1987 190e 2.6 SMOG FAIL in CA

[racnic]

Hope someone can give me some advice. I have a 1987 190E 2.6 that is failing at a Smog Test only station. I've change the spark plug wires, rotors & caps and catalytic converter. The smog check test report is below. Any advice would be appreciated.

HC(PPM) | CO(%) | NO(PPM)
TEST | MAX GP MEAS | MAX GP MEAS | MAX GP MEAS
M1: 15 MPH | 118 293 212 | 0.75 2.25 0.46 | 799 2002 2283
M2: 25 MPH | 93 243 128 | 0.63 2.13 0.26 | 738 1802 911

[Duke2.6]

How was it conditioned? The much improved 25 MPH readings indicate the catalyst may have been too cold on the 15 MPH test. Based on the CO readings the mixture doesn't look too bad, but I would check duty cycle and scope the 02 sensor wave form and ignition wave forms.

Also, go back and edit your first post to include the 02 readings As you will learn, the O2 readings are an important diagnostic tool. Also add the RPM readings, and is it a manual or automatic?

Does it have proper NON-RESISTOR plugs, like Bosch Super H9DC?

Is the new catalyst an OE or aftermarket unit specifically designed for your car or some generic cat that an exhaust shop welded on?
Read the following thread and all the links it references to educate yourself.

http://www.peachparts.com/shopforum/tech-help/117048-successful-ca-asm-emission-test-ke-fuel-system.html#post833484

It might squeak by with some ignition map diddling.

Duke

[racnic]

Here's the updated test results:

TEST
M1: 15mph
RPM MEAS= 1440
%CO2 MEAS=14.4
%O2 MEAS = 0.5
HC(PPM) MAX = 118
HC(PPM) GP = 293
HC(PPM) MEAS = 212
CO(%) MAX = 0.75
CO(%) GP = 2.25
CO(%) MEAS = 0.46
NO(PPM) MAX = 799
NO(PPM) GP = 2002
NO(PPM) MEAS = 2283

TEST:
M2: 25mph
RPM MEAS= 1880
%CO2 MEAS=15.0
%02 MEAS = 0.1
HC(PPM) MAX = 93
HC(PPM) GP = 243
HC(PPM) MEAS = 128
CO(%) MAX = 0.63
CO(%) GP = 2.13
CO(%) MEAS = 0.26
NO(PPM) MAX = 738
NO(PPM) GP = 1802
NO(PPM) MEAS = 911

The car is in good running condition. It's an automatic. I'm not sure if its running NON-RESISTOR plugs, like Bosch Super H9DC? I have to check. The new catalyst is a generic one that muffler shop welded on. I'm not a mechanic so some of your terms are new to me like, "checking duty cycle and scoping the 02 sensor wave form and ignition wave forms". I'm going to read your recommended thread and try to understand. Worst case I can bring the thread to my mechanic.

[Duke2.6]

The relatively high O2 content on the 15 MPH test indicates that the catalyst was WAAAY too cold, which means you need to pay close attention to "conditioning" prior to submitting the car for test. I discuss this in the referenced threads.

Even with only 0.1 percent O2 at 25 MPH the HC is still high but if the catalyst was efficient enough to use all of the O2 the HC would probably be within the limit, but it will be tight. The key is to ensure the cat is hot enough to meet the 15 MPH numbers. In that case the 25 MPH test is usually no problem.

Owners who want to get these cars through emissions without spending inordinate amounts of money for "fixes" should understand how to check and adjust the duty cycle and how to check the O2 sensor. Both have been discussed extensively on this forum (use the search function) and service manual data sites.

My gut level feel is that your duty cycle and O2 sensor are probably okay. The primary issue is proper pre-test conditioning, and if the cat needs a little help to get hot you can use the referenced links to retard the ignition timing by judicious tweaking of the centrifugal advance curve (short the R16/1 pigtail) and block the vacuum advance.

If it currently has resistor type plugs, don't even THINK about a retest until you install the proper non-resistor Bosch Super H9DC (NOT HR9DC).

Duke

[Phalcon51]

Here's what I did:

Almost a week before the test, I ran a bottle of "Guaranteed to Pass" fuel additive to a full tank of gas, ran that tank through and filled up with a fresh tank the morning of the test. The wekend before, I replaced the air filter and changed the oil and oil filter. Don't know if that really helps, but it can't hurt. If your plugs haven't been changed since the last smog test, or you have no idea when they were last changed, put in a fresh set of standard single electrode Bosch plugs of the correct heat range. Check with your owner's manual or the dealer if you're not sure. Next, I disconnected the electric cooling fan plug near the A/C receiver/dryer, hopped on the freeway and drove about 5 mi. one way and then 5 mi. back at 65-70 mph, then sat outside the test facility and ran the engine at 2000-2500 rpm in neutral for about 15 min. till the temp gauge was up to about 100+ deg. C (it was a coolish day, but make sure you've got a full reservoir of fairly fresh coolant), then, without shutting it off, handed it over for testing. It passed with flying colors!

The trick seems to be to get that catalytic converter as hot as you can before the test is run, and try to keep it that way right up to the moment it's tested. If you do it during the cool part of the day, you can control the engine temp when running a high idle by just backing it off to about 1000 rpm, where the engine fan will cool it down a little.

DON'T FORGET to reconnect the cooling fan plug!

Hope this helps.

Gary

[Duke2.6]

Disconnecting the electric fan(s) is a VERY BAD IDEA!!! The car could boil over!

The electrics don't even engage until 105 C and the mechanical fan doesn't pull any significant air until 100C.

Starting the test with the coolant temp between 100 and 105 is good, and the electrics will keep the temp from going over 105C.

Duke

[Phalcon51]

Originally Posted by Duke2.6

Disconnecting the electric fan(s) is a VERY BAD IDEA!!! The car could boil over!

Duke

I've actually found it quite difficult to overheat the engine anywhere near the point of boil-over unless it's a very hot day and I've got the A/C on and the engine under load. At 1000-1500 rpm with no load on the engine the mech. fan seems to pull enough air to keep the temp high, but well under the critical point....at least on my car. YMMV. Obviously you should test it out first so that you're satisfied that you won't do any damage to your engine. I had replaced my water pump, hoses and coolant within the prior 6 months, so that probably helps as well. If it does start to get near the 120 mark, just shut off the engine for a moment, pop the hood and carefully reconnect the fan wires and then restart the engine to keep the coolant moving. You'll be able to see the temp start to come down within moments.

Experiment, use common sense and caution and I don't think you'll experience any dire consequences. But in the end, do no more than you're comfortable with.

Gary

[Duke2.6]

The emission numbers will not improve at temperatures over 105C. It makes absolutely no sense to disconnect the electric fan(s).

Duke