Hey guys, just picked up my first is300 over the weekend. I havent had a project since my 2jzgte swap Sc300 3 years ago. So i picked up an 03 Is300 and it came with some goodies. But also came with some problems. Cel is on saying P0037 for a o2 sensor for the cat. which the manifold been replaced with a header megan racing. so thats a no brainer. random cyl missfire on cyl 4,5,6. i pulled plugs 5 and 6 and they looked like brand new denso. still white porcelen. the wires been replaced with NGK. The guy had spare ignition coils i replaced Cyl 6 cuz it had some corrosion where the plug wire goes in. cleared the codes drove around 5 min later P0037 came on and so did the po300 and cyl 4.5.6 missfire.I checked vaccum had 21HG and put a NoiD light on the cyl 6 coil and then on the cyl 6 fuel injector. The Noid light pulses so harrness is good..I sprayed brake cleaner all around the intake and vaccum hoses to see if there was any leaks any nothing. Engine seems to run good most of the time but sometimes idles little rough and you can smell if you were next to the muffler the raw fuel fumes. I think i hear a slight Exhaust manifold leake or down pipe leak which i know can affect the O2 but started to rain so here i am. I notice i have this stupid Volo performace flash thing. and it lit up green. I doubt it works but i wonder if its causing me to have the cyl miss fire. Anyone had problems with Volo and cause miss fire? It soppose to gain fuel mileage and if missfireing is its idea ill rip it out lol.. ANy Input anyone????

 

Have the o2 sensors been replaced? Commom issue on the IS

 

Change New plugs OEM new wires swap coils aroundreplaced 2 O2 sensors removed Volo performance flash P.O.S chip checked for gasket leaks sealed the Maf sensor port still misses only at idle other wise runs like a rape ape and strong enough to beat a type S rsx and a mustang gt. guess im going to change that last o2 sensor and then if not new injectors..