2000 Jimmy missing badly

[nlb250]

4.3 V6 when going into OD seems to miss slightly and little power. Engine light comes and but will go out after is parked for a while. Runs fine at low speeds only problem is when in OD. Has just started severe miss and feels like it is running on 4 cylinders. Haven't started repairs yet but did replace Ignition sensor and catalytic converter in the last 2weeks. Don't want to waste time and money so would appreciate your diagnostic input.

[Cantolina]

Originally Posted by nlb250

4.3 V6 when going into OD seems to miss slightly and little power. Engine light comes and but will go out after is parked for a while. Runs fine at low speeds only problem is when in OD. Has just started severe miss and feels like it is running on 4 cylinders. Haven't started repairs yet but did replace Ignition sensor and catalytic converter in the last 2weeks. Don't want to waste time and money so would appreciate your diagnostic input.

It would help if you bought a cheap code reader from an auto parts store and read the codes....

[Darren509]

Check your fuel pressure with key on, and also how many PSI it drops 5min after key is turned off. Pull the plugs and see if any are fouled ? Also how long since the last tune up and also what brand of plugs cap and rotor are you using..

[nlb250]

Had the compression tested and low and behold the #3 cylinder has "0" PSi and # 5 has "110". So engine is being broken down as we type and I will update you to the findings when the cheque book is empty.