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1997 Eldorado ETC - Troubleshooting P0300


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First, I have zero history on this car as I just bought it. It was running a little rough, missing.

I installed new AC Delco plugs and wire set. Cleared all codes. After starting it up and letting it come to temp, I got check engine light. Pulled codes: p0300, p0141, p0603.

I tested the ignition coils and got the following results:

Primary - Secondary Resistance

.2ohm - 5k ohm

.2ohm - 5k ohm

.3ohm - 5k ohm

.4ohm - 5k ohm

From the reading I've done, I'm getting that it should be .5 to .6ohms and 8k ohms on the secondary. Is that correct? If so, then is it a valid deduction that all of my coils are going out on me?

Lastly, is it a fair to say that it is possible that the random misfire could be causing the O2 code p0141 because fuel is not being burned correctly?

Thanks in advance for your input/help! cal

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Welcome to caddyinfo forum.

I suggest you check your leads on your MM. Make sure they ohm out to 0.00. If they dont just add the reading you get from the reading from the coils.

Example.

If your leads touched together shows 0.05

then when you test the resistance on the coil add .05 to the reading you get. Even my best multimeter sometimes has a hard time showing 0.

Also I would check the wires good and make sure all are properly seated, not chaffing or getting burnt on anything hot.

Does it feel like it has a miss?

Clear the codes and see if any codes come back

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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How did the coil towers look? Is the misfire more pronounced cold? hot? After driving the car all day and parking it and starting it up that next day, how does it start-up? Rough? smooth?

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It is unlikely that all four coils went bad at the same time. Clear the codes and drive the car to see if the P0300 sets. If it does, you may need to have someone check it with a scan tool that can monitor the cylinders for misfiring in order to see what cylinder is misfiring.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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I would clear the codes, then give it a cold start in the morning. Does the code set while the car is still cold?

If not, let he car idle till it gets to operating temperature, and see if it sets then.

When you find what triggers the code, repeat that the. Next day to see if it is consistent.

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generally if all 4 have the same reading they arent all bad. That would be a pretty rare occurance

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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Cleared the codes, added fuel injector cleaner and a full tank of premium fuel. Drove it and after 30min of driving, check engine came on. Pulled codes and I'm no longer getting the misfire code but just an O2 code. So I'm thinking that the original misfire p0300 I was getting was due to some moisture in the fuel line from setting 4 months.

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P0141 is just reporting the heater for a O2 sensor is slow or failed. Be sure to replace with an oem or specific high quality replacement. Some cheap after market sensors will cause troubles. Btw, when the car is warm, and the codes cleared, this code should not come up again as current if just the sensor is bad. If it does, it could be a short in the wiring to the O2 sensor. 9 times out of 10 its the sensor though.

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Not to go off your subject, but search this forum for advice. Since you don't have a history of the car, change the coolant as soon as you can. And give the car a good looking over for potential age related issues.

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