Hi all,
I have a `98 1500 with a 5.2, 175 K miles. I am the second owner and keep up on the routine maintenance. Up until this problem the truck ran fine, a little hard on gas but not terrible.

When this happened I was on the road about 2 miles from home. Engine was just warming up as normal. Was doing about 45 when all of a sudden the truck lost power (almost like it run out of fuel) and would not rev over 1K rpm. NO CEL appeared. Half tank of gas. Engine was making a deep thumping knock, not like a rod or main knock tho. Much more muted. I limped into a handy Oreilly and borrowed their code reader. NO Codes! Hmm, pulled the plugs in their parking lot and did a quick compression test. Test was decent especially considering the mileage on the engine. Plugs looked fine with one very slightly oily (it has been this way since I got the truck, always the same #2 plug). I limped the truck home a couple miles at 10 mph and parked it thinking I must have Fubared the engine but was too busy to mess with it and used my spare service truck. Please help with any ideas or similar experiences that might get me back in my Dodge! I can't take driving the Chevy anymore, I got to get this thing back on the road.

So far I have...Checked the fuel pressure (new pump 8 months ago), 45-50 PSI. Again, compression test is good. I have changed the crank position sensor and the distributor sensor, cap and rotor. I have wiggled and checked every plug and wire I can find on the engine. No wiring damage evident. The engine will light on ether but barely so I am leaning towards an ignition problem Vs a fuel problem , and it still has the thumping and knocking, no power and dies when you try to load it. Again, no codes no cel. I am bumfuzzled. Any suggestions as to how to proceed? Is there a diagnostic flow chart on these engines somewhere? Any help greatly appreciated.

 

it's a curious condition that we rely on sensors to give us codes, and usually, it's the sensor that's jacked, huh?

did you replace the CKPS with a dealer part? these things don't like aftermarket sensors in CKPS, CPS, TPS, MAP, IAC or any of the transmission electronics.. they cost more in $$ but far less in aggravation to buy from a dealer.. If you bought an aftermarket CKPS, I'd blame that in a heartbeat..

check your plenum gasket..

check for gross unregulated vacuum leaks..

check out your injectors.. specifically the one on cylinder 2..

check out your coil.. DON'T BUY AN ACCEL!!! good ol' OE or OE replacement will serve nicely..

inspect your plug wires, and all your grounds.

 

Roll the engine over by hand to get number one to TDC, in firing position. Pull the dist cap, and see where the rotor is pointing...

 

Had the same problem a while back..intetmittent knocking/power loss and sometime bucking. Changed out my coil and it was fine. A blown plenum will cause the same as will the things listed in the posts above.

 

Exhaust restriction come to mind. If you suspect it, remove the pre-cat oxygen sensor from the pipe and run it/take a spin. If it clears up really appreciably, something behind that sensor is plugged.

 

+1 on possible clogged cat. That may be enough restriction to keep the engine from breathing. If the cat is clogged, it is most likely a symptom of bad plenum gasket.

 

All good points!! As far as the sensors they are OEM Dodge, the cap and rotor is NAPA Eichlen best quality. I have looked for vacuum leaks or anything else obvious but so far no good. I was kinda wondering about the plenum gasket blow out issue and possibly a timing chain issue considering the mileage (175K) but what really gets me is that this happened instantly, IE went from running fine and normal going down the road the next instant the problem manifested. No pop, bang or other indication of problem, just suddenly started losing power and knocking. I think my next step is to pull the timing cover and intake and replace the chain and plenum gasket just to eliminate these from the mix, and I am thinking dropping the exhaust pipe to the cat might be also warranted. I will keep you guys posted as I make progress.

 

By the way, what is a "KEGGER MOD"? And "hardened trans" and SCT tuned?

 

Kegger mod is cutting the runners form inside the intake, and replacing the plenum plate with a 1/4" aluminum plate (to keep gasket from blowing again),Hardened Trans is rebuilt with upgrades including high temp frictions, Sure Cure shift kit, upgrade governor solenoid, modified front clutch for more frictions, and 6 gear plaentary set. SCT tune is a program for the PCM that removes death flash and make it run much better.

After paint and body work, I will be looking to install e-fan and HS rockers.

There is a sticky thread to the kegger mod and plenum in the FAQ/DIY section. Also, you can download the service manual and parts manual for your truck there.

But you have to be careful;. This is my first Ram, and modding the darn thing has started to become an additiction (in my wife's opinion)!

 

That's what's got me thinking that something came loose in the exhaust system. That failure mode comes on instantly. The broken thing is hanging on in its intended position, then suddenly it's blown into the place it's not supposed to be.

With decades of troubleshooting experience behind me, I suggest isolating the failure before modifying things. Get the failure behind you before doing "as long as I'm at it" work. I think it's an absolutely grand idea to get a new timing set in there, but if you do that while you've got an active failure and the truck seems to run worse on the new parts you then have to wonder if you did something wrong or if the problem its just progressing of its own accord. The bigger the matrix the slower the progress.

Unscrewing the pre-cat oxygen sensor is fast, easy, and cheap. If the truck suddenly runs a lot better you know the problem is in the exhaust system behind the sensor. If not, you're out a few minutes of your time but have eliminated the exhaust system as a probable cause. Either way, you're moving forward. Flinging a new timing chain at it? It's highly unlikely to solve your problem, might introduce a new problem, and is not moving forward in troubleshooting.

It's your call. Live like you want to live -- and I mean that very sincerely, not as a put-down. I'm just trying to be helpful.

Good luck with it no matter how you approach it.