Exhaust Pops and Engine Stalls - JKowners.com : Jeep Wrangler JK Forum
 
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post #1 of 6 Old 10-27-2013, 08:57 PM Thread Starter
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Exhaust Pops and Engine Stalls

Lately I have been noticing small "pops" in my exhaust. When the engine is idling, the pops sound like small puffs of air popping near my engine and/or headers. There's no patten to the popping, but they happen fairly frequently. When the rig is in gear and I am driving, the pops result in significant engine cut-out. And at around 4-5k RPM in 3rd gear, my acceleration flat-lines even though I may be only going 55 MPH or so.

Other symptoms...

- On the trail, my engine stalls for (more or less) no reason sometimes. For example, it stalled this weekend when I crawled over a 6" rock right before I crawled up a 5' rock wall without event. After it stalls, I can get the engine to start back up, but it sometimes takes a bit of effort for everything to turn over.

- Occasionally the rig will idle low to the point of almost stalling. This is most noticeable when the engine is idling. And it typically happens when I start the rig up.


Relevant parts of my build:
- 2008 JK fed with 93 octane gas
- 3.8L V6 with RIPP supercharger/header tune
- Stock manual transmission
- RIPP Stage 2 supercharger kit with 10psi pulley
- 180 degree thermostat
- RIPP long tube headers with aftermarket hi-flow cats (x2)
- Flowmaster HP-2 exhaust

No MIL/CEL/idiot light indicator on the dash.

My thoughts on possible root causes:
- One or more bad spark plugs and/or cables
- One or more bad injectors
- Vacuum leak*
- Exhaust leak

*since the engine idles low occasionally (rather than idling high), I am thinking that a vacuum leak is not as likely as the others.


Any idea on what could be causing my problems? If you were me, where would you start with diagnosing the problem?


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post #2 of 6 Old 10-27-2013, 10:19 PM
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hows your fuel pressure when this happens?
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post #3 of 6 Old 10-28-2013, 06:47 AM Thread Starter
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Quote:
Originally Posted by mrmikey32 View Post
hows your fuel pressure when this happens?
I haven't checked my fuel pressure, but that was on the short list of things to check in addition to the four I listed above.


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post #4 of 6 Old 10-28-2013, 12:30 PM
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You have a lot more stuff going on there. Check for exhaust leaks. Popping through the intake is usually a lean condition, popping through the exhaust is usually air being sucked into the exhaust completing combustion -fuel-heat-air. It's called secondary air and unintentional if you have a leak. It also screws up the O2 feedback dependent on where the leak is. Smoke the exhaust if possible. If not preasurize the exhaust with compressed air and spray soapy water around the joints.

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post #5 of 6 Old 10-31-2013, 09:32 PM Thread Starter
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Here's what I know so far: I definitely have a spark plug problem on the driver side of the engine ... two of the three spark plugs on that side light up like crazy when I let the engine idle and shut off all lights in my garage. The spark plug misfire is definitely what's causing the popping. It would also explain the down-idling and engine stalls. I am glad to have found at least one of the root problems.

I have a small amount of condensation collecting where the driver side exhaust and passenger side exhaust converge near my driver side lower control arm mount. (Indicative of a possible exhaust leak.) With the engine idling I couldn't feel any pressurized air leaking out of the exhaust. As a follow up I'll smoke test, pressure test, or soap test that spot on the exhaust to see if i can confirm or rule out a leak. The leak, if there is one, is right near two O2 sensors ... since they aren't throwing codes I wonder how much effort I need to put into testing for a leak.

Tomorrow I'll pick up some new spark plugs, and I might as well replace the wires while I am at it. I was thinking of going with the NGK Iridium IXs ... has anyone run these with a RIPP kit gapped to RIPP's specs (0.032)?


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Last edited by illyb; 10-31-2013 at 09:35 PM.
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post #6 of 6 Old 11-13-2013, 10:25 PM Thread Starter
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A quick update...

I replaced my spark plugs and wires with a set of NGK Iridium plugs and a set of Granatelli Performance wires. Also, I placed some JB Weld on an area of my exhaust I believe had a pinhole leak (the exhaust would collect a small amount of condensation when I fired the rig up). So far I haven't heard any pops in the exhaust, and my idle sounds better. However, I still may have a couple other gremlins to flush out. I'll dig into the issues a bit more this weekend.


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