a new stainless exhaust system, stainless manifold, stainless steel cat and an AEM brute force air intake with the fuel injector spacer installed. The gas mileage and performance improved a whole lot. It feels like a race car. The problem I have if I drive the car, and then park it in the sun the car back fires before I take it off. Then the car is ok. Would you know what the problem may be ? ---
**Author:** ![GreasyJack](https://avatars.discourse-cdn.com/v4/letter/g/df705f/32.png) [@GreasyJack](https://community.cartalk.com/u/GreasyJack)\ **Post date:** [July 8, 2008, 5:07pm UTC](https://community.cartalk.com/t/back-fire-problem/16411/2 "2008-07-08T17:07:09Z")
Your problem is that you have no back pressure. You may be able to fiddle with the timing to get it to a point in which it doesn’t backfire and still runs okay. Otherwise, you’ll probably need a different air intake. ---
**Author:** ![hellokit](https://avatars.discourse-cdn.com/v4/letter/h/6a8cbe/32.png) [@hellokit](https://community.cartalk.com/u/hellokit)\ **Post date:** [July 8, 2008, 5:41pm UTC](https://community.cartalk.com/t/back-fire-problem/16411/3 "2008-07-08T17:41:41Z")
The “car backfires before you” WHAT! Before you take what off? Your vest? Your hat? What? ---
**Author:** ![hcolonna](https://avatars.discourse-cdn.com/v4/letter/h/b3f665/32.png) [@hcolonna](https://community.cartalk.com/u/hcolonna)\ **Post date:** [July 9, 2008, 12:24am UTC](https://community.cartalk.com/t/back-fire-problem/16411/4 "2008-07-09T00:24:17Z")
To answer your question, it backfires only once, after it sits in the sun and I restart it and take off. After it back fires once it is ok. ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [July 9, 2008, 12:59am UTC](https://community.cartalk.com/t/back-fire-problem/16411/5 "2008-07-09T00:59:24Z")
You might want to check to see if there’s a leaky fuel injector. As the vehicle sits in the sun, the pressure in the gas tank increases. If there’s an injector that’s stuck slightly open, it will drip more gas into a cylinder under hot conditions rather than cold conditons. If there’s excess fuel in any of the cylinders when the engine is started, not only does the fuel that’s being injected into that cylinder ignite, but also the excess fuel sitting on top of the piston. This then causes a backfire once, and afterwhich the engine operates normally. Tester ---
**Author:** ![newpony](https://avatars.discourse-cdn.com/v4/letter/n/41988e/32.png) [@newpony](https://community.cartalk.com/u/newpony)\ **Post date:** [July 9, 2008, 5:14am UTC](https://community.cartalk.com/t/back-fire-problem/16411/6 "2008-07-09T05:14:13Z")
Sounds like you nailed it, Tester. ---
**Author:** ![hcolonna](https://avatars.discourse-cdn.com/v4/letter/h/b3f665/32.png) [@hcolonna](https://community.cartalk.com/u/hcolonna)\ **Post date:** [July 9, 2008, 2:16pm UTC](https://community.cartalk.com/t/back-fire-problem/16411/7 "2008-07-09T14:16:22Z")
I agree, sounds like you got it, this never happens to me in the colder weather. My question, would this cause any engine damage. My mechanic said no, since it happens only once. I do get around it by revving up the engine before I put it in gear… Thanks HenryC ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [July 9, 2008, 2:42pm UTC](https://community.cartalk.com/t/back-fire-problem/16411/8 "2008-07-09T14:42:15Z")
Probably won’t cause engine damage, but with repeated backfires damage to the catalytic converter might occur. Better to fix it than replace a cat. Tester ---
**Author:** ![hcolonna](https://avatars.discourse-cdn.com/v4/letter/h/b3f665/32.png) [@hcolonna](https://community.cartalk.com/u/hcolonna)\ **Post date:** [July 10, 2008, 1:36pm UTC](https://community.cartalk.com/t/back-fire-problem/16411/9 "2008-07-10T13:36:54Z")
TESTER, thanks for your help it is appreciated !! … HenryC ---
**Author:** ![hellokit](https://avatars.discourse-cdn.com/v4/letter/h/6a8cbe/32.png) [@hellokit](https://community.cartalk.com/u/hellokit)\ **Post date:** [July 10, 2008, 2:00pm UTC](https://community.cartalk.com/t/back-fire-problem/16411/10 "2008-07-10T14:00:45Z")
An indication, not proof, that the fuel injector(is) is leaking, could be done with a fuel pressure gauge installed, the fuel return-to-tank line plugged. With the engine OFF, and the fuel gauge showing pressure, wait 15 to 30 minuets to see if the fuel pressure drops. If it does, it may be from a leaking injector(s). A more direct way, without a special tool, is to remove all the fuel injectors still attached to the fuel rail. Tie plastic bags around the injectors, Turn the ignition key ON to pressurize the fuel injectors, wait a few minuets to see if any fuel leak from the spray nozzle of the fuel injectors. A pressure cleaning of the fuel injectors may help ones which leak.