need help with exhaust popping at idle.

[DTRUONG9]

when the car(90 tt) is @ idle i will notice a quiet pop from my exhuast(greddy evo) and it is only at idle. the car has no hesitation in higher rpms. i swapped out new plugs and it got better for about a day, then the sound returned. i took it to a reputable shop and they checked ptu and other sensors and found nothing abnormal.I am currently running 740cc nismo injectors that were replaced 5k miles ago, dual intake with selin translator with a jwt chip. is this normal or unsafe to drive.this is my daily and i cannot afford it to crap out on me.

Any help would be appreciated, Thanks

[es.biggs]

Check ignition timing?

[DTRUONG9]

I did, it's at 15 degrees.

[GerryO]

- a "weak" spark at idle, due to a narrow plug gap, fouling, or a weak coil pack or dirty/corroded connector issue?
- an injector with high coil resistance or injector harness connector issue?
- a dirty MAF?
- a CAS issue?

Can you identify the offending cylinder and are you running OEM plugs?

[DTRUONG9]

im currently running new #7 range instead of oem#6 and the reason is that im on 16 psi daily with mods and jwt 550. the noise is only at idle if i tap the gas up to 1k rpm the noise goes away and the car runs and sounds smooth.

I looked at the mafs and did not see any debris on them not even oil from the filters as i thought it might be the case. ill recheck connections but the injectors are brand new nismo 740cc.

i am debating to buy a used COP or a new one to swap around, but if it was a cop issue I should have hesitation and power loss in higher rpms right? iono this mystery is annoying.

I stuck the car on the dyno to see a/f ratio and the car is running a little lean at the bottom, and gets a little bit richer once boost hits. but overall it was around 13s on a/f. i have a jwt tune, and it only started to do this about a week ago, and the car was finished about six months ago from a rebuild.

[Zero to 300]

I have a similar problem with my TT swap, missing/popping at idle, a little rough and then sounds awesome and smooth with a little touch of the accelerator. I checked codes and it popped 11 which is Crank angle sensor circuit, haven't done the work to fix it yet cause i'm pulling the engine to do more work, but i'm assuming dirty maybe loose connector, pins, wires. A/F ratio was fine, checked with the ECU method, looked promising at least.

[DTRUONG9]

I pulled the connection on the cas and saw some corrosion on them and cleaned it, but it did not do anything. I checked the ptu and cop, nothing.
I took it to a shop and the guy is telling me that piston 2 and 6 will miss for a little bit but only at idle.he suggest that my wire harness may have a crack/ corroded wire, but he was not able to find were it is and suggest i replace the whole thing.
And again the popping/missing is only at idle, other then that it drives fine thats what i dont understand. The ecu does not have any codes either.

[93 Z32]

Sounds like an injector going out or bad coil pack.
My exhaust was popping at idle, but when I gave it gas, it cleared up and ran fine. cleaned the iacv and hiac, didn't fix it. Changed coil packs, didn't fix it. Finally found #2 injector was bad. Now it just hums. Sounds the way it should. And while I did the plenum pull to change the injector and fuel rail/plenum insulators, I also did the plenum coolant/vacuum bypass. I suggest if u haven't done that yet, go ahead and do it. And get new vacuum line. Makes for a much quicker and simpler plenum pull. Wouldn't suggest it if u live in the northern states/snow belt

[DTRUONG9]

I hope is not a bad injector because i just bought them 6 months ago and their new style ones, i just changed my coil pack too, iono. every keeps saying CAS and that will be my next thing to check but i hope its not an injector.

[93 Z32]

Did u check the harness itself and make sure ur not dropping voltage to an injector?
Not sure of the exact # it should read, my cousin does all my electric testing.

[93 Z32]

Also, did u check ur coil pack connectors? Mine were bad. I couldn't even pull them off without breaking them cause they were so brittle. I'd go down the road, it a bump, connector would come off. Was constantly havin to pull over cause I was dropping to 4-5 cylinders. Called Z1, got 6 coil pack connectors for about $6 a piece. Fixed my issue. Ran smooth till my #2 injector went out. Then the popping was back.

[DTRUONG9]

It was the CAS the whole time. Shop stuck a new one on and it worked, but now I found a new problem......car wants to stall when in neutral coming to a stop, but it fixes it self. did boost leak and nothing.