Well the time has come to make my first forum post about an issue with my newest Dodge, as I have done all the research I can on the forums and haven't been able to solve it. And let me start by saying thanks for reading all of this, I just tried to give as much information as I can.

Here are my symptoms, under low throttle (say 40 mph in 3rd, my tach is broke) the truck will miss and backfire out the tailpipe. When the ambient temperature is cold outside (<20*) the symptoms are far worse, much more jerking and backfiring than if either: the truck has been driven for 30 or so minutes with the low ambient temp, or the ambient temp is higher (>35*). Under either of these two scenarios the truck runs much better. I do not know about higher temps, I just got it this winter. The truck idles fine (no cat, a little chompy but I dont hear it missing, and the RPMs seem to be fine). To clear up the symptoms while driving either let off the gas, or give it more. Only between say 10%-20% throttle do the symptoms occur. 82k miles on the truck.

If I am going 40 in 3rd and holding steady with low throttle then the symptoms are present. If I keep my foot steady and shift to second, the symptoms go away with the higher RPM. I have ruled out the TPS.

Also, my OD solenoid is out (got the part in the mail, to be installed with fluid/filter change and Transgo Shift Kit), so I do not have OD. I doubt this is related.

My Speedometer is also off. It is steadily about 10-15mph off (fast) up to an actual speed of about 80, when it tapers off to not shoping a speed increase at all.

No Codes

New:
Map Sensor
Charged Air Sensor
O2 sensor (remember, its an OBD I: only one 02)
TPS Sensor
Fuel Pump
Plugs, wires, cap, rotor
Manifold Gasket

I have gone over the vacuum system and replaced what I found cracked, and then went over the lines under the hood with map gas while moving them with my hand, and checked all connections. The equivalent on the plug wires. The IAC and throttle body has been cleaned. The fan moves fine by hand with engine off and cold.

What I have left to do would be cleaning the EGR valve, replace the IAC, get a vacuum pump on it maybe, check the lines under the cap that run to the fuel tank (futile without a pump I would think)? I also could do a compression test. The FSM for hte 95' says the FPR is in the tank with the pump, mine is on the fuel rail. How could I test it? I guess go down the road with a fuel pressure gauge taped to the windshield?

My gut tells me its something silly. Because when you put the foot down it really pumps some air and produces some power.

Thanks for taking your time to read, all advice will be greatly appreciated!

 

I should also mention all of this is in the context of the truck being at warm operating temp.

 

Maybe I can get the ball rolling on this thread. Since I posted last I have deleted all the emissions stuff (egr, evap, ect) and it made it run better. Also my truck had the +2 plugs, which I have replaced with Autolite 9323's. The plugs also made it run better. I also checked my fuel pressure and it is good. Putting 93 octane in helped a lot too.

I have my OD issue resolved with a rebuilt transmission -it was shot.

The problem I still have is under cruising speed (low throttle, between 2-2.8kish RPMS) it will miss, and then start missing worse if I do not let all the way off the gas or give it more (if I only slightly decrease the throttle opposed to completely letting off, it makes the missing worse). It seems like as the vacuum levels off and drops as the engine stops accelerating that I have a small vacuum leak. But I have replaced all the remaining vacuum lines.

Still no CEL. Runs like a raped ape when you put your foot to the floor. Can't really get it to miss just driving around town stop light to stop light (not cruising).

Any help is very appreciated, this is driving me nuts.

 

almost sound like fuel pump having issues maintaining pressure/flow , and or fuel filter, something along that lines

 

I'm having the same problem. did you resolve the problem yet?

 

I just solved this same problem with my 92 5.2 after replacing every possible sensor. It was the oil pump drive gear bushing under the distributor.
First test; Pull you distributor cap and see if you have play in the rotor. If you have more than a 1/16th of an in or so, this is probably why the timing is jumping around.
Next; Rotate the engine around to top dead center. Then pull the distributor out. Take a magnet, like a pickup tool and reach in the hole to the top of the oil pump drive gear. See if it jiggles around a little. If so, you need to replace that bushing. It costs less than $10 and you may have to order it from your Dodge dealership. The oil pump drive gear should be replaced too and it is cheap (NAPA has it).
Then; You have to use two special tools to get the bushing out and to put the new one in. The tools cost about $90/each, unless you can find a shop that has them. Found some suppliers on eBay, but be sure to get both. I got the tool that burnishes and installs the thing, but didn't notice the other tool, so I improvised. I got some all thread 14mm / 2.0 thread. Cut about a foot long piece and put a flat washer and nut on it. Cost about $16 instead of 89. Put some bearing grease on your 10:2.0 tap and cut some threads into the old bushing. Use the big centering washer from the burnishing tool to center. Thread the all thread into the bushing. Drop the flat washer on and turn the nut until it extracts the old bushing. Then you can use the burnisher to install the new one. Here is the entire article/instructions that are easy to follow. http://dodgeram.info/tsb/1993/18-08-93.htm

 

see my post. I have solved that problem recently.