87 Iroc Z 28 refuses to pass CA Smog (Hi NO) - Team Camaro Tech
Troubleshooting Diagnosing problems done here.

 
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post #1 of 11 (permalink) Old Mar 2nd, 10, 08:06 PM Thread Starter
 
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Question 87 Iroc Z 28 refuses to pass CA Smog (Hi NO)

would love help! 87 iroq w/305 engine. Replaced EGR valve, EGR solenoid, knock sensor, wires, plugs, rotor cap, spark ignitor, TPS (throttle positioning sensor), TSU (temp sending unit). Second smog test gives Fail for NO of 916 ppm (max 772) @15 mph but passes with 628ppm at 25mph. Have run 2 cans seafoam through. Stumped! Any thoughts?
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post #2 of 11 (permalink) Old Mar 2nd, 10, 08:18 PM
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Dale
 
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Re: 87 Iroc Z 28 refuses to pass CA Smog (Hi NO)

Does the egr valve work, is it the correct one? Could the EGR intake ports be restricted.
MAF's were a real problem child with the TPI, is it working correctly? They tend to report lower airflow than what is correct, and leaning the AF ratio.
Is the ignition timing set correctly?
Is the cat working?
What thermostat is in the car? Cooling fans working correctly/

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post #3 of 11 (permalink) Old Mar 2nd, 10, 08:29 PM
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Steiner
 
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Re: 87 Iroc Z 28 refuses to pass CA Smog (Hi NO)

The majority of NOx is eliminated by the catalytic converter. If yours is original, 23 years is a lot of time on it.....

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post #4 of 11 (permalink) Old Mar 2nd, 10, 09:02 PM Thread Starter
 
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Re: 87 Iroc Z 28 refuses to pass CA Smog (Hi NO)

Thank you both. I've been avoiding the CAT because for some reason the exhaust is welded on. I have 4-barrel carb on this and EGR valve was replaced. Will post back once we attack the CAT.
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post #5 of 11 (permalink) Old Mar 3rd, 10, 12:08 AM
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Levi
 
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Re: 87 Iroc Z 28 refuses to pass CA Smog (Hi NO)

Replace that cat and I guarantee you that it will pass smog.

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post #6 of 11 (permalink) Old Mar 7th, 10, 04:03 PM
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Re: 87 Iroc Z 28 refuses to pass CA Smog (Hi NO)

Or,,,,,,, put a bigger cam in it.

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post #7 of 11 (permalink) Old Mar 7th, 10, 04:41 PM
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Re: 87 Iroc Z 28 refuses to pass CA Smog (Hi NO)

May also be running a little hot, if you can get the coolant temp down a little it will drop the NOx levels. I've gotten a few to sneak through with a cooler t-stat. Cooler combustion chamber temps lower NOx, running the coolant temp a little lower helps this.

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post #8 of 11 (permalink) Old Oct 31st, 10, 07:53 AM
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EGR solenoid location?

Hey guys, on the 305 TPI where is the EGR solenoid located? My friends smog shop told us it is bad and needs replacement, but we don't know for sure where the thing is.

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post #9 of 11 (permalink) Old Oct 31st, 10, 08:10 AM
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Re: 87 Iroc Z 28 refuses to pass CA Smog (Hi NO)

EGR is under the plenum, center of intake.
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post #10 of 11 (permalink) Old Nov 2nd, 10, 06:05 PM
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Talking Re: 87 Iroc Z 28 refuses to pass CA Smog (Hi NO)

Quote:
Originally Posted by john68 View Post
EGR is under the plenum, center of intake.
Ah yes. I remember my first time pulling the plenum off a TPI motor. The good news is after you take it off and put it back on a half dozen times, you get pretty good at it.

Dave
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post #11 of 11 (permalink) Old Nov 8th, 10, 09:02 AM
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Ryan
 
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Re: 87 Iroc Z 28 refuses to pass CA Smog (Hi NO)

Oxides of Nitrogen tend to form at higher than normal comustion temps...replacing the t-stat would likely help that as mentioned above...but a good old fashioned carb rebuild could help if you are getting a lean condition at the 15mph test.

I would guess if the car is smooth and driveable as is...a new Cat would likely get you there.

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1987, emissions, iroc z28, nitrous oxide, smog

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