LS1 Rough Idle

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May 28, 2011 | 01:25 PM

superstingray_1975

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LS1 Rough Idle

I have a LS1 with a turbo 400 in my 1975 Corvette, and it has been running rough at idle for a while now. When we hooked the scanner up to it, it was running a o2 sensor code for low signal and insufficient switching on the passenger side. The sensor was changed, but the car still runs rough. While looking at the engine data the o2 sensor on the side that was changed, jumps from the 20 or so mV that it should be at to 600 mV at the same pace that the idle changes. We also noticed that it is only when the ECM is running in closed loop. The collectors on both sides of the car have leaks. Any advice would be really appreciated.

I am also planning on having the car dyno tuned this summer if that would be the culprit.

Last edited by superstingray_1975; May 28, 2011 at 01:34 PM.

May 29, 2011 | 09:39 AM

416GTO

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From: Houston, Tx

fix your exhaust leaks first, after that look at your short term fuel trends and see if they match on both sides if they don't than you have an intake runner leaking or a partially plugged fuel injector.

Jun 13, 2011 | 08:23 AM

superstingray_1975

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I haven't had much time to work on the engine, however I did put the scanner back on it and it is now showing a fuel injector circuit code.

Jun 13, 2011 | 08:32 AM

babbage1109

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From: Southside,Indiana

I'd say the leaks. Mine does the same thing. I need to fix mine. I'm getting o2 sensor codes

Jul 2, 2011 | 07:33 AM

superstingray_1975

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I changed out the intake gaskets, fixed the headers, and am currently running injector cleaner through the car, however the idle still hasn't improved. Occasionally it gets worse, to the point where it fluctuates between 400 and 900 RPM and would almost quit. I put the scanner back on the car and watched the fuel injectors and the signal stays the same for the most part but sometimes the two pulses are differ about 0.4 ms. When I took a look at the codes after the car was running worse it showed a crank sensor code, I cleared it and it hasn't shown back up yet.

Jul 2, 2011 | 07:59 AM

RsSean

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From: Pensacola, FL

have you ever done a crank relearn? You need to put a noid light on the failing injector circuit to see see if you are getting signal to the injector. If you are not getting compariable signal to the other injectors I would trace the wire back to the PCM and make sure the wire are good. If the wires are good the injector driver in the PCM has failed and you will need to get a new computer or find someone that can repair it.