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Old 02-06-2006, 12:11 AM   #1
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Default KR issues at mid throttle, TC locked; New Scans 4-7

I mentioned this in my other post, but I think it'* worthy of its own thread.

I'm getting KR while cruising with the TC locked, usually when applying light throttle to go up an incline. I saw up to 7 degrees today on the interstate, and Doug and I saw 9 degrees yesterday. Not sure if it'* false or not, because we suspect something might be rattling on the under the car when the exhaust is 'bellowing' at low RPM under load.

It does NOT occur at WOT. 95naSTA provided a theory that the mid revs are experiencing hotter combustion chamber temps because of the disabled EGR, causing KR at those RPMs. It makes sense, but I would like to know if anybody else has another angle on the problem. I want to cover all my bases.
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Old 02-06-2006, 12:16 AM   #2
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You've covered your two options, but it takes something alot closer to the sensors to rattle and cause false KR.

Your EGR is a prime suspect. I can think of about 3 cars on this forum that can benefit from deleting the EGR, and yours and mine aren't two of them. The EGR serves a big purpose, and it'* not all about emissions.

Hook it back up and run another scan.
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Old 02-06-2006, 12:39 AM   #3
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I would take that spare L36 LIM you mentioned before, drill and tap the coolant ports, and port it.
OR get reprogramed with less midrange timing.
OR get headers.
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Old 02-06-2006, 12:41 AM   #4
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Hmmm....I'd undo what looks to be the most likely CAUSE that you changed to verify it before modifying other parts and throwing more variables into the mix.

You need to understand the problem fully before moving on. Or you'll never REALLY solve it.
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Old 02-06-2006, 01:14 AM   #5
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Well, the EGR is permanently unhooked. We disconnected it from the rear manifold and filled in the hole with a welder, so hooking it up again would take a new manifold.

I unhooked it for two reasons. First, I have always been under the impression that an EGR system robs your engine of potential power if you tune it correctly. Secondly, and more importantly, I never wanted to deal with a failed UIM again. My motor will not melt the composite upper in its current configuration.

So what do you guys suggest? It'* pretty much guaranteed that I'll be getting a custom tune in a few weeks, so I can have the PCM tweaked to account for hotter combustion temps if necessary. Is there anything else you would suggest? Would you say this is not false KR caused by a rattling heat shield?

Set me straight where my thinking is screwy .
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Old 02-06-2006, 01:37 AM   #6
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A rattling heat shield is too far away from your sensors to cause false knock.

EGR'* should only be deleted for intercooler use. They do NOT rob power from you. They CREATE power by efficiently managing combustion temps. It'* only EXTREME builds that should delete them. And there are (as I mentioned) perhaps 3 cars here that need the EGR deleted.

Your hotter exhaust temps are compounded by your compression ratio. Your spark plugs, exhaust valves, and O2 sensor (not to mention your Cat) will suffer over time. You've opened up a whole new mess of potential problems that will need constant care and maintenance. And the benefits are neglible, if they exist at all.

EGR'* help prevent KR. And help solve alot of other issues as well. They are also very efficiently managed by the PCM.

The very fact that you have KR at odd throttle positions tells me you shouldn't have ditched it.

What power do you hope to gain from it'* loss? Where did you get this information?
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Old 02-06-2006, 01:51 AM   #7
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The PCM opertaes the EGR in gear under light to moderate load, varying the duty cycle depending on the engine load.. Not sure what it does at WOT if anthing...

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Old 02-06-2006, 02:20 AM   #8
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Quote:
Originally Posted by jr's3800
The PCM opertaes the EGR in gear under light to moderate load, varying the duty cycle depending on the engine load.. Not sure what it does at WOT if anthing...
I'm pretty sure it'* closed WOT.
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Old 02-06-2006, 02:48 AM   #9
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Quote:
Originally Posted by willwren
What power do you hope to gain from it'* loss? Where did you get this information?
I wasn't expecting gains from deleting it..... however, I was under the impression that an EGR system limits the power you can potentially make. Maybe it only applies to older, less efficient systems.

So I guess I didn't make it very well-known that I was planning to do this as part of the cam/heads job? Nobody gave me this side of the story before I disabled the EGR. Everything I read seemed to indicate it really wasn't a big deal, but it'* a bit late for that now. I need honest opinions on what I should do at this point, and I'm open to the option of getting a different rear manifold if it'* the smart thing to do.

Sorry if I seem a little irritated, but it'* because I am. I thought I was doing myself a favor disabling the EGR, and now I'll need to spend more money and time to fix my mistake. Live and learn, I guess.
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Old 02-06-2006, 02:48 AM   #10
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The EGR is not open at WOT. I do agree that you will really not gain anything from deleting it but after seeing how much of a mess it makes to the upper half of your motor and how many failed UIM it has caused it is worth it to delete it. I don't think that it is the EGR at all anyways, you are running a cam and higher compression. How do your fuel trims look? You need a tune... No cam is a 'slap it in and go' setup.
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