chance2benz

Please HELP- 94 e420 FAILED SMOG Again

My 1994 e420 keeps Failing NV Required Smog Test: for the third time.
So far I have changed spark plugs ( Bosch F8DC4), spark plug wires, 2 New Bosch dist. Cap. New Bosch rotor(2), coolant level sensor, coolant temp sensor.
Here are my test results,,,,,,,,,

Test Parameter. Result. Additional info.

Idle speed CO. 9.99 %. Greater than 1.2 %
High speed CO. 8.24 % Greater than 1.2 %
Idle speed HC. 671 Greater than 220 parts per mill.
High speed HC. 425 Greater than 220 parts per mill.

Also; the smog check " technician" says engine is getting 'way too much fuel' pumped into the engine - so much so that it is also causing a "Misfire" because of Excessive fuel.
OK guys: Please Help, Advise what to repair, replace ; as I really Need to at least PASS smog test !!!!!!!
THANKS ALL for Help, Suggestions, Recommendations etc. Chance

ptoro01

Well with those numbers the check engine light is probably on, what codes are you getting?

Excess fuel is in relation to air and spark, if you don't have enough air, no matter how good of spark, it won't burn.

Have you checked compression?

Vacuum leaks?

Test if your O2 sensors are good.

Plutoe

There is a very specific factory test and adjustment process for your situation.

Subscribe to Startek Info put your VIN in and search document AR0741P0750A and sub documents with special tools required to adjust CO potentiometer--depending on your engine the correct CO value should be 1.5 percent plus point 5 percent.

Additionally find someone who has and is experienced and knowledgeable about the MB HHT. That tool is also required.

Failing that sell the CAR!!

MB300te91

I just went thru a rough ordeal with my 91 300te passing smog It just passed smog this morning. I first fail with high meas. all across the board for" calif meas." I replace the cat. first then I retested again and failed, but some meas. drop O2 and some others an all, but I still had high Noz. found after a few test vacuum did not engage EGR then found out a solenoid was bad that turns on the vacuum. after fixing that my EGR valve had a hole in some where. It would not hold a vacuum pressure.

clarkz71

Unplug the MAF, that will put it in default mode.

If it runs better, the MAF is bad. Quick, easy test.

report back if that doesn't help, I have more info.

Onash

For what it's worth, my 95 failed miserably (I posted the numbers previously). The magic to passing the smog check CRC Guaranteed to Pass. Search my previous postings. It is $12 and they will pay you double back if it doesn't pass as long as the CATS are ok. It worked for me.

Worth a try.