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Old 02-24-2010, 11:25 AM
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More idle/stalling issue questions

So I had my data logger hooked up when it started acting like it was going to stall. I didn't capture the actual stall last night but I did capture some events where the idle started jumping around.

One thing I noticed is the manifold absolute pressure spiked and the RPMS dropped; a near exact inverse relationship.

However, a few frames before that happened, the Long Term Fuel Trim spiked topped out (flooding the engine?).

Any ideas?

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Old 02-24-2010, 11:38 AM
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Re: More idle/stalling issue questions

I should note that second red line on the top graph is the "relative throttle position" and has the same color as the RPMs. I was trying to see if I could find any patterns in any of the other points captured and should have removed it prior to posting.

RPMs track right along with the MAP until the arrow.
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Old 02-24-2010, 11:48 AM
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Re: More idle/stalling issue questions

so brent, do you have any mods? or is the hemi totally stock? I have never datalogged or even begin to understand the graphs above.......but I am wondering your goal? Are you expecting that someone could examine the graphs and by them determine whats up with your Jeep?

Does it throw any codes?
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Old 02-24-2010, 11:54 AM
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Re: More idle/stalling issue questions

Yah, ive got a cai and also magnaflow exhaust.

My goal... I suppose is to connect with someone with automotive repair/troubleshooting experience to get me pointed in the right direction. Searching the net for the issue pulls up multiple possible causes and I thought that having some more data might get a more accurate diagnosis.

This and to learn along the way. I have always let my dealer take care of my Jeep issues under warranty/extended warranty. This is the first Jeep I've really got my hands dirty with and, honestly, I wish I'd started sooner!

Also, no codes.
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Old 02-24-2010, 12:00 PM
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Re: More idle/stalling issue questions

very good. thanks for explaining. there are some very technical folks here.

a few with a WK and Hemi that could help: tim@NCTSLLC is one for sure. Escape also understands the tuning end rather well.

hopefully there are others I just dont know, that can help.

GL
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Old 02-24-2010, 12:19 PM
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Re: More idle/stalling issue questions

I know these are complicated beasts. But I'm hoping that breaking it down into its smaller parts, to take some of the mystery out of it.

Thanks to this site, I've changed my own oil and filter (yeah, I'm a noob), and did my brakes for the first time. Having been a patron of dealerships in the past for things like this, I was happy to do my brakes and save some $. I digress.

Any help on the stalling issue is much appreciated!
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Old 02-24-2010, 12:29 PM
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Re: More idle/stalling issue questions

I think some people that have had stalling issued have found that a new EGR will cure it. Could be a place to start - I believe it is fairly easy to replace, and only about $60 at the dealer.
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Old 02-24-2010, 12:39 PM
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Re: More idle/stalling issue questions

Brent my very talented mechanic friend said he can take a look at it this weekend (your chart) and make sense of it for you ...

I have emailed him this thread already
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Old 02-24-2010, 12:50 PM
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Re: More idle/stalling issue questions

could be the egr dumped a rich mixture back into the manifold causing the little burp. In reality this is the job of the egr. It helps to burn off the rich mixture before its released into the atmosphere.
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Old 02-24-2010, 05:55 PM
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Re: More idle/stalling issue questions

Quote:
Originally Posted by brent View Post
So I had my data logger hooked up when it started acting like it was going to stall. I didn't capture the actual stall last night but I did capture some events where the idle started jumping around.

One thing I noticed is the manifold absolute pressure spiked and the RPMS dropped; a near exact inverse relationship.

However, a few frames before that happened, the Long Term Fuel Trim spiked topped out (flooding the engine?).

Any ideas?


'One thing I noticed is the manifold absolute pressure spiked and the RPMS dropped; a near exact inverse relationship.

However, a few frames before that happened, the Long Term Fuel Trim spiked topped out (flooding the engine?)."

The engine was trying to recover that's why she jumped around, as for the reason why she's jumping around, no idea at this time.

13% in your fuel trims is not great but it's ok (I'd say this was when it was trying to recover at idle), If you hit 33% your O2 sensors are dead or not plugged in. All the other data looks fine/within spec.

Some questions for you...

Was this at idle?

Closed or open loop?

Is the stalling predictable?

Does it want to stall when you come to a stop or when your stopped and turning the steering wheel?

How many miles, what year Jeep?

Tell us some more about how this exactly happens

Off hand I'd say PCV valve, EGR valve or sparkplugs.
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Old 02-24-2010, 06:10 PM
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Re: More idle/stalling issue questions

Thanks all for the help!

Escape - turning the wheel and coming to a stop. Sometimes I don't even notice it and hit the gas and 'nada'.

Seems to happen more when it's cold. I can start it up and the RPMs are high until it warms up, then it comes down to the ~600s and will eventually start jumping around. I let it get cold again and started it up with the hood up and noticed that something is buzzing from my PCV valve area. Once the buzzing stops, the idle seems solid. So you may be right on with the PCV valve maybe?

It sounds damn near like this one...

Couldn't find much on the PCV valve and what it's supposed to sound like, but it sounds pretty close to this one, and eventually stops the behavior.

Thanks again for all the help!
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Old 02-24-2010, 06:13 PM
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Re: More idle/stalling issue questions

If your PCV is buzzing like that, I'd replace it. It's like a $20 part at the dealer.

How many miles are on your Jeep?
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