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Limp mode? WTF?

This is a discussion on Limp mode? WTF? within the General Help forums, part of the LSx Technical Help Section category; Driving home in my 04 gto m6 that has a constant check engine light due to a mysterious maf cade ...

  1. #1
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    1971 Ford Torino GT

    Limp mode? WTF?

    Driving home in my 04 gto m6 that has a constant check engine light due to a mysterious maf cade but runs fine. I stop to get a drink and get back on the road only to have the computer go into limp mode. The CEL light starts blinking and the mileage goes to shit. I stop and get out and check some stuff, nothing apparent and start it back up. It seems fine until I get back on the highway and the light starts blinking again.

    I've replaced the maf and the computer trying to get rid of that code. My next step was a tuner because I think the original code is actually due to the bigger cam I have.

    The limp mode is a mystery. It ran fine with the cam for 1400 miles then randomly decides to do this.

    Anyone have any ideas? I made it home but it barely idles and stumbles everywhere. It had been running fine for a while until this.


    Arg


    Steven

    P.s. Sorry, the if post is kinda hard follow. I'm just besides myself in frustration and well, not thinking coherently....
    Last edited by torinoman; 01-21-2007 at 05:58 PM.

  2. #2
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    How big of a cam did you put in it? Yea the new cam will throw the tune off but I have a hard time believing just a mild cam would make it run that bad.

  3. #3
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    1971 Ford Torino GT

    Its a comp 224/224. Its not huge and it ran great for 1400 miles with the CEL on. I know its not the cam. I was saying the cam was causing the original code. The computer just randomly decided to go into limp mode. The tune on it isn't great. It was a safe tune for a long road trip. Would a proper tune by a real pro fix it? Thats what I'm praying for, but I want it fixed either way.

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    If it just went way short on power outta nowhere then I'd say you're getting knock and your computer is retarding the timing to forest gump status to try and compensate. Now you just gotta try and figure out why you have knock. Chances are the problem is because of the cam even though it might not be the cam that's the problem.

    Either way it would be a great idea to take the car to a tuner to have your cam tuned. Chances are he'll be able to figure out your problem while he's in there.

  5. #5
    The Bandit Wesman's Avatar
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    If the check engine light is blinking, that indicates a misfire code. Don't drive around too long with that, you'll toast your cats (if you still have them).

    First thing I would do is check all your plugs and wires. Make sure that all the wires are connected tightly on both the coils and plugs. If you haven't changed the plugs in a while, might want to pull one out and have a look.

    I'd also have the code pulled, a MAF issue shouldn't cause the car to missfire, there should be another code stored in the ECU regarding that.

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    Quote Originally Posted by Wesman View Post
    If the check engine light is blinking, that indicates a misfire code. Don't drive around too long with that, you'll toast your cats (if you still have them).

    First thing I would do is check all your plugs and wires. Make sure that all the wires are connected tightly on both the coils and plugs. If you haven't changed the plugs in a while, might want to pull one out and have a look.

    I'd also have the code pulled, a MAF issue shouldn't cause the car to missfire, there should be another code stored in the ECU regarding that.
    The blinking light is a hard code. Not neccessarily a misfire. And the MAF might not make you misfire, but it will make your car run like shit and die.

    I've heard that liquid based air-filters(k&n) can take out your MAF on these cars. Are you running one?

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    Slower Than a 3rd Gen juiced99ws6's Avatar
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    check your engine sensors fuse under the hood. in that got blown for any reason your car will run in limp mode and you will spark codes

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    I couldn't feel a miss nor was it popping or pinging. Rather I think the computer was dumping fuel into it. According to the instant mileage thing i was getting about 20 before and then 13ish after the light started flashing. In less than 50 miles it used about a quarter tank. It didn't lose a lot of power at highway speeds. It still pulled but you could feel a little difference and hear it running a little rough at times. Maybe it was a miss.

    The filter is has been on there a while without problem or a re-oiling.

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    if you have a misfire then you will have a code for a misfire. And you don't neccessarily have to hear knock to have it.

    Have you tapped your maf with a screwdriver or something with the car running to see if it dies?

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    no blown fuse.... I would only be so lucky that it would be that simple. All the plug wires seem fine also

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    Quote Originally Posted by 2manycis View Post
    if you have a misfire then you will have a code for a misfire. And you don't neccessarily have to hear knock to have it.

    Have you tapped your maf with a screwdriver or something with the car running to see if it dies?
    Don't have a scanner so can't pull the code now.


    Tapped the MAF with a screwdriver? What do you mean? Never heard of doing that.

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    It's a quick way to check for a bad MAF sensor. Basically the way the sensor is made a hard tap can disturb the readings. On a bad MAP sensor, it'll usually cause the car to die or at least stumble pretty bad.

    Also bring the car to autozone(if you can) and they'll be able to pull all your codes for you.

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    1971 Ford Torino GT

    wait the MAP or MAF?

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    The MAF. The sensor on your intake tube.

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    you mean, that tapping on the maf will tell me if the maP is bad?

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    yea. I use this method all the time when I think the maf could be bad (I'm a tech at a local shop) and it's never failed me.

    Oh by the way, this test will tell you if your maf is bad. It has nothing to do with the map sensor
    Last edited by 2manycis; 01-21-2007 at 07:02 PM.

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    Nope.... keeps running with out missing a beat. Its weird, I go out and start it up and it runs fine. The second I try to drive it it flips out. I also noticed that the instant mileage isn't instant milage its instant fuel usage measured in gal/hr. So the computer was pulling fuel not adding it. Despite pulling fuel it was still getting terrible mileage. The trip mileage average dropped a few points just from this. I just got this car so I'm still learning my way around it.

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    well if it starts and idles fine then it's not going to be a MAF. sry about that. if you rev it in park does it rev ok?

    Also you've mixed up MAF and MAP while talking to me(no offense) is there any way you possibly could have mixed them up while pulling the code?

  19. #19
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    yeah, it revs fine in neutral (m6). It'll even go down the street for minute before it tries die. It seems that hitting a certain point, like 3000 rpm in gear or hitting second gear is the point that it tries to die. Though it never seems to be the exact same point.

  20. #20
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    it honestly sounds like a tuning problem to me. if you have a multimeter you can go check the map sensor real quick, but I'm almost positively 99% sure(I don't care if that doesn't make sense) that you'll be able to work this problem out through a laptop.

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