I just did a motor swap in my car 347,11.8:1,g5x2 112lsa,ported 853's.... we fired it up last night, started first shot but there seems to be a misfire, the SES light flashed when the car ran but when I scanned it and nothing was stored. There are brand new ngk tr55's and taylor wires, Its hard to hear the mis at idle but once you get into the throttle you can, also the primary tubes on cylinders 2,7 dont get hot like the others only warm, both cylinders are getting fuel and spark...is it just that this cam has so much more duration then the stock cam and the computer doesnt know the difference?

 

did you have it tuned yet?

Also make sure the plugs arent cracked and all your wiresare on tight, 2 clicks

 

Check the plugs for a cracked one.

 

Things that cause SES misfire codes:

1 plugs
2 wires
3 coils
4 injectors
5 loss of compression


I'd definitely tune it asap

 

it has a tune for a big dry shot, full bolt on, 42# injectors...I just put in brand new tr55's and taylor wires all check out ok...the two problem cylinders have spark and fuel
also after a minute the idle started to climb to about 1200...I'm going to check for a vac leak later

 

Contaminated 02 sensors during the engine swap? Coolant really affects them. You should make sure that the problem is not a base motor problem before you dive into electrionic devices. Hope this helps!

 

the headers were pulled off and put in a box, the o2's are clean and pretty much brand new....I checked everything over tonight and #7 is now firing with the new plug wires but #2 still nothing..i pulled the plug and it seems to getting fuel in that cylinder and it has spark but the plug is perfectly clean...I'm gonna swap injectors around to be sure

 

check that #2 coil and connecting wires/plug wire.

 

I pulled the #2 plug and its getting spark when cranked over, smells like fuel but is clean...my head hurts trying to figure this out