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  #16  
Old 11-08-2007, 02:18 AM
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Originally Posted by jfreezn View Post
<>

Does the engine EVER run smooth at idle, like cold or hot? Or damp days or dry days? Have you tried driving it without the fuel tank cap on? What about misting the plug wires with water in the dark, any external sparks you can cordinate with the misfire? Is the spark plug you mentioned the correct plug for that engine? I know that trying to upgrade plugs, especially Bosch, is NOT a good idea in a Mercedes.

I am betting it is the ignitor, which I believe has a tired capacitor in it.

Good luck, and be sure and let us know what fixes it!

Jim in Phoenix
For the first 5-10 seconds of starting it in the morning it has no misfires...and then it slowly kicks in. After that, there are no correlations between softer/harder misfires. I know before we did the Valve Stem Seals, when the AC was turned on, (aka more engine temperature), it used to misfire harder...but since fixing that, I haven't noticed it shake harder.
It's difficult to say because it differs every day regardless. There is no consistency at all.

Like tonight on the way home from school -- Absolutely beautiful to drive. The power was quick and it felt really responsive. Other days its feels slow to respond and doesn't want to really want to accelerate faster than it has to.

As for the plugs: Yes they are the Bosch H9DCO's. I scowled long and hard for the non-resistor spark plugs (one site claimed to have them but sent me resistor ones(yes very angry when I got them)), until I found mercedesshop had them on special order
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Last edited by ps2cho; 11-08-2007 at 02:27 AM.
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  #17  
Old 11-08-2007, 01:13 PM
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'94 S500: only 793 sold!
 
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Originally Posted by ps2cho View Post
Ok got it looked at by the local Benz shop...He first adjusted the mixture to the exact place where it should be...

So you guys think that I should find a nice looking used fuel distributor and replace that first?

I wonder if I will ever be able to get this fixed...
You could have it rebuilt . . . or exchanged . . . at "Jaytan". Check MENU#24 toward the bottom for their phone number.

We (Exclusive Motors) sent one to them for rebuilding and it fixed the 'stumbling' in the engine. Prices are reasonable.

Just buying a used one 'could' be ok but it's a crap shoot IMO.
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  #18  
Old 11-08-2007, 07:59 PM
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Originally Posted by JimF View Post
You could have it rebuilt . . . or exchanged . . . at "Jaytan". Check MENU#24 toward the bottom for their phone number.

We (Exclusive Motors) sent one to them for rebuilding and it fixed the 'stumbling' in the engine. Prices are reasonable.

Just buying a used one 'could' be ok but it's a crap shoot IMO.
Well I need to have my car in the mean time, so used would be the best option for me. At least if I replaced it with a used...nothing could be worse than I have right now LOL!

I don't understand how he knows that the Fuel Distributor has rust in it...I pulled off the intake and had a look around and I see no rust...?
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  #19  
Old 11-08-2007, 09:46 PM
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'94 S500: only 793 sold!
 
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Quote:
Originally Posted by ps2cho View Post
Well I need to have my car in the mean time, so used would be the best option for me. At least if I replaced it with a used...nothing could be worse than I have right now LOL!

I don't understand how he knows that the Fuel Distributor has rust in it...I pulled off the intake and had a look around and I see no rust...?
What I meant was there's two (2) ways . . send yours in to be rebuilt or get a rebuilt one from them w/ your old unit as a core. Prices are on their web site.

I don't think that it has 'rust' in it but they are a 'delicate' machine and get 'plugged' easily. When they plug, the car has a steady miss.
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  #20  
Old 11-10-2007, 03:46 PM
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When my 450SL (different car, V8 engine) had an intermittent miss at different speeds, particularly idle, I went through the same process you are determining fuel versus ignition, and after seeing what looked like marginal readings to me on an old Sun LS2000 ignition scope I have, I changed the ballasts and ignition wires on general principle, and then (incorrectly, it turned out) moved on to fuel thinking I had good hot spark on all eight. After quite a bit of head scratching over the fuel injection, I went back and used the old school, old fashioned way of isolating a single cylinder miss and found it was electrical after all. With the car idling, I pulled the plug wires one at a time, listening for whether they changed how it was running. This technique is usually used to isolate whether a single cylinder is completely dead, since the engine will run the same with or without the dead cylinder's ignition wire connected, but in my case I was listening for whether disconnecting some cylinders made it a lot worse while others made it just a little worse. Long story short, I found two different cylinders that made a lot of difference, and then with some horsing around moving whole ignition wires from one cylinder's use to another figured out I had (in my brand new set of factory made to length Bosch replacement ignition wires) not one but two flaky wires. I cut off and remade the plug end on them and the problem was solved. Two morals here. First, if I had taken the car to a shop with a big sensitive ignition scope and a technician who knew how to read it, I am sure the two wire ignition miss would have been visible to a trained eye (even though I couldn't see it on my dim, small LS2000 scope). Second, because my ultimately-ignition-wire fault continued even after changing all the ignition wires, it reminds me that just because a part has been changed doesn't mean it isn't (wasn't) the problem. With other kinds of analysis available, not as many mechanics spend the time to read secondary ignition scopes anymore. Be sure before you rule electrical out entirely that someone has "scoped" the ignition system. A good ignition scope is a good tool for hard to find misses in the right hands. This is the tool "Diesel911" was refering to earlier, and I don't think from your posts that it has necessarily been tried. If you want an idea of what that's all about, look here: http://www.babcox.com/editorial/us/us30224.htm.
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  #21  
Old 11-11-2007, 03:20 PM
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Ps2,

I've tracked your car across 3 sites and see no report on your fuel filter condition. Have you determined it's clean or did you remove it and find evidence of tank deposits?

What's the O2 status when out of circuit?

JimF used the term "crap shoot" on the rebuild. He's right, and a proper disclaimer. The car has a troubled history as you've described. Think of what part(s) dates back to the prior owners woes. Things like the F-distrib. do fall in that range but is a guess.

Before ordering a spendy part, you need to recheck the basic stuff. Actual vacuum tests with a gauge. Squirting cans of various products is a method but leaks hide. Fuel pressure readings would be of value.

The O2 sensor is suspicious from contamination how much SeaFoam, Tecroline and other VooDoo chemicals has she drank? Is the EGR valve stuck open? There still are some easy but critical tests.
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