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1997 Eldorado ETC - Help t/shooting Ignition Coils

740 Views 8 Replies 6 Participants Last post by  cjamen
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
1 - 9 of 9 Posts
Might try a good TB cleaning before doing anything else.
use a hand held scanner and see what cylinder specific code is showing. the onboard scanner will not show cylinder...
The other is an O2 sensor code is it not? please post definitions with all codes and if history or current. And yea clean the TB
Also try checking your intake plenum. When mine had a leak, the same misfire code showed. I used a little cleaner to spray around the plenum. It's worth a shot.


P0300 is multiple misfire, correct?


From what I've experienced, one code will trip other codes. If you're having a random or multiple misfire code, I would start with fixing that and see if the other codes clear.
No plenum duct pre '00.

Codes can not set other codes. Codes are set when certain criteria are met, and detected by whatever module is monitoring the component/system.
The p0300 was pulled with hand held scanner. There are no history codes since I put a new battery in it.

The two possible causes I think I could be facing are ignition coil(s) or I had moister in the fuel lines as it sat in my shop for the last 4 months. When I started it after setting 4mo, it stuttered just a bit then idled fine.

Today I'm going to drive it to town put in some high octane fuel and some Lucas fuel treatment, clear the codes and take it for an hour drive and see what I get. I'll post the results when I return.
You might want to use this to make sure the coil towers are properly connected to the plugs.

Use Chevron TECHRON instead of Lucas.


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The fuel nor additives are going to help. You are probably running 10% ethanol and that will absorb any moisture in the fuel lines.
Try swapping out the coils one at a time with a known good one. If that doesn't help, you may be looking at a new ICM.
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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