190E 2.3-16v, Combustion problem

[canada911]

Hello guys, I'm a active member of 190revolution.net and I hear alot of good things about this forum, so I deceided to ask your help here and hope someone can resolve my problems

So since I have the car (1 year ago) I have those physical problem:
-14mpg
-low performance, max speed of 160km/h
-bad responce, no acceleration
-sometime black smoke on acceleration, engine does some "puff" sound

I did alot of of test with the 190revolution members, but it was useless... until now

Now here are the most bizar parts:
-my lamda, and my O2 sensor output is good on idle (so I'm supposed to have a correct mixture) BUT it really smells fuel at the exhaust (O2 sensor is new) still on idle.
-When I accelerate the lamda goes down (rich) to like 10% and less. and I repeat: sometime black smoke and low acceleration
-there is always some liquid spitting out of the exhaust (more when the outside is cold), I think its fuel. BUt it is not coolant or oil.
-my engine compression is perfect, everything electronic is good(only the EHA that I'm not sure)
-my Fuel distributor, cap, rotor are new, wires are good, oil new, all filter change, etc...
-2 mecanics war not able to diagnostic the problem

SOOoo, the only output that is weird is the lamda going richer when acceleration.

Now here is my ignition pattern, something HAS TO BE WRONG in thoes! But I dont have enough of experiance with them to diagnose it:
Secondary igntion:

Primary ignition:

The ratio (for my probes) where 4000V for each 1V. Example one division of 1V equals 4KV. The zero volt is at the division where the "M1", "M2", "M3" or "M4" is (on the left scale).

For me the burn voltage seems to be really low: like 0.1V(on scope) so 400V... Isnt it supposed to be like 1KV??

Thanks alot for your time and your help!!

[Duke2.6]

The liquid in your exhaust is likely just water. H2O is a major byproduct of burning hydrocarbon fuels and in cold weather it will condense in the exhaust system, especially until the engine warms up, or if it idles for a long period.

One thing you might look at is a constricted exhaust system due to a collapsed catalyst bed or a broken muffler baffle.

One way to check this is inlet manifold vacuum. What are the numbers at idle and 2000, 3000, and 4000 RPM, no load?

Also inspect the exhaust system for evidence of a collapsed pipe or other damage.

Duke

[canada911]

That was one of the thing I suspected last summer, so I getted rid of the precat and cat, I dont think the exhaust is my problem... I agree that it could had been it!
I hope you are right, for the water at the exhaust...

The problem is not easy to resolve like I said, its uncommon...

You guys have to check my ignition tension wave, I'm sure the problem can be saw by looking at it!

There is REALLY a Demon in my engine, even after like 100 post and reply alot of diagnos, but the solution is still not there.... If it wasnt the 13mpg, and the lamda value at higher rpm, I would thought that its only my imagination...

The engine was rebuild last year, by the last owner of the car, I suspect it was principly 'cause he tought it was the cause of the lost of power, but it didnt helped alot so he deceided to sell the car... to me...

[psfred]

Lamba going low indicates excess oxygen in the exhaust, most likely due to serious misfire.

If this was going on before, the cat and precat are melted. You may want to unbolt the exhaust at the header pipe so the end of the manifold is free and see how it runs. Will be loud as all getout, of course, but if it runs normall, the exhaust is plugged somewhere.

According to my MB training manual, that trace looks like bad primary voltage or excessive resisitance -- either a bad EZL ignition system or a bad coil.

Check the coil resistance, and verify that the plugs are good. You should use Bosch or NGK copper core plugs, not platinum with the stardard plug wires.

Peter

[canada911]

Meaby I didnt explain myself corretly for the exhaust, infact I already got rid of the pre-cat and the cat, so actually my exhaust is a straight pipe ( + the raisonnator and the muffler).

Its COOL for your advice with the trace! what is wrong with the trace? I would be really greatfull to know how to analyse it, is it the burn voltage that is too low? Espasially on the primary ignition?

I'll check the coil resistance, to be sure that at least that is correct. For the plugs, they are new.

Any other advice with thoes trace? please?

Thanks alot guys!

[psfred]

OK, here goes.

The height of the tall, thin line is the firing voltage. The sorta straight line after the big peak is the spark voltage. The length of this line is the duration of the spark.

When the spark stops, the voltage will oscillate up and down, eventually dropping to zero. It should go negative during these osccilations.

What I see is OK firing voltage, but low spark voltage with some spikes in the spark line. According to the book, spikes are from fouled plugs, low spark voltage is from excess resistance in the secondary circuit (wires, cap, rotor, plugs).

My guess would be a bad coil, coil to cap, or using high resistance wire ends with platinum plugs.

Also, if it runs very rich due to a bad o2 sensor, the plugs will carbon foul pretty fast.

If it were my car, this is what I would do: Verify the condition of the plug and coil wires. You must check the resistance to do this, eyeball won't work. All the leads must be very similar. Make sure the contact button on the cap to the rotor is good, they can get broken.

Check the resistance of the coil. I don't know exactly what it should be, but I seem to remember 1.5 ohm. This is between the ground terminal and the switchbox terminal, and between the ground terminal and the high voltage (coil wire) terminal.

While you have the coil to cap wire off, chech for burn marks or carbon tracks under the wire end. If you find any, the coil is toast, get a new one.

I'd also check the condition of the connectors on the coil -- corroded wire connections will limit the current and hence the spark, so the spark blows out under load, producing all your symptoms.

What brand of plugs are you using, and what is the gap?

Peter

[Stan Pittman]

Check the valve timing

[canada911]

Your right the spark voltage is way too low! I compared with an other car and it was about 2kV, my 190e has a spark voltage of only 400V!! somethings wrong.

I tried to find high resistance on the secondary side, but unsuccessfully...
The secondary coil is 8.6kOhms (it is in the MB spec.) the primary was about 0.9 ohm (inside the spec too). The wires are all ok and have neglectable resistance. The rotor and cap are brand new, there is now trace of carbon nowhere. I use Bosch copper spark plug.

If the spark voltage is low for ALL the cylinder, that could mean that the problem isnt at an individual spark plug or wire, but at the high voltage coil or before it, no? What else could 'cause that low spark voltage??

Could it be a bad fuel/air ratio? ( I dont think so, cause the firing voltage and the burning time would be false...) Or a bad ignition module?

On the MB service CD, they show only 1 wire connecting to each of the 2 pole of the primary coil. On my car there is 2 wire connecting to each of the primary coil pole... Is that normal???

I really need your help dudes, It now does like almost 1 year that I'm trying to find that freaking problem....Thanks alot for your help again, I really appreciate it!

[psfred]

If the coil is good, the only other thing that will cause low spark voltage that I know of is a bad switching unit. I believe in the 190 this is also an EZL unit, although there may be a distributor rather than just the rotor on the end of the cam.

If the current going to the coil is inadequate, the spark developed with the current shuts off will be weak.

Check for corrosion in the connectors for the coil on both ends (at the coil and at the switchbox unit).

Peter

[Paulwho]

canada911.
As Stan suggested recheck the valve timing this is crucial.

[psfred]

Paul:

I don't understand -- how can valve timing make the spark go wiffy at high rpm? I'd have though the spark is pretty much independent of valve timing, and it looks to me as if it's dying at high rpm.

Peter

[Paulwho]

psfred,
I looked at the secondary photos and saw little that concerned me. Generally speaking when an engine is overly rich the burn time drops drastically. So with his low fuel mileage I dismissed the patterns as pretty ok and thought about the complaints. Low power, poor acceleration, poor throttle response. So I pondered what is easy to check and often overlooked that could cause this and cam timing popped out of my head. Additionally the coil/EZL package is pretty bulletproof and when the fail they fail in a big way not over a two year period. Speriance guides me to always verify the basics first. We do not know what has been checked, and what has been overlooked.

[psfred]

Paul:

Yeah, but! Late valve timing (it's VERY unlikely to go fast, eh?) would give late power -- usually the effect is low power at lower rpms -- the power is still there, but you have to spin faster to get it, until you get to the point that compression goes down because the intake is open part way up the compression stroke. Usually bends valves on a Benz if its THAT late. Easy enough to check, too -- if the chain is stretched enough to make the engine run badly, the quickie line up the notch system will tell you pronto.

Late valve timing won't make it go rich, though -- this is metered FI, it will only add proper fuel for airflow unless the fuel distributor is buggered. I'm no expert on ignition traces, but all the ones I've seen have a fairly straight line for zero voltage, not the jagged bouncy stuff I see here. Could easily be overrich, but why is combustion going to pot at high rpm? Given that fuel flow is determined by airflow, I still think there is a misfire problem first.

This is presuming that there isn't anything else wrong, though, like a hole in the cat or something. Or toasted or disconnected O2 sensor.....

He doesn't say if it runs better with the EHA unplugged -- this would tell me more.

One last note -- if the coil (or wiring) is bad, would it do this? I had a bad coil on my old Dodge Aires that gave similar results -- lost power under load. New coil fixed it.

Peter

[canada911]

Ill continue to check what you said, here is some explaination:

I said everything electrical is good cause I already tested it with and without the EHA connected = no differance,

I changed the fuel distribturor cause I tought it was the problem.

The lamda is good = 50% with the correct variation BUT it smells fuel at the exhaust! How can the air/fuel ratio be good but it still smell gas! I really think it is due to the too low spark voltage...

[psfred]

Does the 16valve have variable valve timing? If so, if the cam is installed incorrectly, the valve timing will be way off.

Raw fuel at the exhaust means either a serious fuel supply problem or a serious ignition problem UNLESS you have a leak in the exhaust ahead of the o2 sensor -- if outside air is getting into the exhaust (it will get sucked in in pulses at idle), the O2 sensor reading will be way off.

Have you tried to set the idle mixuter with the EHA unplugged using a CO meter?

Peter