I have a 1994 Camaro with a 3.4 engine my issue is one day I got in it to go to town when i tried to start it it began popping and snapping like it was way out of time.I thought good grief yet another problem!
So I broke out the Solus Ultra and plugged er in..... no codes! So I figured well lets start with the maintenance since I had not had the car very long and bought it from a buy here pay here lot and I have no background on the car so I bought new plugs and wires, fuel filter and air filter. I installed everything and still same thing. I then replaced all 3 coils and the module.... no change....well actually it did start for a hot second then died I figured well the timing chain must have went out so I pulled the cover and it was spot on it was a tad sloppy so i replaced it as well then put it back together still same popping and backfiring!!!!!!!! Ok so just for the record Im 54 yrs old and have been a tech most of my life and have seen some crazy things on cars and trucks and for the most part have over come them, that being said I've had occasion where sensors go bad and computers not picking up on it and beings this car is that stupid OBD 1.5 junk I suspected just that so I replaced both crank sensors and the cam sensor as well......same deal!!!!!! Next I replaced the PCM and of course no change.
So one sunday Im standing there scratching my head wondering why in all my years I've figured out every dang no start car and/or truck I've ever worked on and here I sit with my own dang car whopping my ***!!!
So I reached over and unplugged the cam sensor, why? well because it just so happens I had a Dodge Neon at my shop that would take forever to start with the cam sensor plugged in, unplugged it would fire right up....well that car was losing its 5 volt reference at the cam sensor (showed 2.36 volts on my fluke) and after unplugging the entire harness it turn out to be a bad input speed sensor on the freaking transmission!!! Once it was replaced the car was fine, now what the hell does a transmission sensor have to do with an engine senor? You'd have to ask these brilliant engineers that lol...... but thing is that car threw a cam sensor code my car shows no codes.....anyway I unplugged the sucker and it fired up like it had been running all day!!! I could then plug it back in and it would hiccup and continue running but once the car is shut off it goes right back to popping and snapping until its unplugged.
I have been driving with it unplugged for a year now and no codes car runs fine yet it bugs the hell outta me and Id like to solve this mystery.
I recently had to pull the trans because the pump bushing had walked out and pushed the seal out causing it to pour trans fluid out and me being me I rebuilt the trans with all the goodys,while the trans was out I had an opportunity to inspect the wiring harness in back of the engine thus everything was in great shape.
I drove it home tonight after it sitting for a year at my shop, it runs well shifts great but guys Im at a loss on this cam sensor deal.
If there's another post on this that I missed I apologize Im new to this and honestly never have asked for advice on any car, but Im not a know it all just been lucky I guess lol and I figure some of you guys are smarter than I and might can help an old school dude out.

 

i would suspect a short in the wiring or plugin