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Discussion Starter #22
Yes, I looked them up, but there was no definitive detail. Resistor plug or no? I even went to the Bosch website, and still couldn't find an answer. Perhaps I should have researched more, but I know the Champion NY11C plugs work, so I went with those.
In truth, I don't know if there is a big difference from a $3.00 plug and a $9.00 plug. Hopefully the Champions will do the job.
 

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Yes, I looked them up, but there was no definitive detail. Resistor plug or no? I even went to the Bosch website, and still couldn't find an answer. Perhaps I should have researched more, but I know the Champion NY11C plugs work, so I went with those.
In truth, I don't know if there is a big difference from a $3.00 plug and a $9.00 plug. Hopefully the Champions will do the job.
I’m sure you will be fine. Was just pointing out that earlier someone mentioned buying OEM Plugs from the MB dealership in order to ensure getting the correct plugs.
 

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Discussion Starter #24
Yep, saw that too, but strangely enough some of the sites I went on said "this plug" or "that plug" doesn't go with my MB yr/model. Very confusing because different sites said different things. Since I'm a 'newbie' with my car I was trying to get the best choice from the recommendations, but there is a plethora of "mis"information out there. Even dedicated MB parts sites had different recommendations.Short of taking it to a dealer, I went with the best DIY option and asked here because there are so many knowledgeable folks here that have "been there, done that" ! Thanks for the input, always appreciated!
 

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That's odd the Benz dealer had resistor plugs. Mine doesn't, has the non resistor plugs with a couple different numbers depending on VIN.
 

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Discussion Starter #26
That's odd the Benz dealer had resistor plugs. Mine doesn't, has the non resistor plugs with a couple different numbers depending on VIN.
I guess I wasn't clear in my response... I never contacted a Mercedes dealership, just a local parts supply house as well as the 2 national chains. I tend to shy away from dealerships as they retail all their parts at inflated pricing. Maybe I should have done that right off the bat, since I spent so much time looking and calling for plugs. I do believe the Champions will be just fine though, based on forum recommendations. Fingers crossed that all this will cure my ongoing 'stumble' issues. It's really not a huge problem, but I'd like to resolve it before it gets worse and possibly creates bigger problems down the road.
 

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I guess I wasn't clear in my response... I never contacted a Mercedes dealership, just a local parts supply house as well as the 2 national chains. I tend to shy away from dealerships as they retail all their parts at inflated pricing. Maybe I should have done that right off the bat, since I spent so much time looking and calling for plugs. I do believe the Champions will be just fine though, based on forum recommendations. Fingers crossed that all this will cure my ongoing 'stumble' issues. It's really not a huge problem, but I'd like to resolve it before it gets worse and possibly creates bigger problems down the road.
I'm sure you'll be fine with those.

Might be worth bearing in mind though that the dealership is very cheap for some things, service parts are sometimes cheaper than I can find from aftermarket sellers on the Internet.
It's a lottery though, and I note that spark plugs are up in price there right now.
They actually review prices often according to supply and demand.

Its very common to go anywhere but the dealer but often worth a try.

Don't go there for a fan clutch though. Hahaha I did have to chuckle at the £700 😂
 

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Discussion Starter #28
I'm sure you'll be fine with those.

Might be worth bearing in mind though that the dealership is very cheap for some things, service parts are sometimes cheaper than I can find from aftermarket sellers on the Internet.
It's a lottery though, and I note that spark plugs are up in price there right now.
They actually review prices often according to supply and demand.

Its very common to go anywhere but the dealer but often worth a try.

Don't go there for a fan clutch though. Hahaha I did have to chuckle at the £700 😂
Good to know re: pricing. I just never even gave it a thought, but I will next time! Except if I need a fan clutch :LOL:
Thanks for the sage advice!
 

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Haha yeah and spark plug leads. Here, you have to buy the ends and leads and self assemble. And it's about £350 for the bits!
However some stuff is worth the money, and these are fit once in a lifetime quality. Which explains why we have 30yr old Mercs running round on their original leads.

Extra bargain stuff often seems to be brake stuff. Rotors are a bizarrely cheap price normally and best quality.

Quite good to have a friendly relationship with your nearest dealer, discounts are easy enough to get. Well, 10% is at least.
My local one turned into such hard work and so much attitude, from being awesome and even sending me the occasional freebie. High staff turnover soon sorted that out, but MB UK is a franchise.
I found one online that is awesome and posts me whatever I need at a good price with very little hassle indeed.

I think there's one or two in the States that are known for that?
 

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Discussion Starter #30
I found one online that is awesome and posts me whatever I need at a good price with very little hassle indeed.
I think there's one or two in the States that are known for that?
That would be good to know. I called the closest one to me (35 minutes away) and he quoted me $6.50 per plug ($52.00 for 8 plus tax), he had to order them but would have them by tomorrow morning, and I would have to spend almost 1 & 1/2 hours driving and paying, etc.. That's over double what the champions cost ($22.00 for 8 online, no shipping, no tax, delivered to my door in 2 days)! I was on hold for 15 minutes total as he kept checking part numbers to see if he had any. In the end he would not tell me the part # of the plug or anything about them, resistor, non resistor, etc., except to tell me they were Bosch and were the correct ones for my car. Meh... I'll stay with my NY11C's ordered online. No wonder brick & mortar stores are going the way of the dinosaur.
 

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Did you check the timing and run it advanced. I would guess around 10 degrees advanced at idle with recommended super grade gas. Maybe 12 degrees if you live up as high as Denver. I use 14 advanced for 380 SEL with regular gas at sea level. Timing being off would explain your original symptom as well. You will need an allen wrench, I think it's 10mm. don't forget to tighten it. 10 foot pounds should be enough. Double check that the distributor cannot turn after tightening. At the end of a long socket extender is easiest. Also, of course a timing gun.
Hope that helps.
 

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Discussion Starter #32
Thanks for your input Alex. I am at sea level in Massachusetts, so that wouldn't apply. Also, when I bought it and used it for the first 6-7 months it ran fine, but I admit, with minimal use. I suspect the dizzy cap may be the main issue, but I'll do the full tune, and see what happens from there. If it's still an issue, I start playing with the other suggestions made here. Keeping my fingers crossed though!
 

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Not sure of your expertise, but before I touched the EHA adjustment I would read all the posts by HD and go from there. But before then I would do two things. First make sure you have non resistor plugs and the correct wires. If you have resistor plugs and resistor wires, not good. These cars are finicky about plugs. You might also try different plug gaps. There are lots of posts on what people feel it should be. It does change things. Before I spent a lot of money though I would build a smoke machine and see if you have vacuum leaks. I think I spent about $10 making one and lo and behold lots of little leaks, well and a couple of big ones. Most of the time though fixing leaks are not costly, just time consuming. Even taking the manifold off, and doing the doughnuts is not expensive, maybe $30. The clowns foot is kinda expensive though.

When the car is running look at your EHA. Does it show evidence of leaking while running? You could also have a slight fuel pressure issue, not likely since it goes well when pushed buy who knows.

Keep us posted, there are lots of very smart people here.
 

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I read through NGK's explanation of resistor and non-resistor plugs, and it's accurate only a generic sense. It is true that resistor plugs will reduce EMI, including in our cars, but I doubt the noise levels in our cars would be anywhere near what's shown on the graph for non-resistor plugs. The reason is that there are 1kOhm resistors built into the distributor cap, rotors, and wires. I'm not sure of the technical details, but the cumulative 3kOhm is close to the typical 5kOhm resistor built into resistor plugs, and additionally, I think the plug wires are spiral-wound, which also suppresses EMI. Meanwhile, companies can "get away" with making almost every plug they sell a resistor plug because there are very few applications that immediately and noticeably degraded by the difference, and it costs less to reduce the number of different plugs. They will work in one sense: they reduce performance to some degree, but more importantly, significantly shorten component life. So that's why I'd recommend finding and running non-resistors if at all possible.

As far as which and where to find them, NGK seems to be the only ones still generally available. I can find them online, but I suspect it seems like they're disappearing from some parts distributors' product lines, sadly. One other thing I'll say about NGK is that their general replacement line (such as the BP9ES) isn't the highest quality plug. Their "racing" plugs are still made in Japan and near top quality, but there has been a downward trend otherwise. I've found several non-resistor plugs that do not check out with an ohmmeter after 5-10k miles, and in the snowmobiling community there has been a rash of problems traced to OE NGK plugs in the last couple years. I have also been able to order a few sets of Bosch W9DC0 (can't remember the MB part number), but it seems to be a very limited-run sort of item. Given the issues with NGK plugs, I'd recommend laying in a supply of those if/when you can find them. I bought two sets around 8 years ago; one's in my SEC, and I'd like to throw the other in the SEL, but I'm hesitant to put them in use since they're my last set.
 

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Plugs: no resistance
Wires: 1K ohm resistance
EZL: 750 ohms resistance built in.
No other part of the ignition system has any resistance. This is all in the Workshop Manual.

Btw, resistor plugs could have 1-2K ohms and up to 5K ohms resistance. No good, muy malo.
 

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I must have a different manual. What I read is "Interference suppression resistors: On distributor cap per terminal 1kΩ, spark plug connector 1kΩ, distributor rotor 1kΩ." There's also something about needing at least 2kΩ of resistance at the high voltage end, and a resistance specification of 700-1300Ω for the spark plug connector, rotor, and per terminal on the distributor cap.
 

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Small production runs of Bosch non resistor W or H_DCO (the O is for larger center copper electrode) plugs are still made. The people I know at the dealership parts dept usually keep some stock for preferred customer, but with their own internal code. Last time they asked $ 9 per plug, ouch.
Bad experience with Bosch made in India, Spain, Portugal, Poland, Czech etc were good.
Online is your best bet.
 

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"Resistor plugs were designed to reduce noise and interference to on board computers, it also makes the spark plug run hotter so it can produce the same spark intensity"

Actually, resistor plugs long predate computers in cars...by several decades if memory serves. They were originally designed to eliminate noise in car radios.
 
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