Time to play "Which sensor's broken?"!!!

[SVX10]

Howdy everybody. I've been having issues getting my SVX to run properly after letting it sit for probably 6-10 months. I'm having a new issue with some pretty unique characteristics that I'm hoping somebody can ID the cause of.

The car starts every time...better than it has in a while thanks to a new battery and clean terminals all around. It idles pretty well when it's cold, also...a bit rough but I think that's related to my 5MT mount more than anything else.

The problem starts as the engine gets warm. The idle slowly drops and drops and drops until it's just barely running (400-500RPM). If I blip the throttle it'll come back to life, then slowly settle lower and lower and lower. Eventually it will stall. Sometimes when I blip the throttle it just dies immediately.

I pulled the diagnostic connector to see what codes I have, and this is when it got a bit more interesting. As I held the engine at 3000 RPM it would stay there no prob for about 15-20 seconds, then it would completely cut power, RPM would drop, and no response from the a-pedal to revive it. About 1-2 seconds later if I was still on the gas it would respond again for about .5sec, rev up, and then cut out again. If I keep my foot in the gas it'll keep cutting in and out in this sequence seemingly indefinitely. If I let my foot off the gas it will stall.

I've been digging through old threads and the closest thing I can find is the Cam Position Sensor. Is that a valid match to these symptoms?

I have a small crack at the base of one of the vacuum hose connections coming out of the end of the main air intake tubing on the driver's side, but I can't believe that would cause the cutout and stalling. It seems like a definite sudden ECU action of cutting all power for 2 seconds, then giving it back for .5 sec, then cutting it, giving it back, etc. A definite limp mode.

Your help is very much appreciated!

[bheinen74]

alternator?

[SVX10]

interesting you say that because i have other odd things going on in connection to the alternator. Why was that your thought?

Here's another thing that happens that points at the alternator:

When I disconnect my alternator wiring mod, everything goes dead. My car needs the alternator wiring mod's alternator + to battery + wire in order to function.

[redlightningsvx]

I would check your alternator grounds then if it only works when doing the wire mod.

[AUSVX]

I have a simple little thought that may help

If you have a car battery charger, charge the battery right up and then re connect the battery to the car and see what happens, if everything's cool for a couple of hours and then gets all screwy it's probably the alternator.

In the next month or so, I'm changing, the crank, cam and cam sensors, my car idles pretty low with no stalling but with other issues, will let you know what happens.

[SVX10]

I've checked the alternator output, and it's @ 14.4V, so it seems healthy, but I could watch it when the engine cuts out and see if anything is changing.

Also, where are the cam position sensors?

The frustrating part is that I can't rev it long enough to pull codes. I may just give up and take it to Subaru.

what would cause a full engine power cut like I'm seeing? Seems like the ECU is trying to protect something.

[AUSVX]

There are 2 Crank sensors right behind the alternator and one Cam sensor next to the battery but it seems the 2 crank sensors behind the alternator are actually 1x Crank and 1x Cam but it's still called "Crank". It's just the same part number as the Cam sensor next to the battery.

Keep in mind 14.4v is at the higher border line.

Check MAF

[redlightningsvx]

Is the 14.4v with the alternator wire mod? When I had mine on it was at 14v without it was 13.8v

[SVX10]

More symptoms to work with:

When it stalls I hear a relay clicking on and off, and the cooling fans are turning on and off.

Today I went to drive it around and see how long it would work properly. When I started it it was idling horribly. I got under the hood and disconnected fuel injectors, and none of the passenger side injectors caused any change in the idle. So, I turned off the car, pulled the front passenger side plug to see what brand they are and to see if there was anything noticeable about its tip (NGK R plugs). Then I realized I can't tell anything by the plug tip =) So, I put it back in, and re-started. It idled fine the second time!

So frustrating.

The second time I let it idle until it died. The idle speed just slowly gets lower and lower and lower until it dies. Once it gets below about 500rpm, if I tap the throttle to revive it, it'll sputter and die.

[Trevor]

Originally Posted by SVX10

More symptoms to work with:

When it stalls I hear a relay clicking on and off, and the cooling fans are turning on and off.

Today I went to drive it around and see how long it would work properly. When I started it it was idling horribly. I got under the hood and disconnected fuel injectors, and none of the passenger side injectors caused any change in the idle. So, I turned off the car, pulled the front passenger side plug to see what brand they are and to see if there was anything noticeable about its tip (NGK R plugs). Then I realized I can't tell anything by the plug tip =) So, I put it back in, and re-started. It idled fine the second time!

So frustrating.

The second time I let it idle until it died. The idle speed just slowly gets lower and lower and lower until it dies. Once it gets below about 500rpm, if I tap the throttle to revive it, it'll sputter and die.

I am fairly sure you will find that you have a faulty water temperature sensor, or associated wiring. Don't mess about, check the fault codes. Easy to do, instructions here in the how too stuff. If I am correct, you will get two long flashes and one short repeating, i.e. 21.

[SVX10]

like I said, I can't pull the codes because I can't rev for 40sec. Maybe if I do it RIGHT when it's cold I can rev for 40sec before it dies.

Would the coolant sensor explain why this only happens when it's warm?

[gezzyg]

I have exactly same symptoms. I'm confused though...you talk about having to rev your car for 40 secs? The test I did was simply put one of the blue leads into the smaller black conector ( top, 2nd from left ), then turn on ignition till the Check Light starts blinking. Counting the code mine was '32', o2 Sensor. Am I doing it right? Is this revving one you talk about something different?
I have also been told that I should clean my MAF Sensor first as it can sometimes be the problem.
Incidently, I too looked at the Alternator as an issue. When I sprayed connection points with WD40, it did lessen symptoms somewhat.

[1986nate]

Originally Posted by gezzyg

I have exactly same symptoms. I'm confused though...you talk about having to rev your car for 40 secs? The test I did was simply put one of the blue leads into the smaller black conector ( top, 2nd from left ), then turn on ignition till the Check Light starts blinking. Counting the code mine was '32', o2 Sensor. Am I doing it right? Is this revving one you talk about something different?
I have also been told that I should clean my MAF Sensor first as it can sometimes be the problem.
Incidently, I too looked at the Alternator as an issue. When I sprayed connection points with WD40, it did lessen symptoms somewhat.

Yes this is the correct process, I'm not sure where he got the idea he needs to rev the engine

[SVX10]

Plugging in without revving pulls codes from memory. You are correct. Revving performs a MPFI diagnostic check if I'm not mistaken.

Regardless, I made some interesting progress tonight that goes back to what somebody mentioned above.


Alternator.


I started the car and it was idling fine @ 14.4V from the alternator + terminal. I watched alternator voltage when it started sputtering and it was down at 12.6V. So, it seems like the alternator is kaput. I wonder why it would die as it got warm?

I'll double check tomorrow, but it seems like the alternator puts out 14.4V when cold, but not when warm.

I still have the issue that when I remove the alternator + to battery + portion of the alternator wiring mod, everything goes dead. This would imply that one of the white wires running from the alternator + terminal is broken somewhere, right?

Thinking just about the alternator, does anybody have any feedback ast o the mechanism that could be causing this?


Thanks

[kwren]

If the sputtering reduced the idle rpm substantially, that could lower the voltage output from the alternator... Normally, I think.

Keith