car running rich

[Sexymeatball]

My car is running rich but its not to an extreme level. The only evidence of this condition is the rotten egg smell occasional present in the car at idle, and noticeable when traveling behind my car, and the less than ideal gas mileage. The cats are fairly new (SHOSHOP y-pipe) and i would really rather them not burn up faster than they should. First of all, the t-stat was replaced during my 60k so i dont think its stuck open. Also, i replaced the O2 sensors with the y-pipe. Its not throwing any codes. The MAF was cleaned during the 60k, and the temperature sender was also cleaned very recently during my radiator replacement. My only thought is the CTS perhaps? Im out of ideas, someone help please.

 

[bradman]

I always thought the "rotten egg smell" was a sign of complete combustion. shrug

 

[rangerj]

Sexy,

Check for any stored codes. If you are running richer than a 14.1 to 1 (fuel air ratio) the O-2 sensors will pick it up. If the O-2 sensors have stopped "switching", between RICH and LEAN, or are switching at a slow rate, the computer will richen the mixture. It is programmed to do this as a precaution.

Note: The o-2 sensors rapidly switch back and forth from rich to lean continuously, when they are working right, AND everything else is normal. They will stop switching if they sense a RICH or LEAN condition that is occurring consistantly.

A lean mixture can burn valves or even burn a hole in a piston. So the computer is programmed to richen the mixture if it isn't getting the information it expects from the O-2 sensors.

Some other posibilities are a dirty or restricted air filter, clogged injectors that are not closing as much as they should, inadequate "spark" not fully igniting the fuel, a faulty coolant temperature sensor (not the temperature sending unit)any other ristrictions of the air flow into the engine, as well as a clogged fuel return line.

Have you pulled the plugs to look for the tell tale signs of rich running, such as black carbon deposits on the plugs, or have a "sniffer" put in the exaust to measure it for unburned fuel? Is your exhaust black, or dark gray, while your running, especially when you "tip" the throttle?

The rotton egg smell comimg from the cats is not necessarily a sign of running rich. Poor fuel milage can be a product of driving habits! (No offense intended)

Start by pulling the codes, if any, and then we will have a better idea as to where to look for the cause of your problem. rangerj

 

[Sexymeatball]

Thanks for the wealth of suggestions. I was always under the impression that rotten egg smell from the cats meant that they were burning too much fuel, and hence the car was running rich. perhaps i was mistaken. I just cleaned out my fuel system with two cans of berrymans (and used it right before my oil change in the oil even though that has no bearing on this post) but i suppose the fuel injectors could still have issues. Ill do all that you suggested and then repost (If the football game doesnt distract all of my attention beer GO PATS!). Thanks again for the great info. The forum rocks!

 

[sdpatt]

The rotten egg smell can also be due to the high sulphur content in the gasoline that you are using. Have you changed sources recently? Some high performance European engines were not imported to the US because the high sulphur content in the fuel caused erosion problems in the aluminum block's cylinder walls. See this link for a discussion of the operation of modern computer controlled engines.

 

[rangerj]

SDPATT,

It is my turn to appreciate the response. Thanks.
I was due for some "continuing education", and that "link" filled the bill.

Usually all you have to do is say the word chemistry and my eyes roll back, but there is no avoiding it. I'll have to grab the bull by the tail and face the situation!

The link article brings up the point about the negative affect of silicone products on the O-2 sensors and the catelytic converters.

Evedently if an RTV is used on an automobile, that is not made for automotive use, the silicone can effectively have a deteriorating affect on the O-2 sensors and the cats.

I get the impression that this is a long term "cause and affect", that is the cats and the O-2 sensors are not immediately "killed", but rather their useful life is dramatically shortened.

Is this caused by some sort of "off gassing" by the RTV after it is cured, or is all the damage done during the curing process?

Whether we understand all of the chemical interactions, or not, the important lesson to be learned by the "do-it-yourselfer" is; that silicone spray lubricants, and silicone RTV that is mot made for automotive use, should NEVER be used on or near an electronically controlled engine with cats.

Sulphur in gasoline:
I can tell when my wife has given in to her thrifty tendencies and purchased some "no-name- off brand" gasoline because of the sulphur "rotton egg" smell. She still does not understand why I get so angry about this.

Sulphur is a cheap substitute for better, more expensive, octane enhansers. So whats the big deal? Every time a piston comes up on a compression stroke a small amount of the fuel air mixture "blows by" the rings.

The sulphor will mix with the water condensed from the air and become sulphuric acid. The acid will eat into the engines bearing surfaces and bearings, as well as other parts.

The acid contributes to premature wear of the engine parts. The few pennies you saved on cheap gasoline will cost you dearly in the long run.

This is also why it is important to change oil regularly. The oil does not wear out, it gets dirty and contaminated.

All of the above is stated with simplicity, and not in the best "scientifically correct" terms. But, the gist of it is in congruity with the automotive literature. Food for thought.

Thanks again Scott, rangerj

 

[91 SHOplus]

I was thinking sulpher, too.

There was an old post from Steve, AKA projectsho89 about that.

 

[dreamsinger]

rangerj:
Sexy,

Check for any stored codes. If you are running richer than a 14.1 to 1 (fuel air ratio) the O-2 sensors will pick it up. If the O-2 sensors have stopped "switching", between RICH and LEAN, or are switching at a slow rate, the computer will richen the mixture. It is programmed to do this as a precaution.

Note: The o-2 sensors rapidly switch back and forth from rich to lean continuously, when they are working right, AND everything else is normal. They will stop switching if they sense a RICH or LEAN condition that is occurring consistantly.

A lean mixture can burn valves or even burn a hole in a piston. So the computer is programmed to richen the mixture if it isn't getting the information it expects from the O-2 sensors.

Some other posibilities are a dirty or restricted air filter, clogged injectors that are not closing as much as they should, inadequate "spark" not fully igniting the fuel, a faulty coolant temperature sensor (not the temperature sending unit)any other ristrictions of the air flow into the engine, as well as a clogged fuel return line.

Have you pulled the plugs to look for the tell tale signs of rich running, such as black carbon deposits on the plugs, or have a "sniffer" put in the exaust to measure it for unburned fuel? Is your exhaust black, or dark gray, while your running, especially when you "tip" the throttle?

The rotton egg smell comimg from the cats is not necessarily a sign of running rich. Poor fuel milage can be a product of driving habits! (No offense intended)

Start by pulling the codes, if any, and then we will have a better idea as to where to look for the cause of your problem. rangerj

I've done nearly everything but an injector service. No codes, installed new coolant temp sensor and TPS, no change. Can the O2's be working slow (rich?) and not trigger a code? Black tail pipes and 18mpg kinda sucks out loud.

JD

<small>[ February 10, 2004, 01:35 AM: Message edited by: dreamsinger ]</small>

 

[shobote]

The rotten egg smell from higher sulfur gasolines results from budget refiners (Marathon, Sinclair, other little guys) who purchase lower grade, (usually domestic) sour crude versus the lower sulfur content sweet crude; more expensive and imported from Kumait, Saudi, Venezuala...
We don't get the high torue/high mileage Direct Injection diesel engines from Audi, VW, Mercedes.. also due to the high sulfur content in domestic diesel fuel, which does not meet EPA regs.
Discount gas stations buy the b-grade sour stuff and charge a nickel less; it's also missing those proven detergents that keep things cleaner (BP-Amoco, Mobil, Chevron, Shell).
I finally gave my wife a Mobil credit card so she would not fill it with the cheap stuff anymore.
Do you have any other mods; like LPM, MAF, or are you running stock ? First thing I would do is check all the plugs, then trace things down from there.