E46 Cylinder Misfire 2004 325 - Bimmerfest - BMW Forums



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E46 (1999 - 2006)
The fourth generation 3 Series (E46 chassis) was introduced in 1999 and set the standard for engineering and performance during it's years of production including being named to Car & Driver's 10 best list every one of those years! ! -- View the E46 Wiki

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Old 11-16-2018, 11:16 AM
adam00_0 adam00_0 is offline
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E46 Cylinder Misfire 2004 325

Everyone - just posted this, but do not see it on the thread. Apologies if this appears twice.

About a month ago, the SEL on my 2004 325 popped on. Had the code read and seemed like it was time to change out the spark plugs. The car has 91K miles on it.

I replaced all plugs w/ NGK plugs and the SEL cleared and the car drove fine for about two weeks. Then, the SEL appeared again along w/ a hard idle when the car was warmed up. The new codes showed:

8 misfires. Multiple misc misfires and misfires on cylinders 4, 5, and 6.

To troubleshoot, I swapped 4 and 1 -- then had the codes cleared. The car drove fine again for the first 20 miles. Then, the hard idle and the SEL flashed on. (Yeah, it was flashing for a while too, before it finally stayed on.)

I had the codes read and they were the same - 4, 5, and 6. The misfire did not follow to cylinder 1. When I turned off the car and re-started, the SEL was gone and the car continued to drive fine. However, I expect in about 20 miles or when the engine is warmer, the hard idle will return along with the SEL.

Any thoughts on what's going on here? Is it the fuel injector? What's best course of action now? Thank you!
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Old 11-16-2018, 01:41 PM
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Fast Bob Fast Bob is offline
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You need to post the exact codes which were found. These are expressed as "P0123", etc. Once we know those codes, we might have a better answer for you.
Also, read the E46 Wiki !
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Old 11-16-2018, 02:56 PM
adam00_0 adam00_0 is offline
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Thank Bob. As soon as the SEL returns, I will get em! Weird... comes and goes!
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Old 11-16-2018, 02:58 PM
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Quote:
Originally Posted by adam00_0 View Post
Thank Bob. As soon as the SEL returns, I will get em! Weird... comes and goes!
Many of the codes may still be present but in a PENDING status. You should read what is there now.
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Old 11-16-2018, 04:04 PM
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Quote:
Originally Posted by adam00_0 View Post
Thank Bob. As soon as the SEL returns, I will get em! Weird... comes and goes!
You can have codes without any CEL displayed.
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Old 11-16-2018, 04:05 PM
adam00_0 adam00_0 is offline
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Just tried getting em read... "no codes found". As soon as the SEL returns, I will grab those codes.
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Old 11-17-2018, 09:36 AM
adam00_0 adam00_0 is offline
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OKay, so after about 20 minutes of driving the CEL returned and so did the hard idle. The codes are

P0300
P0304
P0305
P0306
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Old 11-17-2018, 02:23 PM
adam00_0 adam00_0 is offline
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Quick update and question. Could the hard idle and misfire codes be related to a bad thermostat?

A mechanic friend thinks it's a bad thermostat b/c the hard idle and CEL are only appearing after about 20 minutes. He thinks the faulty thermostat is preventing the engine from getting hot enough and that's why the issue is happening. We plugged in the reader and let the car idle for 10-15 minutes. The temp only got up to about 96 or 97 degrees. He recommends changing the thermostat, but wanted to get a second opinion here.

Thanks again.
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Old 11-18-2018, 04:58 PM
marcozandrini marcozandrini is offline
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No. The thermostat is designed to restrict coolant flow until the coolant reaches the proper temperature. Thatís about 85*C.

Which NGK plugs did you install? The ONLY spark plug that should go in an M54 engine NGK BKR6EQUP. PERIOD. Why? These are plugs that the BMW engineers specíd when they designed the M54 engine.
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Old 11-18-2018, 09:11 PM
adam00_0 adam00_0 is offline
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Marco - thanks. Yep, these are exactly what I used. I replaced all six cylinders w/ the same NGK's BKR6EQUP. Now, just the three are misfiring. I've been reading forums on this and have not seen thermostat ever mentioned as a possible problem. So, I didn't think it was the thermostat either.

I wonder if it's the fuel injector? My neighbor recommended pouring in a quart of techron into the gas tank when I'm about 1/4 fuel. Then, running it hard and then doing an oil change.

Right now, it's back to running fine and the CEL is off. But I know that after another 20-30 minutes, it will again start to hard idle and I'll get the P0304, P0305, and P0306 codes again.
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cylinder, e46, fuel, injector, misfire


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