Last couple months i have had some problems with our minivan. It runs and drives very well for the most part until it decides to backfire and bog on acceleration. This happens so randomly it could be a week or 1 or 2 days before it acts up again.

It doesn't matter if it is a long or short drive it tends to do this when ever. What i have been experiencing is this

I will driving around picking up kids, then all of a sudden you can feel it in the engine, it will start to shudder a bit, then you try and accelerate and it will go but bogs down and it will only go about 5-10mph while popping and lurching forward as if its running out of gas, slip it in neutral and revs fine drop it in gear and right back to major hesitation. If i pull over and shut her down, she starts right back up drives fine for about 10 ft or so and right back to the same ol problem. Driving her while backfiring or misfiring and jerking for about 10 minutes while doing 10mph and all of a sudden she come back to life as if nothing ever happened.

At first i thought it was maybe the transmission ( felt like it was stuck in 4th or 5th gear and wouldn't shift down ) it feels like you are driving a manual trans and trying starting off in the highest gear and it would bog down. So i had a great deal from a family business i used to work for and swapped transmissions. This was not the problem, trans works and i needed it as it was clunking real bad when stopping, it works great but i was wrong.

Fuel pump went out a few weeks ago, had to replace the whole modular part as it is one piece, no change cross that off the list.

I am taking it to the shop in the am, but i really need some help on this as they are as confused as i am. It never wants to do any of this when they have it and it happens so randomly, you never know when its coming.

Any ideas, i am going to have them check a lot of things, fuel filter, wires, plugs, egr, fuel lines, i need this fixed as winter is coming and i cannot let the better half and the kids riding around in a vehicle that does this when ever it wants.

 

Just an addition ( can you edit posts ?? )

I also replaced the cat and muffler about 6 months ago and, if i remember right, this is when the problems started, right after these were replaced. But i highly doubt this would cause the problems i am having.