I have a big problem with my Vehicross Missfire

[stokes_osu]

ok

[Gussie2000]

Ok guys, I dought a vehicross from an older man for 5K it is a 2001 with 56k miles on it. I got it cheap do to it setting for some time, it is in excellent shape and looks like he took great care of it.
The question, OK when he sold it to me he said he had just had it serviced and all of the maintenance done on it, it ran great the first couple of times i had it out, for the last month when i drive it over ~20 miles in one trip it goes to cutting out like it is having miss fire issues, " tech computer said random miss fire code" I changed the spark plugs and looked it all over and everything looks great. super clean and great looking. So recently i changed the oil hoping that this would help, but same o same o.
it dose not do this or act weird at all for the first 20 miles or so but when it gets to that point it goes to galloping and sets the check engine light off... the light will go off if i don't drive it to that point for a couple of days... I don't want to hurt it and i cant afford to take it to some one else but i am just confused why it will run god for 18 miles but dot 20 or 25, now it is not any set # these are approximations

Have the engine code read to figured out where is the issue.

Then come back & post the code number so we can help you better.

[ZEUS]

I had a misfire on my VX soon after I got it as well. After ordering a new fuel injector per a mechanic I discovered the REAL problem was actually very simple... the connector on one of the coil packs wasn't pressed on completely. Heat build up, motion, and what have you, would cause it to creep back just enough to throw a code. A quick snap and everything was good to go again! So be sure to check all your connections before buying anything...

[Y33TREKker]

Random misfire codes could also be fuel related. If the VX had been sitting for awhile, there could have been condensation (water) that collected in the fuel tank which could start to get mixed in with the fuel after driving for a short period of time. A can of Heet to remove any water that may be in the gas would be an easy remedy to at least try. Heet also now makes a version for water removal and fuel injection system cleaning.

And again on the fuel-related side of misfiring, the stock fuel-pressure-regulator can never be forgotten as a possible culprit.

[ZEUS]

Yeah, in line with what Trek said, it is prob'ly a good idea to just replace the fuel filter as well. Cheap insurance...

[Triathlete]

Along with the above...
check for clogs in the fuel rails. I was getting a code for missfire and after changing a lot of stuff out still had it. Took a screw driver and tapped on the fuel rails which apparently loosened it up...no problem since. Although
I was still glad I changed the plugs...the PO had put in some cheap crappy plugs.
Also I used to have vapor lock problems if my fuel cap wasn't on right. This occurs when the vehicle warms up (about 20 minutes) on warm days. If you open your cap and hear a hiss sound as the pressure releases this could be the problem.

[Ldub]

FWIW...If you have your code(s) read & any of them are "low 300's" (301 - 306), it's an indication of which cylinder is mis-firing.

If you switch coil packs with the next cylinder, & the code moves with it, you've found the problem...

Another possibility would be leaking valve cover gaskets, allowing oil into the spark plug wells.