Tearing my hair out! Code E91

[93 Cad Sedan 4.9 FWD1]

Code E91. Park, Reverse, Neutral, Drive, Low Switch Problem.

I ran all the tests. I have the Service Manual. Tests said to replace PRNDL switch, which is also part of the neutral safety switch. I replaced switch. Could not get the car to start in neutral, unless I moved shift bowl, towards overdrive. Ignition key switch does not return all the way to the off position in neutral. Seems to be some kind of binding at shift bowl, and in the column. Any ideas? Car has also has failed two pollution tests, on the I/M 240. HC level at 3.6807. Seems to have a low end to mid-range miss on load. Has new O2 sensor, new cap, rotor, plugs, and has been re-timed to spec. Throttle Body has been cleaned. Rest of computer tests showed no other codes. Help.

[Bruce Nunnally]

high HC levels can be caused by a poorly functioning catalytic converter, or lean fuel mixtures. Have you tested the fuel pressure, and replaced the fuel filter? I would suspect the converter though.

[93 Cad Sedan 4.9 FWD1]

high HC levels can be caused by a poorly functioning catalytic converter, or lean fuel mixtures. Have you tested the fuel pressure, and replaced the fuel filter? I would suspect the converter though.

Bruce, I was under the impression that a high NOX shows a failed converter. And high HC readings mean a rich mixture. Fuel filter was changed 3,000 miles ago, as well as air filter. Car was also run on ODB 1 scanner. Showed no codes, injectors in range. I pulled one plug. Looks brand new. Checked one plug wire with ohmmeter, in range. This car seems to be running rich. Sometimes there is the sound of unburned gas in exhaust

At idle, after I timed car, vacuum gauge read the same. Right on line of Late Ignition Timing, and good motor.

Also, I failed to mention, when I moved the shift bowl in neutral, key on, the engine started "Service Vehicle Soon" light came on and the code registered in the diagnostics.

[Bruce Nunnally]

What was the CO or NoX result you got?

Here are a couple of articles I see:

http://www.dec.state.ny.us/website/dar/bei...al/appendg.html

Helpful Hint: In the event of a multiple failure, there may be a common problem

High HC and CO: Possible misfire or vehicle not at proper operating temperature. Correct HC failure first.

High HC and NOx: Possible lean condition.

High HC, CO, and NOx: If condition only appears in the first phase of the drive trace, a possible cause could be that the converter was not at proper operating temperature.

http://www.aa1car.com/library/2000/ic60032.htm

IDLE EMISSIONS

A vehicle that has sharply elevated HC or CO emissions at idle will usually have a noticeable misfire and/or rough idle. The most likely causes here would be:

Fouled spark plug(s);

Shorted spark plug wire(s) or defective plug boot(s);

Vacuum leak;

EGR valve stuck open;

Burned exhaust valve;

Misadjusted throttle body air/fuel mixture; or

Misadjusted carburetor idle mixture.

An extremely rich fuel condition can also cause elevated HC and CO at idle, while an extremely lean condition will only cause HC to rise abnormally. A leaky EGR valve can act like a vacuum leak and cause a lean misfire at idle.

[93 Cad Sedan 4.9 FWD1]

What was the CO or NoX result you got?

Here are a couple of articles I see:

http://www.dec.state.ny.us/website/dar/bei...al/appendg.html

Helpful Hint: In the event of a multiple failure, there may be a common problem

High HC and CO: Possible misfire or vehicle not at proper operating temperature. Correct HC failure first.

High HC and NOx: Possible lean condition.

High HC, CO, and NOx: If condition only appears in the first phase of the drive trace, a possible cause could be that the converter was not at proper operating temperature.

http://www.aa1car.com/library/2000/ic60032.htm

IDLE EMISSIONS

A vehicle that has sharply elevated HC or CO emissions at idle will usually have a noticeable misfire and/or rough idle. The most likely causes here would be:

Fouled spark plug(s);

Shorted spark plug wire(s) or defective plug boot(s);

Vacuum leak;

EGR valve stuck open;

Burned exhaust valve;

Misadjusted throttle body air/fuel mixture; or

Misadjusted carburetor idle mixture.

An extremely rich fuel condition can also cause elevated HC and CO at idle, while an extremely lean condition will only cause HC to rise abnormally. A leaky EGR valve can act like a vacuum leak and cause a lean misfire at idle.

Bruce,

The first test The HC reading was: 5.0595 grams/mile Limit .08 Fail

The CO reading was: 21.838 grams/mile Limit 15.000 Fail

The Nox reading I don't have Limit 2.0000 Passed

After I timed the car:

The second test The HC reading was 3.6807 grams/mile Limit .08 Fail

The CO reading was 12.0518 grams/mile Limit 15.0000 Passed

The NOX reading was 1.2653 grams/mile Limit 2.0000 Passed

[93 Cad Sedan 4.9 FWD1]

What was the CO or NoX result you got?

Here are a couple of articles I see:

http://www.dec.state.ny.us/website/dar/bei...al/appendg.html

Helpful Hint: In the event of a multiple failure, there may be a common problem

High HC and CO: Possible misfire or vehicle not at proper operating temperature. Correct HC failure first.

High HC and NOx: Possible lean condition.

High HC, CO, and NOx: If condition only appears in the first phase of the drive trace, a possible cause could be that the converter was not at proper operating temperature.

http://www.aa1car.com/library/2000/ic60032.htm

IDLE EMISSIONS

A vehicle that has sharply elevated HC or CO emissions at idle will usually have a noticeable misfire and/or rough idle. The most likely causes here would be:

Fouled spark plug(s);

Shorted spark plug wire(s) or defective plug boot(s);

Vacuum leak;

EGR valve stuck open;

Burned exhaust valve;

Misadjusted throttle body air/fuel mixture; or

Misadjusted carburetor idle mixture.

An extremely rich fuel condition can also cause elevated HC and CO at idle, while an extremely lean condition will only cause HC to rise abnormally. A leaky EGR valve can act like a vacuum leak and cause a lean misfire at idle.

Bruce,

The first test The HC reading was: 5.0595 grams/mile Limit .08 Fail

The CO reading was: 21.838 grams/mile Limit 15.000 Fail

The Nox reading I don't have Limit 2.0000 Passed

After I timed the car:

The second test The HC reading was 3.6807 grams/mile Limit .08 Fail

The CO reading was 12.0518 grams/mile Limit 15.0000 Passed

The NOX reading was 1.2653 grams/mile Limit 2.0000 Passed

HC was really high on both tests. I want to Thank You for the test guides. I am going to pull the plugs, inspect them, run compression test, then replace plug wires. In the back of my mind, I am thinking this could be a check valve, vacuum line, etc. What can I use to spray down the vacuum lines and plastic valves. Soapy water?

What was the CO or NoX result you got?

Here are a couple of articles I see:

http://www.dec.state.ny.us/website/dar/bei...al/appendg.html

Helpful Hint: In the event of a multiple failure, there may be a common problem

High HC and CO: Possible misfire or vehicle not at proper operating temperature. Correct HC failure first.

High HC and NOx: Possible lean condition.

High HC, CO, and NOx: If condition only appears in the first phase of the drive trace, a possible cause could be that the converter was not at proper operating temperature.

http://www.aa1car.com/library/2000/ic60032.htm

IDLE EMISSIONS

A vehicle that has sharply elevated HC or CO emissions at idle will usually have a noticeable misfire and/or rough idle. The most likely causes here would be:

Fouled spark plug(s);

Shorted spark plug wire(s) or defective plug boot(s);

Vacuum leak;

EGR valve stuck open;

Burned exhaust valve;

Misadjusted throttle body air/fuel mixture; or

Misadjusted carburetor idle mixture.

An extremely rich fuel condition can also cause elevated HC and CO at idle, while an extremely lean condition will only cause HC to rise abnormally. A leaky EGR valve can act like a vacuum leak and cause a lean misfire at idle.

Bruce,

The first test The HC reading was: 5.0595 grams/mile Limit .08 Fail

The CO reading was: 21.838 grams/mile Limit 15.000 Fail

The Nox reading I don't have Limit 2.0000 Passed

After I timed the car:

The second test The HC reading was 3.6807 grams/mile Limit .08 Fail

The CO reading was 12.0518 grams/mile Limit 15.0000 Passed

The NOX reading was 1.2653 grams/mile Limit 2.0000 Passed

HC was really high on both tests. I want to Thank You for the test guides. I am going to pull the plugs, inspect them, run compression test, then replace plug wires. In the back of my mind, I am thinking this could be a check valve, vacuum line, etc. What can I use to spray down the vacuum lines and plastic valves. Soapy water?

Also, Let me know if you can come up with anything on my E91 code dilema. Thanks Again.