I have an 00 Monte Carlo ss with an L67 and 4t65ehd swap. I have a decent amount of zzp mods on it. Starting this season once it’s warm the car has a rough idle, dropping from 700 down to 200 up to 1000. I replaced the iac, tps, maf, o2 sensors, crank shaft position sensor, and icm. I don’t have codes for the misfires. I have codes for high voltage and o2 codes. Any idea?

 

Did you replace the MAF with a new one or used from a junkyard??

 

Has the car run with these mods and this tune before without all of these codes?

What are you doing for a tune?

2 of these codes are PCM related. Where the car isn't receiving the signal it wants to receive. Do you have a spare PCM? Have you checked all of the wiring to the PCM?

 

I have a zzp tune. All these problems started after I re did my boost bypass. Zzp didn’t set up my computer to use it so I had no boost. Once I disconnected it and re ran the vacuum this issue started
. I was never able to get the o2 codes off last year.

 

Here is my mods list

 

Well just throwing this out there.. I had multiple misfires from a dirty MAF.. The MAFs in these cars are VERY sensitive and your having a FWI adds to the chance that this is your problem.. Also, this isnt a problem you can check by unhooking it either..