Odd loss of power

kuroneko_sama · #1 06-03-2005, 06:46 PM

92 svx is experiencing a loss of power in in spurts, its happening more frequently and it is now effecting the spedometer (the guages stop)

it just has no pep when the pedal goes down, any suggestions, mechanic is stumped....crank sensor maybe?

#2 06-03-2005, 07:06 PM

Just a guess... Loose harness / Ground to PCM?

Has your mechanic used a scan tool to look for codes?

Any MIL (Check engine light)? Does it light as your gauges drop?

is it all gauges or just speed?

Did these problems present themselves simultaneously or do you think they are unrelated?

kuroneko_sama · #3 06-03-2005, 07:16 PM

normal driving results in spontanious random power loss. the check engine light came on for a second when it was been doing it but only just recnelty the check enginelight started with it, not long enough for computer scan.... the only the speedometer is effected

#4 06-03-2005, 08:21 PM

Even if the CEL is only coming on momentarily, it should still store the codes. Look up the how-to on pulling codes.

#5 06-05-2005, 05:07 AM

I'm still leaning toward a loose connection but now rather somewhere between one of your sensors to the PCM. After thinking about the symptoms I suspect that your PCM has good ground as I believe that the engine would allmost stall and quit running if that was the case.

I am not sure of the method our car uses to obtain RPM signal but I agree that the CKP (crank pos.) sensor should be suspect. Has your mechanic back probed the sensor w/ the engine running? If you have a loose harness or connection somwhere between the sensor and PCM that would certainly explain your issue.

I believe the CKP is fairly accessable but removing the altenator makes it much easier to get to.

The only think I can think of at the moment that would speed up diagnosis would be to call a Subaru specialist and see if they have the ability to access live sensor data and monitor it while duplicating the failure.

At the mercy of my memory, I will ask my instructor if he has any suggestions / thoughts on your driveability issue.

billb · #6 06-05-2005, 08:02 AM

When my 94 was doing that, it was a bad coil pack.

kuroneko_sama · #7 06-05-2005, 10:17 PM

i will look into those, the car belongs to my uncle (who uses it as an unmarked police cruiser.... blue strobes going into the grill soon

) but he needs to get it back to 100% first and that is baffleing him and his brother (our mechanic) who has not been able to find anything on the computer thingo (im not a mechanic)...

but as i said... it jsut doesnt have kick when he tries to accelerate, and only just recnetly has the check engine light flashed, and periodically the speedometer "turns off" we arent sure if its directly a result or a seperate issue as that has also only recently just started. being it a speedometer failure a electrical issue is suspect but we dont know the cause or if a mechanical failure is causing the electrical failure.... we would hate to fix a problem but not fix the cause

it is a '92 AWD

any/all suggestions and theories welcome, esp if you had this happen to you

Rd96SVX · #8 06-06-2005, 12:19 AM

check all the grounds as mentioned before, sounds like exactly the problem I had a week ago, it was the ground on the passenger side/back of the intake manifold..the screw had come loose, just my .02

#9 06-06-2005, 10:26 AM

Sounds like a speed sensor failure.

Dave

svx_commuter · #10 06-06-2005, 11:08 AM

Quote:

Originally Posted by sir_romeo

i will look into those, the car belongs to my uncle (who uses it as an unmarked police cruiser.... blue strobes going into the grill soon

) but he needs to get it back to 100% first and that is baffleing him and his brother (our mechanic) who has not been able to find anything on the computer thingo (im not a mechanic)...

I usually look for Impalas and Crown Vics. Now I have to watch for a SVX if I am in NH.

Earthworm · #11 06-06-2005, 12:57 PM

I also agree with the ground issue. Check the battery grounds and make sure the terminals on the battery aren't loose.

#12 06-06-2005, 04:53 PM

Regarding Speed Sensor failure:
I thought the same thing. However the SVX uses 4 channel ABS. I believe the ABS lamp would also come on during the failure if a speed sensor was the failure point. I have not certified in transmissions however and I do know that some cars have a VSS connected to the transmission. I also know the SVX has 4 speed sensors [one for each wheel] for AWD and ABS. I do not know if it has a separate VSS as well. I also believe the transmission would shift improperly if this was the failure point. - Checking for TCU codes might help. Does your MIL flash 16 times and go out when you start the car? - That would indicate a TCU code is being stored.

Regarding coil failure:
The MIL should flash if a frequent misfire is occurring. Since the SVX uses direct ignition, the code would also identify which coil is malfunctioning. However, unfortunately we are dealing w/ OBDI; this may not be the case. OBDII cars store misfire history. I'm not sure about your '94. If it has that ability then you can narrow the variables even further.

If you still have RPM but no speedo reading, then the crank sensor can be eliminated from suspicion.

Another thought:
Malfunctioning EGR will also reduce HP considerably. It is supposed to not allow exhaust in at WOT. If it is from time to time, the MIL would light while EGR was malfunctioning and you would experience significant power loss.

Again, I suggest taking the car to a Subaru specialist who has the correct diagnostic equipment. I honestly think that will be the most time and cost effective. Even if your friend mechanic will do the work, just pay the diagnostic fee and have a Subaru specialist use the needed tools to properly diagnose your issue.

kuroneko_sama · #13 06-07-2005, 12:32 AM

btw, the lack of acceleration power isnt consitant either it jsut happens here and there while driving

#14 06-07-2005, 05:51 AM

Quote:

Originally Posted by SEA Sleeper

Regarding Speed Sensor failure:
I thought the same thing. However the SVX uses 4 channel ABS. I believe the ABS lamp would also come on during the failure if a speed sensor was the failure point.

I'm referring to the speed sensors on the transmission. One of them is used for the speedometer, and if I remember correctly, it doesn't set a code when it fails.

Dave

oab_au · #15 06-07-2005, 07:32 PM

I can't relate the two faults, Speedo, and no power. If it was the Rev counter, it would make more sense, the crank sensor, triggers the spark, injection and the Rev counter. The speedo is driven from the gear box No.2 speed sensor via the TCU. Got nothing to do with the engine.
If it is the Speedo that is stopping with the engine, it has to be some electrical fault. Check the earths/grounds, especially the one from the back of the engine to the bulkhead/firewall, below the Ignitor pack.

Harvey.