91 Subaru Legacy won't stay started. I just had $1,500 worth of work done on it.

[OldSubaru1]

I have a 91 Subaru Legacy and it will not stay started when I start it unless it has been sitting for awhile, for example overnight. But if for instance I drive to the store and then shut off the engine and go inside and then come back out and try to start it again, then it will not stay started when I try to leave unless I give it gas at startup and I also have to keep my foot on the gas for several minutes to keep it from shutting off.

I just had the following work done on it among other things: engine control module replaced, o2 sensor replaced, fuel pump replaced, fuel filter replaced and entire fuel system cleaned, air intake system cleaned/repaired. This along with everything else that was done came to over $1,500, and the car was in the shop for well over a month. Needless to say I do not want to take it back to the shop or invest any more money in it at this point. However I am curious to know what else could be causing it to not stay started aside from the things that I have already had looked at/replaced.

I realize that it is an older car, but up until a few months ago I wasn't having any issues at all with it. I initially took it to the shop only because sometimes it wouldn't start at all unless I started it with my foot on the gas, but that only happened sometimes (though it did begin to occur more and more frequently and had gotten pretty bad by the time I took it to the shop).

Is there something else that I could possibly do myself to fix the issue that I am having without spending an insane amount of money? Also, is it hurting the car to keep driving it even though it is doing what it is doing? I only still drive it like that because I have no other transportation at the moment.

I also know it isn't the battery because I just had the battery replaced earlier this year, and all of the lights and other functions (radio, e.t.c.) work just fine.

Side note: Not sure if this is an issue either, but if I turn the engine off and just sit with the key turned in the ignition (in the position just before starting the engine), then I hear a humming sound coming from the car which usually only seems to stop if I completely remove the key from the ignition.

Edited December 27, 2015 by OldSubaru1

[DaveT]

Just guessing. .. check the coolant temperature sensor.

[Cougar]

First I suggest you check to see if there are any codes stored in the ECU that may be clues to the problem. The MAF or coolant temperature sensors may be faulty. You also might have a faulty intake manifold gasket that is allowing too much air into the intake. If that is the case spaying some WD-40 around the intake joints while the engine is running should change the idle speed.

[DaveT]

Also, beware - the CTS can fail in ways that the ECU doesn't see as an error code event.

[OldSubaru1]

First I suggest you check to see if there are any codes stored in the ECU that may be clues to the problem. The MAF or coolant temperature sensors may be faulty. You also might have a faulty intake manifold gasket that is allowing too much air into the intake. If that is the case spaying some WD-40 around the intake joints while the engine is running should change the idle speed.

How would I check the ECU codes? I am not a mechanic, so I don't want to do anything that could potentially cause a problem or make things worse. The truth is I have already taken it to the shop three times and paid over $1,500 since this all started, and each time I have gotten it back there has still been something wrong. I know this sounds silly, but I am honestly afraid to even look at the car, let alone touch it at this point. I am so afraid that if I attempt to fix this issue myself that I will screw things up even more and that the car may not even start at all. For now it will at least start and stay started if it has been sitting for awhile, but if I drive somewhere and cut off the engine then it won't stay started when I try to start it again unless I give it gas and leave my foot on the gas for about 5 minutes. If I do this then it will usually stay started, but otherwise it will just shut off when I attempt to start it.

[DaveT]

Some of the car parts stores will read the trouble codes for you. There are also low cost code readers available now.

[porcupine73]

On a '91 I believe you look for a pair of little black connectors under the dash, hook those together, put the key to run and the check engine light will flash out any codes. It's not quite as newer models using a code reader but it's not too difficult. If your check engine light isn't on or flashing while the engine is running there probably aren't any codes in there but I forget for sure if the old ODBI had pending codes.

 

Another easy thing to check is the little tubes that connect underneath the intake tubing. You mentioned it had intake cleaning/work done and sometimes one of these tubes comes off and isn't noticed right away and causes issues, especially if it happens to be the large tube to the idle air control valve. I can understand being afraid to touch it but at the same time that's going to make it difficult to find potential issues.

 

Unfortunately some shops don't bother to troubleshoot it or have no clue what's wrong so they just start throwing parts at it at the customer's expense. A lot of the time that method works because if you replace the most likely 3-4 parts that could cause it you end up fixing it. But when it doesn't then you wasted a bunch of the customer's money like in this case it sounds like.

 

What city and state are you in?

Edited December 29, 2015 by porcupine73