OT (sorta)

Just a guess here, but maybe a new CAT?

High HC is usually the result of incomplete combustion. Make sure the spark plugs for every cylinder are firing, that they are the correct plugs and in good condition, and that the high tension ignition wires, rotor, and coil are in good shape.

Excessive hydrocarbons is an indicator of incomplete combustion, and since that can occur from a rich mixture or someting like a lean miss, the HC number alone cannot be used as an indicator to diagnose anything. Do you have any of the the other figures from the test like co, nox, or o2?

HC Loaded: 127 (passed) HC Idle Reading: 477 (standard is 220) = FAIL

CO Loaded: .85 (passed) CO Idle: .27 (passed)

It passed the Air System, CAT & Gas Cap tests. Thanks.

If the HC higher at idle than loaded, I'd suspect a lean miss. Make sure the throttle body plate moves freely and closes properly, check the ignition system.

Ray, We were working on it for awhile last night and discovered that the EGR had been bypassed. Also, the nuts holding on the EGR will little more than hand tight. Anyhow, we pulled it and it seemed to function alright but we went ahead and replaced it anyhow and hooked it back up (vacuum line). Anyhow, would the bypassed EGR contribute to high HC readings? Thanks. jor

The EGR recirculates some exhaust gas into the combustion chamber to lower combustion temperatures and reduce oxides of nitrogen (NOx). I doubt if the bypassed EGR valve caused the high HC readings. Some people bypass the EGR valve in hopes of improving performance and/or drivability.

A dirty fuel injector could theoretically cause the HC to be high at idle.

How does the engine run at idle? With a set of set of park plug wire pullers, carefully remove one spark plug wire at a time while the engine is running. The engine should run noticeably rougher when the spark plug wire is disconnected. If the engine runs the same when a particular wire is disconnected, then that cylinder was not firing.

It idles smoothly. I don't think any of the plugs aren't firing but we'll make sure. Thanks. jor

Incorrect or bad spark plugs could also keep the fuel from burning completely so pull the plugs and visually inspect. Sniff the end of the plugs for a gas smell.

is it in closed loop?