Need Help, 91 Civic Hatch Base Failing Smog
#1
Need Help, 91 Civic Hatch Base Running Lean
My 91 civic has failed smog twice now because the HydroCarbons where too high. I initially thought it was running rich cause of the exhaust smell, but it is in fact running lean.
So far I’ve replaced the fuel injectors, spark plugs and wires, ditributor cap and rotor, the ignition coil, and the air filter. The fuel filter and O2 sensors are next on my list.
If you have any other ideas on what to do or check next, I would greatly appreciate hearing them. Thank you.
First smog check with old parts
Second smog check with new parts
So far I’ve replaced the fuel injectors, spark plugs and wires, ditributor cap and rotor, the ignition coil, and the air filter. The fuel filter and O2 sensors are next on my list.
If you have any other ideas on what to do or check next, I would greatly appreciate hearing them. Thank you.
First smog check with old parts
Second smog check with new parts
Last edited by Alexander Smets; 07-03-2019 at 04:38 PM.
#2
Re: Need Help, 91 Civic Hatch Base Failing Smog
The engine is not running lean. The most recent HC numbers at 15mph/1500 rpm clearly show that the engine is running rich.
Does the cluster temp gauge show that the engine is able to fully warm up?
Have you measured the fuel pressure?
Any CEL codes?
Does the cluster temp gauge show that the engine is able to fully warm up?
Have you measured the fuel pressure?
Any CEL codes?
#3
Re: Need Help, 91 Civic Hatch Base Failing Smog
The CEL isn’t lighting up, but I know it works because it has come on up recently for other issues.
I haven’t checked the fuel pressure yet, but definitely will soon and I’m pretty sure the engine gets to running temperature fine, but will confirm once I get the chance.
#4
Re: Need Help, 91 Civic Hatch Base Failing Smog
I thought the car was running rich too because of the exhasut smell, but the owner of the smog shop said that the smell was due to misfires caused by an improper combustion ratio of 15.3/1, reflected by the 15.3 %CO2. I can’t find anything online to confirm this direct link of combustion ratio to %CO2, but I think it might make sense chemically.
The CEL isn’t lighting up, but I know it works because it has come on up recently for other issues.
I haven’t checked the fuel pressure yet, but definitely will soon and I’m pretty sure the engine gets to running temperature fine, but will confirm once I get the chance.
The CEL isn’t lighting up, but I know it works because it has come on up recently for other issues.
I haven’t checked the fuel pressure yet, but definitely will soon and I’m pretty sure the engine gets to running temperature fine, but will confirm once I get the chance.
If there's no evidence of engine misfires and no CEL codes blinking from the ECU LED light, then the problem would likely be fixed by replacing the catalytic converter.
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