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Boost Junkie
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12,385 Posts
Discussion Starter #1
Hello,

I finished up the install of the VPC last night. I used the directions off of MKIV.com with a few changes. Instead of putting the IAT in the intake manifold, I threaded the intercooler piping in the brake duct and installed it there. Other then that, I did pretty much everything the same.

I was going to drive the car to work this morning since it is going to be 75 degrees here today and basically couldn't get down my street due to a horrible leaning out problem. Whenever I would try to give the car some gas, my a/fs would go into the 18s, 19s, 20s and the car would stumble. So I drove it back and left it in the garage. Hopefully I can trouble shoot tonight.

The VPC/GCC both have power as their LEDs and lights come on the display so that isn't the problem.

I have a few questions. Obviously the VPC switches the Supra over to Speed Density so my problems could be:

1. No signal/bad signal from MAP Sensor
2. No signal/bad signal from RPM reading
3. Bad VPC chip

One more thing. The directions recommended that I splice into the signal wire for the MAF sensor. Is this correct? It seems that you would want to cut this wire and not splice into it.

Any other suggestions. BTW, car ran great before install and had no problems. It also idles perfectly fine 14.7, but once you step on it at all, it goes full lean on the wideband.

Thanks for the help,

Steve K.
 

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Wholesome creamy goodness
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648 Posts
Try adjusting the response dial on the VPC. That is usually what controls how much fuel goes in right when you press on the throttle. I added about 4% (2 clicks clockwise) on mine and it got rid of my stumble. Also, try reseting the ECU...
 

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Boost Junkie
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12,385 Posts
Discussion Starter #3
I am pretty positive it has to be something to do with the MAP Sensor. Either the signal is screwed up or the sensor is bad. I am going to break out the voltmeter tonight and try to figure it out.

Steve K.
 

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Tom Henderson
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1,236 Posts
i had the same problem, did it stall out?? cuz i changed the chip like everyone said. Also make sure the resistors in the maf sensore are right. But all i did to fix mine was drive the car around for like 30 mins. Someone told me the car has to learn itself, so i took it out and drove it and to my suprise it ran perfect after.
 

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Boost Junkie
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12,385 Posts
Discussion Starter #6
Well,

Thanks for the responses. I hope it isn't the chip, but we'll see. I'll be checking over the voltage on everything and will report back tomorrow. It ran perfectly in the previous owner's car so I am hoping that I just screwed up some wiring or something.

Steve K.
 

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Boost Junkie
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12,385 Posts
Discussion Starter #7
We pretty much tested everything tonight and everything checked out o.k.. Map sensor voltage was right on with the trouble shooting guide as were all other signals. We believe it is a bad VPC chip. Going to call Dusty tomorrow and order one.

Steve K.
 

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I would make sure that the dip switches are in the correct locations and the chip is installed in the right direction. I also had to go through 2 vpc chips before I recieved one that worked fine. The previous two caused the car to run extremely rich and through a check engine code. The car would be puffing black smoke and when any throttle was applied the car would just stumble and die out. If you are sure the install is correct I would bet the vpc chip is bad.

carlo
 

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Boost Junkie
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12,385 Posts
Discussion Starter #10
I got the VPC from a prior Supra owner so I would imagine the dip switches are correct. I'll take it apart and check everything though. Thanks for the help everyone, this is aggravating to say the least.

Steve K.
 

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Yeah, I am having the same problem with my friends car. Did you ever find the root cause? Also, what should the voltage be on the MAP sensor?

His car idles & runs fine in closed loop, but when you floor it (open loop) it goes way lean, and you can not adjust it out, even with the GCC maxed out.
 

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Boost Junkie
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Discussion Starter #13
Sorry,

I had the wrong chip in it....a "B" chip when I should have been running an "A" chip.

Steve K.
 

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Thanks for the response. I know we are running the correct chip. I just do not think that the chip is functioning properly.
 
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