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CA SMOG FAIL: High HC @ Idle Only

Swapped to my spare AMM, that killed the car.

"Cleaned" with AMM cleaner the old one and reinstalled....doesn't seem to idle as "stable" as before.

Now I'm starting to see the AMM could be it....also put volt meter on 02 sensor. cold start at idle and steady .8v with no oscillation
 
Can't help but just wanted to say the allowable emissions numbers for my car in AZ are nearly double what CA allows you and mine is 12 years older lol. Max HC is 220ppm and max co is more than 1.20%. California really does hate the environment don't they, buy and junk a new car every year!
 
You gotta check for oscillation once the ECM exits open loop and enters closed loop. In other words.... it's gotta warm up for a while.

You gotta let the ECM learn too. Disconnect the battery, hold the cables together to discharge the capacitors, and recheck. It takes maybe 100 miles or so for LH2.4 to learn the idle speed and mixture.
 
Your Idle RPM is 772 which is pretty low. Do you have any way to raise it closer to 900- I bet it will be enough to pass. IIRC the max allowable RPM for Idle test is 1000.
 
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There isn’t a idle adjustment on a LH2.4 car
I know. There are some basic mechanical adjustments though that affect it, like throttle plate stop for example. Did you investigate the cause of the fault code that interestingly is related to idle?
Few band aid solutions can be attempted to raise it just for the purpose of passing the test if you can't get into diagnosing right now, some as simple as bumping the idle by adjusting the cable. At least you can verify that the IAC is not stuck or gunked up.
 
Wouldn’t tensioning the throttle cable a bit bump up the idle enough?
That or couple of layers of foil under the throttle stop. That car only needs may be 100 RPM more max to squeak under the HC limit. I would still look at the IAC motor first- the code came up for a reason.
 
I'm not well versed on lh2.4 so correct me if I'm wrong but the temp sensor plays a role in fuel mixture, if it's corroded or old that could possibly throw the reading off enough to make you fail.
 
That or couple of layers of foil under the throttle stop. That car only needs may be 100 RPM more max to squeak under the HC limit. I would still look at the IAC motor first- the code came up for a reason.
Code 1-3-1 is bad RPM signal, no? I have cleared that code, and haven't seen it's return. Since cleaning my original AMM the car spits a consistent 1-2-1 CEL code, which would indicate the bad AMM.
 
I would also peel back the boot on the MAF and check the terminals for corrosion.

I remember now that my 1991 744 had a corroded crimps and terminals for the MAF. I spliced in a clean JY pigtail to fix it.

You are getting close to the fix! It's throwing codes, so that usually helps narrow down the diag.
 
go through all your sensor connections and grounds to ensure you are getting proper feedback from the sensors if there is additional resistance or a warn out sensor this will cause you issues.

California has one of the most stringent test around so everything needs to be in tip top shape

luckily my 400k still passes :-)
 
you could try the pnp or ac circuit pins on the ecu to raise the idle a little bit. IIRC leaving pin 30 floating (the auto pnp pin) will raise the idle. Also either pins 14 and/or 15 (the AC pins) could be connected to battery voltage to bump idle also. on 2.2 the AC pin raises the idle to ~850 from ~750, idk about 2.4.
 
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I had one bad (failing) injector give me exactly the same symptoms. Engine ran fine otherwise. Got a set you could swap out quick?
 
Does it throw the MAF code with different MAFs???

Mine was throwing the code with my spare MAFs installed, which lead me to inspect the wiring more. I found corrosion in the female terminal contacts AND in the crimps for the female terminals. Resistance in the crimps can't always be seen. I've had to "restring" circuits that intermittently have issues.
 
Does it throw the MAF code with different MAFs???

Mine was throwing the code with my spare MAFs installed, which lead me to inspect the wiring more. I found corrosion in the female terminal contacts AND in the crimps for the female terminals. Resistance in the crimps can't always be seen. I've had to "restring" circuits that intermittently have issues.


I don't have many MAF's to experiment with. I have the one that came in the car and a unknown one for a spare. The unknown unit failed to produce a running vehicle.

Since cleaning the "known good" (it confidently got me 2k miles since I got the car) one from the car, it consistently gives the 1-2-1 CEL and runs a bit worse.

Looking around for a replacement MAF...what to do? Can't seem to find options beyond the $1,000 remanufactured option from RockAuto. Gsellstr mentioned NTK as a more reliable option for O2 sensor, are they a viable option for MAF?
 
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