Exhaust popping at idle like if decel.

akirony · Post by **akirony** » Wed Sep 17, 2014 10:52 pm

Okay guys bear with please. 04 full RT swap. I recently had a run in with an improper COP ign setup which caused my pcm to go stupid setting the p0351 over 20 times for about 12mi and misfiring on cyl1-2-4. Junked that and now I'm back on a stock coil. Now since letting it sit for 3 wks I can hear popping from my exhaust tips(snap crackle), as if i was decel engine braking but only at Idle. I read around and some suggested valves staying open as if bent. Others pointed to exhaust back pressure. Has anyone come across this or should I leave it as normal? I thought it couldn't be a valve now. If it is why wasn't it doing the same when I was revving to 8k with the syked tuned almost a yr ago?

Post by **occasional demons** » Thu Sep 18, 2014 7:27 am

Do a compression or leak test. That will tell you if it is a valve, or if you should look elsewhere. Possibly something is still messed up with the coil.

You might have a lash adjuster that is not bleeding off properly, randomly holding a valve just off the seat. That may or may not show up in a compression test.

Depending on how far off the seat it might be, will make a difference with RPM. At idle there is significantly more time for pressure loss than at 2000 rpm.

Is it a steady consistent sound, or just a random pop?

akirony · Post by **akirony** » Thu Sep 18, 2014 10:20 am

It's a consistent random pop if that makes sense. I can hear and feel it while sitting and revving up to 3000rpms until my exhaust drowns out the sound. If I hold the rpms at rest it still pops like a misfire that I can feel.

Post by **occasional demons** » Thu Sep 18, 2014 12:16 pm

how are the plug wires? Possible cross firing situation?

I still say do a compression check, just to eliminate that possibility.

akirony · Post by **akirony** » Thu Sep 18, 2014 8:34 pm

occasional demons wrote:how are the plug wires? Possible cross firing situation?

I still say do a compression check, just to eliminate that possibility.

Plugs and wires are new. Just replaced saturday night. Well I just did a compression check and I'm a little confused on the results.
Cyl 1-165, Cyl 2-175, Cyl 3-175, Cyl 4-150. Had the battery tender hooked up at all times too. As per ALLDATA ( 9. Compression should not be less than 689 kPa (100 psi) and not vary more than 25 percent from cylinder to cylinder. 10. If one or more cylinders have abnormally low compression pressures, repeat the compression test. 11. If the same cylinder or cylinders repeat an abnormally low reading on the second compression test, it could indicate the existence of a problem in the cylinder in question. The recommended compression pressures are to be used only as a guide to diagnosing engine problems. An engine should not be disassembled to determine the cause of low compression unless some malfunction is present.)
So they aren't under 100psi and they're within 25%, but Cyl 4 is lower than the others by a margin. So I'm thinking I'll try seafoaming it or using the MOC induction cleaner we have at work to start somewhere. The MOC is some strong stuff but $30.