1996 B2500 5.2

I'm 975 miles from home - currently at my daughter''s house in VA. During the road trip here, the first leg of about 550 miles went very well - perfect as a matter of fact. Spent the night in a motel. When I hit the road the next morning, I noticed a very slight flutter at certain points - mainly when I was backing off the accelerator in a very light load. Under full acceleration, the engine ran fine. No check engine light.

I thought I had bought bad gas from the day before and some how, over the night, water settled in the tank. As I drove, it got more noticeable. I stopped at a Walmart, and dumped in a can of Seafoam into the tank. No difference - only worse after another 50 miles.

The problem never occurs under full load (hard acceleration). As long as I have the gas petal to the floor, it runs like a champ. When coasting at highway speeds, and I give it just a little petal, it bucks.

After 200 miles more on the second day, I got pending codes to show up on my Torque App. P0300 - (Random/Multiple Cylinder Misfires) and P0303 - (Cylinder 3 Misfire). After another 100 miles, the Check engine light actually came on. P0300, P0303 and pending P0301.

By the time, I got to my destination, it was bucking hard but always under a light load. When the petal is almost to the floor or to the floor, it runs smoothly.

In preparation for this trip, I went through the cooling system (water pump, tstat (180 - FL driver), temp sending unit, temp sensor, hoses, flush, and coolant.) Earlier this summer, I put in a matched set of injectors, dizzy cap and rotor, coil, checked and cleaned the plugs, and valve cover gaskets. Plug wires are routed according to the TSB.

Today, I will pull the plugs on the cylinders with codes and look at them. I will look for vacuum leaks.

I don't think it's the CAT as it runs great at full throttle. Likewise, I don't think it's fuel pressure. I have seen a handful of posts regarding "buck under light load" (or similar) but none that I have found have had a definitive answer.

Do you guys have any good ideas about what I could do to find and fix this problem before I head back south in 5 days?

 

WAG: cam position sensor inside of the distributor.

 

Based on my own (one and only) experience having misfires on 6 and 8 a couple few months ago I'd say swap those plugs and or injectors (I didn't have to do injectors) to another location nearby if you want to try to see if the misfire moves and diagnose.
Though, if they (the spark plugs) looked kinda corroded when you had cleaned them up but you didn't replace them ( as I read it) you might just want ot replace them all with something like the NGK coppers if there are 20k+ miles on them, $2. bucks a piece is cheap fix. I'm sure you are aware the cap should be brass contacts not the aluminum ( and consider swapping plug wires or get new plugs wires if you don't know how old, you may just have one bad one there, hard to tell...
I know number 1 and 3 ain't the easiest to get to same as are 2 and 4 in the front side of the motor.
Recheck your cap and rotor and the pickup coil (cam sensor) contacts too that is under the rotor as tjkoko above mentioned.
Another thing

I'd start out and try ignition stuff first, fuel pressure test (tester gauge is only $30-$35 at most any parts place) and google or youtube the howto's to diagnose misfires, fuel pressure check it's pretty straight forward. Compression check if all else (the easier stuff) fails.

also, try that Gumout All in one product for the fuel system cleaner instead of the seafoam or others! It actually proved it works for my van so recommending it!

Hope it"s an easy one for you

 

Hows you plenum gasket? It will give you multiple miss fire codes(P03XX)

http://www.hughesengines.com/Index/p...p?partid=27091

 

Started with the cheap and easy. Pulled the plugs that were showing up on the codes P0303 and P0301 as they are more point specific than the general P0300.

I dropped the heat shield to get to the left (odd) bank. When I pulled the plug wire from #3, the metal part that clips to the plug separated from the boot. I drove immediately to a parts store and bought a new set of plug wires and put them on in the parking lot. I followed the plug wire TSB closely (as I have done for years).

BOOM GOES THE DYNAMITE!! No more stutter or bucking at half throttle. I drove it about 40 miles today with about 10 miles on the interstate. Never missed, stuttered, nor bucked. No codes - not even pending!

thanks for your help. I would not have guessed the plug wires could cause such a problem in the middle of a road trip.

 

tsb???

 

Technical Service Bulletin. Specifically, TSB 18-48-98 which details how to route the plug wires to prevent induction misfires.

http://dodgeram.info/tsb/1998/18-48-98.htm

 

Hey!! Glad to hear that you found the problem and was somewhat easy Enjoy what's left of your visit and hanks for the update!

As mentioned in another thread and also above, my misfire was the P0300, 306 and then 308 popped up too.
First thing I checked was the cap and rotor and the 2 spark plugs involved. The cap and rotor contacts did look like should be replaced and the 2 plugs too.
I bought 8 new NGK copper plugs and the cap and rotor, but only replaced the #6 n #8 plugs, swapped the 6 n8 wires with #5 n #7, cleared the codes and drove it for the day and no more misfires. Changed the rest of the plugs that following weekend and called it a day. It's running well ever since

 

Just finished 975+ mile road trip. Perfect performance. I will pay more attention to plug wires in the future when doing a tune up. The wires "looked good enough." LOL