Broke down at rest area

[MandyRH]

I have a 1985 fleetwood pace arrow. When I first got it. It backfired so badly it blew out the muffler. Replaced it and for a couple months. There were no backfiring issues. But nearly 2 weeks ago we took it on its first trip. Only 2.5hrs one way. A few days later when we got ready to go home it happened again. So we replaced it and got on the road. About an hour into the drive it started backfiring while going down the highway. Then, you guessed it, a big boom. We got to a rest area and parked for the night. Replaced it again the next day. And the muffler blew again. We've been here since. Boyfriend thinks it could be something in the manifold. But says replacing it is his last resort. Anyone have any ideas?

[Bigd9]

Originally Posted by MandyRH

I have a 1985 fleetwood pace arrow. When I first got it. It backfired so badly it blew out the muffler. Replaced it and for a couple months. There were no backfiring issues. But nearly 2 weeks ago we took it on its first trip. Only 2.5hrs one way. A few days later when we got ready to go home it happened again. So we replaced it and got on the road. About an hour into the drive it started backfiring while going down the highway. Then, you guessed it, a big boom. We got to a rest area and parked for the night. Replaced it again the next day. And the muffler blew again. We've been here since. Boyfriend thinks it could be something in the manifold. But says replacing it is his last resort. Anyone have any ideas?

I don't see where the muffler has anything do do with it. Backfire like you describe tells me the carburetor needs work. It sounds like the engine is running rich (too much fuel) and when the unburnt fuel collects in the muffler it ignites with a exploding sound.

[Rkesselus]

Backfire like you describe can be caused by faulty Fuel Pump or a stopped up fuel filter. I would start with changing the fuel filter and then the fuel pump.

[Ndrorder]

If the backfire is on deceleration, that is an indicator of an air leak in the system. That leak could come anywhere from the manifold to head seal, cracked manifold, manifold to pipe seal, or a hole in the pipe. The fuel for the backfire is either an overly rich carburetor or a dead cylinder pushing raw fuel to the exhaust.


If the backfire is on acceleration, that is a timing issue. Plugs fire too close to the exhaust valve opening which pushes active flame down the pipe. Could be caused by bad plugwires, plugs, distributor, or ignition timing.

[GypsyR]

You don't have to have a muffler to drive. It will be very loud and get you some dirty looks and possibly some unwanted attention from cops but whether or not you have a muffler doesn't stop you from being able to drive.

Mild backfiring is usually an ignition timing problem. Backfires big enough to blow mufflers apart means there is an excess amount of fuel (too).

So it runs fine and smooth until it takes a backfiring fit?

[Bill Gail]

First thing , stop buying mufflers until you have found the problem.

It would help to know the engine size , probably a 454ci GM and what is the milage ?

Start with the easy checks . Check the engine timing . If timing is correct and steady do the following.

My experience with 454 engines with high milage are worn valve issues.

I suggest doing a compression test and leak down test. This will tell you if it's a valve problem.

I suspect it could be a worn exhaust valve because it's back firing through the exhaust.

Good luck and let us know how it goes.

Originally Posted by MandyRH

I have a 1985 fleetwood pace arrow. When I first got it. It backfired so badly it blew out the muffler. Replaced it and for a couple months. There were no backfiring issues. But nearly 2 weeks ago we took it on its first trip. Only 2.5hrs one way. A few days later when we got ready to go home it happened again. So we replaced it and got on the road. About an hour into the drive it started backfiring while going down the highway. Then, you guessed it, a big boom. We got to a rest area and parked for the night. Replaced it again the next day. And the muffler blew again. We've been here since. Boyfriend thinks it could be something in the manifold. But says replacing it is his last resort. Anyone have any ideas?

[HarryStone]

Originally Posted by Bill Gail

Start with the easy checks . Check the engine timing . If timing is correct and steady do the following.

Base timing is a start, but the distributer needs to be checked as well, advance springs, advance cams moving freely, cap and rotor clean and functional, then check base timing and advanced timing, making sure the advance cam is working as it's supposed to.

[F4Gary]

Has the carb ever been overhauled?

[edgray]

Originally Posted by Bill Gail

First thing , stop buying mufflers until you have found the problem.

It would help to know the engine size , probably a 454ci GM and what is the milage ?

Good luck and let us know how it goes.

I guess you could be right, and if so theirs will be a P32 chassis, however my first MH was a 1988 Pace Arrow. It had a Ford 460 / 3 speed in a chassis made by John Deere. It was a real money pit, and that was in 1998

[baraff]

Originally Posted by HarryStone

Base timing is a start, but the distributer needs to be checked as well, advance springs, advance cams moving freely, cap and rotor clean and functional, then check base timing and advanced timing, making sure the advance cam is working as it's supposed to.

THIS^^^
The best way to tune a carb is check the ignition. Do this before anything else.
I would add, a 1985 vintage engine is likely to have points and condenser and not electronic ignition. Could be as simple as points and condenser replacement and timing.
If it were me, I would convert to electronic ignition. Not that expensive and 100% more reliable.

[robertkathy]

What engine do you have? Could be many things bad value seat glogged cat bad carb even a dead cyclinder

[ShelbyM]

I'd start by driving it home w/o the muffler. A rest stop is not a good place to be diagnosing and/or repairing your vehicle.

[chuckftboy]

A lot of great suggestions but if it were me, I would start with the easy things like spark plugs or plug wires. A bad plug wire or 2 will dump a lot of unburnt fuel into that exhaust system.

[shootist]

Gm high energy distributors all, and I mean all, eventually short the distributor cap inside. Look for cracks and brown residue. Put on a new cap, coil and rotor first. Odds are it will fix the backfiring. Proceed with plug wires and plugs from there if not. frequently the whole center of the cap will be burnt away under the coil and the stupid things would still run , the spark jumping well over an inch to the rotor.