All,
Hope you can help. My 90 YJ with a 4.2 six has just developed a periodic power loss problem when cruising at highway speeds and having to climb a slight hill. It seems to happen in 4th gear, RPMs seems to remain steady at
200 RPMs. It seems like it is fuel starved but I really cannot tell.The Jeep has 143,000 miles. Here is what I have done/checked.
1) New factory distributor about 6 months ago (4K miles ago). 2) Plugs cap and rotor 10 months ago (10K miles ago). 3) Just tested resistance on all ignition wires - all ok. 4) Just put in new fuel filter after problem developed. 5) Tested fuel pump pressure - 7 PSI, with engine cranking (not running - seems a bit high). Factory service manual calls for 4-5 PSI. 6) Tested fuel pump capacity - 20 ounces in 30 seconds. Factory service manual says at least 16 ounces. 7) Problem will randomly happen with fuel cap removed. 8) Problem will randomly happen with vacuum hose to EGR valve disconnected and plugged. 9) Problem will randomly happen with vacuum hose from back of carb to charcoal canister purge valve disconnected and plugged. 10) 200 miles ago, I rebuilt the carb and set the float level and other setting to specs. It was running great up until this week. 11) All gauges read normal when it is acting up. 12) Problem does not happen at low speeds around time. 13) About 6 months ago, I recall once or twice experiencing similar symptoms for a few seconds, but much less noticable. There after never saw it again until this week (but more severe now).I am beginning to think that it may be the ignition control module or possibly a catalytic converter going bad. How long do timing chains last on the 4.2 six? Do any of you other suggestions?
Thanks.
mpv