As you mention this I remember watching a video on the distributor which the guy removed the cam sensor and the metal piece that passes through the sensor was loose on the distributor base. It was held together with like plastic rivets and his moved around hitting the cam sensor. Just something I thought I'd mention as well although it wasn't my problem when I was having issues but it certainly made me look.

 

After replacing the Crank Sensor, ignition coil, cap, & wires along with testing the cam sensor, TPS, intake air sensor, CTS, MAP sensor, and unhooking the IAC solenoid it turned out to be the O2 sensor.

I'd have never guessed a bad O2 sensor could have caused that kind of havoc. When I unhooked it all together the problem quit and the truck ran fine.

Mike

 

I hate to start a new thread on this subject, but I'm also stumped as to what's going on with my SLT.

So, I bought this 98 SLT 3.9 with 142,000 miles on it back in April in Atlanta and drove it back home to Wisconsin. Soon after it started developing an occasional surging while accelerating from a stop light, and the exhaust smell is very rich smelling. I've replaced the following;

New Denso O2 sensors (1&2)
TPS - twice
MAP sensor
IAC
Cleaned Throttle Body
New NGK plugs
fixed a broken exhaust stud on the right side exhaust manifold

The 1st owner (I'm #2) really took care of the truck very well. He gave me a bunch of receipts with all the work he had done and he did a great job of taking care of it. New Catalytic Converter at 120K, Timing chain and distributor were both done around 130K and he's taken care of front suspension work and all new brakes within the last year or so.

I'm really stumped with this one.
I understand these 3.9's have a bit of a rough idle, but the exhaust smell just stinks. Also, the problems are more prevalent when the engine has warmed up and been running for a while. Perhaps a coil isssue ??

 

Do you have a scanner you can plug in, and see what the PCM thinks is going on? I would be most interested in what it thinks engine temp is when fully warmed, and what long-term fuel trims are.

 

Thanks for the response. I do have a scanner. No codes currently, pending or otherwise. The coolant sensor reads 201F at idle when warmed up, and when I'm driving the vehicle it fluctuates between 196-206 degrees. This leads me to believe the coolant sensor is reading accurately. I have to admit I'm not familiar with the Long Term and Short Term fuel trim stuff. I have those options on my scanner, but it's Greek to me... I also tested the O2 sensors, and they (granted they're new) seem to be working correctly as well.

I thought about the coil, but not sure if it can be tested.
I've read about intake gaskets failing on these 3.9's, but I'm not sure if that's something that I should be looking at yet. If I open the engine up to do that intake gasket, I'll pull the timing chain cover and verify the chain was installed correctly.
I assume it is, as there is no noise from the front of the engine and it seems to idle smoothly when it's cold.
When I purchased the truck back in April, and drove it from Atlanta to Milwaukee, it ran great. So these problems have all developed since getting it back home. I did get the CEL for the O2 sensor while I was driving home, but other than the light, the truck ran fine the whole drive home. MPG was around 23-24 on the freeway.

 

If it's doing it after it warms up, leads me to believe something is warming and expanding. Possibly a hairline crack in the coil/wires, that after warm, allow just enough arcing to bring the power down. Same could possibly be said for the dist cap/rotor arcing the towers. I would try replacing the coil, cap, button, and wires before tearing it apart, could also try running it with the air filter out to see if that changes anything. Other possibilities could be crank/cam sensor. I recently fought with my crank sensor (contsant bank 1 misfire codes with no miss) and it only resolved when I pulled a mopar one from a wrecked in the junkyard.

Crank sensor do get mopar, even if from a junkyard (I told them it was a temp sensor and paid $4). If these don'tfix it, might be looking at the intake manifold gasket. Also be sure to check your vac lines, one could be opening up when it gets warm causing a vac leak.

 

Hey Skree;
It's got a new Distributor on it which was installed about 10,000 miles ago. New cap/rotor/wires at that time as well. I may have 2 separate problems with this thing.
(1st problem) It runs fine when cold, but the exhaust smell is extremely rich smelling.
(2nd problem) After it's been driven a considerable distance/time, along with the exhaust burning my eyes, it develops this hesitation problem, where it won't get out of it's own way.
If I shut it down and restart it, it runs fine again, but still has very rich exhaust.

I have looked for vacuum leaks, but the hoses all look to be in very good condition and I'm not seeing any evidence of cracked/brittle hoses.

I thought about the CPS, but I'm not sure if that would cause the rich smell when cold.

 

As I recall, the CPS is what controls the injectors, it tells the pcm where the dist is to fire each injector. If it's lagging and firing a bit too late, the spark won't have enough time to burn all the fuel, thus rich. Now that I think about it, a coworker had the exact same problem in a 1999 Dodge Ram 1500, although a 5.2. His problem was carbon buildup on the cps magnets. It's easy enough, so check there?

 

Interesting... It's probably worth buying a replacement, since no doubt the original is almost 20 years old...

 

For all of you following this harrowing tale, I'm going to start with a few basic part changes. Coil and Crank Position Sensor. We'll see if that makes a difference. After that, I'll probably park it for the winter and start up again in the spring. With 142K on it, I'll probably pull the intake and change that manifold seal next spring, just to make sure it's not the problem. While I'm in there, I'll verify the timing chain is correct and within limits.