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Replacing Your Spark Plugs and Coils
 
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Pelican Technical Article:

Replacing Your Spark Plugs and Coils

Nick Czerula

Time:

1 hour1 hr

Tab:

$100

Talent:

**

Tools:

Set of sockets (10mm, 5/8 spark plug socket), flathead screwdriver, and a 12” extension

Applicable Models:

BMW 323Ci Coupe/Conv (1999-00)
BMW 323i Sedan/Wagon (1999-00)
BMW 325Ci Coupe/Conv (2001-06)
BMW 325i/xi Sedan/Wagon (2001-06)
BMW 328Ci Coupe (1999-00)
BMW 328i Sedan (1999-00)
BMW 330Ci Coupe/Conv (2001-06)
BMW 330i/xi Sedan (2001-06)

Parts Required:

Spark plugs, Ignitions coils

Hot Tip:

Work with a cool engine

Performance Gain:

Engine runs well

Complementary Modification:

Install performance plugs and coils

Replacing the spark plugs on your BMW E46 is recommended routine maintenance. BMW recommends replacing the spark plugs on E46 models every 100,000 miles and every 60,000 miles on M3 E46 models. With all the major engine design changes over the years, spark plugs now last up to three times as long as they did in years past. This is good and bad. It means you save money and time not having to service them so frequently, but run the risk of a spark plug seizing in the cylinder head.

I suggest replacing your spark plugs every three years regardless of mileage. If the last time they were serviced is unknown, replace them right away. If possible include pictures of these as well. I do not have stock photos of faulty spark plugs but I can add a description of failure modes. I did so below, right after the spark plus is removed.

BMW E46 models utilize an individual ignition coil for each spark plug, referred to as coil over plug (green arrows).
Figure 1

BMW E46 models utilize an individual ignition coil for each spark plug, referred to as coil over plug (green arrows).

When servicing your spark plugs, be sure the engine is cool and leave yourself about an hour to do the job. Be careful not to drop a spark plug, if you do, replace it. The spark plug insulator can crack and can lead to an engine misfire. Remove the E46 engine covers on the cylinder head. See our Pelican Parts Technical Article on how to Remove Your Engine Covers.
Using a small flathead screwdriver, release the ignition coil electrical connector retainer by prying up and pulling the electrical connector out of the ignition coil (green arrow).
Figure 2

Using a small flathead screwdriver, release the ignition coil electrical connector retainer by prying up and pulling the electrical connector out of the ignition coil (green arrow).

Next, remove two 10mm ignition coil fasteners (green arrows).
Figure 3

Next, remove two 10mm ignition coil fasteners (green arrows).

Remove the ignition coil from the cylinder head by it pulling straight up.
Figure 4

Remove the ignition coil from the cylinder head by it pulling straight up. If coil the resists, twist when pulling up to break it free from the spark plug. The ignition coil rubber boot can become stuck to spark plug over time.

If you find engine oil has contaminated the ignition coil boot you will have to repair the oil leak and replace ignition coil boot (or ignition coil). The source of the oil leak will likely be the cylinder head cover gasket.
Using a 5/8 spark plug socket on a 12” extension, remove the spark plug from the cylinder head.
Figure 5

Using a 5/8 spark plug socket on a 12" extension, remove the spark plug from the cylinder head. With spark plugs removed, inspect the firing end condition. This can tell you a lot about the condition of your engine.

Expect a spark plug that is functioning optimally to have a brown or light gray firing end. A firing end covered in a dry or wet black coating indicates a rich condition. This can be caused by many factors, from a bad spark plug to a leaking fuel injector. Usually when this is found, there is a drivability problem with the vehicle. Look for a leaking fuel injector or weak cylinder. A firing end covered with deposits is a sign of oil or coolant contamination. This usually leads to a rough running cylinder or misfire. If you find oil deposits, you could have faulty valve stem seals or oil rings. Coolant deposits could be from a faulty head gasket. Thread the spark plugs into cylinder head by hand, as this will prevent accidental cross-threading. Torque spark plugs per your vehicle's specs. Reinstall the ignition coils and reconnect the electrical connectors. Be sure to re-route the wiring harness as it was before and reconnect ignition coil grounds. Install the engine covers and check your work.
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Comments and Suggestions:
Victor Comments: Why is there a washer like thing the cover on one of the plug tthat prohibit me to access the nut part of the spark plug?


December 5, 2016
Bimmer Comments: What I meant was is there an order in which the spark plugs are aligned? Like are they ordered 1-6 from left to right or from right to left?
November 21, 2016
  Followup from the Pelican Staff: Cylinder 1 is closest to the drive belts, then count toward the firewall until you reach cylinder 6. - Nick at Pelican Parts  
Bimmer Comments: What is the number alligment for the spark plugs?
November 12, 2016
  Followup from the Pelican Staff: I don;t understand your question. What do you mean by number alignment? - Nick at Pelican Parts  
John Comments: Is there a way i can test the coils?
October 12, 2016
  Followup from the Pelican Staff: Yes. Either by viewing the primary or secondary voltage using a lap scope. Or use a spark tester. See this info:

http://autotechdiagnostics.com /?p=454 - Nick at Pelican Parts
 
Pete P Comments: I had my 2001 BMW 325i towed into a shop and they diagnosed that one 1 cylinder was not firing. Prognosis was it needs an ignition coil, connector & a spark plug. Question: Can I only replace 1 ignition coil or do I have to replace all the coils coil pack I want to get rid of the car because it's too costly for me now.
April 18, 2016
  Followup from the Pelican Staff: You can replace only one coil. - Nick at Pelican Parts  
ragreene801 Comments: "Torque per vehicles specs". how do I know my vehicles specs?
March 24, 2016
  Followup from the Pelican Staff: I don’t have that info.


I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 
chace Comments: It is a 2001 325xi. The piece in question is almost a large bean shape post blowing out, with a resistor sticking out of the end. it is wired directly into the harness beside the sparkplugs.
August 27, 2015
  Followup from the Pelican Staff: Likely a condenser, it comes with a new harness. - Nick at Pelican Parts  
chace Comments: on the wires next to the spark plugs, I have noticed this device with a resistor on the end. Glass is in the tray so I assume it blew, but have no idea what it is. Help??
August 22, 2015
  Followup from the Pelican Staff: What is year and model of vehicle? Could be a condenser. it is not available separately, you will have to replace the harness.- Nick at Pelican Parts  
Anno Comments: should you remove spark plug when engine is hot or cold?
July 17, 2015
  Followup from the Pelican Staff: Cold. - Nick at Pelican Parts  
RUBMW Comments: I have a misfire in one of my cylinders. Do I need to replace the ignition coil with the spark plug or have others had success just changing the plug?
April 29, 2015
  Followup from the Pelican Staff: I would check spark, fuel and compression on the cylinder. You need to determine what is missing.- Nick at Pelican Parts  
pat Comments: I'm using the NGK4 electrode plugsplatinum thanks for response. The question was how to pull the coils, what I found was that a twist and pull will get them out, there are no bolts holding them in. DIY hint, I put rubber hose on a pair of long needlenose pliers, this let me grasp the top of the coil firmly enough to pull the stubborn ones.
November 9, 2014
  Followup from the Pelican Staff: Right, like I said earlier. They are the pencil style coils used on later E46 and other models. - Nick at Pelican Parts  
pat Comments: My 04 325xi has different coils, no bolts and a rubber gasket. I'm just trying now to determine the best way to remove the coil.
November 7, 2014
  Followup from the Pelican Staff: Those may be the later pencil style coils. They pull straight out. - Nick at Pelican Parts  
Altimized Comments: What type of brand spark plug is recommended? Or if after market what do you prefer?
August 8, 2014
  Followup from the Pelican Staff: Try this page for some recommendations:

http://www.pelicanparts.com/catalog/SuperCat/BE46/BMW_BE46_ELignt_pg1.htm - Nick at Pelican Parts
 

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Page last updated: Wed 12/7/2016 02:19:28 AM