Checking Spark Plug Wire and Ignition Coil ?

[HTSS_TR]

My 2000 MB E430 had CEL last week and the code was P0303 Cylinder 3 misfired. I clear the code and after a week it didn't come back.

I suspect two spark plugs and wires(2 plugs and 2 wires per cylinder) of cylinder 3 may be bad. I have spark plugs but didn't buy the plug wires yet(they are expensive and sold as pack of 16 and I don't like to throw 1 part after another at it), I am thinking may be I need to check the resistance of the wire, what is typical resistance of good spark plug wire ? Also, what can you check to see if the ignition coil is still working or not ?

 

[Nick1994]

Swap the coil to another cylinder and the wires to a different cylinder as well and see if the check engine light moves. If it does then you'll know your problem.

Don't let it get to be like GHT's Expedition! Lol

 

[oldhp]

Check your other wires and see what resistance they have. If possible change places of the coils, and see if CEL lights again. How many miles? How old is the car?
Didn't see other post.

 

[HTSS_TR]

The car is 2000 MB E430 with 160k miles. The 16 plug wires and 8 coils are original. The spark plugs are Bosch designed specific for MB engines from around 1998 to 2003.

The CEL didn't come back for a week, so swapping wires and coils may not work, I mean the CEL may not come back.

Yes, measure resistance of other wires to get approximate value, then check cylinder 3 wires with those value. But these wires are 15 years old and 160k miles, the resistance may increased over time and more than new wire.

 

[OneEyeJack]

Originally Posted By: Nick1994
Swap the coil to another cylinder and the wires to a different cylinder as well and see if the check engine light moves. If it does then you'll know your problem.

Don't let it get to be like GHT's Expedition! Lol


+1

 

[Merkava_4]

Originally Posted By: HTSS_TR
what is typical resistance of good spark plug wire ?


Right around 10-15 K-Ohms per foot.

 

[Lubener]

Originally Posted By: Merkava_4
Originally Posted By: HTSS_TR
what is typical resistance of good spark plug wire ?


Right around 10-15 K-Ohms per foot.


That's too high, I have two manuals that state 5K Ohms per foot. When you measure, move the wire around to see if it momentarily opens. Before that, when dark, spray down the wires one at a time with water in a spray bottle. Watch out for the light show. Most of the time, the insulation breaks down, if the wires were rough handled, the cores get damaged.

 

[Vikas]

Don't you think at 160K miles, wires and plug don't owe you anything and should have been replaced? At this age, you might disturb the one which is not giving any trouble by just removing it and re-installing it. I understand 16x wires and plugs are expensive but you knew that going in!

From following Ken of mercedesource on you tube, neglecting ignition components on MB cars seems to be number one issue.

 

[46Harry]

Somewhere around 3 kilohms per foot of plug leads is what I look for, but after 15 years and 160k miles, the insulation on the leads could be breaking down and causing a misfire also.

 

[HerrStig]

Resistance depends on the type of wire. I doubt Benze uses carbon string wire so the construction is probably a monel wire wound in a spiral on an insulating core. Resistance ought to be near 3000 ohms per foot as the OP said. The carbon string wire doesn't last long, the monel is very durable. There may also be a resistor in the plug boot which adds to the reading. Turn on the AM radio...is there a pop pop pop when the engine is running?

 

[Cutehumor]

Originally Posted By: HTSS_TR
The car is 2000 MB E430 with 160k miles. The 16 plug wires and 8 coils are original. The spark plugs are Bosch designed specific for MB engines from around 1998 to 2003.

The CEL didn't come back for a week, so swapping wires and coils may not work, I mean the CEL may not come back.

Yes, measure resistance of other wires to get approximate value, then check cylinder 3 wires with those value. But these wires are 15 years old and 160k miles, the resistance may increased over time and more than new wire.


15 years/160k plugs and wires with a check engine light? what is the owners manual say about changing the plugs and wires?. I would change them all out. This isn't one of these things to be cheap with.

 

[HTSS_TR]

Well, I'm spoiled by the reliability of my 1994 Lexus LS400. It has the old distributors and long plug wires, they are original after 21 years and 370k miles. I changed spark plugs in the Lexus 3 times at 100k, 200k and 300k with NGK platinum plugs but all wire are original without any misfired.

The MB owner manual didn't say anything about changing ignition coil and wire, only changing plug every 100k miles which I did at 80k miles(they were in excellent condition when removed) and probably will do again this weekend or next. Probably will buy a Bosch wire set and 16 iridium spark plugs. I will try to get all parts ready and when the code P0303 or P0300 comes back I will replace all plugs and wires.

I still like to measure resistance of the old wires and keep some in good condition in case I need a few some years down the road. I think the wires are fairly short, some are about 8 and some are a little longer at about 10".

The cost of 16 iridium plugs and wires are about $300 which isn't too bad, but the 8 Bosch OE coils can be more expensive.

 

[Vikas]

so why not just replace the plugs now and wait for the code to come back or do the plugs/wire swap with two different cylinders and and see of the code moves. If the coils can be swapped, I will do that too. That is the only real way to diagnosis. The resistance test will come back negative because if the wire were bad enough to show up on the multimeter, you would be tripping the code pretty much instantly. This is not happening in your case.

Replacing coil(s) without determining if it is bad game can only be played if you have money to burn

 

[HTSS_TR]

Received made in Germany Bosch spark plug wires today. There are 4 different sizes, 9 wires at 9.5" long, 5 wires at 10.5" long, 1 wire at 11.5" long and 1 at 12.5" long. All wires have 2k-Ohms stamped on the metal end.

Tried to measure resistance of 1 wire but the strobe isn't long enough to touch 1 end.

Now I have 16 Champion iridium spark plugs, 16 Bosch wires and 1 Bosch ignition coil. Since there were 2 codes P0300(random misfired) and P0303(cylinder 3 misfired), I will change the ignition coil for cylinder 3, plugs and wires for all cylinders whenever the CEL comes back with similar code(s).

The parts cost is about $250, not so bad. The labor is probably about 3-5 hours, so I need to do it on a weekend with some cold beer.

 

[Vikas]

Why so much in labor hours? Do you have an impact gun or impact driver? Even a cheap one (under $100 from HD/Lowes) would cut down the hours in half or more.

 

[Trav]

$250 isn't bad at all, your time is spot on, figure closer to 5 hrs for this one with a coffee break.

 

[Vikas]

Is it because the engine bay is too cramped for the E-series? On the S430, replacing spark plugs "looked" straightforward.

 

[Vikas]

Just found a youtube video which had one bank done in 14:06 seconds running real time and showing and explaining what he was doing. he did use air ratchet but that is why I suggested a cordless impact.

Five hours looks like something a mechanic would charge to the customer and NOT the wall time for this job!

If I end up with an S-class, I will definitely time myself and I am confident that 5 hours is way too outrageous of an estimate for this job.

 

[HTSS_TR]

No, I don't have impact driver I just have some hand tools.

I usually do everything very slowly, a simple oil and filter change with Mityvac 7201 should be done in 15-20 minutes took me almost 1 hour.

The driver side bank is easy to replace coils, plugs and wires because there is nothing interfere. The passenger side has intake tube and other parts on top the coils and plugs, they are needed to remove to gain access. My estimate up to 5 hours(may be longer) because I think this job should be done in 2-3 hours by a competence mechanic, I double the time because I don't have all right tools and I am slow and don't want to make mistakes and break some parts.

Vikas, if you end up bought the S430 you should think about buying a fluid extractor to do oil change(I like Mityvac 7201, I had it more than 10 years and it is still working great). The cartridge oil filter is on top of the engine so you can change oil&filter without getting under the car. You should also get an oil filter cap wrench too, I think it is 76mm(may be 74mm, I need to check mine) 14 flutes. You can do oil change for S430 with dress cloth and not a single drop of oil will be dripped anywhere. You only need a glove to remove/install oil filter from/to filter holder.

The fluid extractor can be used to change ATF and bleeding the brake too. I think Mityvac 7201 is one of the best of my tools.

 

[Vikas]

Buy an impact driver. Those are quite cheap these days. 18V or 20V Lithium can be had under $100 on sale. Get hex-to-3/8-adapter plus get hex socket sets and you will be zipping through this job so much faster. Use it only to take off things if you feel uncomfortable to use it during the installation.

I have that Mityvac on my list of tools to purchase for a while.

I suspect that engine is stuffed in your e-class. On s-class, everything seems to be accessible without having to remove anything else.

Here is the video for the s-class. At the end of the video, he is done with the passenger side even though he is explaining everything on the way. The video itself is 14 minutes and he is showing almost everything in realtime with no edit cuts or fast forwards.