ok my truck ran good for the first 3 weeks ive had it now it runs like crap, on the highway i cant get past 80km, it backfires and generally runs like crap, ive replaced the cap rotor and spark plugs and recently replaced the fuel press regulator (i found out from much searching that the fuel filter is part of the regulator).
any suggestions on what to check next.

 

First of all what year and engine do you have? Next it truly can be thousands of things. You should double check your distributer make sure it is where it needs to be. Check the plug wires, make sure they are in the correct spot on the distributer. Then check fuel pressure.

 

its a 94 with the 3.9

 

I'm with Crazy on that...you should definitely check the fuel pressure because you could have a clogged fuel filter and/or dieing fuel pump. With the distributor you could have bad timing so you should make sure it's not loose and have someone check the timing. Good idea to also check the spark plugs, wires, etc. It could be the IAC going bad but it's not likely. Lots of times when you have both power loss AND backfiring it's a timing issue especially since I've never had any backfiring issues when I've had a clogged fuel filter or bad fuel pump and I've been down that road a few times with my '95 3.9liter. Only time I can remember experiencing both is when I had timing issues with the distributor. If none of those turn up as the issue, you could check out the IAC valve on the top back side of the throttle body, it could be clogged or have stopped functioning completely.

 

ok thanks, im trying to find a timing light to borrow, it has good fuel pressure, when i relieved the pressure on the fuel rail it sprayed pretty good.

 

that's not an accurate way to check fuel pressure. See if you can get access to a fuel pressure tester and see what your pressure is. Should be around 39 PSI. I would bet that your fuel pump is bad, the exact same thing happened to me when I bought my '95 V6; had it for 3 days and wouldn't run, backfired, missed, had no power at all. $187 for a new fuel pump (which comes with a new filter and regulator) and it has been running strong ever since.

 

i hope not, i cant really afford to replace that, the fuel pres regulator was $130, i need to get it running so i can go to work.

 

i was having similiar troubles with my '96 dakota 3.9, long crank time, loss of power, pinging/backfiring, interemittant, but got worse all of a suddnen.. finally stalled on me two days ago... no pressure on rail, even after priming several times.. banged on fuel tank, got it running enough to barely make it home, sputtering..thought it must be pump, popped a new one in today.. ran fine for a while, then after 30minutes, same thing as you all are describing: loss of power, pinging..

not sure if i can offer anything to help Thager, tho i agree about the pressure test...would be interesting to see what the gauge reads when yours is running.

oh, and as far as the IAC..in the past i have fixed rough idling/stalling at idle by pulling the IAC and cleaning.. seems to get gunky and clog up the tiny gap that needs to remain at its "closed" position....

 

also you can not check your timing with a light. these have to be set with a scanner in reelation to the crank pos. it's called crank cam synch signal. it need to be 0 +- 5 degress. would be a good idea to see if it's setting any codes while your at it.

 

thanks guys , i think im going to tahe it to a shop and see if they can figure it out, when i do get it fixed im going to sell it or trade it in for something newer, this truck is a lemon.