misfire problem HELP!

[DarksideGA]

I have a 99 se 3.4 and it seems when the engine bay is fully saturated with heat and im cruising along between 1200 and 1900 rpm the engine will have slight random misfires, and it also does it when there are grade changes in the road, i.e. when the road is sloping upwards, it will only misfire once when i start climbing the hills and thats when the load is placed on the engine at the bottom of the hill. wtf is going on?? i checked the plugs replaced the wires and its sitll doing it. has anyone else had a problem like this with their 3400? if so and u found the problem let me know, or if you have any other knowledge about this problem. thanks in advance!!!

[RussGAGT]

Hey, I am curious if you ever found out anything about this problem...I just swapped a 3400 in my car and had everything working fine...but now i have a misfire on the #5 cylinder, I changed plugs, wires, coil packs.....I am boggled unless there is a fuel problem

[Danmuzicman]

id guess something wrong with a sensor in the timing system. knock sensor perhaps, sensing knock and retarding to much.

[RussGAGT]

how common is a problem like that?

[gran_dam98]

thats really wierd russ.. i have the same problem p0305 is the engine code.. cylinder 5 misfire.. what the hell

[RussGAGT]

when did you start having the problem?

[gran_dam98]

Less than a week ago.. the SES light was blinking, I shut the car off , it went away, day later it started blinking and i let it go this time then the SES light went solid...
i thought it was bad gas.. but it's kind of wierd that we are both having the same misfire happening

[RussGAGT]

well, i am having my car checked out at a shop on friday to better determine the problem, then I am going to attack it

[gran_dam98]

let me know what happens

[RussGAGT]

well, misfire on #5 cylinder was caused by a #5 injector which was stuck open, I changed the injector and it is working wonderfully, they also told me that I had a few vac leaks on the upper plenum, so I changed uim gasket and tb gasket....I am still however, having a few idle issues. I think I still have a vac. leak somewhere

[gran_dam98]

how much $$$ did that run ya to fix.. i'd be willing to bet I have the same problem, which would be really wierd..

[RussGAGT]

well, the shop would have charged me 350 parts and labor, I went to autozone and picked up the parts for 150 bux or so, that was including an upper intake gasket and a tb gasket, the injector was around 75 bux...you can find them cheaper, but it got the job done

[3100GAGT]

i had a misfire on cyl 3 but that was because my plug wire was just chilling on the plug so i poped it back on and it ran fine.