Project 8: Replacing Spark Plugs

[Wayne 962]

Got any questions on Project 8 for your E36 or E30? Ask them here!

-Wayne

[eman]

What is the spark plug gap on an 04 325XI supposed to be ..Thanks

[Jeron]

AFAIK, all modern BMW's call for plug types that come pre-gapped. Those plugs are usually a bit expensive but they last 50-100k, so they are worth it.

For grins, I looked in Bentley and I didn't find a spec.

I suggest using a decent torque wrench for installation, 18ft/lbs.

[bill_schuster]

I'm doing some maintenance for the first time on my 1990 325is - Can anyone help me with some information re: replacing the spark plug wires?

I've referred to 101 Project (seems to capture the process for an E36) and the Bentley manual.

1) I having some difficulty (by looking) seeing what wire/connector comes off of the 2nd spark plug wire, where it goes, or the best way to route it through the engine compartment.

2) The Bentley manual also directs taking off the fan shroud and fan in order to get to the distributor cap and rotor. I was wondering if this is the best course or if it is merely a recommendation and can be performed with fan/shroud installed.

Does anyone have pictures for doing this project on an E30?

[Terryxj]

1. I think the wire you're referring to is the speed sensor. It snakes around in front of the engine and connects to a conector on a bracket under and behind the main harness diagnostic connector on the driver's side. If you have Bentley's look on page 2:5 (I'm not sure if they are all the same or not). The top right image shows the diagnostic connector (with an arrow) and the two wires are connected to a bracket under and behind. The path this wire takes makes it a pain to replace.

2. I didn't have to remove the shroud to replace the cap. It probably just makes it easier. You have to jiggle the cap a little and it's kind of a tight work area, but it can be done.

[Selfish]

Hi, everybody has their own rule of thumb when it comes to choosing spark plugs. Which ones do you choose for your bimmer? I have bosch platinum +4 on mine (5 spd 1991 318i)now, but I don´t notice much of a difference.

[Jeron]

I've had several bad experiences with Bosch. I prefer NGK.

You wont notice anything with new plugs unless one of the old ones was seriously bad or damaged. Plugs are like oil, you change them on an interval and there is usually a lot of useful life left when they are replaced.

[5stick]

I spoke with a technician at Bosch and he said that older cars do not have the features that the +4 plugs are designed to enhance. Go to the Bosch web site and there is a parts finder function and it will give you spark plugs and other parts for your car.

[Jeron]

Originally Posted by Jeron

I've had several bad experiences with Bosch. I prefer NGK.

Let me amend that, I prefer NGK and single electrode.

[porsche1]

what is the wire induction for? what number wire is this wire connect too?

[daryldaryl1]

Firstly, I must commend, the instructions and pictures for project 8 were great. Very easy to follow, and good pictures like these are hard to find. I'm not what you'd call a gear head so I appreciate the help.

As for the grounding wires that I found on my engine, the one on the right was missing and the left one was disconnected. I just left them as they were because I haven't had any problems but I hope to correct them later once I can replace the missing one. Can someone tell me what exactly they do?

Also, a bit off-subject, does anyone know where I can get a diagram of the engine labeling all the components? Sometimes I find some component or hose and cannot figure out what it is or what it does.

Thanks,
D

[Jeron]

Most diagram sets require you to know something about the item you are looking for to find the correct diagram. Bentley Repair manuals have pretty good pictures and diagrams. Realoem.com has great diagrams.

[PeterLech]

I don't know about the 3 series, but the Bentley E34 manual has zip on the plugs or their replacement. That is why I am looking here.

I heard from an engine builder that the Platinum plugs do not work as well - he recommended the NGKs, which have 2 electrodes.

[JhwShark]

I am inserting a quote from the P side (DanielDudley) of Pelican...for older models '70's-early 90's...I have found copper (old single electrode) works best in all my 93< cars. I tried +2 and +4 electrodes with only cost being higher not performance. Also, I have heard form a different source that the precious metals in the small electrodes becomes plasma tht deposits in the engine (not sure about this issue as I have not broken down an engine after using them)...

"Iridium plugs are best used on boosted cars with water/ methanol injection, provided that ypu keep the gap tight. In this application they can prevent the flame kernel from being blown out, causing misfires.

In general, regular plugs work well in our cars because they have a large electrode of solid metal that gets warm and stays warm. Platinum and other precious metal plugs have a very tiny center electrode that is surrounded by ceramic. Under ordinary running conditions, the ceramic can develop odd fluffy deposits and over time the center electrode can erode way back into the ceramic.

I have run Platinums in Bosch fuel injected cars of our era, and they tend to last no longer than 20 to 25,000 miles. An ordinary plug will run until the gap is so large that the plugs will no longer fire and the distributor cap looks like a science experiment. The platinums will often have wierd deposits, while the most ancient stock plugs will look like textbook pictures of perfect combustion. You could regap them and run them some more, even at 80,000 miles, which I have seen, BTW.

There is enough metal in a standard plug tip that when you really get them hot, they will burn all the deposits away from the tip. Platinum plugs do respond to ''Italian tune ups'' but they still will have a shorter lifespan than you might expect. When I was doing tune ups for a living, I would get poorly running cars from cutomers, and take them out and rev the piss out of them. They would always run fine. I had one customer who would come back every week, until I finally changed out the plugs for stock NDs . Bosch and NDs were the best, and I tended to use Japanese plugs on Japanese and Italian cars, and Bosch plugs on German cars. Stay away from Champions.

BTW, it is true that some cars absolutely would not run on Platinum plugs when they first came out. FI Fords come to mind. Many people continue to run these ''superior'' plugs in applications where they do not work well. Large metal center electrodes work well in our cars, and especially in lower compression, less extreme environments."
Jon