1990 MM 4G64 Faill Smog Check

Hello Everyone,

My MM just Failed the Smog Check with high HC and Co HC was at 290 should be below 70 and CO at 10 and should be below .5

My truck is at 100k original miles and my dad didn't use it for year sat there not being used it runs Great a other then the occasional smoke once and a while, I feel that the valves might be leaking because of the occasional smoke and I think this is why it failed the smog check.

What do you think I should check do? you think I should get a new Engine or rebuiled the old 4G64?

I have a backyard mechanic that will charge me $250 to swap out the engine or about $500 plus parts to rebuild it.

I think rebuilding the engine is the best bet because Finding a 4G64 engine for my MM is going to be hard.

Does any know where I can located a 4G64 engine in Southern California for my 1990 MM ?

It's a bummer that the stupid smog isn't passing cause its a great little truck with no great issues other then that occasional smoke!

It runs great with No rough Idle or anything!

Thanks,

Roinhood

As long as it was taken decent care of these motors are barely broken in at 100k and should pass no problem. My guess is you need to do a little tlc to it, maybe new plugs and wires, new o2 sensor, etc.. Also pull off and clean out your EGR valve.

Things that cause high HC(hydrocarbons-unburnt gas) are vacuum leaks, defective cat, bad air injection parts(EGR and the like),defective ignition components/incorrect timing.

High CO(carbon monoxides):dirty air filter, faulty o2 sensor, bad/dirty maf, bad/incorrectly adjusted tps, bad engine coolant sensor.

These should get you on your way to getting it to pass smog. My old 2.0l would pass smog and it has over 200k on it never rebuilt, just gotta do proper maintenance.

Quote:

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Originally Posted by DroppedMitsu

As long as it was taken decent care of these motors are barely broken in at 100k and should pass no problem. My guess is you need to do a little tlc to it, maybe new plugs and wires, new o2 sensor, etc.. Also pull off and clean out your EGR valve.

Things that cause high HC(hydrocarbons-unburnt gas) are vacuum leaks, defective cat, bad air injection parts(EGR and the like),defective ignition components/incorrect timing.

High CO(carbon monoxides):dirty air filter, faulty o2 sensor, bad/dirty maf, bad/incorrectly adjusted tps, bad engine coolant sensor.

These should get you on your way to getting it to pass smog. My old 2.0l would pass smog and it has over 200k on it never rebuilt, just gotta do proper maintenance.

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Hello Dropped Mitsu,

My dads Old MM was well taken care but I think that its sat unused for like 3 years and and then used a couple times a month and I think some of the seals might of dried up.

let me ask you a question lets say that the valve are leaking oil occasionally do you that little oil being burned and spraying into the exhaust system might contaminate the Cat or even damage it?

Is there a way to test o2, MAF, and Coolent sensors?

Also I just sprung a Leak on the Radiator, it cracked just below the Radiator Cap should I just get it repaired? I heard that new Radiators are plastic and crack with in a few years and that the old Radiators are more efficient in transferring Heat out.

Thanks for your Help,

Robinhood