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2007 ML 350, 2000 Corvette, 1969 Yenko Camaro
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Discussion Starter #1
Thanks for all the valuable feedback guys.
OK I installed the new cap and rotor today, no change. I also replaced the soaked plug just in case.
I left the new #4 plug installed, pulled #4 wire and attached it to the old plug and started the car - and grabbed the #4 plug wire with the old plug dangling off the end. WOW!!! It sure is getting spark!!! I felt it clear up in my fillings. Let out some colorful words as I watched the old plug resting on the frame sparking like hell. Tonight I'm gonna do the darkness test just to see.
Someone previously suggested testing the injector. I'm now leaning toward a fuel problem - like way too much getting in #4. When it is running the exhaust is thick and rich with unburned gas. When I rev it the fumes and smoke are really bad.
How do I check the injector?
 

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One of the BW Old Guard/R129, W204 Moderator
1997 SL500- 40th Anniversary
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7,166 Posts
...When it is running the exhaust is thick and rich with unburned gas. When I rev it the fumes and smoke are really bad.
How do I check the injector?
Where the hell was this pearl of information when you started out this query? What else are you holding back?

:)
 

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82 380SL 96 SL500 03 SL500
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6,164 Posts
Just a tip.

It helps to continue with a thread to its conclusion rather than start several new ones concerning the same problem. It's pretty hard to help when you need to look up multiple threads to see what's been suggested and what's already been tried.
 

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2007 ML 350, 2000 Corvette, 1969 Yenko Camaro
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58 Posts
Discussion Starter #4
My bad....

Thanks for the tip. Guess I figured I'd save some reading as I eliminated some suspected trouble areas.
Yes now that I ran the engine in the garage I realized just how rich and thick the exhaust really is. It fills the garage and smells like unburnt gas.

I did the darkness test to look for any plug wire arcing and saw nothing.
Thanks guys
JZ
 

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Premium Member
1986 560SL with M120 V12 Engine, 1988 560SL Stock
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10,211 Posts
Hows compression on #4. You will need a CIS fuel system pressure gauge and follow the directions on the CD or the online manual. Checking the injectors without a CIS injector tester is difficult. If your creative you can make your own CIS pressure tester using a pressurized fuel reservoir with a valve gauge and liquid pressure regulator.
 

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1976 450 SLC. (working, in need of paint)/1987 300E/1989 635 CSI/2004 Honda Element (appliance)
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142 Posts
Just one cylinder fouling the plug? And only #4?
When was the last time a bottle of Techron hit the tank? Before you start taking everything apart, go to the closest auto shop, and get 2 bottles of techron, or other fuel injector cleaner. If you can get a can of lubro-molly, go ahead.
Now what you want to do is take one full can of techron, and use it when the tank is at about 1/4. Run the car in the highway as far down as you dare. Then when you tank up, use the second can.
If you live in a relatively unpopulated area, take the can of lubro molly, and disconnect an easily replaceable vaccuum hose close to the intake, and let it suck it up. It will want to die on you, but just feather the throttle a bit. Once the car dies, do not try restarting it. Just let it sit all night. Next day, just turn the car on, let it idle a bit so that all the soot comes out, and take it for a drive.
Last, but not least, when was your O2 sensor last checked/replaced? a burned out O2 sensor will make your car run rich.
Do the easy things before you get into the taking stuff apart Phase. The CIS injectors are very cheap, if it is the injector you are looking at a whopping 15-20....
 

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2007 ML 350, 2000 Corvette, 1969 Yenko Camaro
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58 Posts
Discussion Starter #7
Thanks Smolina

Just picked up a big bottle of Techron. I'll have to siphon off some gas, it has 3/4 tank.
And yes it is only #4 cylinder flooding the plug. The other plugs look great.
The PO only put 5k miles on in the past 5 years and hasn't driven it much for months before I bought it.
Don't know when the O2 was last checked.
The rich exhaust smell was gas of course but it had a funny smell to it. The only way I can describe it - it smelled a bit like camfor. To me that's old bad gas. What puzzled me is, he drove it 55 miles to show me the car and 55 miles home with no problem. He put 1/2 tank gas in and the miss started the second I pulled away a week later from his house.
 

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1976 450 SLC. (working, in need of paint)/1987 300E/1989 635 CSI/2004 Honda Element (appliance)
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142 Posts
These cars are the opposite of US cars. They feel and act better when they are driven, and driven at autobahn speeds. They were designed for the Autobahn, so when they sit, things tend to stick.
Your gas might be stale, so you have 2 options. Drain the tank and use the gas in the lawnmower, snowblower, or if you are in CA the water pump, or just use the car for a bit, and put some fresh gas in it until you have burned through the old gas.
The Techron should help. If it is still fouling the #4 plug, I would just get a new fuel injector, although at that point, you should also replace the insulator, and the fuel injector seal (also dirt cheap).
If you feel up to it, just drive it on the road for a bit and see if it gets better.
 

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2007 ML 350, 2000 Corvette, 1969 Yenko Camaro
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58 Posts
Discussion Starter #11
Still #4 cylinder

Finally got some time to spend on this #4 cylinder miss.
Today I replaced #4 injector along with injector holder and O-ring, cleaned the fuel line out, added a large bottle of Techron to 1/2 tank of hi test gas. Fired it up - at first it seemed fine, running smooth. As soon as the high idle kicked off the exhaust was clear and lean. I put it in gear and the idle was relatively smooth so I took it out on the road and it still felt great.
I did about 5 miles with some WOT driving, power felt really good. By the time I pulled in the driveway it was missing again. I pulled #4 plug wire and it made no change in the idle - so #4 is still missing and gas soaked.
 

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1976 450 SLC. (working, in need of paint)/1987 300E/1989 635 CSI/2004 Honda Element (appliance)
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142 Posts
Do a compression test, and do not panic.
I had a cylinder with 85 and the rest were at 160. It turned out that the car had not been used in a while and I had a stuck valve.
Now is the time for the Lubro Molly. I think that Advance has it.
If you have a low compression on that cylinder compared to the others, then what you might want to try is to find a suitable vacuum port (the one going to the booster will do nicely), and just dunk it into the can of lubro molly.
The engine WILL hesitate, so just feather it, and when just a bit is left, let it die. leave it over night.
Next day, start it up, and remember there is going to be a ton of smoke, so do not panic. Drive the car for a bit, see if it improves. I find it strange that you have spark, you have gas (and a working injector), and still it soaks only one. One last thing... Any blowby coming from the oil filler cap?
I am not sure (as my engine is a 450 with hydraulic "lifters") if you can take a look at the lifters and see if they are soft or collapsed? (lots of articles about THAT...:) ) I think that you have something stuck somewhere.
 

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2007 ML 350, 2000 Corvette, 1969 Yenko Camaro
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58 Posts
Discussion Starter #13
Thanks Smolina

When you say Lubro Molly do you mean oil or an injector cleaner?
I'll go get some tomorrow and try it.
I guess the thing that confuses me is this engine ran fine when the owner drove it 55 hiway miles to show me and 55 miles home and it ran fine. Then all of a sudden it developes this miss. He said in 2007 he experienced a rough idle and took it to a Benz dealer. They did new plugs and wires and fixed it.
So far I did Techron, new plug, cap, rotor, injector and seals on #4.
Thanks so much
JZ
 

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2007 ML 350, 2000 Corvette, 1969 Yenko Camaro
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58 Posts
Discussion Starter #14
P.S.

Don't see any blowby at the cap but it is wet underneath, from splash, and the breather tube feeding from valve cover up under the air cleaner shows a little oil wetness in the tube. Plus there is no engine tap or noise.
 

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2007 ML 350, 2000 Corvette, 1969 Yenko Camaro
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58 Posts
Discussion Starter #16
Pulling my hair out!

Did a compression test on #4, even with my leaky old Hastings I got
120-130.

Went to 4 different parts stores, no one carries Lubro Molly but all said Marvel Mystery is about the same. So out of desperation I bought a bottle. Ran the motor and started dumping it in (my booster tube is a solid line).
I smoked out the whole neighborhood for blocks with white/gray smoke. Kept the motor running til it cleared. The miss was worse. Pulled the plug and cleaned it, it was oily. Drove the car, miss was there through all rpm driving. Pulled the plug again and it looked oily again.
I'm afraid to drain the oil and look at it.
 

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Premium Member
1984 380SL, 1973 450SLC
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2,174 Posts
You can pull the dipstick to check the condition of the oil, feel it and smell it. I can't see where you ever swapped the plug wire. I saw where it gave you a kick, but a weak spark will still light up the average person, and not jump the gap on the plug... just a thought..
 

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1976 450 SLC. (working, in need of paint)/1987 300E/1989 635 CSI/2004 Honda Element (appliance)
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142 Posts
Thinking a bit.... You replaced the spark plug right? Did you remove the connector bit and let it be a plain thread? I did that to mine when I changed the spark plugs, and could not figure out why the cables were always falling off.... Until I read a spark plug thread, and saw that you actually had to remove the tip (that is like a weird ball) and leave the threaded part. Dumb on me, I know, and worthy of another current thread.... :rolleyes:
 

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2007 ML 350, 2000 Corvette, 1969 Yenko Camaro
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58 Posts
Discussion Starter #19
plug wire

Yes I removed the plug cap and used just the threaded stud. I also swapped the #4 and #3 plug wires. The miss was still there so I pulled off #3 wire, which was on #4 plug, and the miss was still at #4 plug.
When I checked the spark on #4 wire with the extra plug freely attached, I grabbed the wire inches away from the spark plug and it still lit me up. I was going to ground it on the frame to check the spark but I guess the spark was jumping from the wire thru me as a ground.
I really appreciate you guys working with me on this issue.
Thanks so much
Jeff Z
 

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1976 450 SLC. (working, in need of paint)/1987 300E/1989 635 CSI/2004 Honda Element (appliance)
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142 Posts
Lets work our way backwards then. We can assume that the spark plug is OK, and the cable is OK. Now how did the cap and rotor look? Check the insulator below the rotor. They tend to crack, and get brittle with old age, and arc inside the distributor.
On the fuel side, you Might have a bad fuel distributor. The only real way to test it is to crack open the fuel injector and measure the rate of fuel coming out. There are several charts of what that flow needs to be, but I do not know it off of the top of my head. There is currently a thread about somebody "fixing" a fuel distributor with a new gasket as the gasket was damaged and was allowing too much gas on one cylinder.
Go for the easy part first though. Make sure that your cap and rotor are perfect (even though you might have changed them I do not remember) and that the insulator is in good condition.
 
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