ENGINE IS UNDER LOAD WILL START TO SHUDDER RUNNING EXTREMELY ROUGH

1994 Subaru Legacy

Tiny

danielkelsey

April, 14, 2012 AT 2:34 AM

Hi guys I have taken it to 2 guys one a mechanic and one an auto electrician but neither have been able to diagnose the problem successfully.

The symptoms are as follows:

1 - When the engine is under load i.E on the motorway or driving up a hill the engine will start to shudder running extremely rough, even when the car slows to idle the engine will be shuddering and surging, sometimes the engine will cut off entirely, if you turn the car off at this point and leave it 10 minutes most of the time it will start as normal

2 - when driving at around 2000rpms not putting the engine under load the car will run relatively fine until it heats up to operating temperature then it will start to idle extremely low and surge and there is a loss of horse power, once again if you turn the engine off and give it 10 mins it will start back up fine.

What i've done so far:

1 - new spark plugs and leads
2 - new coil pack
3 - new air filter
4 - new fuel filter 5 - new fuel pumpNone have done the trick,

any help would be appreciated,

Thanks

Daniel

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3 Answers

Tiny

fixitmr

April, 14, 2012 AT 3:49 AM

CEL on?

Tiny

danielkelsey

April, 15, 2012 AT 10:36 AM

Yes, I was told that CEL codes could not be read due to it being an older vehicle and there being no OBD port but I have since found out a way by connecting some wires under the dash and watching the CEL flash in a type of morse code, the code that it has bought up is code 42 - idle switch, is it possible the idle switch/Throttle Position Sensor which is all built in together could cause all the above problems?

Thanks again

Tiny

mhpautos

April, 15, 2012 AT 1:57 PM

Fair chance that that is the case, I asked a Subaru tech I know and he suggested that this would be a good place to check, he said to check that the connector is tight and that there is no corrosion on any of the terminal pins and all pins are seated firm in the plugs.

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