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Old 08-29-2010, 11:53 PM   #1
ThaPuertoRican15
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Default n/a "limp mode" is gone....now the engine is stalling out...

i recently did an engine swap in my car. its a 97 impreza L with an 02 impreza TS engine.

i dont know why, but for some reason the engine will only rev to about 3000 rpm. im not sure why, and i cant tell the exact RPM cuz i dont have a tak.

im VERY confused...any suggestions??
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Last edited by ThaPuertoRican15; 08-31-2010 at 10:04 AM.
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Old 08-30-2010, 12:21 AM   #2
PhilSine
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disconnected MAP sensor will cause a limp mode.
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Old 08-30-2010, 12:41 AM   #3
ThaPuertoRican15
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Quote:
Originally Posted by PhilSine View Post
disconnected MAP sensor will cause a limp mode.
the car wouldnt idle without the MAP, would it?
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Old 08-30-2010, 10:09 AM   #4
snoopyone8
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Bad speedo sensor (located on trans) will do the same. Any codes?
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Old 08-30-2010, 04:23 PM   #5
Yint
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I'm the one helping him do the swap. The speed sensor on the tranny is a mechanical sensor that sends mechanical rotation to the cluster, where it is used to show vehicle speed. Now, the TS ecu we have running the car needs the electrical signal to know how fast the car is moving and take the car out of limp mode. does the mechanical speedometer in the 97 cluster have an output signal that runs to the ecu? I will have to check my wiring diagrams.
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Old 08-31-2010, 01:25 AM   #6
PhilSine
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Car will idle without a MAP just fine.

Good call on the speed sensor, I forgot about that one.

I know there is an issue with the signals the speed sensors put out fron one year to the next. I know the 2.5RS speed sensors put out a signal that was half of what the non 2.5RS' were. The speed sensor from the 98+ 2.5RS is the same as the 02+ Imprezas whereas all of the 01 and older GC8's (non-2.5RS) used an older style that is not compatible with the newer clusters and ECU's. You'll need a newer speed sensor and swap the cluster. One problem there is that the 2.5RS' used a very different cluster in terms of connectors than the non-2.5RS'. The newer speed sensor is a 3 wire iirc (open for correction on the amount of wires).
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Old 08-31-2010, 08:55 AM   #7
ThaPuertoRican15
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Quote:
Originally Posted by PhilSine View Post
Car will idle without a MAP just fine.

Good call on the speed sensor, I forgot about that one.

I know there is an issue with the signals the speed sensors put out fron one year to the next. I know the 2.5RS speed sensors put out a signal that was half of what the non 2.5RS' were. The speed sensor from the 98+ 2.5RS is the same as the 02+ Imprezas whereas all of the 01 and older GC8's (non-2.5RS) used an older style that is not compatible with the newer clusters and ECU's. You'll need a newer speed sensor and swap the cluster. One problem there is that the 2.5RS' used a very different cluster in terms of connectors than the non-2.5RS'. The newer speed sensor is a 3 wire iirc (open for correction on the amount of wires).
well we fixed the speed sensor problem, but we have run into another one. instead of hitting a rev limiter, the engine just cuts out at random times now....

any thoughts on that?
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Old 08-31-2010, 10:01 AM   #8
snoopyone8
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Do a wiggle test..."Random" cutouts sound to me like a loose connection...i.e., vibrations from the engine shaking and shorting a non-secure plug at different revs.

Just a thought,
-adam
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Old 08-31-2010, 10:44 AM   #9
ThaPuertoRican15
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i think i found the problem....fuel pump wires started to fall apart....
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Old 08-31-2010, 04:23 PM   #10
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problem NOT solved...











it has to do with the VSS (vehicle speed sensor) going into the ECM...is there any way to make the ECU not look for the signal in anymore?

i have a mechanical SS coming from the tranny, not an electrical one...
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Old 08-31-2010, 04:48 PM   #11
snoopyone8
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Like PhilSine said, The sensor in my 98RS is mechanical (i.e. It threads into the tranny, and has a tongue that fits into a slot--> which is driven by the differential in the tranny). As the tranny spun, the slot spun, making the tongue in the sensor spin).

I am assuming that the sensor itself converts the mechanical action into an electrical voltage and sends that to the ECU as he sensor has a pigtail and harness plug that connects to the main engine harness.

Is this how your 97 tranny is set up?
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Old 08-31-2010, 05:57 PM   #12
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Quote:
Originally Posted by snoopyone8 View Post
Like PhilSine said, The sensor in my 98RS is mechanical (i.e. It threads into the tranny, and has a tongue that fits into a slot--> which is driven by the differential in the tranny). As the tranny spun, the slot spun, making the tongue in the sensor spin).

I am assuming that the sensor itself converts the mechanical action into an electrical voltage and sends that to the ECU as he sensor has a pigtail and harness plug that connects to the main engine harness.

Is this how your 97 tranny is set up?
its set up so that the tranny spins a wire looking thing that goes all the way up to the cluster. it spins the thing on the back of the cluster which makes the spedo go up, and sends out a 5v 0v 5v 0v signal. this signal is supposed to go out to the ECM to let ECM know that the car is moving...

before i wired in that signal wire, the car was in "limp mode" with a CEL code about the VSS (vehicle speed sensor). once the signal wore was in, the "limp mode" was gone. it drove fine for about a 1/2mile, then the engine just started cutting out at random times (during acceleration)...

i removed the wire and am driving in limp mode until i can find an actual resolution fro this problem...
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Old 09-01-2010, 09:26 AM   #13
ThaPuertoRican15
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car is out of limp mode. and its not cutting out anymore!

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Old 09-01-2010, 10:26 AM   #14
snoopyone8
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Quote:
Originally Posted by ThaPuertoRican15 View Post
car is out of limp mode. and its not cutting out anymore!

Niceeeee, well done!
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Old 09-01-2010, 11:02 AM   #15
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Congrats on solving it!!! Now tell us what the problem really was, and how you solved it. Resolutions are awesome
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Old 09-01-2010, 05:22 PM   #16
ThaPuertoRican15
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Originally Posted by motohippy View Post
Congrats on solving it!!! Now tell us what the problem really was, and how you solved it. Resolutions are awesome
the ECM needs to get the signal from the cluster to tell it how fast the car is moving...

what we did was put in a series of resistors and things to make the ECM get a 5-0-5-0V signal from the cluster...

im not sure exactly how to explain it...if my cousin looks at this threat again, im sure he can explain it better than i can...
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