hard to start and runs rough v6

My sons truck was running fine when he drove home from work but when he got in it to leave again an hour later, it started, ran really rough then shut off. he couldent get it restarted. it would try, you could hear it stumble but wouldent start. We replaced the plugs and wires just to eliminate them but it didn't help the issue. I went out this morning and was able to start it by patting the gas several times then holding the throttle wide open. It barely started, you could hear it backfiring through the intake and it smoked like hell then it leveled off and started idleing fine but if you gave it gas it would stumble, it ran rougher and rougher until it shut off.
I was beginning to think that it jumped time until it started running smooth again. He said it was noticeably running smoother than usual just before it craped out. any ideas?

 

Sounds like a fuel pressure regulator or a fuel pump problem. Also, it wouldnt hurt to clean the throttle body/IAC valve.

 

I loosened the plug at the end of the fuel rail and it had a good bit of pressure. I don't have any way to check it but it was pretty high. I was surprised there was that much. Fuel pump was my first thought

 

Hooking up a fuel gauge would be your best bet. My truck had a problem where it wouldn't start when hot. It would try and barely run then stop. After it cooled it ran fine. It drove me crazy. I replaced the fuel pump and fuel pressure regulator at the same time. Hasn't happened again. Not your exact problem, but similar. Is it a V6? If so, pull the vacuum line from the fuel pressure regulator and check for fuel in the line. This will point to a ruptured diaphragm in the fuel pressure regulator. It really sounds like the pump isn't making enough pressure though.

My first thing (as I already said) would be clean the throttle body and IAC valve and see if it helps. Then go form there. Good luck.

 

I have been reading about cleaning the IAC valve a lot on this site and it is something ive been going to do as much as it is talked about on here. I need to do some research and figure out how to clean it and if I will need any gaskets or orings when I do it. Thanks for your help so far kigmob. Do you know off hand what the fuel pressure should be?

 

Unplug the two connectors (electrical) from the Throttle Body. On my V6, the upper left one (lookin from the passenger side of the engine) Is the TPS, the one on the bottom of the throttle body in the middle is the IAC. You do not have to remove it. When cleaning it, you just use a bunch of throttle body cleaner and a bunch of Q-Tips, getting it to where you can easily move the cylinder with the Q-tip to open and close.

Also, you mentioned Plugs, is it a V6? Did y'all use dual electrode Plugs?

 

Sounds like a vacuum leak how it goes and comes.

 

It is a V6 and I did not use dual electrode plugs, I went with NGKs just the standard plug. I looked for vacume leaks but didnt see anything. That doesent mean its not there. When it was running, I didnt hear any hissing. Im thinking fuel air mixture is my problem but its just a hunch

 

I have cleaned the MAF sensor, Throttle body and the IAC. Also changed the fuel filter, just in case, still having the same issues. Im thinking I may have jumped time. I can get it running after with playing the throttle just right but it runs like crap and constantly back firing and hard to keep running. I have to constantly move the throttle mostly wide open or close to it to keep it running. Any ideas in how I can check timing on a non running motor without taking everything apart? Does the V6 have a chain or a belt?

 

Im having the same problem wth my 4 banger. It wont stay running for 30 seconds, and if it does, you have to rev it up a bunch just to get it to smooth out. How do you know if you have jumped time??

 

They have a belt I believe.

 

Fuel filter? Cheap and easy to replace on the v6. Could be that the pump is fine but not able to push enough fuel through a clogged up filter.

Edit: damnit @Arctic Taco this thread was 3 years old lol