98OBL- massive power loss when engine warms up- plz help, my car is stranded

[aaron.cavosie]

Hi foks,

 

I'm stuck on a power-loss problem, but I've got some good info/observations-

 

The problem:

My car is a std trans, and runs fine on start up (full power, 'peppy', normal sounding engine, normal idle). After the engine warms up (i.e., after about ~5 minutes, when the temp gauge goes to the normal level), the 'Check Engine' light comes on, the car runs very rough, and it experiences a major power loss. I can barely keep it running (gotta keep tapping it), and can't go up any hill of any size. This is a problem, as I live in the mnts, and I can't get my car out of my own hilly driveway to take it in for service. When the car is cold again, I can start it, and it behaves normally until it heats up again.

 

One other odd behavior is that when I come to a stop going downhill, my car stalls. It starts up right away, but it never used to do this until this 'power loss' problem.

 

I'm no veteran troubleshooter, but its obvious that the problem starts when the car gets hot. I'm hoping its not warped heads (very bad), and might be some sensor that controls the idle. When it is cold, its very peppy, and runs normal.

 

Info/observations:

- No burned out fuses

- I put in new spark plugs and wires

- I put in a new air filter

- This may be unrelated, but around the same time the 'power loss when hot' problem started, my speedometer quit working (tach is fine, so instrument panel is functioning).

 

Outlook for my Outback:

I live in the mountains in a rural part of Puerto Rico, where parts and service are hard to come by. My goal is to try and figure this out so if I don't fully solve the problem, I can have enough power to at least make it out of my driveway to where a tow-truck can come for me and take me for service, about an hour away. My driveway is far too crazy for any sane tow-truck drivers to take on.

 

Any thoughts or suggestions about what else I could trouble-shoot would be appreciated.

 

Regards,

 

Aaron

[Rester5350]

Could be your one of your cats are clogged. I am no expert but have had something similar happen to me.

[jarmerson]

Once it warms up, does it idle normal? Could be a bad sensor(s).

[aaron.cavosie]

Once it warms up, does it idle normal? Could be a bad sensor(s).

 

No, it does not idle normal once it warms up. Everything is fine when its cold, but once it warms up, it idles and drives very rough (when I say 'drives', I don't really mean drive; I can get the car to crawl along, but it doesn't drive normally.

 

Any advice for how I troubleshoot a sensor?

 

thanks

[jarmerson]

A friend had this same issue with one of his cars and it was a temp sensor. He went through and unplugged a few sensors and that was the culprit. Car ran fine with it unplugged so he replaced and like magic it ran strong again.

 

I don't know too much myself, possibly be fuel pump over heating?

 

Some one should chime in on this.

 

 

"The only reason I look at other peoples cars is so I can see my Subie in the reflection." -Carver Snell

 

Sent from my stupidphone.

[snederhiser]

Hello;

Number one cause is faulty/ plugged fuel pump. Disconnect the return line and see if there is any fuel flowing out. This would be the lower 8mm line, not the one coming from the fuel filter. The other 6mm line is the vent. Could also be the temp sensor as mentioned above. Another thing to consider is the MAF(mass air flow sensor). If you have a good buddy with a code reader would be a great help! Just my 2 cents, Steven.

[aaron.cavosie]

Hello;

Number one cause is faulty/ plugged fuel pump. Disconnect the return line and see if there is any fuel flowing out. This would be the lower 8mm line, not the one coming from the fuel filter. The other 6mm line is the vent. Could also be the temp sensor as mentioned above. Another thing to consider is the MAF(mass air flow sensor). If you have a good buddy with a code reader would be a great help! Just my 2 cents, Steven.

 

Hi, and thanks for the response.

 

You mentioned in a post that I might have a bad fuel pump, and that I should check the return line to see if fuel comes out. I have some questions about checking this:

- Do you mean the return line that plugs into the fuel pump (FSM says there are three lines)?

- Do I check this without first releasing the pressure in the line (as the FSM suggests to do)?

- Do I need to have the car on (idling) when I pull off the return line (seems to me like this makes sense...); will this (should this) spray gas everywhere inside the car (do I need to have a container at the ready to direct the return line into when I remove it?

 

thanks,

 

Aaron

 

Thanks for the advice

[snederhiser]

Hello Aaron;

I congratulate you for having a copy of the FSM! Look under the hood and look for the secondary fuel filter. The output of the filter (8mm rubber line) runs into steel lines on the drivers side of the engine. The return line (8mm rubber) is just below the feed line, remove clamp and twist. Use a rag to deflect any fuel. If you have a good flow coming out of this line, the pump is good. If it suputters or low/no flow you know that the pump or filters are weak/plugged. Hope this helps, Steven.

[GEORGEROV]

Hi Aaron , Aside of what's been mentioned then watch the following : There are a number of important earth points around the engine . One at the back of the engine bay , next to the ignition amplifier. Another on the right hand inner wing , low down . One on top of engine next to ignition coil pack , and others on both suspension turrets . All should be carefully inspected and taken off and cleaned back to bright metal if in any doubt . Vital for the whole engine management system . Other possibilities include the temp sensor as mentioned , although when this goes faulty symptoms are usually difficulty starting when cold , with the cooling fan running continuously then when it does fire the motor will be reluctant to rev . Faulty crankshaft sensor would usually result in the car being difficult to start when hot . What happens is a winding breakdown within the sensor which goes o/c when hot but reverts to normal when it cools down . Knock sensor if faulty would not affect running at idle . Heat could be affecting the coil or ignition amp such that they are ok on start up but not when up to temp . The mass airflow sensor ; you could try unplugging it . If no difference to the symptoms then this could be faulty . There's a few things to ponder over .

[jarmerson]

To follow what GEORGEROV mentioned, here's a useful write up from broknindarkagain - http://legacygt.com/forums/showpost.php?p=3506952&postcount=5

[aaron.cavosie]

Hello;

Number one cause is faulty/ plugged fuel pump. Disconnect the return line and see if there is any fuel flowing out. This would be the lower 8mm line, not the one coming from the fuel filter. The other 6mm line is the vent. Could also be the temp sensor as mentioned above. Another thing to consider is the MAF(mass air flow sensor). If you have a good buddy with a code reader would be a great help! Just my 2 cents, Steven.

 

 

A big thanks to all who have responded so far. I'm still stuck at home, but have made progress. Here is where things stand-

 

(1) Several folks suggested it might be either fuel pump or MAF sensor. My simple-minded approach (so far) has been to replace parts that might be the cause of the problem; I froze in my tracks when I found the price of a fuel pump ($450) and a new MAF sensor ($330). I decided I should be more circumspect.

 

(2) I went out and bought a code reader from my local parts store (OBD2 reader, Actron Auto Scanner CP9575). It cost ~$130.

 

(3) Only one code was stored: P1507. I cleared this out after recording the conditions stored, and then started my car to see if I could reproduce it. I had my care on for 30 minutes, and the CEL still wouldn't come on. So I started driving it on my driveway (very hilly), and after about another 10 minutes the CEL came on, the rough idling condition returned (as before) and massive power loss (as before). The new code was again P1507, the same one stored previously.

 

(4) After poking around on-line, it seems that P1507 is associated with "idle control system fault". Others (forums, youtube) have found that P1507 can be caused either by a bad 'neutral safety switch', or a dirty 'idle air control valve'.

 

(5) With this in mind, today I ordered (on-line) a new neutral safety switch ($30) and a new gasket for the idle air control valve ($6). When these parts arrive (things take about a week to get to Puerto Rico from the US), I'm going to replace the neutral safety switch and see if this solves the problem. If not, I'll go ahead and clean the idle air control valve, following some procedures I've read about on-line (check here for an over-the-top post on this topic at nasioc: http://forums.nasioc.com/forums/showthread.php?t=781242).

 

So this is where I'm at.

 

I'll post an update after my new switch arrives and I install it. If anyone has any other suggestions about things to troubleshoot, or other help, I would welcome it. This forum has been a great lifeline so far for this DIY'er. This is definitely the hardest DIY problem I've taken on with my Outback so far. The good advice so far let me to get a OBD2 reader; to be honest, I can't believe it took this long to get one...! Many thanks.

[snederhiser]

Hello Aaron;

Seeing that you have a copy of the FSM look at testing the components. I would look at the throttle position sensor (TPS). I have seen these crack thru the resistance carbon and open up, causing the exact problems you are having, Steven.

[jarmerson]

I would imagine that if the approach you are now undertaking yields little resolve, it might be something else causing the IAC valve to fault and throw a P1507. Just throwing out ideas but I know very little of your current problem.

 

Good luck!