Misfires Showing Up on Scan Tool Only

[2001seabreezer]

I have a 2001 Sea Breeze motorhome with a 454 L29 engine. My scan tool shows random misfires but there are no other symptoms of a misfire, no codes set, no check engine light. In fact I just got a smog test done last week and everything passed easily and it runs fine with decent fuel mileage. I am using a factory GM Tech II that is the best scan for this vehicle. Anyone else run into this issue? I will be installing a new coil & control unit to see if that changes this condition. I don't mind replacing these items because to the age of this vehicle. It has just over 95,000 miles.

 

[rvlifer]

I would try a 2nd scan tool to verify. It may not be the vehicle

 

[2001seabreezer]

I would try a 2nd scan tool to verify. It may not be the vehicle

Previously I have used a generic scan tool, same issue. This has been an on going issue since I got the motorhome. It hasn't been a derivability issue but since I have taken care of all other maintenance I would like to resolve this.

 

[rvlifer]

Sorry you are having issues and welcome to the forum. I cant help much on this cause i never owned a motorized rv but there are plenty here that can. I am sure they will be replying soon

 

[Arch Hoagland]

Have the plugs and wires been changed?

 

[Utclmjmpr]

Don.t fix what ain't broke..>>>Dan

 

[John From Detroit]

I'm kind of reminded of one trip south for the winter.. I clearly heard the big hunk of ICD (8.1 L Vortec) Misfiring.. Wife said "Sounds ok to me" (Different scan tool (ears in this case) Mpg was down too.. that is the kicker.

Shop found two problems.. Fixed and purrrrrrrrrrrrr once again.

 

[darsben]

Could the coil be breaking down enough for the scan tool to notice but still have enough wattage to fire the plug? Changing out the parts may save a breakdown later

 

[2001seabreezer]

Have the plugs and wires been changed?

The plugs have. The wires will be next if a new coil and controller don't resolve it.

 

[2001seabreezer]

Could the coil be breaking down enough for the scan tool to notice but still have enough wattage to fire the plug? Changing out the parts may save a breakdown later

I already have a new controller on order. I will try replacing those as my first step.

 

[Arch Hoagland]

I've got a dime that says the wires will fix it.

 

[IBTripping]

I've got a dime that says the wires will fix it.

I'll see your dime and raise you a quarter.

 

[jubileee]

Suggest swapping ignition relay with nearby like one.
Have seen several over the years cause flutter.

 

[John From Detroit]

I've got a dime that says the wires will fix it.

Had that problem on a car. NOTICABLE issue... Right after a tune up.
They put in new plugs.. NOT new wires.

That shop is no more (State padlocked it for fraud).

 

[Bobtop46]

When I had this issue it's was the wires that needed replaced to fix misfires.

 

[TheBar]

There was no noticeable misfire but opening the hood in complete darkness showed a spark jumping from one wire to the exhaust manifold. Replacing that wire helped the gas mileage.

 

[DonTom]

I have a 2001 Sea Breeze motorhome with a 454 L29 engine. My scan tool shows random misfires but there are no other symptoms of a misfire, no codes set, no check engine light. In fact I just got a smog test done last week and everything passed easily and it runs fine with decent fuel mileage. I am using a factory GM Tech II that is the best scan for this vehicle. Anyone else run into this issue? I will be installing a new coil & control unit to see if that changes this condition. I don't mind replacing these items because to the age of this vehicle. It has just over 95,000 miles.

Same issue in my Y2K RV--kinda--I get a code P0300 randomly & with the check engine light. Perhaps every 500 miles or so. I just reset it and forget about it. I have a Scangauge Two in there. I can reset the check engine light as I am driving. I got the code twice during my trip in AZ last month.

Same engine as yours.

It continued to do this even after I did a complete tune-up, changing just about everything possible with new. It runs perfectly at all times.

While I live in a smog testing area in NV, with a NV plate, fortunately, they do not care if the check engine light is on (with motorhomes only). They only check the emissions from the tailpipe on motorhomes and it always passes, sensors "ready" or not.

-Don- Auburn, CA (it would never pass a smog check here in CA).