94 M104 engine misfire
 

Its been raining heavily here in Toronto since last night and i drove 3 hours in such conditions. The car was great yesterday but just as i was pulling out a parking lot for my final drive home the engine semed to misfire when i dabbed on the brake. Same deal this morning while i was turning out of my parking after a few minutes no misfires. Any ideas why this could be happening?

Thanks
JM

Do a search on the engine wiring harness. Thats the same problem I had except my car would flat out die in the rain. :( Im sure if yours has not been replaced that is the problem. Hope this helps.
Chris

THanks for the reply.
Today its been about -1 - -3 Degrees celcius here in TO, CA.
And my car would misfire everytime the gear was in Drive and i was stopped at a light or stop sign.
Can this be a wiring harness issue since its only severe cold temperatures thats been causing these engine misfires...

Thanks

JM

What could be happening is the cold weather with the warming engine is causing condensation that is effecting the wiring harness?
Chris

I've been reading talk of ignition coil connectors needing to be changed. i.e M104 engine misfire problem.

http://www.peachparts.com/shopforum/tech-help/53900-e320-help-2.html?highlight=m104+misfire

JM

Here is the general process on 104 waste spark ignition misfires ..
You can go in and get the codes for misfire and you can use a scope , etc..
But , the easy way is to first check for a visually falling apart wire harness ,, if that looks half-way decent , pull the 3 coils and change the 3 plug connectors .. they are so cheap and infamously known to cause misfires on 104s , that it is common pratice with Techs to just change them and see where you stand with new ones before wasting a lot of diagnositic time and part chasing... second notorious 104 misfire is the use of plugs other than Bosch F8DC4 copper plugs .. so , do them at the same time .. again, Bosch's cheapo plugs.

Thanks Arthur Dalton

I've been looking on fastlane for the coil connectors and i'm not sure which ones they are. Isi it the spark plug connectors or Ignition coil connectors...
Can you give me the part no. or a link?


Thanks

JM

Thanks Arthur Dalton again...

Is there anyway for me to check for bad spark plug connectors?

cause i just bought my car a month ago and i'm not sure if they were changed. Will call dealer tomorrow. but will take a look at it now.
Forgive my inexperience but how do i take out the plug connectors ?

Thanks

JM

<<Is there anyway for me to check for bad spark plug connectors?
>>

Yes , there is .. you hook up an Oscilloscope and check out the wave shape patterns of the Primary and Secondary ignition circuits..

,, but, if you read my post again, you will note that I recommend just changing the connectors b/c of the PROBABILITY that they may solve your problem...
if you really want to know for sure , build a code reader/scanner and go get codes , then hook up a DSO scope abd do some electronic diagnosis with the proper equipment.

Thanks A D,
Don't mean to be a pain by asking so many questions but...
One more thing about the misfire. It only happens in D engine is fine in P.
Is it still probable that the connectors need replacing or could it be a bad ecu ?



Thanks

JM

Sure .. it could be the ECU .. or, the harness , or, the coils, or , the OVP , or, an injector, or ... well , you get it now..

What I am trying to tell you is.... IF a 104 engined car with DIS ignition comes in with a misfire complaint, before anything gets done, tested , looked at , etc... an experienced tech changes the connectors under the coils ..
WHY ????? b/c of their known fail rate !!!!!
..,and they should be changed with a plug change anyway... so it is an all gain, no lose situation.

If you want futher testing and more specific diagnosis , build a code reader and go into the ECU fault memory and see which plugs are misfiring, if you even have a misfire ..
But if you want a MOST PROBABLE misfire fault cause on a 104 engine educated guess, it is the coil connectors , hands down .. that's all...
Change them and then you will know or bring the thing in to a Dealer and have it diagnosed .. connectors will cost you $30, a diagnosis will cost you in the Hundreds...with the results probably being "You need new plug connectors, Sir ""

Hey Arthur Dalton

I called the dealership and they told me that i needtwo sets of three. One set of three for cylinders 2 4 and 6 and the other set for the other cylinders...

Do i change all for a total of CAD$150 (MB dealer quoted me)
or only 2, 4 and 6 ?

Thanks

Do what ever you want , but we are back to my original statement/diagnosis.
"It is the 3 plug connectors under the coils that are infamous for causing the misfires in 104 engines "... period.

You want to change them all , feel free . You wan tp change the ECU .. go ahead.. you don;t seem to want to take my advice.
I would change the ones under the coils like we always do. ... b/c they are a different type connector and that is why they fail..the ones that are not under the coils have a snap connector and they are NOT infamous fail connectors.............
It is that simple....
You asked , I answered... now I have to do half a dozen explanations....

You can buy them for less than $10 right here....

Alright I changed the three sonnectors under the coils they cost me ~ $70
And happy to report that misfire is gone!

Thank YOU Arthur Dalton.