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  #31  
Old June 23rd, 2011, 11:19
bigdaddyjlove bigdaddyjlove is offline
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Re: Chasing the root cause of heat soak (2001 XJ)

I have a '88XJ, '96XJ, '98TJ, and had a '98XJ - NO heat soak problems

I have a '01, always been in GA and came with pre-cats had serious heat soak issue last year. Ditched the pre-cats - no more problems.

Its the the pre-cats, no question in my mind

Last edited by bigdaddyjlove; June 23rd, 2011 at 11:23.
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  #32  
Old June 23rd, 2011, 11:25
Redsnake Redsnake is offline
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Re: Chasing the root cause of heat soak (2001 XJ)

Quote:
Originally Posted by bigdaddyjlove View Post

I have a '01, always been in GA and came with pre-cats had serious heat soak issue last year. Ditched the pre-cats - no more problems.

Its the the pre-cats, no question in my mind
Care to share the details? I'm interested in this.

I've had a stupid Check Engine P0432 code since I picked up my '01 Used about 7 months back. I'm not convinced the Pre-Cats are bad... but I don't want to spend the money to replace those when perhaps I could just get rid of them all together. Guess I'd have to swap out the PCM or something to compensate for those O2 sensors.
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  #33  
Old June 23rd, 2011, 11:39
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DrMoab DrMoab is offline
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Thread closing nazi's to attack in 3....2....1....
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  #34  
Old June 23rd, 2011, 12:10
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Re: Chasing the root cause of heat soak (2001 XJ)

Yup.

doesn't want to get in deep ca-ca with Big Brother... (It's understandable that they just want to legally protect themselves).
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  #35  
Old June 23rd, 2011, 12:54
bigdaddyjlove bigdaddyjlove is offline
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Re: Chasing the root cause of heat soak (2001 XJ)

Off road only?

And, I still run the federally mandated catalytic onverter downstream. Its been through the emissions process and it is well within spec for the year and vehicle. The pre-cats only help in initial startup
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  #36  
Old June 23rd, 2011, 12:57
Redsnake Redsnake is offline
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Re: Chasing the root cause of heat soak (2001 XJ)

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Originally Posted by bigdaddyjlove View Post
Off road only?

And, I still run the federally mandated catalytic onverter downstream. Its been through the emissions process and it is well within spec for the year and vehicle. The pre-cats only help in initial startup
Agreed ... Offroad only.

I'd still be running the downstream converter either way. PM me info if you'd like... I'm interested in knowing the ins-outs of doing something like this on my '01.
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  #37  
Old June 23rd, 2011, 13:18
anthrax323 anthrax323 is offline
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Re: Chasing the root cause of heat soak (2001 XJ)

Thanks guys - please keep that whole topic to PMs not only due to the questionable nature of it, but also because it's not what this thread is about (FYI: a thread of mine discussed this very topic not too long ago, so look up my history).

Do we have any chemists in the house that can better explain the relationship between gasoline pressure at operating temps vs. cool? I'm really curious as to whether or not my fuel rail pressure tests say anything conclusive about the health of my injectors.
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  #38  
Old June 23rd, 2011, 13:22
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EMSJEEP EMSJEEP is offline
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Re: Chasing the root cause of heat soak (2001 XJ)

The pre-cats are an issue, but, IIRC, my 01 just started doing this at some point. Off the lot it was fine. So, root cause and all...

In the abstract it is hard to comment on the pressure/temp issue, as it involves alot of variables. Given a space of fixed volume though pressure varies directly with temperature, especially if you are talking about a liquid that can enter a vapor state.

Pressure would decrease with temperature, but you have no direct way of measuring temperature, or, without lab tests, you don't know how much heat it should shed and how fast in the complex system it is in...all you could do is try to keep temperature at a constant to try to eliminate it as a variable.

You don't know volume, you can't determine fuel temp in the lines reliably...all you can measure is pressure...you need to fix another variable, and volume (ie. a leak) is essentially the question, so you need to fix (or measure and determine the normal behavior of gasoline) temperature.

Last edited by EMSJEEP; June 23rd, 2011 at 13:31.
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  #39  
Old June 23rd, 2011, 13:24
anthrax323 anthrax323 is offline
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Re: Chasing the root cause of heat soak (2001 XJ)

Quote:
Originally Posted by EMSJEEP View Post
The pre-cats are an issue, but, IIRC, my 01 just started doing this at some point. Off the lot it was fine. So, root cause and all...
Agreed. Something degrades or changes about the affected XJs over time, as few seem to experience it from day one. Which is exactly why I'm hell-bent on determining the true root cause (Chrysler's response of installing an insulator sleeve on injector #3 was utter BS, IMO).
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  #40  
Old June 24th, 2011, 05:42
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Talyn Talyn is offline
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Re: Chasing the root cause of heat soak (2001 XJ)

One thought I had was the cast iron exhaust manifolds are holding more heat and then cooking the injectors after shut down.
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  #41  
Old June 24th, 2011, 09:22
O-Gauge Steamer O-Gauge Steamer is offline
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Re: Chasing the root cause of heat soak (2001 XJ)

You would think that a set of stainless steel headers would dissipate the heat faster than the cast iron due to the thickness of the material. How do you feel about header wrap?
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  #42  
Old June 24th, 2011, 09:41
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Re: Chasing the root cause of heat soak (2001 XJ)

That is my thought on tube headers as well... they may help. Headed wrap would help but would eat the manifold/headers. Most header warranties are void of header wrap is used.
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  #43  
Old June 24th, 2011, 10:58
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BlueCuda BlueCuda is offline
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Re: Chasing the root cause of heat soak (2001 XJ)

So what does the heat soak condition consist of? Hard starting or is there more involved?

My XJ has a problem where it picks up a miss on occasion. What will usually always cause the miss is wheeling. I can be wheeling and it be 40* outside and have this problem. After bieng on the trail if I let it idle of if I shut it off I will have a dead cylinder. It will ALMOST never do this on the road. I let it idle in my driveway yesterday with the AC on for almost 20 minutes, it was 101 outside. The miss did not pop up, but take the concrete out from under it and it would have been a problem LOL.

I need to add some hood vents and go from there I guess?
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  #44  
Old June 25th, 2011, 06:56
O-Gauge Steamer O-Gauge Steamer is offline
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Re: Chasing the root cause of heat soak (2001 XJ)

Basically, the fuel boils in the fuel rail. This extra pressure drives the fuel back to the tank through the notoriously bad check valves. Creates a hard start rough running condition until fresh (cool) fuel arrives to save the day.
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  #45  
Old June 25th, 2011, 15:59
anthrax323 anthrax323 is offline
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Re: Chasing the root cause of heat soak (2001 XJ)

Quote:
Originally Posted by o-gauge-steamer View Post
Basically, the fuel boils in the fuel rail. This extra pressure drives the fuel back to the tank through the notoriously bad check valves. Creates a hard start rough running condition until fresh (cool) fuel arrives to save the day.
That is a beautifully simple way to explain it - I need to remember that. I had to explain it to a lady friend of mine a short while ago (was doing her brakes and needed to make a run to Advance, where it occurred) and, well... I really should've just saved my breath.
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