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Old 12-02-2013, 09:39 PM   #1
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Thumbs up Help! 89 VG30E - Fails smog check at idle only

1989 v6 VG30I - Fails at idle (800rpm Test) yet Passes 2500 Rpm Test.

Smog Test Results:
All equipment passed inspection

Idle 800 Rpm test results: Failed/Gross Polluter
%C02 = 11.6
%02 = 2.1
HydroCarbons (HC) = 415 (Max allowed 120, Gross Polluter >330)
%C0 = 3.26 (Max allowed 1.0, Gross Polluter >2.5)

2500 RPM Test: PASS
%C02 = 14.2
%02 = 1.1
HydroCarbons (HC) = 48 (Max allowed 180, Gross Polluter >270)
%C0 = 0.18 (Max allowed 1.0, Gross Polluter >2.5)


What I know, and have done already:
- ECC = Only produces 55 code (all normal)
- Idle RPM set to 800
- Timing at 12 Degrees
- Cap + Rotor + Plugs (Platinum 41gap) = New
- Cylinder Head Temp Sensor = New and tested working (<250 ohms at 176%)
- Coolant Temp Sensor = New and working
- Thermostat = New and working
- AIV System= Tested and working
- EGR = Tested and working
- AB Valve = Doesn't pass the test the dummy book says ("should have vacuum at idle, but in no other conditions") AB Valve has barley noticeable vacuum at idle if any, but opens properly on throttle off as it should logically should) I also installed a new AB valve from dealer and it acted the same as my old one so I returned it.
- O2 Sensor reads 1.1 volts consistently at idle but fluctuates from 0.01 - 0.9 above 2000 RPM.
- ECC never goes into closed loop at idle, which according to Nissan repair manuals it only does on acceleration and at RPM above 2000.
- Starts easy, Idle is smooth
- Cat produces water at idle

SOOOOO!?! What the heck is this motor suppose to be doing at idle that it's not. It's obviously not burning the gas at idle, but is fine at high RPMs when it's closed loop and egr open etc.

Please help.

EDIT Update... Thread says VG30E... it's actually a VG30I. Dunno what I was thinking sry

Last edited by tgramm; 12-04-2013 at 01:37 AM.
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Old 12-02-2013, 09:56 PM   #2
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CHeck plugs and ignition system after that you might try seafoaming the engine(not the fuel system. Anything after that would be in the sensors(TPS would be my best guess)
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mine's a complete shitheap, bought from a guy who hacked it, who bought it from a complete retard.
i put 3k on it with a horrible rod knock before it barfed up a tranny.
it's ugly, loud, uncomfortable and smelly, but i'll be damned if it's not reliable.
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Old 12-02-2013, 10:15 PM   #3
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Originally Posted by fbccars924 View Post
CHeck plugs and ignition system after that you might try seafoaming the engine(not the fuel system. Anything after that would be in the sensors(TPS would be my best guess)
Everything "checks" out.
160 compressions on all 6
idle changes when disconnecting plug wires one at a time etc.

I've seen people recommend seafoaming via the brake vacuum line. What does this product physically do? Isn't it just to help valve issues?

If I had a typical issue that ignition and valves would cause shouldn't it be get worse at high RPMs instead of better?

Throttle Position Sensor is working properly, tested by ECC diagnostic mode 4
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Old 12-02-2013, 11:07 PM   #4
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service the maf? how about a new air filter? lastly it may be a leaking or broken injector
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Old 12-02-2013, 11:08 PM   #5
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a lean fuel mix and a bad cat converter will cause a high reading, Defective Air Injection Components - Faulty smog pump and related emissions system components will cause high HC. The air injection system is designed to introduce additional oxygen, after the metering system, to the engine exhaust as it exits the exhaust manifold, or directly before it enters the Catalytic Converter; thus burning whatever remaining fuel (HC) in the exhaust completely.
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Old 12-02-2013, 11:11 PM   #6
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the one thing i dont see.....the EGR valve. that will do it too.
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Old 12-02-2013, 11:16 PM   #7
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you do know that most nissans DESPISE any plug other than NGK plugs. what kind do you have?.......i put champions in mine once and it backfired, idled like it was on 4 of the 6 cylinders and was very hard to start.

put NGKs in there and it runs like a top. and that was the only thing that was changed. i went from NGKs to champions, it was running fine before, then like poop on the champions, then back to new NGKs and it runs like new.

oh and FYI, your plug gap is wrong. its supposed to be set at .031 to .035 per the Haynes Manual.
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Old 12-02-2013, 11:17 PM   #8
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he tested the egr and that cat is probably ok considering he passes at high idle
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Old 12-02-2013, 11:19 PM   #9
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+1 on ngk plugs with the right gap
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Old 12-02-2013, 11:20 PM   #10
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Quote:
Originally Posted by JohnnyRingo View Post
service the maf? how about a new air filter? lastly it may be a leaking or broken injector
Air Cleaner = new
MAF = doesn't have one, uses a flow sensor but not a hot wire type. This failure would throw a check engine light. But it's not.

Quote:
Originally Posted by cadillacdude1975 View Post
a lean fuel mix and a bad cat converter will cause a high reading, Defective Air Injection Components - Faulty smog pump and related emissions system components will cause high HC. The air injection system is designed to introduce additional oxygen, after the metering system, to the engine exhaust as it exits the exhaust manifold, or directly before it enters the Catalytic Converter; thus burning whatever remaining fuel (HC) in the exhaust completely.
The AIF system isn't a pump type but a pulse type it passes all the tests... vacuum here blow there etc.

It's possible it's a bad Catalytic Converter. But is just doesn't act like a bad cat. IE HC's are fine at 2500 RPM, then 415 HC at 800 RPM with no chance for Catalytic Cool down. Plus there is h20 generation at idle.

41 is the gap for the 89 they dropped to 33 in later years... no idea why.
Using NGK G-Power Plantinum Alloy Plugs.
Haynes Calls for BCPR5ES-11 but these are BCPR5EGP.

- Also my tune up, cap, plugs, rotor etc made no difference in my HC results before and after. I've had 5 Different tests with all the simular results only thing that seemed to make a HC difference was retarding the timing out of limits CA will allow.


What am I missing?

Last edited by tgramm; 12-02-2013 at 11:32 PM.
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