Why does my Chrysler 5th Avenue Backfire out of the carb, timing is set dead on?


Asked by Oct 18, 2007 at 05:42 PM about the 1985 Chrysler Fifth Avenue

Question type: Maintenance & Repair

I am thinking it may be a valve sticking, but how can I tell when it doesn't always happen?  It happens mostly when I step on the accelerator, but does occur, sometimes, when stopped and in Drive.  It's a1985 Chrysler 5th Ave, 318 motor.  As far as the sticky valve goes, I have heard of this stuff that GM sells called "Top Engine Cleaner", but wanted more to see if someone has any other ideas before I go sticking stuff in my engine.

5 Answers


Sounds like a carb flooding. If the float bowl is leaking or the carb itself is feeding too much fuel into the system, this can happen. The GM Top Engine Cleaner is excellent. I used some on my 1984 Lincoln Town Car in college with no ill effects, and an instant improvement in throttle response and fuel mileage. It is important to keep it in the engine NO LONGER than 2 hours, don't do it overnight or anything. Follow the directions and you will have no problem.

1 people found this helpful.

it could also be the accelerator pump sticking i would try a carb cleaner that might clear it it helped on mine i had the holley 2 bbl on mine but eliminated that and got a 600 cfm edelbrock carb now i have no problems i changed the 2 bbl carter to a holley then to a rebuilt carter but none worked that great i then eliminated the lean burn that helped a bit but the 4 bbl is great and improved fuel mileage with 4 bbl and a true dual system plus lean burn conversion


carb cleaner!!! probably got some build-up in there. my dads fairlane was doing the same and we cleaned the ever lovin "crud" out of it and it never happened again till some years later


Lose the Lean burn, you can get kits to do this.

4 people found this helpful.

I am not going for the sticky valve . If it idles SMOOTH most of the time, then I am inclined to believe it is electrical, as in fire jumping in the distributor cap/rotor. Old chrysler v-8 engines have lifter issues, but those issues produce a loud tapping noise upon start up and generally quiet down within seconds. A stuck valve will also produce a loud tapping noise, but I have never seen that in a chrysler V-8.

2 people found this helpful.

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