Missfire

[ekim]

My 4.0 chim has been running a bit flat for about a week now and sounds like its only running on 7 for most of the time, I have changed the plugs and leads and cleaned the dizzy cap and rotor arm (which looked pretty good).
Any one any ideas where to look next

[That Daddy]

How about the plug extenders,try removing them for a short period to see if this removes the misfire,if it does slowly replace them one by one to find the culprit.

[GreenV8S]

See if you can track it down to any one cylinder - the cable tie on the exhaust headers trick is a quick and easy way to do that if you don't have access to an IR thermometer. Then see if the problem moves when you swap all the HT components with a neighbouring cylinder. If not then check whether the injector is working - you'll find you can hear them with a stethoscope, a screwdriver blade will do in a pinch.

[Paul (93 Chim)]

When you have found out which cylinder it is (with the cable-tie or temperature probe) remove the injector mini plug and measure the resistence across the injector terminals, each one should be approx. 16.9 ohms. If the reading is way out or you get an open circuit the injector has died. It's a bit of a game changing them out.

Regards,

Paul.

[ekim]

Tracked it down to one cyl not fireing and one missing every so ofter. looks like its the sparkplug end caps. got a set of 8 on order so fingers crossed.