I have a 1998 Ram 1500 quad cab 5.9 4x4 federal emissions truck that has some serious pinging between 2200-3000+ rpm under load going up hills or hard acceleration. Motor is stock no cam,intake, heads, headers or anything like that. It has the stock 3.55 gears with 285/75-16 tires it is stock height no lift kit. The truck had 190,000 miles on it when I got it has 199,000 now and runs great other than the pinging issue transmission shifts perfect it's really a great running truck. I live at 6000' elevation in case that helps in diagnosing this issue and the pinging gets a lot worse the closer to sea level I get. Truck had a bunch of vacuum leaks when I bought it used in february I fixed all the leaks and my 4WD, heater & cruise control all work great now. It had a very blown out plenum gasket confirmed by crankcase being under vacuum with pcv system blocked off so I pulled the intake and fixed that. Now it builds pressure in the crankcase now like it should so my repair was a success but the pinging is still there. No check engine light or codes stored.

Checked fuel pressure and its dead nuts on at 49psi at idle and under load. I have a obd2 scanner with live data and my fuel trims are +/- 3% except when under deceleration from wot run then longterm trim will spike to -17% for a few seconds then return to +/-3% the fuel trims usually mirror eachother if one is positive the other is negative always around 3% though. Upstream O2 sensor fluctuates from .1-.9 volts as it should. Map sensor sits at about 11.7 key on engine off 4.5 psi at idle and about 11 or there abouts under full load could be wrong on the under load reading have to recheck that to verify. Tps position reads from 11.5% at Closed throttle to 75% at WOT. Intake air temp reads about 120°-135° usually with outside temps 50° or colder. Coolant temp sensor reads 179°-180° on scanner. Pulling the plugs they all look like they are running perfect no fouling or signs of running lean. The calculated engine load on the scanner reads about 65% under full load which doesnt seem right to me but I don't have any idea what that reading should be.

Now this is where I think my issue comes from. The spark advance with the scanner hooked up shows around 19° at idle and if i rev the engine up a few grand it will peak at 40° advance. Under heavy load it peaks around 34° or so but sometimes the Spark advance PID goes blank on the scanner when it goes into power enrichment mode called open loop cruise on the scanner screen so I can't see what the advance is under WOT. I hooked up my scanner to a friends 2001 1500 5.9 and his spark advance peaks at 32° when revved up a few grand compared to 40° on my truck and sits at around 10° at idle his truck doesnt ping one bit. So I am thinking this may be the cause of my pinging having too much timing advance. So I think that maybe my pcm was reflashed by the previous owner with a performance tune for 93 octane gas.

Maybe another member with the same truck could post what their trucks spark advance is at idle, revving up to 3 grand and under load. So I could compare and maybe get an idea as to what it should be from the factory. The truck has no deathflash/software update sticker anywhere under the hood or on the pcm. I am at a deadend here and cannot think of any other cause for the pinging. The pistons all look pretty clean with very little carbon on them just looking down the spark plug holes. I removed all the dirt holder/plug heatshields so I can see in the cylinder pretty good.


This is everything I have replaced so far I work at napa auto parts so I take full advantage of my emloyee discount. Most of these were replaced just for piece of mind figured all the high mileage original sensors would fail soon enough so what the hell.
New alternator old one was growling
Map sensor
Tps sensor
Mopar pcv valve the napa/echlin one I had in there rattled like crazy was very noisy could here it inside the cab the mopar one is quiet
IAT sensor
IAC sensor
Ect sensor
Replaced catalytic converter with flowmaster one the old one was broken inside and rattling is why i replaced it
Installed hughes plenum plate because old plenum was severely blown out
Replaced both O2 sensors with Nok/Ngk sensors
Installed 180° thermostat
Installed autolite 3923 1 heatrange colder plugs gapped at .042
Seafoamed the motor 3 times full can each time not 1/3 like the bottle says after replacing plenum truck smoked like crazy
Cap
Rotor
Plug wires& rerouted per TSB

 

You've done it all. Welcome to the world of Dodge(we don't believe in knock sensors)Ram forum!

Well informed and educated post. No ideas on fuel advance etc. That's way over my head.

All you can do now is use 89 octane. Or replace the heads. I had to run 89 for years then one day I tried 87 again and ping was gone! I still hear it once in a while lugging it.

 

What comes to mind...
You don't say it, but typically people are putting on new timing chains when they repair the plenum. If you haven't, and want the engine to run better, replace the stretched chain.
Have you tried 93 octane to see if it reduces the noise?
Fresh coil, would put more voltage at the plug - so that makes some sense.
Sure you have found and solved all the vac leaks?
The round air cleaner isn't sourcing cool air from the fender, you may want to go with the uglier but effective stock air box setup.
I don't know what the factory spark advance profile should be, but 40 degrees doesn't sound outrageous.

 

I have ran 87,89 & 93 octane it pings less on 93 but it still pings. I was gonna do the timing chain this summer its pretty cold out right now and I don't have a garage at the moment. I'm pretty sure all the vacuum leaks are fixed because I pulled all the vacuum lines off of the intake and capped off the nipples to see if it would still ping (which it did) to eliminate possibility of any leaks as well as hooked up my mity vac vacuum pump to each line and they all held vacuum. The round air cleaner doesn't really add any hot air except at idle at a stand still maybe. The intake air temp sensor with the round air cleaner actually reads about 10 degrees colder on my scanners live data vs the stock air box. But it's so cold here it doesn't really matter if it did in my opinion.

Everything I have read about speed density setups say that vacuum leaks don't cause a lean condition because the MAP sensor will notice the extra air and compensate unlike a mass air flow setup which will lean out with a vacuum leak.

But The timing chain may be stretched to the max like you said so I may just have to change that when it warms up in a few months. I will probably pull the heads then too if I can't get this figured out. Thanks for the help though I would like to get this figured out. I appreciate the help.

 

With 199K on it, it's LONG past time for the timing chain to be replaced.

Will your scanner read fuel sync? That would be the next thing I think I would check. Not sure if using four hole injectors would require any adjustment to the factory 'ideal' setting though.....

Might try a compression, or leakdown test as well.

 

It's comments like this that scared me into doing a t-chain job at 200k. When I opened it up, it looked just fine. The slack is on the back side if you will and when the new chain went on, guess what, same slack. So really, unless we have actual proof of how much the chain actually "stretches" I would maybe avoid telling people to spend money and time on this job. I'm not saying it didn't help the engine, but it wasn't causing my ping nor any other issues. Timing belts on the other hand, are a must at that mileage.

Some engines just ping more. Mine's one of them. Had a special warranty for 1 year for an "engine noise" which I dismissed when I bought in 2001. Turns out that's what Dodge meant: ping. Also got deathflash a year later when it pinged so bad a friend thought it was going to blow. I have been scared into all sorts of expensive repairs chasing my tail on this. I've done everything the OP has and at 228k, it still pings. Could be a certain hot spot on the head, could be the plugs aren't indexed. Who knows? That's why Dodge ditched the magnums and moved on. They don't care past 3yrs anyway.

Here's some more ancient reading on ping OP:
http://dodgeram.org/tech/gas/Trouble/ping.htm

 

Any slack at all alters cam timing. The more the chain stretches, the further off it is. I believe that the manufacturers 'allow' up to 10* of slop in the chain. To my mind, that's too much. Mine, at around 170K was so sloppy, I could lift the chain off the cam gear, and pull the chain, without having to remove either gear.... Yes, it was *that* bad. (and I was VERY surprised it hadn't slipped.....)

If someone wanted to test the chain, just turn the engine to TDC on number 1, pull the distributor cap, and rotate the engine backwards till you see the rotor start to move. At that point, you can just look at the timing mark, to see how much slop you have.

These trucks use a morse-style chain, VERY prone to stretching......

 

 

Mine pushes near 40 when engine load is low....... I haven't actually driven it and watched data.....

 

You could take it to a dealer and have them flash your PCM back to stock. I had a replacement PCM flashed for my 2004 a couple years ago, it was only like $75 (I called around, other dealer wanted $125 for the same service). Or you could pick a junk yard one and have the dealer flash it instead, if you think your PCM is in a state of no return.