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  #1  
Old 03-22-2004, 10:26 AM
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incompleat combustion 190E 16V

Hello guys,

a couple of month ago I posted here to have help with my car problem, since that I checked everything you guys said and I have a bit more of developpement:


Here is the probleme on my 2.3-16v 190e 1987:

- Unburned fuel smell at the exhaust, it is worst when I press the gaz pedal!

-Very low mileage : 13mpg

-low performance

-When the car is cold (30C) and I press hard on the gaz pedal, The engine is loosing alot of power and I here Puff-Puff-Puff-Puff inside the engine bay and that until I release the gaz pedal.

-Low acceleration at higher speed (80km/h +)


I've checked almost everything:
-fuel mixture is great: O2 reading are PERFECT (the O2 sensor is new), a scope reading on the ignition is also perfect(correct burn time and voltage), AND the sparkplug tips are also perfect( nice brown). So I beleive the problem isnt in the mixture.

-Ignition timming is great and ignition voltage to (scope).

-Valve timming and valve clearance is perfect.

-No exhaust leak.

-SUmmary: injection and ignition seems to be fine, but there is still alot of unburned fuel passing to my exhaust system...!!

Hypothesis: there is a part of unburned fuel that doesnt expode in the cylinder OR the explosion in the cylinder is too long and the extra fuel just goes in the exhaust: where I smell it.

-Also: the engine had been rebuild 10K km ago, but I think only the head had been done.


What could be the problem??

Thanks!

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  #2  
Old 03-22-2004, 12:41 PM
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Location: san diego.ca.
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hi canada, from a fellow montreal area person.
in order to know for sure how your car is running you need current tail pipe readings.this is the best way to know what is going on. it is hard to smell the problem.easy to be fooled. with your bad gas milage you have a problem. tail pipe can say more than most other test. make sure you get all 4 numbers. hc, co,co2,02, and if they have it ,nox
this helps alot with finding a cure
sure miss french canada alot
rich
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88 300E White, sold 9-04
88 190E Black 2.3 sold
90 300CE White, Grey sold 12-24-04
92 400E White,Grey Sold 5-06
90 300CE 91K Signal Red,Black Sold 2007
1989 300CE Smoke silver,Tan Sold 1-08
1993 300E 3.2 M104 motor
1991 300CE White,Grey
1994 E420 beautiful car,gone to new home
1994 E320 Smoke an Parchment.Beautiful car
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  #3  
Old 03-22-2004, 01:30 PM
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About the only thing you haven't checked is exhaust blockage. Catalytic converters (and mufflers) have been know to collapse and block the exhaust system, and the symptoms you report could be due to the high backpressure caused by something blocking the exhaust system.

Sticking a potato up the tailpipe of someone's car is one of the oldest practical jokes in the world. The engine barely runs and no one can figure out why.

Duke
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  #4  
Old 03-22-2004, 01:42 PM
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Location: Montreal (Canada)
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Hello guys!

Thanks for your help!

I got rid of the pre-cat and cat a while ago last summer 'cause (like you) I suspected that! The muffler is Ok to. The problem really comes from unbearned fuel, but I dont know how comes there is unbernead fuel at the exhaust... But I agree with the fact that doing a gaz analysist at the exhaust tip would probably confirm that fact. I'll check what I can do to have the gaz analysed. But like I said, after 1 year of diagnose I am 99% sure it is raw fuel.


Why raw fuel??
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  #5  
Old 03-22-2004, 09:38 PM
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OH, I forgot to mention that I did a compression test on all 4 cylinder and it is perfect too...
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  #6  
Old 03-22-2004, 09:45 PM
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What are your readings on the O2 sensor?
I would recheck the O2 sensor, just to make sure.
I cannot imagine the sparkplugs being a nice brown if the car is using that much gas, it just doesn't make sense.
If that much gas is going into the combustion chamber, it must be black and sooty. Regardless of whether the problem is O2 sensor or fuel distributor. Too much gas in combustion chamber = sooty and black sparkplug tips.
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  #7  
Old 03-22-2004, 10:08 PM
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^^

I really agree with you Pesuazo!
Thats why I dont understand nothing...
I paid a specialized mercedes mecanic to find the problem 1200$Can, he didnt find the source of it! So I started searching myself by doing all the possible diagnose test, now it does almost 1 year and I still didnt find the problem!!


I changed the spark 3 month ago, and beleive me: the spark are perfect! Brown!
The scope graph is also perfect! (it indicat a perfect mixture)

AND:
The O2 is giving me the correct value!! BUT like you I was having BIG doubt about a correct mixture (even with all the problem) SO I deceided to put a brand New O2 sensor, result: the same reading = a perfect mixture!!!!

I went trew all my ressource, that is why this tech forum is my last resolt...

Beleive me: it smell fuel at the exhaust and I have some major misfire if I have the bad idea to press full throttle when engine cold(30C)!!

The 4 cylinder condition seems to be the exact same: 'cause the scope gives me the same reading to the 4 cylinder secondary ignition AND the 4 spark plug has the same condition.

BUt still that headack fuell smell!

EDIT: And it really comes from the exhaust, raw fuel! Also the lack of power and low mileage...

help...please!
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  #8  
Old 03-22-2004, 11:28 PM
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bon jour, hey you really need those tail pipe readings. get them at idle and at 2500rpm. when the car is warmed up.
thanks
rich
__________________
88 300E White, sold 9-04
88 190E Black 2.3 sold
90 300CE White, Grey sold 12-24-04
92 400E White,Grey Sold 5-06
90 300CE 91K Signal Red,Black Sold 2007
1989 300CE Smoke silver,Tan Sold 1-08
1993 300E 3.2 M104 motor
1991 300CE White,Grey
1994 E420 beautiful car,gone to new home
1994 E320 Smoke an Parchment.Beautiful car
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  #9  
Old 03-23-2004, 10:25 AM
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Are you sure that you don't have a gas leakage at the tank or the fuel pump/filter/accumulator, that would give a smell of gasoline at the rear of the car as well.... (and high fuel consumption)
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  #10  
Old 03-23-2004, 05:23 PM
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^^

Yap, I'm pretty sure that I dont have one:
I jacked up the car to check everywhere (especially closs of the tank and the pump). I even removed the rear seatbench too check under it... There's no leak...

I'll try to bring the car at a mecanic who does gas analysis...
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  #11  
Old 03-23-2004, 05:51 PM
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Location: Montreal, Quebec
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Canada 411: Something is fishy.
You said all tests gave good results (mixture ok, O2, plugs are OK, ignition is perfect, valvesOK, and everything else.
???????????????????????????????? and you get 13mpg.
Have you had these tests done at idle only? or at different RPM.
With and without load on the engine?
You said the engine is missing at a certain RPM and you smell gas: Could it be your fuel/air mixture goes wild under certain conditions (vacuum leaks, leaky injectors, fuel distributor?) Have you eliminated all possibilities of fuel leaks(filter, pump, fuel line, which wpould happen only when the car is moving or with the engine running?
How's you air cleaner? Any restrictions in the air intake at speed?
You have to take this problem with a different approach instead of throwing parts at the problem.
Do you deal with a competent mechanic?
JackD
Montreal
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  #12  
Old 03-23-2004, 06:45 PM
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^^
First of all, I learned my lesson with all the mecanics of my region(I dont wanna bless someone here, 'cause I'm sure that those mecanic are good, but not on my car)!
That is why I will be the only rare personne touching my engine and that for a while: silverstar inspected it first = they didnt found nothing fishy, then I bring it at this other mercedes specialist = nothing found. All of that had cost me ALOT of money! Beleive me! Diagnostic cost alot around here!


But thanks for your answer, here is mine:
the mixture is great and that always: at idle and at 4000rpm. Under load or at idle. I have a portable scope and I just had to plug it on the O2 sensor while driving (not a big deal).

But I didnt said that valve where ok (only that the timming, clearance and compression is perfect).

The engine is only missing when engine is cold and on WOT (on but condition at the same time)... at least I hear that PUFF-PUFF-PUFF.

Anyway the Mixture isnt the problem: I changed the FD, the EHA, the O2 (2 times), the AFM...and checked every sensor... but the question isnt there 'cause the mixture is good (even under load).

EDIT: Btw, my mixture is richer on WOT (but that is normal)

Air filter is new, no restriction.

Still that gas fuel smell (even on idle)... Could it be mecanical inside the engine?

Last edited by canada911; 03-23-2004 at 07:10 PM.
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  #13  
Old 03-23-2004, 08:58 PM
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Location: Montreal, Quebec
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How can the fuel/air mixture be OK if you smell raw gas in the exhaust and you only achieve 13mpg?
The only mechanical part in the engine that could cause anderratic fuel/air mixture is the valve train. Hace you worked on the camshafts? A cam with a few degrees off can cause lots of problems.
Silverstar: They are the one who wanted to replace a heater fan on my car and a climate control mudule on my car. The problem was a blown fuse. Go figure
JackD
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  #14  
Old 03-23-2004, 09:08 PM
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Location: Montreal (Canada)
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Quote:
Originally posted by Jackd
How can the fuel/air mixture be OK if you smell raw gas in the exhaust and you only achieve 13mpg?
I dont know man... I dont know....
But I really wish I would!

Since the start of this diagnose process, I had to play alot with mixture, and I noticed this: Whatever was the mixture setting (rich, normal or poor) I was still smelling that fuel and had low performance...

Meaby the gas analysis will help...

I was talking about engine problem 'cause I heard that carbon depot could cause HC to escape the flamme. I also heard that if the piston or cylinder wall are used that HC could also escape flamme... But of that much?? (13mpg)

I need more hypothesis here...please...

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