Service Engine Soon light on, Discovery II

[07James]

Prior to light coming on, with smog check coming due, I added CRC Guaranteed To Pass Emissions Test Formula to a full tank of gas (Chevron). Immediately went on 250 mile roundtrip for the day. No problems. Next day, during errands, car hesitated then recovered from stop sign. Following day, starting trip, car stumbled on incline, then 2miles later Check Engine Soon light came on. The next day, local AAMCO testing results: test code P0300 (Random multiple cylinder excess emissions detected). P0308 (Cylinder #8 misfire). P0306 (#6 misfire). P0305 (#5 misfire). P1300 (rapid multiple cylinder misfire detected). P0301 (Cylinder #1 misfire). Shop didn't know what fix would be. Went to leave, vehicle would not start. Towed home, had a beer, was able to start car and reposition in driveway. Disconnected battery overnight. Reconnected. Engine started, light was out. Idling smooth. Test drove, light stayed out until I tried heavy acceleration in passing gear. Light came back on. Looking for diagnostic direction, suspected problem. Mileage 75K.

 

[Disco Mike]

First how many miles on it, when was it last tuned along with new plug wires?
Never take a Rover to a muffler shop, don't you have any good rover shops in your area?
How mechanical are you and how well can you follow directions?

 

[07James]

Hi Mike,
Just under 75,000 miles. New plug wires at 41,000 4yrs ago. Local Rover dealer sketchy. Have more time than money. Am mechanically inclined, generally do my own car repair. Can follow instructions very well. Just need some direction.
Thanks,
James

 

[Disco Mike]

So, you need some help, if you want it, PM me your number and I'll call you tomorrow.