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RamblinFever · 07-13-2015, 03:04 PM

Well mabe not backfire, but exploding sounds down below that might be in the catalytic converters. We have a 2004 Bounder with about 60,000 miles on it The engine runs smooth on the level and does not burn oil. However when I start up a grade and the transmission shifts down, the explosions start. Because the engine runs so well I suspect it may be a bad sensor that is dumping too much fuel in it. I don't want to walk into a shop cold and get taken for a ride so would like to hear from anyone with a similar problem.

paz · 07-13-2015, 03:53 PM

Had the exact same thing happen on our 2005 W24. The next thing that will probably happen is the engine will start running rough and loosing power. As soon as ours did that, I replaced the spark plugs and wires. The roughness went away and so did did the backfiring on downshifts.

RandyKathyM · 07-13-2015, 03:55 PM

Check spark plug wires. That would be my first guess. My 94 Bounder did that until I replaced them with after market ones. My Workhorse does that in heavy rain and they get wet. A lot of other thing could do it though.

edgray · 07-13-2015, 04:36 PM

Quote:

Originally Posted by RandyKathyM

Check spark plug wires. That would be my first guess. My 94 Bounder did that until I replaced them with after market ones. My Workhorse does that in heavy rain and they get wet. A lot of other thing could do it though.

Next time it starts happening, check the air filter to see if it is wet. If so, the reduced air flow will cause the MAF to send faulty info to the ECM and that can cause the same symptoms. SOME of the early W-series air boxes did not seal out the fine mist/spray that is rampant in the wheel well and moisture got sucked in enough to affect performance. Been there, done that. Pictures are posted under my name in the iRV2 photo section.

az bound · 07-13-2015, 05:39 PM

Other possible causes. Clogged fuel filter or dirty MAF sensor.

Arch Hoagland · 07-13-2015, 08:11 PM

You probably need plugs, wires, air filter and clean the MAF.

IdahoSRT10 · 07-13-2015, 08:16 PM

Quote:

Originally Posted by Arch Hoagland

You probably need plugs, wires, air filter and clean the MAF.

And distributor cap if that year has one. (hairline cracks cause backfire issues)

Arch Hoagland · 07-13-2015, 09:39 PM

Quote:

Originally Posted by IdahoSRT10

And distributor cap if that year has one. (hairline cracks cause backfire issues)

No distributor cap on the 8.1.

RamblinFever · 07-14-2015, 05:01 AM

Quote:

Originally Posted by paz

Had the exact same thing happen on our 2005 W24. The next thing that will probably happen is the engine will start running rough and loosing power. As soon as ours did that, I replaced the spark plugs and wires. The roughness went away and so did did the backfiring on downshifts.

Thanks, that is very encouraging info.
My next question is where you recommend buying the spark plug wires - GM dealer or auto parts store? Also, is there more than one configuration of the wires on an 8.1 engine?

RamblinFever · 07-14-2015, 05:04 AM

Just saw all of the other replies - thanks for the suggestions. The air filter is good but I have not changed the fuel filter.

kkeever · 07-14-2015, 05:46 AM

Try OEMY's web site for the parts.

paz · 07-15-2015, 05:39 AM

Quote:

Originally Posted by RamblinFever

Thanks, that is very encouraging info.
My next question is where you recommend buying the spark plug wires - GM dealer or auto parts store? Also, is there more than one configuration of the wires on an 8.1 engine?

There are high temp aftermarket wires available, but I just bought wires and plugs from the local auto parts store. The MH version of the 8.1 uses the same wires as the Chevy/GMC pickup.

Some motorhomes have more problems with burned wires than others because of poor air flow around the engine and/or because of harsher driving conditions (more mountain climbing, faster speeds, heavier coach, etc.). In those cases, the high temp wires are better. IMO, plug wires starting to fail at 60k miles does not indicate a big heat buildup problem.

tomwalt · 07-15-2015, 07:44 AM

If you are going to order a lot of items (plugs, wires, filters) try Rockauto.com
You pay shipping, but on multi-item orders it works out well.

Arch Hoagland · 07-15-2015, 09:21 AM

Over the years my experience with after market electrical components has been dismal.

I now buy all oil filters and electrical items from the dealer and stay with the OEM parts that came on the vehicle.

As paz mentioned, wires failing at 60,000 miles says they were pretty good to begin with so I stayed with the OEM wires when mine were replaced at the Workhorse dealer.