So tired of this problem. Help me please.

[CTS13]

Ok so its been months of diagnosis and i still can't figure out this problem

Engine specs.

Cp pistons stock CR. Compression is good btw.
Eagle rods
JWT S1 Cams. These are heavy cams and i had to shave the bucket holes so the lobes would pass through it.
Stock valves.

Problems:

Crappy idle

Detonation pings from unknown location. What happens is when i rev up the car to about 4k rpm, it goes up fine but when the rpms come down, you can hear couple pings right after you let go of the throttle. Ive done the distributor like 25 times, i just did the timing chain over again cuz i thought maybe i had it wrong the first time but same issue. This is not my first time building an engine but first ka24de ive ever built. Also, when i look down the spark plug hole, i can see wet pistons and does smell a little of fuel.

So my guess would be im running rich. I do have an aftermarket FPR and its set to 40lbs and i kept playing with it to see if that would help but still the same. I cleaned my MAFS, IAC and even adjusted it all the way back and forth and nothing happens.

Recently i was doing research and apparently s13s have a injector resistor pack. What the hell does that do. I have stock injectors running on stock ecu without the resistor pack. Would that cause the problem. Please ayuda cuz idk what else to do. Thanks.

EDIT: just to add that on my compression test, i pulled about 125psi on all cylinders. I thought that was kinda low but consistent. And the number on my ecu is 28. Ther are so many numbers out there, i have no idea which one is for a 91ka24de.

[neverlift]

ecu is the right one..
the backfire on decel is normal, its a pop not a ping..
video?

[CTS13]

you wont hear the ping in a video. And also, its not a backfire, its a predonation happening inside the engine. it pings like you take 2 metal pipes and hit them together.

[neverlift]

like physical metal to metal contact? my bad, by your explanation it really sounds like backfire, all ka's have a pop when you lift. But It should not sound like metal pipes hitting.

IMHO its gotta be timing related if your getting knock with 125psi compression. Thats lower than an sr with miles.. Is the timing set, via fsm(ignition timing)

[CTS13]

I did the timing chain twice thinkin i got it wrong the first time. Ive done the distributor NUMEROUS TIMES. I have a vacuum pull of about 15-17 inches. I just know im running rich. But the quesiton is why does it ping only on engine decel and right after throttle release. It wont ping on the way up.

[CTS13]

And i have a code for knock sensor but only that. No other codes.

[neverlift]

knock codes can wreak havoc on the running of an engine.. Mine played retard until I disabled it via my ecu tune.

video brother! I am still not 100% its not decel pop.

[TheRealNap0le0n]

your compression numbers are super low btw

[CTS13]

I k now what a backfire is and i know what a predetonation knock is. Take a hammer to th side of a cast iron block and thats what it sounds like coming from the engine under decel. You wont hear it out of the exhaust.

I did think my compression is low but its consistant across the board so i didnt concern me. How can it be that low on all 4. Doesnt make too much sense.

[neverlift]

possibly piston slap?
still waiting on a vid, you do realize how many sounds an engine makes, I have a loud knock narrows it down to nothing.

Something is wrong with the motor, 125 is very low for a stock compression ka... I've seen a 8.6:1 sohc bring more.. All 4 being low could be a few things.

[CTS13]

Piston slap was suggested but thats only the case on a cold engine. I think im gonna pull the head and see whats going on.

[CTS13]

I just spent today cleaning up my garage. so tomorow, im gonna warmn it up, do compression test over again and also record the pinging noise for you guys. Now thinkin about it, i think i remember doing the first compression test on a cold motor and the rings gaps are just a tad oversized so warming up might just fix that. hopefully

[neverlift]

why are the gaps oversized?

[CTS13]

why are the gaps oversized?

I have the engine blue print at my other apt. Either way, CP has specific recommended rings gaps depending on how much boost, power, nitrous, etc. So I told the shop, i was planning on running over 25lbs so he decided to make the judgement on that. Ill post up the exact gaps once i get over there tonight.

[CTS13]

ok i have the blueprint. Here are the specs on the ring gaps.

Top Ring: .023-.024
2nd ring: .025
Oil ring: .111

and then also, for some reason the print has another set of specs for gaps which im confused on and this set says

top: .040
2nd: .048

Maybe the first one is stock specs and the second set is the machined specs

more info on the block.
Piston to bore clearance is .004 which im sure once heated up expands to .001 so i wouldnt think piston slap would be the ping we hear.

[neverlift]

vid

[CTS13]

vid

sorry, i went to start the car and a fuel line burst. Wont be able to get to it till monday agin.