carbon monoxide reading it to high

15

Asked by Oct 04, 2011 at 04:25 PM about the Ford Bronco

Question type: Maintenance & Repair

how can i reduce my carbon monoxide reading. i am at 91.00 and should be 55.00. i have adjusted the air/fuel mixture and it only brought it down to 91. any tips would be appreciated.

4 Answers

replace the oxygen sensors.

1 of 1 people found this helpful.
2,595

How did you adjust the air fuel mixture? Is the engine carbureted?? Assuming it is a fuel injected system, as the other responder did, I'll continue on that premise: Oxygen Sensors are a good suggestion for starters. If you do this, make sure you change the upstream sensors, not the downstreams (if equipped). On an OBD-II system, the upstream sensors should be mixture control while the downstreams are for emissions and the ECU compares the reading between the two sensors as a means of measuring the catalytic converter's efficiency and to verify its proper operation. High CO is caused by a rich fuel mixture. Though one or more old and poorly functioning Oxygen Sensor(s) could certainly be a potential cause for this, there are other possibilities as well. If you have access to a scantool that can linkup with your Bronco's ECU, it would be useful to get baseline readings from several of the sensors and compare them to known-correct values. Though I believe the last Bronco's were manufactured before OBD-2 was mandated and I believe they run Ford's OBD-1 system, known as EEC-4. Does your vehicle have a proper idle? Oftentimes when I come across a rich fuel mixture in an EEC-4 system, long before the system will ever turn the engine light on, it will have difficulty maintaining a smooth idle. A rich mixture is typically indicated by a low and/or surging idle, hesitation upon throttle opening, and when revved once, the engine will dip to a lower rpm than normal idle and then rebound up once or twice back to the correct idle speed. It goes without saying to make sure the engine is in a good state of tune, as in good spark plugs gapped properly, good spark plug wires, a clean air filter, and a clean MAF sensor element (if it is a MAF system). If possible, test Throttle Position Sensor voltage with a digital voltmeter. Base idle voltage should *probably* be ~0.98v, with a smooth sweep up to a maximum of ~4.5v. Check ignition timing as well if adjustment is possible. Ignition timing that is retarded relative to stock recommendations will be a problem. Note that it MAY help to remove the battery cables for approximately 15-30 minutes, while turning the light switch on and putting the key into the "On" position and back off again. This will hopefully ensure that the ECU's memory is erased. The goal in doing this is to erase the existing adaptive fuel trim tables, which may be skewed rich, and to allow the ECU to create a fresh set of tables from baseline. The vehicle will likely need to be driven a few miles (NOT aggressively!) to bring it back to proper operation.

15

sorry for the lack of info. it is carburated. 5.8L 1984. i changed the O2 sensor. i installed new cats. thanks for your replies.

15

O2 sensor have been replaced

1 of 1 people found this helpful.

Your Answer

Bronco

Looking for a Used Bronco in your area?

CarGurus has 183 nationwide Bronco listings and the tools to find you a great deal.

ZIP:

Ford Bronco Experts

  • #1
    tennisshoes
    Reputation
    430
  • #2
    Js08016
    Reputation
    170
  • #2
    Clayton Cameron
    Reputation
    170
View All

Related Models For Sale

Used Ford F-150
2,246 Great Deals out of 179,996 listings starting at $1,300
Used Ford Mustang
709 Great Deals out of 38,398 listings starting at $895
Used Jeep Wrangler
307 Great Deals out of 16,134 listings starting at $2,972
Used Chevrolet Blazer
1,048 listings starting at $950
Used Ford F-250
454 listings starting at $1,800
Used Ford Explorer
813 Great Deals out of 62,574 listings starting at $1,000
Used Chevrolet Silverado 1500
2,098 Great Deals out of 167,326 listings starting at $1,888
Used Ford F-250 Super Duty
378 Great Deals out of 43,935 listings starting at $2,400
Used Ford Ranger
164 Great Deals out of 5,460 listings starting at $1,499
Used Toyota 4Runner
262 Great Deals out of 21,370 listings starting at $1,700
Used Chevrolet Tahoe
663 Great Deals out of 39,225 listings starting at $1,000
Used Toyota Tacoma
595 Great Deals out of 42,094 listings starting at $1,995
Used Ford F-100
161 listings
Used Chevrolet Camaro
384 Great Deals out of 30,498 listings starting at $3,500

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use.