My year 2000 XJ8 was driving well. Then the wife parked for 30 minutes. Then she tels me that on start up and pull off the RESTRICTED PERFORMANCE came on and the engine is lumpy at tick over / idle.

Battery disconnect and reconnect then restart led to immediate restricted prfomance on start up.

Then driving the car with "restricted performance" the lumpiness completely disappears above 1500 or 2000 rpm. Car then drives with normal power above tick over revs. It drives normally as long as you don't hit the restriction or try to idle.

I do classic cars... so from an old fashioned point of view it would feel like an engine running on 7 cylinders at idle but then progressively running normally as revs increase. Since this isn't 1970s technology, I know I am out of my depth on diagnosing this !!!

Hopefully someone will tell me that the lumpy tick over progressively clearing as revs increase to 1500 or rpm is a MAF or coil or some new fangled high technology sensor sensing the ozone content of something !

I don't have a code reader (but am thinking of getting one !) Without a code reader... What sounds likely and how can I dagnose... (or do I have to get a code reader )?

Thanks again,

Graham

 

Unless your check engine light comes on, there will be no codes to read.

 

No telling what you got going on but you can read my experience with it and how I found it. http://www.gusglikas.com/AutoRepairR...erformance.htm I hope it helps! Also get a code reader it is a good investment.

 

Thanks everyone. I have read Gus's page and searched through the forum

I hadn't realised this. No engine check light means no codes ??? Is this correct... as it would mean a code reader would be useless for me in this problem ???

If the code reader will help then could someone comment on whether the following looks reasonable and I'll get one
http://cgi.ebay.co.uk/ANY-CAR-DIAGNO...ools_Equipment

If code reader is not going to help then I'll clean the MAF and look for air leaks as per old posts by others.

Does the fatct taht the lumpy / misfire on idle clears to normal running as revs come above idle point to any particular fault that I should check first. (or should I read codes befre taking up anyones time ???

Thanks

Graham

 

Erm - both my upstream O2 sensors went and had to be replaced. Plenty of P1646/1647 codes but NO ECL so I don't think that is true in all circumstances (1999 Sovereign LWB)

Jim

 

With no codes it is a guessing game and I am not sure if the system will hold a code without a check engine light. Assuming that it would I would check for codes and, then check the obvious. It certainly will not be an easy task.