xk8 rough idle lack of acceleration

[rogerpalin]

Following upper tensioner change and service took car to Yorkshire moors for long weekend. Ran like a rocket never missing a beat, although did get interference on radio (plugs changed at service, coil?) After about 500 miles interference vanished and idle started to get progressively rougher, now kicks up a stink when try to accelerate, although at low throttle/steady revs more or less OK. Hooked up laptop to OBD port, but since is a '96 model not much info. Confirmed MAF sensor is responding OK and no fault codes - oxygen sensors OK. Removed all plugs to see if a coil has packed in, but all a nice dry condition/good colour. Running out of ideas.

[jagtech]

Radio feedback is common if a spark plug or coil is faulty if extreme you may have melted your catalyst (oops expensive) what is you MAF meter reading at idle shoud be 1.5 volts these can give incorrect readings

[rogerpalin]

Thanks jagtech. I don't know what the voltage from the MAF sensor is, I got the raw data from the system and can convert it to a grams per second figure. Do you know what the conversion to/from volts is?
I will try substituting plugs/coils - I have a spare coil - and see if I can sort it. Should be grateful it's not a V12 I suppose!

[rogerpalin]

Have now substituted old plugs on RH bank for new ones. Have noticed old plugs are NGK BKR5EVXA 13, whereas new ones are PFR5G 13E, as per NGK website. Problem is all but solved, just a slight suggestion of uneveness. Hard to believe from state of plugs that this was the problem, could it be the new plugs needed a beefier spark and a coil is slightly down? Have also removed the connector on the MAF sensor when changing plugs, and re-seated it, so this must be another candidate I guess. Now car is driveable again, I am going to put together some software to monitor the MAF sensor reading so I have a benchmark figure, and if the problem recurs I can check for any change.