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Chevrolet/Geo Metro



  • Tried a new iat sensor, and still the same problem. Cooler days, after hot..restarted in about 1 or 2 hours. Now with the hot weather, won't start all day. Inside car, computer stays very hot, therefor, must be computer problem. I have done everything else. Any help, thanks. AJ
  • zaken1zaken1 Posts: 556
    edited September 2011
    In my first response long, long ago; I said that it was either a short in the sensor, OR IN ITS WIRING. You reported that you tried a new sensor; and added that you "have done everything else." Did doing everything else include testing all the wiring and other components (such as the throttle position sensor and MAP sensor) between the coolant temp sensor and the computer for shorts; which would be what is usually done to test the wiring; or just how did you test the wiring and what portion of the wiring did you test? It is not reasonable to conclude that it is a computer problem because the new IAT sensor didn't fix it. If it was a computer problem; your dummy coolant temp sensor wouldn't fix it; either.
  • zaken1zaken1 Posts: 556
    Now that I've cooled down a bit, and had a chance to consider this issue; I realized that the stock coolant temperature SHOULD BE doing exactly the same thing as your dummy sensor (having between 5,000 and 8,000 ohms resistance); when the vehicle is cold. But since the car won't start with the stock sensor connected, but starts consistently with your resistor in place; this means that either the sensor has a manufacturing defect; or the wiring connector to that sensor is wired wrong. This is a 3 terminal sensor. It is intended to serve two functions at once: provide temperature signals to the gauge on the dashboard; and also provide temperature signals to the ECU.

    If you have rewired the sensor harness plug; it may be that you exchanged the positions of the gauge and ECU leads. This could conceivably put 12 volts battery voltage into the ECU; when it is only intended to receive a 5 volt signal in the coolant temperature sensor lead. That would throw the calibration of the ECU temperature signal way off. But when you hook up the dummy load; that connection would not also have the dash gauge wiring connected to it (or so I would imagine). If you are with me on this one; I'd like to see what happens if you connect the ECU section of the sensor to the wiring harness, in the correct polarity; but leave off the wire for the dash gauge.
  • Thanking you again for your help. Will conduct your recommended testing. Today, started the engine at 8 am, turned off after 10 seconds. Started at 9 am, off after 10 seconds. Again, started ok at 10 after 10 seconds. Same at 11 am and most likely all day. Now I'm thinking Fuel Pressure Regulator and Fuel Pump. But again, how are they associated with HEAT? Thanks, AJ
  • zaken1zaken1 Posts: 556
    edited September 2011
    After re-reading your posts; just would like to add that the fuel pump relay would cause this heat related problem if it were going out; so I would definitely try exchanging the fuel pump relay with one of the other identical relays on the car; or just replacing it. BTW; if the fuel pressure regulator diaphragm was leaking or there was dirt under the needle; it could be flooding the engine. This would cause the motor to run way too rich; which would tend to make it stall as the temperature got hotter, or the motor ran for longer periods of time. If you used NGK spark plugs; which in my experience are grossly unsuitable for use in this motor; they would foul very quickly; which would possibly cause this problem. I would recommend Autolite # AP5224 plugs (which I know are not what the book says). These plugs require a 5/8" socket; but otherwise will fit perfectly.
  • Thank you again. Will follow your advice again and try the relays first. Fuel pressure regulator next. AJ
  • Progress...thanks to you. Switched the Fuel Pump Relay and added gumout to the fuel. Drove around for 1/2 it starts all day long hot or cold. Today, went up a long hill...heavy on gas. Motor went dead but problem. Drove around again...easy, ran fine for 1/2 hour. Now I'm thinking fuel pump or fuel pressure regulator...any ideas. Thanks again, AJ
  • zaken1zaken1 Posts: 556
    In addition to a bad fuel pump or fuel pressure regulator; this could be caused by plug wires which have excessive resistance (should not have more than 1,000 ohms resistance per inch of wire length) a bad ignition coil, or spark plugs which are worn, or gapped too wide, or are an unsuitable choice for this motor, or a throttle position sensor that is out of adjustment. Only after determining that all the other items are not faulty; if the loss of power under heavy load continues; Try loosening the 2 mounting screws for the throttle position sensor; and turning the sensor just slightly clockwise (which richens the fuel mixture under load). This is a VERY sensitive adjustment; so first mark the sensor in a way which will enable you to return it to its original position if necessary, and then only move it in very small increments. Then drive the car and see if it responds better. This may require repeated changes before finding the best position.
  • zaken1zaken1 Posts: 556
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  • Added 12 oz bottle of stp fuel injector cleaner and it started all day or cold all week long. Now after burning 1/2 tank of gas, it is doing it again...won't start when hot. Thanks again for all your help. AJ
  • zaken1zaken1 Posts: 556
    Since this discussion began; I have given you many different suggestions about things to try to deal with this problem. You often thank me for my help; you usually say you'll try my suggestions; but you almost never give me feedback about what you ended up trying; what worked; what didn't work; and what you didn't try. In order to be able to work with you and help you effectively; I need to know what the results were of the things I suggested; even if none of them worked. Failures are just as important to know about as successes; I don't mind hearing that my suggestions didn't work; but I can only be able to figure out where to go from here if I know what worked and what didn't.

    There are some people on this site who don't like to be told what to do (I sometimes wonder why they even bother to write in and ask for advice) and there are many others who pick and choose what suggestions they will try and what they will ignore. I don't know what your feelings or attitudes are about following suggestions, nor whether you have all the tools or knowledge necessary to do all the stuff I suggest. So, after writing a bunch of suggestions and getting no feedback from you about those particular things; I am now in the dark, and feel totally out of touch with what you have done or haven't done to test the car.

    If you haven't been giving me feedback because you almost always try everything I write, and you of course would say so if you found bad plug wires or low compression or anything else that was not right; if that is what is going on here; please at least tell me that. That way, I'll know that you'll let me know whenever something I suggest uncovers a problem.

    It is probably hard for some people to accept that I know more than they do about the problems they write in about. But this is very true. And what this means is that when I suggest they test something; I do so because I know it could have an important effect on the problem. So, if someone decides not to test something that I asked them to test; because they don't see how that could affect this problem; they are acting out of ignorance and this puts me in a bind.

    The way I find the cause of a problem is to test all the possibilities, and eliminate them one by one. But today I don't know any more about your car than I did when you first started writing; because you told me almost nothing about the things I asked you to test.

  • Thank you again and again. Really, you have been a great help. I did try all your suggestions, however, same problem exists. When you mentioned fuel related, as I previously mentioned, I added fuel cleaner to the gas. Used up about half a tank and will run it down to empty. It runs better, and now starts hot or cold. Could be the cooler weather, not sure. With your great help and knowledge and advice, it's down to the fuel pump or fuel pressure regulator as you previously advised. I will continue testing it and see if there is more improvement. Many, Many thanks. AJ
  • zaken1zaken1 Posts: 556
    edited September 2011
    Sorry but I do not remember whether or not you changed the fuel filter. If you haven't changed the filter; please do so before anything else. I would also locate the ground point for the fuel pump wiring, take the ground bolt out and scrape it, scrape the body panel at that location, and file the wiring connectors until they are shiny clean. Reassemble and securely tighten the bolt.

    In addition; the battery ground cable clamp should have a second, smaller wire going to a bolt in the inner fender. If that wire is in place; remove the fender bolt and clean the body panel and wires as described above. If there is only the main battery cable coming from the negative post; make up a length of 12 gauge stranded wire with ring terminals on the ends; and connect it to the negative cable clamp bolt and to a nearby bolt in the fender (after scraping any paint off the fender at that point).

    Furthermore; locate the ground point on the back of the intake manifold, a little to the passenger side of the throttle body, which has several wires attached there. Remove and clean all the connectors and metal surface, and securely tighten the ground bolt.

    Let me know whether or not you find any problems in those areas. Thanks!

    Then, measure the voltage across the battery terminals with the engine off. Write the figure down. Start the motor and measure the voltage with the engine idling. Write that down. Then, with the engine idling; measure the voltage between the battery wire at the ignition coil and ground. Write that figure down. Please post all three readings here. Thanks.
  • Hi Fellow Metro Owners,

    I bought a 1996 Geo Metro a couple of weeks ago. The body is rough but it runs great, I bought this for the gas mileage plus it looks like a fun car to drive. The headlights did not work but after scouring this forum, I found a bad connection at the fuse box and corrected it. My new problem after driving it to work a few days is the oil consumption. It uses a quart about every 75 miles. It has no visible leaks so it must be burning it. I checked compression and #1 has about 60 psi while #2 & 3 have about 120 psi. A squirt of oil in cylinder makes no difference. Cylinder 1 has a cloud shoots out when the engine is cranked with plugs out. I have concluded a bad valve in #1 cylinder but can't imagine why that would cause my oil problem.

    Any advice or hints would be greatly appreciated. I am fairly handy around cars and have done almost every repair to my vehicles but haven't done a valve job in more years than I can remember. I have gotten prices for valves and gaskets from local auto parts store but have to wonder if I am being soaked a little on price. The parts are adding up almost to what I paid for the car.

    Thanks for your time and expertise.
  • zaken1zaken1 Posts: 556
    My oh my!!! Another Metro with a junk engine bought because the compression was never checked. WHEN WILL PEOPLE LEARN??? The stock compression on a 3 cylinder Metro is 195 PSI. The MINIMUM allowable factory compression spec on this motor is 165 PSI. If you read through this forum; you'll see post after post with the same sad story. These motors are EXTREMELY vulnerable to abuse; and all too many people are insensitive or uncaring about how to treat these cars right. This probably happens because they are so low priced; and people don't seem to respect things they get for cheap.

    The reason that oil does not improve the compression on #1 cylinder is the same reason it is consuming so much oil: There is either a big gouge in the cylinder wall (which is too deep to be sealed when you squirt oil into it) or the oil rings and compression rings are stuck; or else there is a warped head and oil is leaking from an oil passage into that cylinder. You have a major repair job here; and it most likely will have to include the bottom end as well as the head.

    Check for the best parts prices. has the best prices and quality on premium remanufactured engines (with a 7 year, 100,000 mile warranty). They get about $1,600 for the complete Metro motor.
  • alan87alan87 Posts: 9
    Thanking you again...I shall conduct the tests you mentioned. AJ
  • HI this is steve i am great fan of chevrolet their design technology is awesome
  • hi this is steve before choosing the sensor please see the specifications
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