Ok lets know that I am not a mech first. I am a retired bricklayer and not able to do the tests even though I have an old vac gauge that has not been calibrated in 20 years. I do not know where to attach it anyway. If you could let me know I could do it. The miss fire is only at idle that I can tell. If it was at a higher rpm the gas mileage would drop and it's at the top of it's game. It accelerates like a beast for a 2.7 6 cyl in a 4x4.
Mostly happens when on a new tank of gas. If I pull the battery and reset the system it will usually stop the problem but this last time it didn't. It still settle's into a rough idle and sometimes stalls. As for a vac leak if there was one at idle wouldn't it get worse at a higher rpm? I have thrown more money than I care to at the dealers to guess on what is going on. Seems like if I replace the ign coil on the missing cyl it straightens out for a while but that could just be coincidence because I replaced one and it lasted about 1200 miles then started to miss again but cleared up when reset.
Fuel pressure checked by first dealer in Aug. They replaced an injector on #4 cyl. That wasn't the prob. I think that they must of checked fuel pressure before they replaced said weak inj. I will go out and see if I can find the codes on a receipt. From Auto Zone the codes are PO302, PO303, PO430, PO101, PO401. The dealers didn't list any codes on the receipts that they gave. Hope this helps.
Thanks I guess that I never thought that it could be a vacuum leak because all the lines look good. Also I was told by one dealer that the cat conv on the port side is not functioning fully. But wouldn't this cause all the plugs on that side to misfire instead just one or two?
On the old cars (pre 80's) we used to check for vac leaks by spraying the lines with starter fluid. If the rpm went up we found the leak. Can this still be done? or is the starting fluid not safe to use any more? Also can a vac leak be intermittent? Bear with me on these questions. I will go our and wipe the computer then have it rechecked. Is there a way to get back to you after I have that done?
Just wiped the computer and drove to Auto Zone for a reading. Absolutly nothing wrong or no codes showed up. Manager suggested cleaning the throttle body so I did. Idle restored and no more problems. Thanks for the help.