1986 190E 2.3-16 Chain Guide Rail Replacement - Page 12 - PeachParts Mercedes-Benz Forum

JimSmith · #**166** 05-16-2008, 01:42 PM

Racing,

I just sent him an email. I hope we have not pestered him to the point where he figures we are going to be a bigger pain in the rear than it is worth to him.

If you have any ideas on how to change the fuel mixture on these CIS equipped cars, it would be helpful to know. I have the 1986 Euro with the factory installed catalytic converter/O2 sensor/electronic fuel control system that I cannot get to pass an emission test here. The cars seem to default to a rich running condition that eats cats. So, we replaced the cat, and the O2 sensor which made the NOX emissions drop to well below the allowable limits, but the car still runs too rich - HC and CO2 are orders of magnitude too high - you can smell the stink and see puffs of black smoke shoot out when you pump the accelerator pedal. The manual says to adjust the lambda, but I am at a loss for how to adjust lambda. We have tried to adjust the 3mm Allen head screw just behind the air cleaner on the fuel distributor, but that seems entirely random. When we try to read the duty cycle from the diagnostic plug using a multi-meter set to read duty cycle we get numbers that do strange things, like hang around 50, dropping to 40 then rising to 60, or we can get it to hang around 20 and rise to 30, then drop to zero and reset at 30. All the while it blows black crap out the tailpipe and and leaves a black stain on the driveway.

The runs like a banshee. Idles smooth at 1,000 rpm. But it won't pass emissions blowing clouds of black crap out the tailpipe. Is there something fundamentally off, and what actually adjusts the lambda? Manual says make it 50 =/- 10, and that it should oscillate a bit. That condition can be achieved but it still blows black crap out the rear. O2 sensor test in the manual comes out with about 600 to 700 mV, which is greater than the minimum of 475 in the manual.

I am confused. I hope you can shed some light on this. Thanks, Jim

Tinker · #**167** 05-17-2008, 06:59 PM

Jim,

If your duty cycle reading is fluctuating, then it appears the car is in closed loop and functioning normally. When checking it, you need to take an average reading which is easier with a multimeter like a Fluke that has that function. As you are probably aware, right around 50% is what the factory states as desirable. But much like yours, mine tends to hunt around but usually is within a 5% tolerance with averaging. Just watching the readings can result in fluctuations from 30% to 70%.

Black soot does indicate a rich mixture so you will need to lean it out. Mine use to stain the garage floor until I got it correctly adjusted.

The 3mm allen wrench the correct tool with only slight movement of the adjustment resulting in significant changes.

Tinker

JimSmith · #**168** 05-17-2008, 07:50 PM

Thanks, Tinker. I have one more question, which way makes it lean. We have been operating under the suspicion that it is clockwise to lean it out, but we have had little luck and I am reluctant to keep turning it any particular way as eventually it becomes hard to start and won't idle smoothly. Jim

Tinker · #**169** 05-18-2008, 05:00 PM

Jim,

Counter clockwise to lean. Small increments make significant changes so don't get crazy. Ideally, in closed loop the EHA in conjunction with the other parts of the CIS-E injection system should constantly be trying to achieve lamba. You want to make sure its good and hot while setting and you need to make sure the allen wrench engages the adjuster as it is spring loaded. Give it a some time to stabilize between adjustments.

I'd be interest to hear how your duty cycle reacts to your changing of the mixture. Mine appear to move inverse to what I have read to expect. Higher duty cycles are a richer mixture.

If you can't get it to lean out, you could have a leak at the fuel distributor or EHA.

How far off is it from the standards?

Tinker

JimSmith · #**170** 05-18-2008, 08:55 PM

Thanks for the help. We were thinking lower duty cycle numbers were lean. I think that is backwards from what you did to lean yours out. I will try counter clockwise.

Before we put the new cat in (the old one had completely disintegrated and was gone - no trace of it anywhere) the numbers were reasonable for HC and CO, not passing but within 10% of the state specifications. The NOX were very high, like twice the state limits. The first thing we did was change the ignition timing - this is a Euro car and has a 7 or so position ignition timing setting device instead of the US car's resistor. The device is a set of resistors calibrated for worse than regular fuel to premium, and then a position with no resistor. We had been running with no resistor. I tried leaning it out after we put the cat in and turned the adjusting device clockwise, following a post from the site, but the author indicated he wasn't sure. Anyway, the NOX values came way down, to probably 25% of the state limit, but the CO and HC values were off the charts. HC is an order of magnitude high and the other is about twice the limit.

So we put a new O2 sensor in, thinking it was so old it might be sending bum signals to the CIS computer. Again, no real benefit - the really high HC value dropped to half its former ten times the state limit, but neither CO or HC passed. I will try again tomorrow. Thanks for the help, Jim

Tinker · #**171** 05-18-2008, 09:15 PM

Much the same situation here. Mine is a pain to get through the Ca. rolling dyno tests. They run both a 15 and 30 mph tests. It will usually just squeeze by the 30 irregardless of its state of tune, but it's a battle royal to make the 15. Something about a 20+ year old CIS system and the ever tightening noose the smog proponents advocate for ever few years. It's a major challenge.

Make sure you get it nice and hot before they test it and let us know how it turns out.

Tinker

JimSmith · #**172** 05-20-2008, 12:43 AM

Tinker,

I consulted my local MB mechanic who does work evenings out of his garage at home. He deduced I had turned the adjusting screw so far it was no longer useful to try to read the lambda numbers. Apparently once you get far enough out of whack the adjustment screw produces random or at least inconsistent results, which leads to more mis-adjusting. His cure is to unplug the EHA connection and tune it by ear to a high, smooth idle. Then plug the EHA back in and start tuning with the lambda adjuster, in small increments. Well, I didn't get the car retested, but my younger son (the one who's car was the subject of this thread) made the adjustments and the engine runs at a 0.5 +/- .05 or so and smooth as silk. No excessive stink from the tailpipe.

The next step, assuming the car fails emissions testing tomorrow, is to check the injector spray pattern. According to the mechanic, no lambda adjustment can counter an injector or two that is not properly atomizing the fuel as it is injected into the intake manifold. I will post the results tomorrow. Jim

JimSmith · #**173** 05-20-2008, 08:05 PM

Tinker and all,

Well, the procedure we used worked remarkably well. We may have crudded up the cat a bit, but after having HC's in the 350 ppm range (acceptance level is 217) and CO in the 5.5% range (acceptance levels are 0.70%) we ended up at 38 ppm HC's and 0.02% CO. The NOX numbers climbed quite high from a low of around 270 ppm when the cat was new to 1504 today, with an acceptance level of 1522. But we did put the spark curve back on the most aggressive to try to burn the fuel better, which gives higher combustion temps and gets you higher NOX. The time at those very rich mixtures, while less than 20 miles on the new cat, may also have damaged it somewhat. Oh well. Until next year.

Jim

Tinker · #**174** 05-22-2008, 10:47 PM

Congratulations. Over here on the left coast they test us every 2 years so one gets a small reprieve. If you are going to hang onto the car, you might consider adding some flanges between the cat and substituting a straight pipe to save the cost of a cat. These car tend to run rich with the aftermarket cats typically are undersized so they don't last as long as original equipment.

Tinker

JimSmith · #**175** 05-22-2008, 11:27 PM

Tinker,

We have an every other year inspection too, but in this case my son let the testing date pass by and the registration actually expired and we couldn't renew it until we got it through the emissions testing. As a result they penalized us and only gave us a year.

The cat in this car has been flanged since we had a Timevalve system installed that attaches to the headers a few years ago (I did the cat back when the car had about 70,000 miles on it and failed at a weld joint where the pipe entered the resonator - weld repaired it twice and then for half the cost got a lifetime warrantied Timevalve system and installed it). The Timevalve guys are local and they were reluctant to supply us with a cat at all because they apparently don't last long. So, we flange it in.

The aftermarket cats are kind of small compared to the original one, but they cost $85 instead of $1100. So, it is a pain that we have had to replace it twice but we are still over $1000 ahead of the option to put the OEM stuff in. The flanges make it easier to get in and out. Getting the O2 sensor out without wrecking the threads in the boss was a chore.

Glad the car passed and is properly registered again. Jim

JimSmith · #**176** 04-25-2009, 06:44 PM

Anyone know what happened to Racing? He was such a help - generous with his time and know how - I hope all is still going well for him.

My son is finally finishing his VEMS installation. He is in college and has limited time to work on the car - it is here at home and college is a 3 hour drive now. Jim

JimSmith · #**177** 07-11-2009, 07:12 PM

Well, still no sign of Racing. He is missed. We would like to share the excitement with him as we approach the completion of the VEMS installation. Plug wires (new solid state "distributor" has different connectors) and waiting for a fuel pressure gauge to set the fuel pressure regulator.

Lots of custom fabricated linkages and brackets to mount the new stuff. Should be ready by the end of the next week.

Jim

RdSnake · #**178** 08-08-2009, 01:58 AM

Im in the process of removing the timing chain cover and I have a question:
How many allen head bolts inside the head (below the camshaft sprockets) are there that hold the timing chain cover? TIA

JimSmith · #**179** 08-08-2009, 02:07 AM

Not near a manual at the moment, but as I recall there are 4. Two across the front, and one on each side, with the one on the tensioning rail side kind of hidden by the rail.

Hope this helps,

Jim