i have a question, i am working on a 2000 XKR convertible, i originally had codes p0300,p0301-308, p1316, p1000 and i RESTRICTED PERFORMANCE LIGHT. so i read changing out all the coils, so i spent 1000+ on 8 new coils and plugs. now RESTRICTED PERFORMANCE is intermittent ive checked the MAF, my STFT is weird when nothing on the dash is reads ok but when RESTRICTED PERFORMANCE comes on it goes to 0.0 flat, no ups or downs and if im at a stop and the RP light comes on STFT goes to -25%!!!! what does all this mean help me please lol, thanks

 

One thing to check is the intercooler aux. coolant pump. Check the fuse on the pump circuit ---it's located in the engine compartment on the passenger side near the firewall. I don't remember the fuse # but you can find it in the owners manual. I would get RP on occasion because my I/C pump wasn't working.

 

Another possiblity is a clogged fuel filter, or one of your two fuel pump may be bad. Checking fuel pressure might be a good start.

 

well i checked all fuses, they all are intact, how would i determine fuel pump? it doesnt drop pressure and have a hard start. i cannot figure why its happening, it runs perfect, until i try to go over 2900 RPMs. im at a loss

 

Most likely you have a intake leek some place. Check the underside of the bellows "flex part" on the intake tube. This is common to have cracks due to heat.

-25% is enriching the fuel to compensate for the extra un-metered air getting in.