I know I have the original opti on there 130,000 miles and still running mid 8s but this weekend 2 i have got a ses light for a po300 all ignition is new msd coilplugs wires are about 1 year old msd the car runs fine no hesitation can anybody help me.

 

oh it does not flash just stays on steady..

 

Reset PCM and see if it returns. P0300 is a random misfire. That means even the computer cannot pinpoint where it came from.

 

I found number plug 8 loose a little and i will see if that is it but sat it turned on then it did again today same code....so if it comes on again whats next if it cones on agin whats next...shoebox remember I have original opti on car....

 

ONE plug or plug wire can cause the P0300. I know, cause it happened to me. I'd check all wires and plugs before buying an opti. It is possible the next time the SES comes on that the PCM will pinpoint the cylinder.

 

Thanks MoparMan the plug was really loose. So you have had the same prob, so let me ask you this why could it not detect which cylinder.... it was coming from

 

I had a wire burned in two, and my car would only miss when it was raining or high humidity. The miss would stop once the car warmed up. As to why the pcm does not always pinpoint the cylinder, I don't know. One morning the car was barely missing, and the SES came on and it gave a cylinder number, so I knew where to look. If you have a scan tool that can read individual cylinder misfires, you could probably look at that. I'm gonna upgrade my scan tool to that option.

 

will a cpsensor make it throw a misfire

 

Ok shoebox anybody I got multiple cyl misfire tonight all plugs are tight and checked no arching, will a cps cause a misfire. I was also was leaning torwards the ignition module right above the coil, could that be also causing a misfire.... I in the past had gotten cpsensor code because it rained and it got wet but could the cps be bad also , and causing my car for the code 300 or is it my opti. Now lets say Plugs my plugs are couple of months old bosch platniums regulars, could it be plugs...thanks shoebox anybody..

 

replaced cps came back tonight I think its time for my opti

 

Before I replaced the opti, I'd take the coil and IM and have them tested. Also the coil wire.

 

The multiple cyl misfire usually means more than one cyl is missing if you could get ahold of a scan tool that would show you a misfire table that would be very helpful, remember nobody here has seen the car so diagnostics are a little harder. I have never known a cps to cause a p0300, although i have never had a set of bosch plugs that have not missed. I've tried three sets one on my car one on my sisters a 98 monte carlo and one set on my dads truck an 01 dodge dakota all vehicles started missing not long after the plugs were installed. i also saw this problem often at the independent shop I used to work at. Thats where I would start hands down put acdelco in it, maybe autolite ive never had trouble out of them but i run ac. I would try my hardest to eliminate everything before going to opti they're expensive and not real fun to change.

 

This time its says cpsensor out of range I just replaced it last week. I think Its the rain everytime it rains it throws this code its the harness. I have changed plugs since then a/c delcos to be exact no misfires...