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PLEASE HELP! - FUEL related, no Computer CODE


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I posted a message a while back, and have done tons of searching in this forum on this topic. I've gotten some clues, but still have no idea what's going on or where to start:

 

1997 Subaru Legacy Outback, 2.5L

 

The problem is mainly with starting. It happens randomly - the car won't start, so what I've learned to do it to hold the accelerator down and it will start and run rough for a while. This tells me that the car is flooding. The black smoke tells me that, too. What is wrong? The car also has a problem with idling fast, to the extent that the car will lurch forward. This is also random.

 

Because the problem comes and goes, I suspect a faulty sensor. Maybe a bad o2 sensor? But there is no check engine light or code to check. And it has two o2 sensors, so how would I know which is bad?

 

Once the car is running, it drives down the road just fine.

 

Also, I have read about problems with idle control valve (IAC), and that it needs to be cleaned. Does this sound like the culprit, and if so, what's the right way to clean it?

 

Any other ideas? Where should I start?

 

THANK YOU!!

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My guess would be the coolant temp sensor sending the wrong messages to the ECU. Should cause a CEL though. Test it if no other solution presents itself. If the no start situations happen mostly when the engine is already hot, then the likelyhood of the coolant sensor being the culprit goes near 100%.

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Hi,

 

If you need to hold the accelerator down and you think it's flooded, you probably have an injector that is leaking down. This causes loss of fuel pressure, making it difficult to start, plus a flooded engine.

 

As for the O2 sensor, most engine management systems ignore the sensor till a certain temperature is reached, that is, it's open-loop for a while. That's why it runs fine once it warms up.

 

Does the random fast idle problem happen even when the engine is warm?

 

Regards,

Adnan

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Andan - Fortunately, I've never had an injector problem with a car before. I'm not sure how to test for a bad one. Or, is there a way to fix a "leaking" one? If there were a problem with an injector, wouldn't the problem happen ALL the time?

 

 

I have run some injector cleaner though the system twice, to no avail.

 

 

frag - Yes, normally, the engine is usually warm when the no-start problem happens. There have been a couple occasions when the engine was cold and it happened. How do I test the coolant sensor?

 

 

One thing I've noticed with the idle - if I put the car in Neutral, the RPM's usually drop down. Otherwise, the idle stays up near 1200+. Then I have to really push the brake to keep the car from moving.

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Andan - Fortunately, I've never had an injector problem with a car before. I'm not sure how to test for a bad one. Or, is there a way to fix a "leaking" one? If there were a problem with an injector, wouldn't the problem happen ALL the time?

 

 

I have run some injector cleaner though the system twice, to no avail.

 

 

frag - Yes, normally, the engine is usually warm when the no-start problem happens. There have been a couple occasions when the engine was cold and it happened. How do I test the coolant sensor?

 

 

One thing I've noticed with the idle - if I put the car in Neutral, the RPM's usually drop down. Otherwise, the idle stays up near 1200+. Then I have to really push the brake to keep the car from moving.

Hi,

 

Isolating a specific injector is one thing but you should be able to determine whether the system is holding fuel pressure or not by hooking up a gauge to the rail. If you don't have the equipment, it may be best to take it in for that. Once you confirm the issue, you can have them identify the exact cause. You can't fix a leaky injector, you'll have to replace it. The problem may not happen all the time, depending on how it gets stuck open.

 

If you are having an intermittent hot-start problem, your problem may be elsewhere, except this flooded thing still points to injectors. Other hot-related problems may stem from a flaky check valve or regulator. I'd start simple, with the more obvious stuff first.

 

Have you changed your fuel filter recently?

 

The coolant sensor can be tested in-car by using an ohmmeter and measuring the resistance, both when cold and when hot. The values must be published somewhere in a manual. That would tell you if its okay or not.

 

BTW, what happens to the idle RPM when yo turn the A/C on?

 

Regards,

Adnan

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If it is a hot-start problem it may still be the coolant temp sensor. The sensor could be telling the ECU the engine is cold, the ECU gives more fuel. Holding the throttle wide open helps to offset the extra fuel by adding extra air.

 

Here I posted the resistance values for the CTS:

 

http://www.ultimatesubaru.org/forum/showthread.php?t=13783

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Here's an update:

 

The starting problem has definitely been happening with more frequency - almost all the time when the car is warmed up. It will almost always start fine when cold. I've also noticed that now the car will stumble a bit from a stop, when warm.

 

Idling: Still not as huge a problem. When warm, it idles at about 1200 RPM. If I put it in N or P, the RPM's briefly go up to about 1700 RPM, then back down to 1200 RPM. When cold, the same test starts at about 1300 RPM, then up to nearly 2000 RPM, and then clear down to about 750 RPM. I don't what all this means, but it seems abnormal. The idling range in part varies from below 1000 RPM to occassionally near 2000 RPM. I guess the conclusion is that the idling is erratic and unpredictable.

 

Sounds to me like the coolant temp sensor is a good place to start. I'll check that and/or replace it and see what happens. I don't think I have the tools to test fuel pressure. I haven't replaced the fuel filter, but that's not a bad idea, either.

 

Note, the problems seem to only be at start-up and idling. The cars runs down the road just fine, and is getting OK gas mileage.

 

This is a great resource, please keep the comments coming!

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Possible final update:

 

I just installed a new coolant temp sensor this evening, and my first drive seems to indicate all is better! No starting problems, and the idle is back to normal (700 RPM range).

 

Thanks to everyone for your help in identifying this possible cause. I figured at $20, it was worth the risk to replace the sensor, so that's what I did. It took me a while to find it (I looked up some pictures on this message board, and that, too helped tremendously).

 

Hopefully my test drive was not a fluke :cool: !

 

Thank you!

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