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https://depts.washington.edu/vehfire/fuels/flashpoint.html
I'll go for a drive and take it's temp.
(Engine experts needed) Chirp, Vibe, Pop (What is Wrong?)
- Thread starter toximus
- Start date
https://depts.washington.edu/vehfire/fuels/flashpoint.html
I'll go for a drive and take it's temp.
Just for kicks if your looking into exhaust temps - does your OBD scanner log cat or EGT temp? As an FYI - the stock PCM software does log cat temp and enriches the fuel mixture at about somewhere about 1500-1700 degrees (don't recall the exact temp), to cool and protect the cat. An excessive temp would also be another indicator of a lean tune condition under boost. An over temp exhaust and subsequent fuel enrichment could also play a role in the rich 10's AFR condition you are eventually seeing. Anecdotally - exhaust temps can get hot enough to ignite unburnt fuel. Back in the day, I had a mustang and exploded Flowmaster as a result of thinking more is better with the accelerator pump and secondaries.
Mine is a 2004 LJ. I only have upstream O2 sensors and stock there was also downstream O2 sensors but no EGT or O2 sensors after the second cat.
Can you guys check your stock 4.0s idling? Does the belt have some characteristics of the belt moving around leading up to the steering pump and the tensioner moving up and down gently? I checked my other TJ (stock 4.0L) and it appears to be making the same movements as my LJ (supercharged 4.0L) when both are idling just much less exaggerated.
Exhaust and cat looks normal. The little metal balls are from when the shop welded a flange to the pipe.
Id be willing to bet by the time the exhaust gets there, its under flash point. On my Rs7, a known tuners downpipes moved the cats too far away from the turbos creating o2 CEL, they couldn't get hot enough and you're talking maybe a foot. I don't think the 4.0 EGTs are higher than the Rs7 TTV8 so couldn't imagine the cat would do much.
I had to remove the skids to wash up after my last wheeling trip anyway. So no worries.
Mine is stable at idle. If I rev the engine the tensioner moves up 1/8-1/4" and that's it.
CobraMarty (boosted 4.0L enthusiast) got back to me about his thoughts:
"I still think it is the bearings or the rotors or sc gears.
Sure no load it spins fine easily and no noise.
When under load and boost and puts the strain and deflection on the sc, things happen. Like the rotor is shifting in the housing or something.
Sounds like the sc needs to come off and be broken down and checked out or even replaced."
"I still think it is the bearings or the rotors or sc gears.
Sure no load it spins fine easily and no noise.
When under load and boost and puts the strain and deflection on the sc, things happen. Like the rotor is shifting in the housing or something.
Sounds like the sc needs to come off and be broken down and checked out or even replaced."
Yes. Well, no. Eh, sort of. They're used GM Eaton M90 superchargers that came off 90s Buicks mainly. They're rebuilt by BoostedTech and the intake is modified to fit the Jeep throttle body.
I've put on 1400 miles on it and I've had the issue since the first day I drove it fast enough.
Armed with knowledge of all of our research (thanks guys! you're all the best!), I called BoostedTech! I will be sending the SC to them to take a look. There will be a 1-2 day turn around time once they receive it.
That is exactly the size of a #8 flat head screw about 3/8" long. Missing one anywhere?
It's not lost if I found it inside the engine.
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