Changed plugs, here are the old ones.

[n8it]

I bought a new P32 chassis that was built 05-02 that now has 42k miles. I started getting CEL from the drivers side knock sensor. I would clear the code and it would be OK for anywhere from one hour to a couple of days and then it would set again. I bought a set of 41-101 plugs and Taylor extreme plug wires and changed them yesterday. It was nice that they had never-seize on them, they came out easily. The drivers side bank looks very different from the passenger side bank of plugs.

Here are the passenger side plugs:



And here are the driver side plugs:



Is this normal for the 8.1 engine?

[iRV4FUN]

Nothing is normal when it comes to 8.1L combustion.

Could you provide your MH manufacturer and model. Some of us are trying to see a pattern here?

Did your old plug wires look O.K.?

Thanks for the pictures!

[daveshan]

Don't have any experience with the 8.1 but if I pulled those out of any of my 5 gas vehicles I'd say you have either an oil fouling or very rich problem on the driver's side.

Knock was probably pre-ignition from a hot spot on all that carbon on the plugs. Probably built up pretty good in the combustion chamber also.

How's your oil consumption?

[CoastieSCPO]

At 32000 miles on my W-20 I changed out the 41-983's for a set of 41-993's. I did not take a photo of them but just looked at them to compare the old ones to your old plugs. The dirtiest of all 8 plugs was the # 7, driver's side and it looked comparable to far right plug on your passenger side images. None of my old plugs had as much carbon showing than those on your images, especially the drivers side.

So, what is "normal"? I'm no mechanic, but I would think that those driver's side plugs are not "normal", especially since the scan gauge was indicating a problem with the driver's side knock sensor. Now, my rig has 45000 or so miles on it and maybe, if I get motivated, I'll take a plug or two out and see what I can see.

Great pictures, by the way.

Bob

[n8it]

The original plugs were Denso TJ14R-P15. The plugs in the pictures are in order from left to right, passenger side 2,4,6,8 and drivers side 1,3,5,7. The old plug wires looked OK. The color of the sleeve inside of the metal shields were orange except #5 which was a little darker and #7 was very dark. I use a 1 qt of oil every 4k-5k miles.

[pkmesser]

That's pretty low oil consumption, so that's not the problem. I would say you are running very rich on the drivers side. How does the exhaust look on that side? If it shows the same signs, there may be a problem with the O2 sensor on that side. You could take it to a shop or smog check station, and see what that side looks like for O2 and CO, I would expect the O2 to be at 0, and the CO elevated. Or you could just change out the O2 sensor.
That #2 on the other side isn't the greatest either. ??? How is power, if it is down, I would say a compression check is in order instead.

[n8it]

The exhaust on the drivers side looks black and the passenger side is clean. Plug #2 looks better on the other side, but still the worst on the passenger side.
I was thinking about the O2 sensor, but thought it would throw a code if bad. Or does it only do that if it fails? I just went out to check for stored codes and run the engine since I had not started it since replacing the plugs and wires. Before starting it, I checked and found one stored code, P0131. Generic description is O2 voltage low on bank1, sensor1. Now to try and find a part number.

[Mr JP]

When the 02 sensors went bad on my 8.1 there was no check engine light. The only indication was a problem passing smog test (went into second chance) & a low voltage code (on both) on a OBDII reader. Good Luck JP

[max49]

Your left bank definitly looks like it running rich. That's better than too lean for your engine. If you have a Scan Gauge, what temps have you been running. If all 8 of your cylinders were running about the same, I think I would rather have that than have white hot. I was looking for a colder plug, so I could get more like you have , but apparenty they're not available. And your plugs are much blacker than mine, so one of us is not normal; if there is a normal for this engine.

[speed racer]

An O2 sensor won't set a code unless it fails. It looke like yours could just be reading wrong due to carbon build up. If you replace it replace both of them they are the same age and carbon builds up on both of them. I don't know if you unit has a down leg O2 sensor after the cat. converter but if it does it could be trying to lean the engine out and causing the knock sensor code.

[oemtech]

1) 5 & 7 Shields are dark and not orange... Heat build up.

2) There are only upstream O2 sensors on the Workhorse chassis. Consider replacing both sensors.

3) 86 the Denso plugs and get some AC-Delco's

4) Consider new plug wires

[Joe Gilbert]

I'm not sure that never-seize was uesd by GM. These are cast iron heads so plug removal should not be an issue. I'm not sure that never-sieze is a bad idea; but not necessary. I also changed plugs this week. Mine had not been out in over 40,000 miles and I know that I did not use never-sieze when I regapped them 40,000+ miles ago. My plugs could be removed with my fingers once I broke them loose with a normal 3/8 socket.

My pluge all looked great. I agree you should replace the 02 sensor(s). I would do that and than look at a couple of the plugs after your next trip. Let us know what you see.

JoeG

[wa8yxm]

Normal would be for all the plugs to look the same, The lighter color plugs look normal to me per picture, however I do better "live"than "Photo". The dark ones are clearly fouled, I can not tell if it's rich as one poster suggested or something else.

But they are NOT normal.

[iRV4FUN]

n8it, Does your 8.1L have any modifications aftermarket mods?


Did anybody notice? n8it only has 42,000 miles on long life plugs!

That’s 42% of the 100,000 mile long life plug life! My “Short Trip / City Scheduled Maintenance” as per the WHCC Owner’s Manual recommends 100,000 miles. Seems that 30,000 mile change interval may be more proactive and appropriate.

Spark plugs also help to remove heat from the combustion chamber by acting as a heat exchanger. A spark plug produces no heat on its own, but rather transfers combustion heat to the metal of the hole it's screwed into, and ultimately to the coolant surrounding that metal. Spark plugs are rated from cold to hot on the speed at which they can transfer heat away from the combustion chamber.

It is important to run a spark plug at the correct heat range, for the right rate of heat transfer is required to keep the spark plug electrodes clean. At the proper temperature, combustion byproducts are burned away and the spark plug cleans itself. Too cold a range and the spark plug may become fouled with carbon or combustion deposits and misfire or cease to create a spark. Too hot a range and the tip of the spark plug can actually melt away and the spark plug will fail.

I’ve seen 3 different part numbers bandied about on this forum for replacement spark plugs. My questions are;

Which is the better plug brand and has anyone successfully tried cooler heat range plugs? Please provide part numbers.

I assume I can walk into my local GM Delco parts Department and order O2 sensors without going through WHCC. Also, has anyone used aftermarket O2 sensors? Any part numbers would be a bonus!