I had noticed a slight fuel smell in my exhaust, so this weekend I borrowed a PID (used to test volatile organic chemicals (VOCs) in the air/atmosphere) from the office (I'm an Enviro. Eng.). As I suspected I have about 150ppm of gas in my exhaust. I did not test one of our 2005 trucks to see how they test, but this number seems high. I then tested the vacuum line from the FPR and found it to have about 50 ppm.

I tested my O2 sensor last week and it is fine. What else could be causing this problem? Shouldn't my catalytic converter burn this gas off?

This car has never in all it's life failed an emissions test.
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85 240DL 189k; 91 240 169k

Bosch recommends O2 Sensor replacement at 60,000 miles. I have seen them fail in a lot less . . .

A Temperature Sensor, could also contribute to a false signal, forcing a Rich condition. A sudden in fusion of cash could force a Rich condition.

A Temperature Sender, could contribute to a false signal, forcing a Rich condition.

The difference: Sensor in modern computerised cars is specifically for Mixture.

Sender could serve dual purpose, to Coolant Temp Gauge and to ECU.

Thermostat failure with a Catalytic Converter car could cause a wide range of problems, including Mixture isssues.

Then there are the obvious ones.

Good luck.

Might be a leak in the fuel pressure regulator. A pinhole leak in the diaphram will allow gas to be drawn into the intake manifold through the vacuum hose attached to the regulator. This results in gas smell and rich mixture.

Howard

This is beyond the scope of my first hand knowledge, but I just had a relay to the O2 sensor replaced in order to correct a rich mixture. Since I didn't do the work myself and I haven't picked up the car yet, I can't tell you much more than that - but maybe someone else can chime in.

I'd be interested to hear if people have anything to add.

Did you check the engine coolant temperature sensor?

Maybe your problem is an old, inefficient cat, or one that hasn't had sufficient warmup time (warm the engine up and actually *drive* the car before testing). For all that it's worth, the state limit for HC in NJ is 167ppm and my car put out 71ppm when they tested it last Saturday.


-b.

Good call, the engine was not warmed up. I'll give it another shot this week after driving for a bit.

I need to pull out the last owners records and see what kinds of numbers she produced the last 4 years.
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85 240DL 189k; 91 240 169k