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I just finished rebuilding my 94 formula lt1 and now I believe I am having computer trouble. The car starts and runs fine but it will not shift into a higher gear than first. I did research and I guess this is called limp home mode. The car on functions to minium capabilities to get you back home. I'm going to assume it's not a transmission problem because the trans was just rebuilt. my next thought was maybe one of the sensors are bad so I replaced all of them (02 sensor, maf sensor, and such), still no luck. Also when I plug the maf sensor in the car dies right away so I dont understand whats going on there either. The engine was just rebuilt and we told them to build it just enough so we dont have to swap out the chip. They street ported the heads and put in a bigger cam (266in 276exh with a 110 centerline). they also slapped an msd ignition on it as well. I called msd and they said the ignition works on the stock chip so that narrows it down further. Im retarded with computer cars, this post is for my dad. So does anyone have any ideas here? Also im not sure if the cars showing any codes either, I just thought of checking that now.
 

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The "Senior" Member
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Also when I plug the maf sensor in the car dies right away so I dont understand whats going on
Right there is your problem. The MAF is bad.
When you disconnect it the car is in limp home mode.
 

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4th Gen (LT1) Tech
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I just finished rebuilding my 94 formula lt1 and now I believe I am having computer trouble. The car starts and runs fine but it will not shift into a higher gear than first. I did research and I guess this is called limp home mode. The car on functions to minium capabilities to get you back home.
The car will run pig rich in this mode.
I'm going to assume it's not a transmission problem because the trans was just rebuilt.
Don't assume anything. Who rebuilt it? Do they know 4L60E's? See if the harness on the side of the tranny is plugged in.
my next thought was maybe one of the sensors are bad so I replaced all of them (02 sensor, maf sensor, and such), still no luck. Also when I plug the maf sensor in the car dies right away so I dont understand whats going on there either.
That is weird. You can unplug my maf and you can hardly notice a thing. I have done this with both of my cars.
The engine was just rebuilt and we told them to build it just enough so we dont have to swap out the chip.
There is no chip on a '94
They street ported the heads and put in a bigger cam (266in 276exh with a 110 centerline). they also slapped an msd ignition on it as well. I called msd and they said the ignition works on the stock chip so that narrows it down further. Im retarded with computer cars, this post is for my dad. So does anyone have any ideas here? Also im not sure if the cars showing any codes either, I just thought of checking that now.
If the check engine light is on, it has a code stored in the computer. I'm going to guess and say it has several codes stored right now.You need to get it scanned.
 

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4th Gen (LT1) Tech
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Right there is your problem. The MAF is bad.
When you disconnect it the car is in limp home mode.
That will not trigger "limp mode". The computer still has more than enough data to perform. A bad MAF combined with several other things "may" trigger limp mode, but not the maf itself on its own.
 

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Unplug the MAF on my 96 and it won't even start.
 

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4th Gen (LT1) Tech
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Unplug the MAF on my 96 and it won't even start.
Oh really? lol, your car has issues then since an LT1 doesn't even have a value in any table for the MAF on a cold-fire start up. It is relying on presets and ZERO sensors on start up. You can unplug a MAF sensor and the car will monitor air based on TPS and the MAP sensor (determines vacuum/load on motor) and o2's once it's in closed loop. You'll see very little difference in how the car runs when you simply unplug it. Some cars actually run better, but usually they run a tad richer.
 

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Unplug the MAF on my 96 and it won't even start.
don't know much about computers but could it be because of the OBDII on your 96?
 

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Oh really? lol, your car has issues then since an LT1 doesn't even have a value in any table for the MAF on a cold-fire start up. It is relying on presets and ZERO sensors on start up. You can unplug a MAF sensor and the car will monitor air based on TPS and the MAP sensor (determines vacuum/load on motor) and o2's once it's in closed loop. You'll see very little difference in how the car runs when you simply unplug it. Some cars actually run better, but usually they run a tad richer.
Well, all I know is that it has been that way since day one.
Tried to start it without reinstalling the maf and intake elbow after changing a thermostat.
No joy.
Had it in a shop to have the water pump changed.
They called and asked if I would bring a spare key because they could not get it started.
Went to the shop and saw the air inlet parts on the shop floor.
Told them it would never start that way.
They put it together and it started.
OBDII is a different animal than OBDI
 

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4th Gen (LT1) Tech
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Well, all I know is that it has been that way since day one.
Tried to start it without reinstalling the maf and intake elbow after changing a thermostat.
No joy.
Had it in a shop to have the water pump changed.
They called and asked if I would bring a spare key because they could not get it started.
Went to the shop and saw the air inlet parts on the shop floor.
Told them it would never start that way.
They put it together and it started.
OBDII is a different animal than OBDI
It's quite different, especially for emissions. The OP's car is OBD1.
 
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