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Subaru Impreza, hard to start, check engine light on

I have a 95 Subaru Impreza.

In the last 6 weeks the check engine light goes on and off. At cold startup it is always on. In the last week it has been on permanently. With the key in the on position the system runs the fan at all times cold or hot and it continues to run when the engine starts even when it is cold, like 30 degrees and stays on when the temp is up to normal. When connecting the diag system under the dash to get the the check engine flash codes it seems to be pointing at almost every sensor in the car.

11 crank 13 cam 21 temp 23 O2 33 speed

After the engine is up to operating temp it runs fine but, the check engine light stays on and so does the fan.

It takes 10 to 20 attempts to get it started. Each time it will turn over a few more times until if fumbles around enough to keep running, then it smooths out and runs fine. No power loss, it seems to run fine and then will restart fine. It seems as though the system can't tell the engine temp so it does not know how to manage the fuel at cold startup. As the engine warms up the temp gage seems to show valid readings.

------ Questions.

Is the temp sending unit used for the dash gage and the EMU?

Where is the temp sensor on this engine and is there more then one? I know where the other sensors are buy I don't know where the temp sensor is.

Is there any particular sensor to replace to just do a test. I have two of these cars so I can swap parts looking for the problem. As usual the dealer will not tell me anything.

Reply to
mountaindog
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I had the same problem on my daughter's Subaru last year. Look if you can start the car with the ECM reset connector on -- look on the web, as there are several sites that will show you how to do this.

If it then starts, it is most likely the thermosensor. It is sitting near where the coolant comes in op top of the engine. Let me know if you need help locating it.

Hope this helps, Remco

Reply to
Remco

A bad crank or cam sensor would cause hard starting, and a bad temp sensor that's always indicating hot would result in the fan running all the time.

The one thing they have in common is an engine ground. Check the ground wires to the engine to make sure they're not rusted out at the connectors. And check the battery cable connections for corrosion build-up which you can scrape away with a flat-blade screwdriver. This will clear the codes from the ECU, so that you can see which trouble codes come up first next time you start the car. And make sure the battery isn't undercharged (13 volts when the car is off).

Bob

Reply to
Bob Bailin

That's a good point, Bob. I forgot to mention that the fans are running even with the engine cold, if the thermosensor is bad. That is a surefire way to tell if the sensor is bad.

Reply to
Remco

I connected the EMU reset and diag connecters together (under the dash), one brown set and one green set. Yesterday the car started right up and it was cold outside, 19 degrees yesterday here in Utah at 8000 feet. The next day I unplugged the connectors and the problem is back.

My wife and I each drive Imprezas hers, the one with problem is a 95 and my car is a 94. For a test I unpluged what seems to be the Temp sending unit on top of the engine, near the alternatory on the 94. I was expecting a check engine light but this did not happen and the car started just fine and the fan did not run. After doing this the temp gage is no longer working. So I am still wondering if there are 2 temp sensors on the car. One for the gage and one for EMU. Why would I not get a check engine light when I unplug this sensor?

Bob Bail> A bad crank or cam sensor would cause hard starting,

Reply to
mountaindog

Right - there is one temp sensor for the dash, one for the computer. Are both your fans on when it is failing?

I am pretty sure I made pictures of the repair - let me know if you want me to dig them up. It is in a little bit of a weird spot; not hard to get to, but hard to find.

Remco

Reply to
Remco

I dug out a couple of pictures of where the thermosensor is located on a 95 Impreza:

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You won't have to drain a lot of coolant, but do drain some of it because it will make a mess if you don't. The draincock is on the bottom of the radiator, along the back, towords the passenger side. It looks like it has plastic "mickey ears". Be careful turning it because they tend to snap, being plastic (don't ask me how I know :)

On picture 1 drop down along one of the rubber tubes next to the arrow. You'll see that tube in picture 2 and the socket to the sensor as well (it was brown on mine). You'll need a deep metric socket (I forgot the size) on an extender because you can't access the thing with a socket. You can work it in using the approximate angle of the arrow in picture

  1. You won't have to remove anything (besides of course the thermosensor) but the extender will just clear what is around it.

Don't be tempted to use teflon on the threads -- it doesn't need it and, from what the dealer told me, will actually screw things up. Also be sure to include the brass washer under the sensor.

After you've done the repair, reset the computer with that green/black connector -- just replacing the sensor is not enough as the ECM will still think it has overheated.

Hope that helps. Let me know how you make out.

Remco

Reply to
Remco

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