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  #121  
Old September 14th, 2016, 17:13
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Re: Overheat at Idle

I goofed on the above....it should read "B1S2, B1S1, B2S2, B2S1 from left to right."

Obviously the O2's with more carbon are pre-cat.
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  #122  
Old September 15th, 2016, 19:02
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Re: Overheat at Idle

You can't tell the condition of an O2 by a visual inspection, unless it's obviously broken. I apologize if you've mentioned this already, but have you gotten an O2 sensor code? If not, they are more than likely fine. As per the other thread, I highly doubt the injectors are the problem.

In my experience, a lot of idle over heating conditions are simply due to an old A/C condenser blocking air flow. Road debris will smash up the fins which substantially blocks air flow. At speed it isn't an issue because of the additional air pressure in front of the cores, but just sitting there any small blockage can cause a substantial decrease in flow. I've fixed two cars idle overheating problems by simply pulling or replacing the condenser. Do you have a picture of your core and the fans you've added?

I would also definitely check the cats out as well if you haven't already done so. If you can get them red hot simply by holding the throttle open for less than 30 seconds, you may have an issue.
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  #123  
Old September 16th, 2016, 19:05
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Re: Overheat at Idle

Quote:
Originally Posted by Boostwerks.com View Post
You can't tell the condition of an O2 by a visual inspection, unless it's obviously broken. I apologize if you've mentioned this already, but have you gotten an O2 sensor code? If not, they are more than likely fine. As per the other thread, I highly doubt the injectors are the problem.

In my experience, a lot of idle over heating conditions are simply due to an old A/C condenser blocking air flow. Road debris will smash up the fins which substantially blocks air flow. At speed it isn't an issue because of the additional air pressure in front of the cores, but just sitting there any small blockage can cause a substantial decrease in flow. I've fixed two cars idle overheating problems by simply pulling or replacing the condenser. Do you have a picture of your core and the fans you've added?

I would also definitely check the cats out as well if you haven't already done so. If you can get them red hot simply by holding the throttle open for less than 30 seconds, you may have an issue.
No CEL for O2's.

I might just discharge the A/C system and remove the condensor temporarily since we're entering fall here in Ohio. I have no need for it and could tell if that's the issue, but looking at it head on it doesn't seem so bad. Fins look OK to me.

When you say run throttle open for 30s to get the precats warm, are you saying WOT or just 2-3k rpms?

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  #124  
Old September 16th, 2016, 19:13
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Re: Overheat at Idle

Try 3500 rpm for 30 seconds in the dark at night.
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  #125  
Old September 19th, 2016, 20:57
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Overheat at Idle

Something I never brought up until now, but thinking about it I wonder if there is any impact.

Back in June, roughly the time this issue first started appearing (at least that I can remember) I had to replace my flexplate. In doing so I cut the entire exhaust system off pre-cat & back. After the flexplate was finished, I took a new muffler and rear Cat Converter to the shop and had them fab up the mid pipe and tail pipe to get back together.

The PO had the rear cat cut out.
I put it back in.

I don't know how long the Jeep operated without a rear cat, but would putting a brand new one of these in a system with the stock (worn, 175k miles) pre-cats have any negative effect on system back-pressure or O2 readings?


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  #126  
Old January 24th, 2017, 10:56
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Overheat at Idle

So it's been a chilly one this fall/winter in Ohio. Since October, it's been cold enough to mask any overheating/hot running temperature issues. But, I know this problem will soon resurface again here in early spring.

Going through all of my shenanigans once more, I recognize that my exhaust system is still a likely culprit. The pre-cats are still stock (180k miles). Overheating coupled with the loss of power or sluggish power high in the RPM band leads me to believe they could be clogged or in need of quick replacement.

So today, after running around the block a few times, I used my IR Gun to measure the pre-cat temps.

1. I measured the unit at the upper O2 sensors and right around the welds prior to entering catalytic chamber. Temps ~675-700F.

2. I then measured at the lower O2 sensors and right around the weld after the exhaust gases leave the chamber. Temps ~400-500F.

My understanding is that even for pre-cats, the exhaust gases leaving the converter should always be hotter than those entering correct?

I plan to use my vacuum gauge at the intake port later this week to test vacuum at idle and 2500k rpms for any irregularities, but I believe that just based solely on the temp readings above it is indicating my pre-cats are defective and/or clogged.

Anyone else agree with this logic?

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  #127  
Old January 24th, 2017, 16:32
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Re: Overheat at Idle

Sounds like you may be onto something there.
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