so my car has a bit of low compression on the rear rotor, AND the timing cannot be set but I'm sure it's somewhere near where it should be (the marks on the pully have been removed from rust and stuff)
The car runs good but sometimes at around 2500rpm at light throttle let's say in 5th gear just trying to slowly reach highway speed I will hear a few events of what sounds like pop corn poping in a tin can.. I let off, then get back in it and it does not happen again, then maybe a few minutes later it will happen again, or it just wont happen for a few days.
it's a S5 TII, my buddy (Terrh on here) suggested that the trailing coil could be dying and firing randomly sometimes.

just looking for some more opinions.

 

Couple of things to consider. First, find the timing marks on the pulley, and mark them with a paint stick. After that, check the timing! It almost sounds like the timing is too advanced, and when under heavy load, is pinging.

Second, check, check and recheck your plug wires for the trailing, making sure T1 goes to the front rotor and T2 goes to the rear rotor.

 

yeah for sure i would pull off the pulley, clean it up and repaint the marks and time the motor. nothing will kill that engine faster than detonation.

 

man i've seen motors blow from bad timing marks or mismatched pulley/hub combos. it sounds like you need a rebuild already, why don't you pull the motor now before you drastically increase the cost by throwing an apex seal?

 

it already lasted a year like this, I just need it to go a few more months.
Dare I say there is a LS1 waiting to go in.. but it's my DD until the weather warms up.

I'll check the pully again and clean it to see if I can find the correct timing marks.. I never changed the pully or set the timing.. once the distributor came loose and turned it's self, I just set it back to where it was before.

 

Hmmm... well, possibly you have some carbon build up now, and with the timing not quite right, could be leading to the pinging.

You *should* be able to see indents on the pulley, where the marks should be, even if the marks are gone. If you cannot find anything to indicate marks, there are other ways we can go about this.

 

ok, so I found the marks on the pully after a bit of cleaning, then I followed the directions here
https://www.rx7club.com/2nd-generation-specific-1986-1992-17/another-timing-thread-868482/
to check if the timing is set correctly and the tooth is lined up perfectly cutting through the edge of reluctor, someone actoually marked the tooth and edge of the reluctor with paint and they match up perfectly.
I removed the plugs and cleaned them, there was a bit of a buildup.

but the detonation still happens around 2400-3000rpm at light throttle (like 10-20%)

from the looks of the plugs, the front rotor plugs were a light brown, and the rears were dark.. this could mean that it's running a bit lean. The injectors could be plugged I did have a rust in the tank issue from when the car sat before I bought it, the fuel filter and pump sock were so clogged both actually burst from the pressure (suction on the fuel sock)

AND I believe my TPS may be out of adjustment, at low throttle at slow speeds in 1'st the car will buck horribly.