Edmunds Answers



  • preeves 03/13/09 10:04 pm PST

    This is an addition to the above posted question, I did change the o2 Sensor approximately 1 year ago and have had no check engine lights associated with this problem.

  • zaken1 03/13/09 11:04 pm PST

    Well, Joel is hard headed about Geo Metros; because I know all too well how touchy they can be. I also don't know what you mean by having cleaned the Mass Air Flow sensor. That car does not have a mass air flow sensor!!! And my experience with Metro exhaust systems is that they cannot be modified AT ALL or have ANY leaks without ruining the mileage. So if you insist on running it with those exhaust modifications, and don't fix the leak and replace the muffler or whatever is making it loud; and return it all to stock; I cannot be sure that anything I suggest will help you. That's my insight for today! Take it for what it's worth.

    A few other things you can do are to thoroughly clean out the EGR valve and passages, replace the fuel filter, check the coolant temperature to be sure it comes up into the normal range within the first 5 miles (replace the thermostat if it doesn't), CHECK ALL THE VACUUM HOSES TO THE ENTIRE EGR AND EVAPORATION CONTROL SYSTEM to be sure they haven't come off and are not improperly routed. Be sure you shorted the proper leads before checking the ignition timing (or you'll have a timing error).

    Once the exhaust system is free of leaks, and contains all the right parts; if it still runs rich, install a new set of Bosch # 4306 platinum "+2" spark plugs (do not adjust the gap on those plugs). Make sure the igntion timing is set properly (see previous paragraph). Then readjust the throttle position sensor by loosening the 2 bolts and turning it slightly counter clockwise. Drive the car a few miles, and be sure it doesn't hesitate. Keep moving it further and further counter clockwise, until the car begins to hesitate or jerk at light throttle. The desired setting is for it to be turned as far counterclockwise as possible without encountering hesitation or jerking. THIS ADJUSTMENT CANNOT BE DONE PROPERLY IF THE EXHAUST SYSTEM IS LEAKING, OR HAS BEEN MODIFIED. But it is the key to optimizing fuel economy on the Metro.

  • preeves 03/14/09 4:02 pm PST

    You are exactly right, will deal with exhaust system. Also the sensor I inaccurately referred to cleaning is the inlet air temp sensor (I believe!!) located within the air filter housing.
    The first thing I will do is address the exhaust, my wife has been hounding me to do that for 6 months, nothing aftermarket to make it loud just old and in need of repair, after that I will reset the timing disconnecting the MAP sensor and plugging the vacuum lines and disconnecting the wiring, then I will give the TPS a go and adjust accordingly.
    Thanks for the input and quick response. My problem is that I don't trust my cars to auto shops, sometimes when it is a problem that is beyond my skills/tools i will but for troubleshooting I have been burned with astronomical bills, replacing this replacing that and not fixing the problem. Heck I can do that, as I have proved thus far and havent had to pay for my labor....Anyway thanks again might take a few days/ weeks for the exhaust but i will let you know what becomes of my little red convertible. Have to be a manly man to drive this too work every day or thats what my wife says anyway.

  • zaken1 03/14/09 5:43 pm PST

    I agree, it takes an independent sense of ones identity to drive a car like this (But I once met a woman who became very excited when she found I drove a Metro).

    Since you mentioned the IAT sensor, and said you had cleaned it; I should point out that if that sensor becomes defective, it will be one more potential cause of excess richness. And if there is any resistance in the electrical plug for that sensor, or if one of those stupid gadgets misrepresented as "performance chips" has been wired into the IAT sensor, it will trash your mileage.

    And, regarding mufflers, I have found that there is a substantial difference in the performance of various brands of stock replacement mufflers. The best performing stock muffler I have ever found for Metros is the lifetime muffler made by Meineke. It even outperforms the original factory part.

    Like yourself, I got into auto diagnosis and tuning for self preservation; when I found that all too many "professionals" were hopelessly ignorant, dishonest, or too arrogant to read manuals.

  • pete97 10/16/09 7:19 pm PST

    when removing the iat sensor i found that the wire had become weak next to the plug for the sensor itself and had broken. removed the terminal connectors out of the plug and resoldiered the wires back to the connectors now the sensor works and i then removed one of the batteryterminals for a minute to clear the code and the service light off the dash. thats my experience. careful one of the wires had shrink tubing over the wire and connector and would have not seen if curiosityhadnt got to me do use new shrink tubing over the freshly made new connection in the same manner as the one you removed to gaurd against corrosion.

    possible cause : by doing tunes ups and and removal of the air intake repeatedly over the years and corrosion broke the thin gauge wire.


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