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Lt1 Closed Loop issues

Old 08-14-2018, 01:56 PM
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Default Lt1 Closed Loop issues

So, I'm having a new issue that is leaving me scratching my head. I haven't had time to do a full inspection checking for burnt plug wires or harness. All of a sudden my car has a lack of power, shakes/shudders at WOT and backfires at low rpms. Went through the ignition system and ICM tested bad. Replaced it but didnt fix the issue. 02 on the scan tool is within proper V range although I'm wondering if it's a false positive. FP at wot is good, hooked a FP Guage up and taped it to the window. Car pulls like a raped ape in open loop with no issues. Wondering if anyone else has experienced the same issue. Freaking just dont have the time to do a full diagnostics right now. Barley even have enough time to enjoy the car. Mods in my sig

Last edited by Ruken; 08-14-2018 at 02:05 PM.
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Old 08-14-2018, 02:49 PM
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I believe the car goes into open loop when at WOT. On that note, unplug your O2 sensors and see how it drives.
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Old 08-14-2018, 05:22 PM
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Additional checks:
CTS & IAT (resistance value at ambient temp with engine cold and/or hot... hot should be resistance equivalent to 170-215*F)
MAF (you can unplug it but if the speed density tables aren't populated it'll just run a different or additional flavor of crap)
And yeah, PE mode ignores O2 output and goes straight to PE mode VE & timing tables so it'll clear up at WOT if spark and fuel are good, which you verified...
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Old 08-14-2018, 08:10 PM
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Originally Posted by SS RRR View Post
I believe the car goes into open loop when at WOT. On that note, unplug your O2 sensors and see how it drives.
Didn't even cross my mind, although I did think about doing that for the MAF. Just havent had the opportunity to spend more then 30min looking at it since the problem started. But I am going to give it a try, also I should clarify that when the car is first started and in open loop the symptom isnt there. Once's it gets to operating temp thats when it starts having issues.

Originally Posted by Gojira94 View Post
Additional checks:
CTS & IAT (resistance value at ambient temp with engine cold and/or hot... hot should be resistance equivalent to 170-215*F)
MAF (you can unplug it but if the speed density tables aren't populated it'll just run a different or additional flavor of crap)
And yeah, PE mode ignores O2 output and goes straight to PE mode VE & timing tables so it'll clear up at WOT if spark and fuel are good, which you verified...
I was going to try the MAF, IAT's look normal but you and I both know that doesn't necessarily mean anything with out breaking out the DVOM. Ill take a closer look and do some more diag on it when I get some free time. When I do discover what is causing the issue, Ill let you guys know for sure. Ill probably start on it Sat Afternoon.
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Old 08-14-2018, 11:21 PM
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How Many miles...
also cant do much Unless you inspect the spark plugs
.................................................. ...........................+1 on the MAF
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Old 08-15-2018, 09:47 AM
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Originally Posted by Ghostinthemachine View Post
How Many miles...
also cant do much Unless you inspect the spark plugs
.................................................. ...........................+1 on the MAF

54k miles on body and motor, if my visual inspection and further diag dosent prove fruitful. The next step is checking plugs, Compression and leakdown test
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