Time to play "Which sensor's broken?"!!! - Page 3

SVX10 · #31 09-25-2009, 08:24 PM

will do tomorrow. Can somebody link me to the MAF test procedure. I know the cam/crank sensors require an oscilliscope to check, so I'll just have to wait for my temporary replacements to arrive from Tom soon.

Are all 4 of these sensors in a default tuning map when the vehicle is warming up?

Seems like it couldn't even idle cold without a crank angle sensor as it'd have no basis for timing. What about cam position sensors...can it idle cold without those? How about MAF? If my memory serves me correctly, it can idle cold without MAF input.

SoCal LS-L · #32 09-25-2009, 10:02 PM

Quote:

Originally Posted by SVX10

will do tomorrow. Can somebody link me to the MAF test procedure. I know the cam/crank sensors require an oscilliscope to check, so I'll just have to wait for my temporary replacements to arrive from Tom soon.

Are all 4 of these sensors in a default tuning map when the vehicle is warming up?

Seems like it couldn't even idle cold without a crank angle sensor as it'd have no basis for timing. What about cam position sensors...can it idle cold without those? How about MAF? If my memory serves me correctly, it can idle cold without MAF input.

The car wont run at all without a MAF input.... it needs to know how much air the engines ingesting in order to supply the right amount of fuel. A bad MAF would act up cold or hot. Crank and cam sensors can be visually inspected, and also tested to some degree with a multimeter, using a metal object paseed back and forth in front of the magnet and looking for a voltage jump.

You have already thrown a code for the Crank sensor, I dont believe some of the others have read through the entire post or that would be the first recommendation made, to inspect the sensor AND wiring/harness, clean, and replace if the cleaning and inspection didnt help solve the problem.

TomsSVX · #33 09-25-2009, 10:15 PM

Just read this and sounds familiar...

Recently I had to do a knock sensor job so I rinsed the warm engine down with some cool water... Well the water worked its way into the crank angle sensor wiring... Car would idle perfectly, but would not rev over 1600RPM. No codes, no lights just loss of ignition... Check that harness for resistance from the angle sensor connectors all the way back to the bulkhead harness connector at the back of the engine. If you find a wire with high reisistance, it is likely the harness dealing with some signal contamination

Tom

SVX10 · #34 09-26-2009, 01:18 AM

great...thanks for the tips. I'll dig in with my digital multimeter tomorrow

Kinda excited to do a little diagnosis!

SVX10 · #35 09-26-2009, 01:42 PM

checked the cam and crank sensors and connectors. found 2.7k ohms resistance across rhe sensors and .87k ohms across the connectors. i know i can`t really test the sensors by resistance but i did anyway =) swapped the position of the 2 sensors that are the same and wrapped electrical tape around where the wire insulation was broken @ the connector for the sensor on the side of the engine. still stalls when warm. starts again no prob though. runs for a few sec then stalls. ugh

TomsSVX · #36 09-26-2009, 01:45 PM

im sorry but you try changing the MAF right??

Tom

SVX10 · #37 09-26-2009, 06:57 PM

yea...but I don't know how to know if either of the 2 I have are any good.

SoCal LS-L · #38 09-26-2009, 08:01 PM

Quote:

Originally Posted by SVX10

yea...but I don't know how to know if either of the 2 I have are any good.

If the symptoms are the same with either one installed you can pretty much eliminate the MAF itself as a cause.

Quick question, you DID replace the coolant temp sensor with a new one yes?

The fact that the car runs fine cold but starts acting up when it gets warm really seems like a timing or mixture problem. One possibility I came up with while racking my brain going over your thread, is maybe the ECU is constantly detecting a cold engine via the CTS and not going into closed loop. The ECU adjusts timing and mixture based on the temperature signal it receives from the CTS, and that may be why it runs great when cold but after the engine warms up it starts giving you problems.

If you have already replaced the CTS, test it with a multimeter (cold and hot), and also check the harness connector. If yours is like mine, the wires bend almost 180 degrees from the wire loom to the CTS connector because of where the wires come out of the loom, making a wire problem very possible.

Another thing could be the Auxilary Air Control valve sticking, I believe this valve provides the extra air to increase your cold idle speed. If this valve does not shut when the engine warms up, it will make the engine run too lean causing idling and stalling issues. The bypass air control valve (aka IAC valve) could also be a problem, if its clogged, once the auxillary air control valve closes when the engine reaches normal temp theres nothing else to supply air to the engine without the throttle being pressed, which of course will stall it.

Hope this helps, if I can think of anything else ill post it up, keep us informed of any more tests or symptoms you have.

SVX10 · #39 09-27-2009, 02:49 PM

Thanks for the additional input. I'll try swapping the MAF again to make sure. I did install a new Coolant Temp Sensor bought from Subaru. What voltage/resistance do I want to measure on that thing?

It definitely seems like a timing/mixture issue as the engine switches into closed loop operation, and I would assume that unplugging the CTS throws it into a default map that runs well. But even this trick didn't work last time (Monday).

I cleaned the IAC, and I think I checked the aux air control valve also. It's been acting up so long I can't even remember what all I've checked. However, it stalls even if I have the throttle open to 2k rpm or so...not just at idle. So I don't think it's that. It's something that controls mixture/timing at all times, not just idle.

Here's to hoping the cam/crank position sensors or MAF will fix it.

I'll keep you posted

TomsSVX · #40 09-27-2009, 03:00 PM

you have checked the timing marks to make sure the belt didn't slip right? If they are aligned properly, I would pull the LH gear off and make sure it hasn't backed the bolt out enough to allow the cam and gear alignment to become trashed (have seen this before more than once)...

Tom

michael · #41 09-27-2009, 05:45 PM

Quote:

Originally Posted by SVX10

Thanks for the additional input. I'll try swapping the MAF again to make sure. I did install a new Coolant Temp Sensor bought from Subaru. What voltage/resistance do I want to measure on that thing?

It definitely seems like a timing/mixture issue as the engine switches into closed loop operation, and I would assume that unplugging the CTS throws it into a default map that runs well. But even this trick didn't work last time (Monday).

I cleaned the IAC, and I think I checked the aux air control valve also. It's been acting up so long I can't even remember what all I've checked. However, it stalls even if I have the throttle open to 2k rpm or so...not just at idle. So I don't think it's that. It's something that controls mixture/timing at all times, not just idle.

Here's to hoping the cam/crank position sensors or MAF will fix it.

I'll keep you posted

Was it the proper CTS? Not the sensor for the gauge. Is there a CEL present?

SoCal LS-L · #42 09-27-2009, 07:41 PM

Quote:

Originally Posted by michael

Was it the proper CTS? Not the sensor for the gauge. Is there a CEL present?

He mentioned earlier they pulled a code for the crank sensor..............

Since the car dies even when revving, this is #1 on the list of things to replace, assuming you have already verified that the wiring and harness are ok.

SVX10 · #43 09-28-2009, 02:20 PM

Quote:

Originally Posted by TomsSVX

you have checked the timing marks to make sure the belt didn't slip right? If they are aligned properly, I would pull the LH gear off and make sure it hasn't backed the bolt out enough to allow the cam and gear alignment to become trashed (have seen this before more than once)...

Tom

Wouldn't this cause it to run poorly even when cold? If none of the sensors fix the issue, then I'll start to dig into stuff like this. I'll try re-soldering both MAFs as well.

Why did Subaru make it so freakin hard to check timing marks.

I'm getting close to just paying $700 for a lower mileage engine swap.

TomsSVX · #44 09-28-2009, 04:30 PM

Quote:

Originally Posted by SVX10

Wouldn't this cause it to run poorly even when cold? If none of the sensors fix the issue, then I'll start to dig into stuff like this. I'll try re-soldering both MAFs as well.

Why did Subaru make it so freakin hard to check timing marks.

I'm getting close to just paying $700 for a lower mileage engine swap.

Low mileage does not always mean better IMHO

It is pretty simple to check the timing marks, just remove the two end covers (4 bolt each) and get the marks on the gears to match the ones on the cover. Don't worry about the marks on the belt or on the crank yet.

If they line up, its time to pull all the belts and center pulley to check the timing between the crank and the cams. If this is good, it is time to pull the timing belt and cam gears to make sure they are not worn out.

Tom

michael · #45 09-28-2009, 04:31 PM

Quote:

Originally Posted by SoCal LS-L

He mentioned earlier they pulled a code for the crank sensor..............

Since the car dies even when revving, this is #1 on the list of things to replace, assuming you have already verified that the wiring and harness are ok.

I'm just a little suspicious of this OBD1 code reader. If there is a code present the CEL would be on. I would want to check it myself after resetting the ECU. If he replaced the temp sensor it is possible he got the wrong one from the sales person.

Have you checked the ground on the back of the manifold yet?
P.S. If you go checking the timing marks turn the motor by the bolt on the crank pulley and not the cam gears. This could easily cause the belt to slip.