detonation? or something else?

[pvogt38]

Folks,
I have a 2002 Ram 2500, with 5.9L (gasoline) V8.
Recently I had the timing chain and sprockets replaced after it jumped several teeth. (Loud noise, and truck was dead on the interstate)
I had symptoms prior to the chain jumping, and these symptoms are still present after the repair. Naturally i am worried about another failure.

I'm not a mechanic, so here is my best effort to describe the symptom:
Driving at highway speed, infrequent and randomly, the truck makes a loud "CHUG" noise, and the truck is jolted by something. My first suspicion was that it was related to the transmission. It's a fairly violent sound, but not a backfire. This may happen 0 to 3 times during an hour long trip on the interstate. Once in a great while, it would happen much more often, so I would pull off the road. It seemed like simply letting the truck cool off made it stop.

Perhaps related, about 8 months ago, the coil pack was replaced after the truck simply died on the interstate. Now, during this timing chain event, the mechanic said it had "Weak Spark". He elected to replace the distributor cap and then the coil pack, in order to get "good spark". despite this, the "CHUG" symptom is still happening now and then.

Please help me if you have any idea what could be going on with my truck. My mechanic is stumped.
Thanks,
Paul Vogt
Charlotte, NC

 

[Tat2hemi]

Paul have your mechanic pull your valve covers and check for broken valve spring. Oops not a hemi,
Those engine have two piece intake usually the intake belly gasket blows and carbon ups the engine

 

[MyOhFive]

There was a common issue with the plenum gaskets on the intakes on the magnum engines. Basically allows oil to pool in the bottom of ur intake manifold. It COULD be that. Are you using a fair bit of oil between oil changes?

Also (but less likely) a bad cat. In years prior (I had a 99) the cats went bad. But that was just a severe loss of power, not so much a "chug"

 

[pvogt38]

Yeah, my symptom is...runs perfect for days, then "CHUG" and a big lurch. Regarding oil, It does seem to use oil a bit. I'll check it tomorrow and post the result. Also, I've been running 87 octane gas, with 10% ethanol. I put in some 89 octane today. maybe that will change things.

 

[pvogt38]

Three updates:
1) oil level is fine, with about 2500 miles since change.
2) Symptom still persists even with mid-grade gasoline
3) The problem got severe today... probably coincidence but, When I turned off the Air Conditioning (which has its own problems) ,the "chug" issue stopped. Not saying there is a connection, because the symptom comes and goes anyway. But I'll watch it.

 

[MyOhFive]

Disconnect your a/c compressor and drive it for a couple days to see if the issue persists just to rule it out. Not sure what it could be doing to cause these drivability issues, but u never know.

How is the idle? No pulsing or hesitation?

 

[pvogt38]

Yes, I'll leave the AC off for a few days and see what happens.
The idle is fine, and 99% of the time, the engine runs like a top. Frustrating.
-paul

 

[ExpressRules]

While this may be way off base, a worn universal joint can cause some of the symptoms you describe.

 

[pvogt38]

I was hoping to get suggestions like this. Thank you. Can you think of any way to confirm or rule that out?
-p

 

[MyOhFive]

Actually disconnect the electrical connector at your a/c compressor under the hood. Even tho you haven't turned the a/c on, the compressor can still engage on its own depending on what you have your HVAC set too, defrost for example.

 

[pvogt38]

OK. Based on these suggestions, I'm going to disconnect the Plug that connects to the clutch on the AC compressor. I'll do this before I head home tonight. Thanks very much for the input.
-paul

 

[pvogt38]

the truck did "Chug" one time with the Compressor clutch disconnected. I'm starting to focus on the CAT. there is a code in the scan related to the CAT. More to come.

 

[pvogt38]

Ok, New information! Yesterday morning, on the interstate, A warning light came on saying CHECK GAUGES! I noticed the temp gauge pegged! Pulled over, all my coolant was gone, burst radiator..
150 bucks for a tow, 600 bucks for a radiator (installed) and now the truck is running much much cooler than it used to, and so far, 150 miles, and no "CHUG" symptoms. Prior to this, the temperature gauge was always right at the 210 mark. Now with the new radiator, it is way-way below that. Like I said, so far no misfires... Also, at the shop, I learned that the CAT in this truck had been removed before I bought it!

 

[pvogt38]

meant to upload a photo, not figuring that out yet....

 

[MyOhFive]

you have no cat and no CEL?

you may be custom tuned my friend...

 

[pvogt38]

No, The Check Engine light as been on since I bought the truck. The CAT code says low CAT efficiency or some such thing. Best news of the day: My wife used the truck all day to pull a horse trailer, no engine symptoms at all. Right now, the only thing changed is new radiator, and much cooler running engine as a result. Maybe It's solved.. hope so, and thanks for all your comments.

 

[MyOhFive]

oh ok well hopefully it is solved for you. Could be your rad was plugged? If it happens to re-appear then I would start with getting that 02 code fixed either by putting a cat/sensors back in or a wideband. The truck doesn't really know how to fuel itself right now.

 

[pvogt38]

Thanks for your comments Oh5. The truck is due for it's inspection this month so I'll be clearing up all of the emission issues this week. That means new CAT, and probably new 02 sensors? To be honest, your comment about the truck not knowing... is over my head. but based on your comment, and cuz the inspection is due, I'll be taking care of all these things. Thanks for your knowledge and for caring enough to comment.
All The Best,
Paul
Charlotte, NC