Failed smog high HC/NOx

[goldenE30]

Bought a motor with m50 inj. And new spark plugs. resealed before installation



heres my measurements

Going to put back on m20 injectors and buy new air filter

I have new rotor/distributor/coil/wires/fuel filter

Does have worn muffler with rotted holes, don't think this would cause a bad leak for the sniffer because it's so far back in exhaust stream.

Any ideas on other things to look at before I retest the car? Would like to avoid cat replacement to last possible repair, but most likely is the original one so probably needs to be replaced.


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[diggity_1031]

I dont think the injectors have anything to do with the test results. Looks like your CAT efficiency is 0% on the 15mph asm test. I have m50 injectors in mine and passed with flying colors on a 4 year old cat. Did you heat it up real good before the test?

[goldenE30]

Sure did, about 20 minute drive and idled until smog was performed


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[diggity_1031]

Have you tried a new o2 sensor?

[Best_name_available]

Have you tried a new o2 sensor?

This. I had numbers like yours and all I did was a new o2, a seafoam treatment and oil change. Passed with flying colors

[goldenE30]

Only have a one day moving permit, expires tomorrow. Unless I can find a new o2 sensor at a local parts store, I'll try out the o2 that came with the motor when I bought it. I'll post the readings after the next smog, hopefully it passes


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[goldenE30]

Ok, so I replaced the o2 sensor, unfortunately it had the late model harness connector and my e30 vert being an 87, I had to swap the connectors. Luckily the motor came with the late model harness so I swapped it last night and installed the sensor. Found a slight exhaust leak and fixed this this morning. Also Did a seafoam treatment(intake,oil,gas). Still failed. Cut my Nox numbers in half and hc's dropped too, just barely failed on the hcs. I'm most likely going to be replacing the cat because when I bought the car it had a blown head gasket and going to say the coolant/oil ate up the cat.

Any ideas before I look for replacement cat?

Here are my new numbers





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[reelizmpro]

Did you check for vacuum leaks? check for cracked hoses, evap purge valve hose, all the connections on the throttle body such as the ICV, etc. I don't think the cat is your problem since it looks great at 25 mph. Do the simple things first before diving into a new cat.

[Best_name_available]

Did you check for vacuum leaks? check for cracked hoses, evap purge valve hose, all the connections on the throttle body such as the ICV, etc. I don't think the cat is your problem since it looks great at 25 mph. Do the simple things first before diving into a new cat.

I forgot to mention I had a vacuum leak going to my brake booster that I fixed before I passed.... Also the fitting from the booster hose to the throttle body likes to come out a little bit so check that.




Do the rpms drop way lower than idle when you let off the gas in neutral?

[goldenE30]

It does drop Rpms after getting off the gas on idle, I'll try and bring it to the shop and smoke test it


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[Best_name_available]

It does drop Rpms after getting off the gas on idle, I'll try and bring it to the shop and smoke test it


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Take the icv off and spray the hell out of it with carb cleaner, like a lot.
I used wd40 actually

[jhaurimn]

Take the icv off and spray the hell out of it with carb cleaner, like a lot.
I used wd40 actually

Do NOT clean your ICV with wd40, OP. Get throttle body cleaner.

[Best_name_available]

Do NOT clean your ICV with wd40, OP. Get throttle body cleaner.

I did. And then dried it out as best I could and sprayed the little bit of carb cleaner I had through it. No issues and fixed my problem. I did have an extra just in case but I mean it worked.... What was the potential damage sir?

[jhaurimn]

I did. And then dried it out as best I could and sprayed the little bit of carb cleaner I had through it. No issues and fixed my problem. I did have an extra just in case but I mean it worked.... What was the potential damage sir?

Who knows. Might be fine