think300E, strongly recommend that you remove the distributor cap and inspect the condition of the terminals before doing any other work. Scrape away any thick deposits on the terminals, or replace the distributor cap ... same for the distributor rotor. Buy a new large O-ring for inside the distibutor cap since over time it gets dry/brittle.

Distributor cap screws are 5mm and the rotor are 3mm. Removal is straightforward with the most difficult part being the removal of the spark plug wires from the cap. Each terminal on the cap is numbered for the corresponding cylinder (1 thru 6, front to back).

The black plastic cover has a tab on either side that snaps into place to secure the cover. Gently pull the tab out on one side and the cover should release and lift off.

Thanks Ferdman,

The new wireset and new sparkplugs did make a difference, did the work on Saturday, and Sunday the car started right up.

I didn't check the distributor cap because I didn't have the time nor the correct size tools to remove those screws.

However, I have ordered a new distributor cap / rotor (to arrive on Wed) and will get a new O-ring from the dealer, then just replace them, once I get the correct allen keys.

I cannot locate all of my receipts (I moved about a year ago - I am sure I will eventually find them), the only receipt I have located that shows dist/rotor replacement was more than 30k miles (thinking that maybe it has not replaced in a while, I will just do it).


Question: how do you measure torque for the rotor screws, as well as the dust cover screws? What tool can I use? I have a very large torque tool I use for the sparkplugs but I dont think I have room between the fan/radiator and the screws.

think300E, for small screws I snug them up being careful not to overtighten them. While I use a torque wrench for lug bolts and other critical bolts I do screws by feel based on years of DIY experience.

What tool do you use to pull the cables at the distributor end?

I used the 45deg pliers but It was a challenge to pull them off (probably it wont be so bad to pull them off again since I just recently installed the wireset and added new fresh dialectric grease.

I've never had too much of an issue pulling wires off at the distributor cap end. As long as you are grabbing the entire length of the plug with a firm grip, you can pull as hard as necessary without worrying about damaging the plug end. I'd say you have more of a risk doing damage pulling with pliers than your fingers. Now for pulling the wires off the spark plug ends those special pliers do come in handy every now and then.

A good rule of thumb I've learned for torque on non-critical and often non published torque areas is bolt size. Smaller the bolt head size, the smaller the torque required.

think300E, use your hand to turn the ignition wire boots on the distributor cap terminals before attempting to pull them off. Engine heat causes the boots to bond to the terminals.

Ferdman, the distributor cap and rotor very much needed to be replaced. I am glad I finally was able to do so.

Bottom hex screw was a challenge to remove because I was not able to insert/lineup allen key, until I figured out to use the long end (instead of the short end, that I used for the top screws). Seems logical, but being my first time doing this it was not apparent at first.

Does the car need to be driven for X miles in order for the the onboard computer to adjust timing? does it build historical information? or is that an instant process, instant adjustment as the car is running?

I recall reading somewhere (a few years ago) something about running the car for 100 miles or so to reset the error codes or something like that (or to generate new codes if they were cleared), not sure if the same is applicable to the EZL module.

When I started the car after replacing the distributor cap/rotor it started rough, but subsequent starts seem smoother.

think300E, I'm unaware of the need to do anything to reset the computer. I simply replace the distributor cap, rotor and spark plugs and I'm done. You should notice an immediate improvement in engine performance.

The computer and mechanical fuel injection system on these cars are stupid simple, it doesn't really learn anything per say compared to modern cars. There's no resetting necessary.

Thank you for the replies.

Currently I have the CD Manual from MBZ and also using the index files from Steve Nervig. http://web.mac.com/dakota/Mercedes/Indexes.html

Btw, if you do not have the index, it is priceless.. a better way to navigate the electronic manual (specially for us new DIY). Plus additional resources.


He has included a fault code manual and while reading it, in page #8 I noticed the following paragraph.

This paragraph appears at the bottom of the page, topic being (Check Engine Light (MIL) Diagnosis.

Under subtopic Mixture Adaptation:
The engine control module automatically performs a mixture adjustment. The degree of correction is calculated constantly and stored in KAM (Keep Alive Memory) RAM. The self-adaptation is performed at idle and under partial load. Maximum correction towards rich or lean is 25%. After reapir work is performed, the engine control module will automatically adapt itself again after approx. 10 trips. After eliminating a malfunction or after trial installation of an engine control module from another vehicle, the self-adaptation feature must be reset to its mean value.

(This is not where I originally read the info - interesting that I found it here again).


I have another issue that has appeared off/on over the last half year.
I will create a separate post for that.