jgull1g

I have 1999 GT 4.6L that has been sitting for over 8 years and only has 45k original miles. After extensive work on replacing many parts I have 1 issue left I am having trouble solving. I am having a rough idle and hesitation when driving. Feels like a misfire but have no codes. I did have codes for po303 and found no compression. Pulled valve cover and the rocker arm was completely off (never seen that before) and the lifter was slightly damaged. replaced lifter and popped the rocker back in. Cleared codes and runs so much better with more horsepower but still feels like there is a misfire somewhere but I am not getting and codes. I checked all injectors and they all seem to pulsing properly and all COP are getting proper volts ( I also changed out 2 and inspected the rest). The plugs are pretty new also. I checked TPS and its working properly and I also checked for vacuum leaks and that's all good. When I unplug MAF and IAC I codes do pop up so I don't think it could be that. Should I replace all the injectors and COP? Hopefully someone has some ideas for troubleshooting because I am stumped. Thanks

jwog666

the cam followers will pop off on startup if the valvetrain is too dry, i suspect that you may have more followers off. is the fuel old? if so that might be your cause. did you run a compression test on all cylinders? if not start there to make sure that all is well, then i suggest removing the old fuel and replacing with new.

WJL

+1 on the old fuel, sitting for 8 years i would replace every filter and fluid.

oxfordgt

Start with a compression test.

Derf00

If there car hasn't been driven in 8 years I would suspect fuel injector varnish or partially plugged fuel injectors (1 or more).

Injectors are cheap enough anyways (even for a matched set) so aside from the obvious mechanical issue that you found, i'd look at the fuel system (filter, lines, and injectors).