CRX VX(D15Z1) Failed Smog (HC & CO) in California - Fuelly Forums
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Old 04-09-2014, 01:28 PM   #1
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Join Date: Apr 2014
Posts: 5
Country: United States
CRX VX(D15Z1) Failed Smog (HC & CO) in California

Hello Fuelly! I recently swapped the D15Z1 into my 1986 CRX SI and took it out to the referee. Passed inspection but failed smog
My build thread:

I'm hoping someone can help me figure out what is causing me to fail HC and CO.

Here are the results for reference:

The difference between test 1 & 2 is that I fixed my EGR. Results were improved a bit since the EGR was no longer stuck open. The EGR was stuck open initially because the vacuum lines were run incorrectly between the EGR valve, EGR solenoid, and EGR Controller, which is now corrected in test 2. Since the EGR is not stuck open, it appears the NOx went up but I didn't fail because of it.

Things that I've done or tested prior to the smog tests above:
1. New O2 sensor (4 Wire)
2. Tested EGR Valve by applying vacuum to the valve. The car dies during idle if I apply vacuum to the EGR valve. This should handle NOx but I'm uncertain if it causes HC or CO.
3. New Sparkplugs, spark plug cables, and distributor cap & rotor

Possible things I plan to check
1. Coolant Temperature Switch
My coolant temperature switch is rigged right now to always be on. Given that there is a connection for the ECU to know if the switch is grounded, I'm not certain if it impacts HC or CO but it is possible that it could trick the engine into thinking it is running too hot and therefore not run as hot as it needs to be. Just a theory. Please chime in with your thinking and advice.

2. Fuel Injectors
The high HC means I'm running rich. Could it be possible that there is too much fuel or if it isn't atomizing?

3. Figure out if there is a misfire
There is a possibility that the engine is misfiring as there is HC and O2. Fuel and oxygen with spark should result in combustion but there is left over air and fuel so is there a possible misfire occuring? How to check if my engine has a misfire? I tried pulling spark plug cables but the car runs as I didn't pull anything. This happens on all cylinders. Only upon removing 2 spark plug cables in any combination will the engine stagger.

4. Change the CAT?
Theres a good possibility I might need to change the Catalytic converter but if I do so before fixing the cause of running rich, the CAT will simply be destroyed by the excess fuel.

5. Find out if double CAT is causing an issue
I have both CRX Cat and VX cat on the car. Is there a possibility that due to double CAT, the car has back pressure, misfires and is resulting in high HC and CO? I initially thought having double CAT should instead help the HC and CO issue as it would burn the extra fuel.

Your guidance is welcome. Thanks!
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