About a year ago I bought a Class B conversion van based on a 1999 Dodge 3500 van chassis. It’s got about 50,000 miles on it. It was well maintained and is generally in very good condition. I use it for one or two big trips per year, and in between I try to drive it around town about once a month just to keep it running well.
Ever since I bought it it seems to ping a lot under load. The engine does not run hot, but it pings when climbing hills that cause the engine to work, but not so much that it downshifts. For example, I’ll have the cruise control on, I’ll be doing maybe 55 or 65 (it’s a heavy beast and I don’t like driving it any faster than that), and when I get to a gentle incline that causes the engine to work harder, it starts to ping. If the incline gets any steeper it downshifts to a lower gear and the pinging stops. I’ve never heard it ping at high RPM. Running it on 91 octane helps a lot, but this engine is supposed to be able to run on 87 octane. I don’t know if this is a hint or not, but I think the engine seems to ping less at high altitude (above 5000 feet). Don’t know if that’s relevant.
The first mechanic who I took it to, who came well-recommended, advised against against using high octane gas. He said the problem is most likely a dirty injector or carbon deposits, and recommended running a bottle or two of Techron fuel additive through it, which I tried on a recent trip. It doesn’t seem to have helped.
He’s now on vacation, and I needed some work done so I took it to a different mechanic. Mechanic #2 said, eh, the pinging is normal. I should just run high octane if that makes the problem go away.
What I want to know is - is it possible there’s a problem with the knock sensor and/or the oxygen sensor, and if so, is there a test you can do for these sensors, or do you just have to replace them and hope that resolves the issue? I’ve never owned a Dodge before, but the amount of pinging I hear sounds excessive to me. But what do I know?
Thanks in advance,
Dave
DOnt know what year or type of motor, but a friend of mine has a 6.0L hemi charger that pings and knocks all the time. The dealer told him it is “normal”. It might just be a dodge/chrysler thing.
It’s normal to have less pinging at higher altitudes. You’ll find that up in mountains of Colorado they sell gas with octane lower than 87. Since it pinged when new I don’t think it’s deposits. Higher octane gas won’t hurt anything but your wallet. I think it’s a combination of a heavy load and a transmission set up for early upshifts, in an attempt to reduce fuel consumption. Note that the ping stops when the tranny is forced to downshift. If the tranny gets its throttle signal through a cable (going to the throttle body) it might help to tighten that cable a little if it’s adjustable. That would cause it to downshift more readily.
Use the high octane fuel. Isn’t that what your Owner’s Handbook instructs? The function of higher octane fuels is to reduce pinging. Pinging is less at higher altitudes.
You’re correct to suspect the knock sensor circuit. There’s a simple test for checking the sensing and response to knock. It’s in Haynes, and Chilton’s, repair manuals. Some mechanics know how to do it.
There are other things which can cause pinging. Carbon build up in the combustion cylinders can. Use a throttle body cleaner which also helps remove that carbon.
A dirty MAF (Mass Air Flow) sensor can cause a rich condition at idle, and a lean condition at higher power. Use an MAF Cleaner and see if there are any differences.