2002 volvo s60 Do I have a bad engine computer?

[doublebug]

I recorded some parameters of working B5244S 1999 MY

First part is stable idling.
Then I switched off ignition and started engine again. So you can see how much
time it takes until Actual spark advance becomes stable again.

[turtlehead]

Дзякуй, Henry!

I will compare those parameters with mine after I get home from work tonight. New video to come.

[abscate]

Did you rule out a fuel problem on this car?

What is the fuel pressure on startup and how does it hold pressure in the rail after 20 minutes??

[turtlehead]

Abscate:

I attached a fuel pressure gauge to the rail a couple days ago and it read about 50 psi as the engine was running, and didn't change after it stalled. I did not leave it attached, however, but I will give that a try tonight. Vadis hasn't given me any codes relating to the fuel pressure, but I'm willing to test every theory at this point.

I tend to think that fuel pressure is not the problem because the engine stalls only if the cam position sensor is connected- the engine runs and the car is drivable if I unplug the cam sensor. I checked the fuel pressure b/c I thought maybe the faulty cam signal was causing the ECU to shut off the fuel pump, but the fuel pressure remained steady even after the stall, so I pretty much ruled that out.

I'm also going to go back through and re-examine the wiring harness in the morning. I'm really interested in Henry's (Doublebug) point that the car seems to run okay initially, but at the 20 second-or-so mark it seems to be looking for additional input and, not finding it, shuts down. Maybe a wiring issue, still?

[abscate]

We just had a V70'thread where some found tapping the ECU made the car stall. Almost certainly this is a bad ECU connection which might be fixed by reseating. I think you need a tool to remove the very expensive ECU carefully. The ECU is all solid state, there are no moving parts. Tapping on semiconductors generally doesn't help the electrons or holes find the right place to go.

[turtlehead]

Abscate, I had exactly the same thought. Since I already replaced the wiring harness, I thought maybe it was the ECU connectors, so I removed the ECU and cleaned them, I even went so far as to gently rub a little small grit sandpaper on the pins. But when I reinstalled the ECU, same result.

Next I want to test the wiring for continuity. Once I take out the ECU again, can anyone tell me which pins I should be testing? I mean for the crank sensor as well as the cam position sensor. The wiring harness I replaced includes a portion (the front half, actually) of what the ECU plugs into so I know this is a long shot but I gotta be thorough. A lot of guys (doublebug, especially) have told me it isn't likely the ECU but I need to eliminate every other possibility before I decide, especially since I've tried about everything else.

Thanks

[turtlehead]

Doublebug, I just sent you a PM requesting more info about the process of programming my spare ECU.

[precopster]

Funny; 20 seconds is usually the time the O2 sensor takes to go through the warmup cycle and go closed loop.

When I fitted the wrong O2 sensor to a 10 valve Volvo it ran perfectly for 20 seconds then looked for input from the (wrong) O2 sensor and that's when idle and performance went South.

[turtlehead]

Mike, I will take a look at the 02 sensors. I don't recall disconnecting them when I replaced the head, but its possible the previous owner was messing with them for some reason. IIRC the plugs are identical so it might be possible for someone to plug them in backwards.

I will first try unplugging them and see what happens, then reverse them. I'll let you know.

[precopster]

I wouldn't worry too much about the plugs as I don't believe they're interchangeable. I would be looking for evidence of joining/soldering in the O2 wires.