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Discussion Starter #1
Hi,

just failed a smog test - here are some numbers

idle 711 RPM
%CO2 - 13.6
%O2 - 1.0
HC(MAX) - 120
HC(GP) - 270
HC(ME) - 469 (oopsy!)
%CO - 0.84 (max - 1.0)

2500RPM

%CO2 - 14.3
%O2 - 0.3
HC(MAX) - 180
HC(GP) - 330
HC(ME) - 54 (awesome)
%CO - 0.52

Well as long as I never idle things are ok :)

Anyone have any ideas why it would spit out so much HC at idle.
EFI light is off - (bulb works I think!)

Why would it spit out so much unburnt fuel at idle but run so clean at 2500 RPM.

gonna go at it with a multi-meter/vacuum gauge etc. later but any thoughts would be appreciated.

plugs/cap/dizzie/IAC all new, new fuel pump (though I don't like it much)


Again any help much appreciated

Cheers
 

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Anyone have any ideas why it would spit out so much HC at idle.
EFI light is off - (bulb works I think!)

Why would it spit out so much unburnt fuel at idle but run so clean at 2500 RPM.
what's the mileage?

If HC is high at idle that could indicate that there is unburned fuel coming through the exhaust. may need a little bit of tune up with some plugs? what does it tick over at.. have you checked the timing ?
 

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Discussion Starter #4
Hi,

Had a fuel pressure at 29 psi - so I swapped out the fuel pump and now it gives about 36 psi. Not sure if this could be it.
Haven't had it tested since but there is a noticeable phut phut from the exhaust so I am guessing that is spark related. Am building a test harness from http://alum.wpi.edu/~colinb/14cux_interface.html - so maybe this will tell me what might be bad.

I have pretty new spark plugs and leads but I am going to pull them to look for a wet plug and/or loose leads.

thanks for the replies appreciate your help - keep the ideas coming.

Cheers
 

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JACK'S GRANDAD
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9,235 Posts
I'd stick to testing/inspecting parts before making a cable thing, but if it doesn't take long etc....
Pull the plugs after some idle time and see how they look.
Is there anywhere local that can flow test fuel injectors?

Martin
 

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Had a fuel pressure at 29 psi - so I swapped out the fuel pump and now it gives about 36 psi.
Both those figures are correct depending on whether you have vacuum to the fuel regulator or not. With full vacuum (like at idle and vacuum hose connect) the fuel pressure should be 2 bar (29psi). Under acceleration with no vacuum, it is suppose to be 2.5 bar or 36 psi.
 

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I agree that it is most likely a faulty injector. You could try adding a bottle of injector cleaner into the fuel tank. That may help.

The other thing it might be is a faulty fuel regulator. They can develop a leak and such fuel into the motor through the vacuum hose.
 
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