Ok, i've got a diagnostic question for you guys.
I have a 1998 S70 T5 (manual) and am having an issue with it suddenly losing power and killing the engine. It does this most often when starting the car. I will turn the car on and then within about 5-10 seconds the engine suddenly loses all power and just dies. 80% of the time after this I will start the car and it will run just fine the other 18% of the time it will start and stop like that 2-3 times and then run fine. The 2% that's left it will continue to start and stop for quite some time... only a couple of times so far but its annoying as heck. I'm talking like 15 minutes of attempting to start it, often times when this happens it will also crank without firing up in the in between time.

All of this happens while trying to start the car. the other related symptom is that two or three times now since i've owned it (getting close to a year now) it has done the same engine-losing-power death but while cruizing along on the freeway at 70mph. So it seems to be related but not caused by a cold engine in anyway.

Now, you are going to ask about codes, yes it does throw a "o2 sensor slow response" (p133 I believe) code but it's not a failed o2 sensor just a slowly responding one. (and there are two right?) is this caused by my o2 sensor or is there something else that is causing my troubles? the thing that I don't understand is someone told me that "anytime the engine stops, and you didn't turn off the key, it will throw a code" but I have checked it on multiple occasions immediately following these events and often times the code has not showed up yet and the other times I don't know if the code has been thrown but not triggered the CEL yet.

Did I make any sense? should I just replace the 02 sensor or are there other things i need to check first? I want to go all "Dr. House" on it

 

no takers? (shameless bump)

 

Have you checked the fuel pump relay?
I would suspect the fuel pump relay or fuel pump.

 

I have not checked it yet.
do you think the "o2 sensor slow response" code could cause this?

update:
ok so I looked at the fuel pump relay. (its the relay with 103 on top right?) nothing is visibly blown or scorched and it does not have the o-zone smell. what am I looking for with this thing is it possible to test with a DMM? Also I saw a post on another forum about the coolant temp sensor going out and people would have problems starting in the cold, the telltale sign was that the fan was running when the key was in the "on" position. I went out and tried to start the car which didn't work, did its usual dying thing and the fan did not stay on when i left the key on. but there was something buzzing, I tracked it down but I don't know what it is or if it is supposed to buzz when the engine is not running. I'm attaching a couple of pictures, one for frame of reference with my fingers on the motor-like device, and one that is a close up of the 'mystery thing'

Update 2:
I found another forum that was talking about testing the fuel pump relay for the volvo 850 or some such similar vehicle. someone was asking how to check to see if it was the problem and they got a response that said to pull the controller and short between the connections for pins 15 and 87 with a paperclip or some such device. Which I tried, and success! the car started up and ran just fine for a minute or so at which point i was satisfied that it was working fine. but to be sure though I put the fuel-pump controller back in and started it up, and it ran for about 5-10 seconds and killed just like it usually does. Also during my voyage inside the car I noticed a decent amount of water in the compartment which houses the fuzebox and the relays, could this have caused my troubles?

This brings me to my big question now, does the this mean the fuel pump controller is bad? Or does it mean there is a sensor or something that is getting tripped which I bypassed when I shorted the two connections? :-/ sorry, amateur at work here.

 

I think your mystery part is an idle control valve/motor. When I turn my 960 on, I hear that thing humming to.

Don't have a clue about your jumping situation. One good thing to know, seems like your fuel pump is fine.

 

The idle motor humming is normal. Pull the relay again and pull the outer cover off and check for cracked solder joints. If you have a solder iron and solder laying around resolder the joints and check the car again.

 

Well cracked solder joint is seeming more likely. Read that post this morning before I headed to work. Started up the car and it started and ran fine for about a minute and a half. Then I was thinking "hmm... cracked joint eh?" gave the fuzebox/place where the relays are a couple of swift knocks like "hey anybody home?" and the car immediately died and then wouldn't start up again but I had to run so that is how I left it.

I'll hit those solder points tonight with a soldering iron and see what happens.

 

Hopefully that is it!

 

Well it seems that was it. I was hitting the resistors with the soldering iron and got to one in particular and when i melted the one solder point the whole resistor moved! I'm thinking to myself... "gee... i think i found it a-hyuk" re-soldered the whole thing back down and haven't had a single problem with it yet... I'm not holding my breath but it does seem to be 100% cured.

hooray! thanks all you peeps!

 

I hope that is it!! Fingers are crossed.

 

Hasn't skipped a beat since I fixed that solder joint! Thanks again!

 

Congrats!