'93 SC400 Engine Power Cuts Out Intermittently
08-19-19, 06:02 PM
#1
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Thread Starter
'93 SC400 Engine Power Cuts Out Intermittently
Hey all!
Just picked up a problem child '93 SC400, and it has an issue where it will drive fine but the engine power will cut out completely for about 1.5 seconds and then return. It is obviously most noticeable when engine is under load, however as I spend more time with it, I have found it cuts out while steady cruising at a given speed as well. It will cut once every couple seconds if engine is under heavy load, and will cut once every minute or so if holding speed steady. Engine appears to return to idle when this power cutout occurs, and it is abrupt (car jerks decelerating). Previous owner chased this issue for a couple years (!) and has done all of the common stuff, including:
Rebuilt ECU
New MAF Sensor
New coils/plugs/wires/caps/rotors
New fuel filter/pump/pressure regulator/12V Fuel Mod
Multiple new TPSs
EGR Delete
All of this said, I personally did not do any of this, so I'll likely have to start going back through these things and checking them one by one.
Car fires up first try and idles like a dream.
I had cat restriction ruled out today as a possibility.
The PO included an extra ECU that had been rebuilt at some point. I took both the current ECU and the extra ECU apart, and the one that's currently installed looks clean/undamaged. The extra rebuilt one looks like it's had some janky stuff done in there. Truthfully, I don't trust either and am a little suspect of these. I may send the better-looking one off to get rebuilt.
Does anyone have any thoughts or insight as to anything else I may be missing?
Thank you!
Just picked up a problem child '93 SC400, and it has an issue where it will drive fine but the engine power will cut out completely for about 1.5 seconds and then return. It is obviously most noticeable when engine is under load, however as I spend more time with it, I have found it cuts out while steady cruising at a given speed as well. It will cut once every couple seconds if engine is under heavy load, and will cut once every minute or so if holding speed steady. Engine appears to return to idle when this power cutout occurs, and it is abrupt (car jerks decelerating). Previous owner chased this issue for a couple years (!) and has done all of the common stuff, including:
Rebuilt ECU
New MAF Sensor
New coils/plugs/wires/caps/rotors
New fuel filter/pump/pressure regulator/12V Fuel Mod
Multiple new TPSs
EGR Delete
All of this said, I personally did not do any of this, so I'll likely have to start going back through these things and checking them one by one.
Car fires up first try and idles like a dream.
I had cat restriction ruled out today as a possibility.
The PO included an extra ECU that had been rebuilt at some point. I took both the current ECU and the extra ECU apart, and the one that's currently installed looks clean/undamaged. The extra rebuilt one looks like it's had some janky stuff done in there. Truthfully, I don't trust either and am a little suspect of these. I may send the better-looking one off to get rebuilt.
Does anyone have any thoughts or insight as to anything else I may be missing?
Thank you!
08-19-19, 07:10 PM
#2
Pole Position
Thread Starter
Videos of Issue
Here is a video of behavior with ECU1 installed. This issue also comes and goes. The CEL you see in this video is Code 31 for MAF (which has been replaced). I can drive it for a while without seeing this instability at slight loads:
Here is a video of behavior with ECU2 installed. This ECU makes the engine idle very rough (rocks car back and forth) but is smooth once the car is put in gear. This video shows the power cuts better, although the power cut makes a slightly different sound with this ECU installed vs the first ECU.
Here is a video of behavior with ECU2 installed. This ECU makes the engine idle very rough (rocks car back and forth) but is smooth once the car is put in gear. This video shows the power cuts better, although the power cut makes a slightly different sound with this ECU installed vs the first ECU.
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