This van is driving me nuts.
First, 118K miles,
5.2, 2002, 3500 15 Pass van.
Bough knowing of occasional misfiring.
History.
New Cat and both 02 sensors at about 100K
New plugs, Wires, Cap, Rotor, TPS, Coil, Crank Sensor, Distributer sensor thing> Sorry I forgot what it is called.
All just done in past few miles.
Cold engine all is fine, Must run engine for 30 min or so, Driving or just sitting in driveway, Either will accomplsh making issue happen,
Driving down the highway feels like engine turns off for 1/2 second.
Driving slow,, 40 MPH or so, Coming up on hill, Starts to lose power and starts to backfire into intake, ( No oil in intake) I already looked, Engine feels like it is missing and skipping,, Floor it and sometimes it will downshift and take off, other times it will just bog worse,,,,, It will never stall nor will it idle rough, EVer thus far.......
Put fuel pressure gauge on rail and drove about, 47 PSI idle, Quick stab will drop to 45,,,,, When it is bucking and throwing it's fits it will bounce to 40 psi and back to 47... Turn engine off will drop to 30 immediately.
I ordered a fuel pup assy today.
Wondering if I am barking up the right tree???????
Also, Never throws a code.
I have read much about these issues, But it seems like no-one ever posts what fixed it......
Any suggestions or ideas are welcomed ! ! ! ! !
Engine runs beautiful when cold. Again, about 30 min of run time needed to make issue happen.
Thank you for anything you may have!
Peter and Eileen.

 

Did you put in Bosch O2 sensors. They are junk for the Magnum series engines.

 

I am unsure of the brand of 02 sensors, They were installed by dealer as well as CAT by previous owner,
I can crawl under there and check.
So, How long does an original fuel pump last?
Peter

 

It sounds like you're on the right track with the fuel pump. The pressure should be constant +/- 1 or 2 PSI.

 

New pump installed,
Pressure is at 51-52 Psi.
Took truck for good drive and issue is still here.
It will do it mostly as you are driving on a flat and begin to go up a hill and depress the throttle just a tad, Trans does not down shift and starts to backfire into intake,
Does this point to anything I havent replaced???
Please help ! ! !
Need truck to move soon!
Thank you
Peter and Eileen.

 

clogged cat con?
2 wire coolant temp sensor.

Add an engine to frame ground if one does not exist

 

Check for any vacuum leaks as well. Check your vacuum lines, evap system, HVAC vacuum system, brake booster and its vacuum line, PCV vacuum line, and cruise control system if your van has one.

 

I added grounds a few weeks ago with some 10 gauge THHN wire,
Batt to body, Body to engine, Body to front frame as well.
Vehicle has cruise which works well, I will put under vacuum test this week.
As fer as the two wire temp sensor, Where is it and how can I order it VIA Rock auto, I could not find it last night while ordering a MAP and a Speed sensor.
I am really now just tossing parts at it hoping I get the right one.......
I guess it is something to do with engine RMS and trans gear, Then fuel,,,
for first 30 min or so, The trans will downshift with small grades,,, Once nice and warm it does not and that is when this issue uccures.......... Aside from the highway (Shut off) engine feeling for 1/2 second.
This cant be a complicated issue, BUT WHAT IS IT????????????????????????????????????
About ready to lend van to friend who gets in a accident each and every year.
Peter

 

The only thing left that will cause a backfire into the intake is a worn timing chain.

 

I keep going through this in my head and I wonder, Can the intake plenum leak air without pulling oil into the intake?
I can look down there with a mirror and it is not wet, But can the leak be in a place or small enough to mess up intake air but not have it filled with oil?
~~~~~~~~~~~~
Now on the cam chain.
If it is stretched, Would I hear it?
Peter