LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

car running rough and 02 voltage low

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Old Dec 4, 2012 | 08:12 PM
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car running rough and 02 voltage low

Finally got the car running after months of trial and error again. Replaced opti, coil, coil pigtails, and finally the spark plugs(autolite 103's gapped@.035). Was running ok not the best but it was running! My O2 voltage was screwey on the scanmaster hanging out around 054 or so. Cycled thru to individual readings and it was more so the right bank reading bad. So anyway, I went to the carwash to wash the car and acorns and rat turds from under the hood. Car drove home fine. When I left for work it was running rough this morning and no ses light was on but the scanmaster gave code 18. I got the noid lights out and all harnesses checked out ok but it still runs rough as hell. I'm going to swap sides on the oxygen sensors to see if the low voltage follows. Any idea what could be wrong? They are delco oxygen sensors btw.
Old Dec 5, 2012 | 05:32 AM
  #2  
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Re: car running rough and 02 voltage low

This happened after you sprayed water under the hood? How much of the engine did you spray down? High pressure?

I know you tried the 'noid light, but did you verify 12V on the pink wire at each injector clip, and verify 12-15 ohms across each injector? DTC 18 indicates an injector circuit fault. Did you clear the code, and did it come back? It may have been a stored code.
Old Dec 5, 2012 | 03:50 PM
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Re: car running rough and 02 voltage low

I sprayed the top mostly, had to spray off the intake, strut tower by the battery, and under the brake booster and condenser box. I used high pressure on the brake booster side the other was just regular pressure(not pulling the trigger). No I didn't check the voltage I will do that asap. Is that 12v with just the key on or cranking or what? I'll go clear the code real quick and see what it does.
Old Dec 5, 2012 | 05:11 PM
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Re: car running rough and 02 voltage low

Key on/engine not running, pull the harness connector off the injectors one at a time. Measure the voltage between the pink wire in the connector and a good ground (not the other wire in the connector). If you have 12V you are OK. The PCM supplies the ground on the other wire in the connector to fire the injector.

With the plug still off the injector, measure the resistance across the two pins of the injector - should be in the range of 12-15 ohms.
Old Dec 8, 2012 | 09:53 AM
  #5  
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Re: car running rough and 02 voltage low

One of my injectors is dead. Checked all injector connectors all read 12.4 volts. All injectors read 13.4-13.6 ohms accept one and it didn't register nothing
Old Dec 8, 2012 | 10:32 AM
  #6  
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Re: car running rough and 02 voltage low

That would indicate a short in the injector coil.
Old Dec 8, 2012 | 04:02 PM
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Re: car running rough and 02 voltage low

I got a set of racetronix #32's that I'm goin to try to put in. I don't know what to set my tune for tho
Old Dec 11, 2012 | 09:35 AM
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Re: car running rough and 02 voltage low

Zero reading indicates an open coil in injector, a short would read point something or .1. Open or shorted are both bad readings for injector. Sorry injuneer, as an electrition I could not resist posting
Old Dec 11, 2012 | 09:50 AM
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Re: car running rough and 02 voltage low

Zero ohms resistance indicates a short as Injuneer stated. An open (infinite resistance) is indicated as 1 on most digital voltmeters. This can be proved by shorting the meter leads together on a resistance scale, and 0 ohms will be indicated.
Old Dec 11, 2012 | 10:53 AM
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Re: car running rough and 02 voltage low

Yeah I messed up. An open would be infinite ohms, indicated as OL on a fluke meter, which means out of limit for the meters range. It would not be 1, this would indicate one ohm. If you hold the leads together you will read .1 which would be the resistance of the leads. No reading on the meter or an OL on the meter with the leads on the coil terminals would indicate an open in the coil wire or a very high ohm value, a short would read as a very low reading like .1 or something lower than the known good resistance range of a good coil. Also a very high resistance or a mega ohm reading on the meter would pretty much indicate an open in the coil. So with no reading as indicated by the original poster you would have an open coil not a shorted coil. You will probably never see a zero reading on a good meter
Old Dec 11, 2012 | 01:12 PM
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Re: car running rough and 02 voltage low

Thanks for all the info
Old Dec 11, 2012 | 01:23 PM
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Re: car running rough and 02 voltage low

Originally Posted by don
Zero reading indicates an open coil in injector, a short would read point something or .1. Open or shorted are both bad readings for injector. Sorry injuneer, as an electrition I could not resist posting
Is electrition:electrician in the same relationship as injuneer:engineer?
Old Dec 11, 2012 | 01:37 PM
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Smile Re: car running rough and 02 voltage low

Yep I'm not an English teacher
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