i need help.. my 1993 mercedes fail emission test low speed but pass high speed. i have new plugs and wires any ideals how to pass this emission i need a sticker thanks.

Why are you running 87?

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Did the car fail HC, CO, or NOx??

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i took it in friday and it fail the low speed but check this out. today i had my wife to take it back and another guy pass it he said the young man that check it friday. did the wrong test on it and was new so now im good to go thanks for the help.

Don't run 87 in it for much longer. The compression ratio on these cars requires high octane. The knock sensor is also very rudimentary on these engines and does not pull timing like a modern car. You can have pinging/detonation and not even hear it in the cabin. Will it cause catastrophic damage in the short term? Probably not. But long term engine health will be compromised.

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