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Overfueling at idle

This is a discussion on Overfueling at idle within the General Help forums, part of the LSx Technical Help Section category; Hi, I have a 98 camaro ss, replaced motor with one from a 99 vette. Trying to get it running ...

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    Overfueling at idle

    Hi, I have a 98 camaro ss, replaced motor with one from a 99 vette. Trying to get it running again. It will start and idle but smokes excessively from exhaust and can smell fuel at tailpipes. Got it scanned, shows that engine coolant temp was reading -39 deg even though it was in a heated shop. replaced sensor and still runs the same. Also had EGR code, don't know if these are related or not, but just installed new EGR and no change. Checked and had 5 volt reference at coolant sensor. Not real experienced with this and not sure what to try next. Fairly certain all wiring,grounds, etc are all hooked up as I have checked and rechecked. Any help or ideas appreciated. Thanks

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    That guy thearborbarber's Avatar
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    Did you use the computer from the 99 vette?

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    Senior Member ss~zoso~ss's Avatar
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    not sure if it could happen, can an injector be stuck open, do you have damaged plugs, but either of these two would create a noticeable vibration in addition to smoke and the smell, so these may not be the case

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    That guy thearborbarber's Avatar
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    I was kind of thinking that the computer was pooring on the fuel because the temp sensor reads -35 degrees.

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    Veteran 0rion's Avatar
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    Quote Originally Posted by thearborbarber View Post
    I was kind of thinking that the computer was pooring on the fuel because the temp sensor reads -35 degrees.
    that's exactly what's going on. You need to figure out what's wrong with your sensor or wiring to and from.

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    The Bandit Wesman's Avatar
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    Quote Originally Posted by 0rion View Post
    that's exactly what's going on. You need to figure out what's wrong with your sensor or wiring to and from.
    Exactly. Even if you had a stuck injector or something, the coolant temp sensor should still never read -39 degrees, thats unrelated.

    Excessive resistance in the circuit can cause all kinds of problems, check out your wiring.

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    no, I used all the factory computer, wiring, etc, from the camaro. When I got the car the original motor was wrecked so don't know if the problem was there before or not? Installed new plugs on install.

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    Hi, after further investigation found that temp gauge in dash will come up after vehicle is warm, but idle speed varies between 800-1300 rpm and starts are hard sometimes having to hold gas pedal to floor while cranking with occasional backfire. I've checked and temp sensor is getting 5volt reference. any ideas? Would a gm dealership be the best place to have it diagnosed? Thanks for the reply.

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    That guy thearborbarber's Avatar
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    The computers are quite different from 1998 and 1999. This could be the root of your problems.

    The 1998 computer is unique to that year on camaros.

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    Veteran 0rion's Avatar
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    Quote Originally Posted by thearborbarber View Post
    The computers are quite different from 1998 and 1999. This could be the root of your problems.

    The 1998 computer is unique to that year on camaros.
    I didn't even notice that. What pcm are you using? If you have it up and running I would assume you knew about the differences and repinned everything if you kept the 98? I think I can dig up the pin differences if you need them.

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    All the computer, wiring, etc is factory original that came with the 98 camaro. The motor only,(longblock) is a 99 from a vette. I used all the original intake, injectors, sensors,etc from the 98 camaro. Wasn't aware I would have to do any "repinning." I thought the motors were the same, aren't they? What is repinning? Thanks for the help so far, I'm really getting frustrated with this thing.

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    TunedbyFrost.com Tuner Frost's Avatar
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    Quote Originally Posted by cmcdonald View Post
    Hi, after further investigation found that temp gauge in dash will come up after vehicle is warm, ....

    This mislead you... I imagine that you (as many) assumed that since the dash is reading correctly the PCM is, but it is not. For the 98s, temp is measured for the gauge and separately for the PCM. The value you listed for ECT (-39degF) when scanned indicates an open circuit between the +5VDC reference from the PCM and it's returning leg. Either the sensor is bad to the point that it is open (possible but not common) or there is an open point in it's circuit (most likely).

    Best of luck.


    -edit-
    re-read that the engine is a 99.... make sure to use the right sender. Sounds like the dash is being fed the temp and the PCM is not in this case.

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