Cold start problem, sudden onset.

I just found this group and I don't see any currently posted info on this problem.

My Subaru is a 1993 Legacy (wagon, 4wd, a/c) with 151,000 miles. When it is running it is a super little car. Great handling, decent mileage, very comfortable.

I bought it used about 4 years ago. From the first it always started instantly, hot or cold. One morning in Fall of 2004 it got cranky. When I cranked it, it would fire, but not stay running. Repeating this process from 6 to 18 times would get it going. [This was in a garage with a temperature never below 60F.) After the first start, it always started just fine the rest of the day.

I took it to local service station. I dropped it off at night so they could see the "first start" phenomenon first hand the next morning. They couldn't find anything wrong.

Our nearest Subaru dealer is not all that close, so dropping the car off the "night before" is not attractive.

We are a Subaru family; my wife has a '99 SUS. I'm retired, so I took my wife's car up to the dealer for it's annual service. While I was there I asked them about my problem. If they had suggested I bring the car in and leave it overnight, I would have done so. Instead he said to me, "Oh the older ones do that." That wasn't much of an answer, but that's all the answer I got.

The problem came on quite suddenly; one day it was fine, the next day it was not.

My guess is that there is a temperature sensor somewhere that is telling the central computer that the engine is hot when it is not. That would set the mixture too lean for a good start. My cranking and short run bursts may warm things upo enough that it will start.

Outside, with the temperature around 30F, requires more cranking than the battery can handle, but, with an outside power source, it will eventually start. I should point out that, at first, the cranking is quite vigorous: Both the starter and the battery are doing a great job.

One thing I noticed today is that the electric cooling fans come on when I turn the ignition to the "run" position, even though the engine is at ambient temperature, about 60F in the garage. If that is controlled by the same sensor as the mixture -- and why not? -- that would support the notion of a failed temperature sensor.

Have any of you seen this problem and have you any idea how to fix it?

Any help will be very much appreciated!!

Thanks

Ken

Reply to
93Legacy
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The hard starting, combined with the fans coming on when cold, do indeed point to a bad coolant temperature sensor. Although a fully failed sensor would be expected to set a code and turn on the check engine light, it's entirely possible for the resistance value of the sensor to shift so it remains within the acceptable range for normal operation but is no longer reporting temperature accurately. When this happens no codes will be set, but the initial air/fuel mixture used for starting (which is determined by this sensor) will be incorrect and result in the symptoms you are having. The sensor is a relatively inexpensive part and can be changed using basic tools so you could do it yourself. I'm not sure but there may be two different sensors on your car, one for the temperature gauge and another for the ECU. In this case it's the second one you would need to change.

Reply to
mulder

Thanks very much for your input. In fact the "Service Engine Soon" has been on and off for quite some time. I am told that my car is old enough that it doesn't "remember" codes when they go away. Catching an "intermittant" is a bit of a game. I've not won it.

Can you tell me where the sensor is and how to identify it to buy a replacement?

Thanks again,

Ken

Reply to
93Legacy

I don't know that the info you were given is true, the code may be retained in memory. You should try following the instructions at this site and read out any stored codes-

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any rate it can't hurt to replace the sensor anyway since it'scheap enough and not a difficult job. I can't give you the exactlocation but I believe it's in or under the manifold someplace.Hopefully someone with more exact information will see this and post.Also you can pick up one of the Chiltons or Haynes manuals, I'm prettysure they have them for your year. The part should be available as an aftermarket replacement at manyparts stores, have them check in in their computer and see if it comesup. If not you should be able to get it from Subaru directly, it maybe a bit more expensive that way but you will know it's the correctpart.

Reply to
mulder

The Engine Temp Sensor on at least some soobs is near the Gauge sender but has 2 wires. Try searching the forums over at

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.

Carl

Reply to
Carl 1 Lucky Texan

My girlfriend's Subaru seems to have a similar issue, I'm going to check on those things for her. Thanks

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Forums

Reply to
xblazinlv

I had the exact same problem on a 1995 Subaru Legacy about 2 years ago. It was the coolant temperature sensor and was located right under the intake manifold if I remember correctly. The only difficult part was finding the sensor in town at a decent price. I believe Advanced Auto was around $20 where the dealer wanted $50-$60.

Reply to
rwessley

Thank you all for your very helpful advice. I really appreciarte it. I am confident that you've identified my problem and, with your help, I've located the failing sensor and a replacement.

Thanks,

Ken

Reply to
93Legacy

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