Stalling engine has stumped three mechanics
 

I have a '95 850 SE which stalls 6 minutes after start-up when I tap the accelerator (but especially under load).

It does this for about 5 minutes, and then it's stable. But sometimes it's still unstable after 15 minutes of warmup.

If it stalls enough times, it becomes unstartable.

I've had THREE mechanics (two of them decent) trying to solve this problem, and all have given up.

Currently throwing Code 223 from port 1 - IAC Valve Signal Absent Or Faulty, but over the 6 months it's been looked at, it's thrown lots of different codes (and they've been cleared by the mechanics).

Besides turning it into a cube, what should I do?

These older models had a mechanical throttle so generally the problem lies with the idle switch on the throttle body.

Start by removing the throttle body and cleaning both sides. When the inside and the butterfly blade are clean, test for proper operation of the idle switch. When you just open the throttle, it should just click. You will hear it. If not, you need to adjust the switch so that the moment that it goes off idle the switch clicks.

If your does not have the style that clicks, then I would recommend replacing the throttle position sensor. This will take a bit of calibration with a scan tool to get the right reading at idle.

https://www.rockauto.com/en/moreinfo...288896&jsn=357

The other thing is to check for a voltage signal to the IAC (idle air control). You could have damaged wiring but the main culprit is usually the control valve itself.

https://www.ebay.com/itm/Standard-Mo...UAAOSwp85bI8WY

don't rule out the fuel pump relay under the fuse panel

Thanks for the replies, guys.

I think the fundamental problem is that no mechanics - even the dealership - can/want to work on a car this old. Parts hard to get, they've not seen another one like it...

There isn't a lot of difference between the 5-cylinder engine in a 1995 model versus a 2005 model. The big changes were variable valve timing and an update to the timing belt hardware.

The problem that I see is that trying to diagnose this thing will cost a lot of money and if you end up with a day's labor to diagnose the problem, that's over $800. Most people will not spend that much on a car of that age so no one wants to do the work then never get paid when you abandon the car on them.

Offer to pay up front and see how it goes. Remember, this is your car and your problem, not theirs.

I mislead you. I said in the original post that I've had three mechanics look at it (and I've spent the money), but I don't think they've done the hard work of figuring out where the sensors are, how they work, etc. They just check the distributor cap, fuel pump, etc.... all the stuff that's worked for them on 90% of the problems they've seen.

Whether it is hard work of routine work, there is a price to pay for diagnostic time. On a problem like yours, you have to be willing to commit a day's labor, or more, to solve the problem. I'm not saying that it will take that long, but at $100 an hour or more, how many hours do you want to buy?

I'm certain that whoever looked at it did so respecting your wallet. No one is going to spend all day on the car and then come back and tell you that they've not found anything unless you give the all-clear up front.

It is your car and your problem. The problem is not that of the mechanic that you hire. He is not under a court order to fix your car.

I just get tired of people who expect things to be fixed in a snap. This is an old car.

Thanks for the reminder to be a good human being and a responsible consumer. I'm there. As stated, I've been paying for diagnostic time.

Your note about the throttle position sensor and the eBay find for the Idle Air Control Valve may be just the tickets. I'm taking it to a new guy next week and will let you know what happened. I'll also take your advice and offer to pay up front.

Hey Tony, would it be the IAC valve if the problem only shows up when I tap the accelerator? In other words, the thing idles fine for 30+ minutes...

Is it random stalling, or stalling when it comes to a stop?

Most common causes to stall:
1. MAF
2. Dying fuel pump.
3. Fuel pump relay.
4. Open intake piping.
5. Another sensor.
6. Another relay, like the fuel injector relay.

These cars are NOT complicated and love to run.

Has anyone installed a jump wire in the fuel pump relay and ran it for a few days?

Only on pressing the accelerator, and can be in motion or at a stop.

The fuel pump relay has been replaced, but that doesn't mean the new one isn't the problem. What would I expect to happen if I jumped the fuel pump relay?

As you said, they're not complicated... except for the ECU, which is what I'm starting to fear is the problem.

I have never seen an ECU fail on a modern Volvo. I did see one in an old 240 where the fuel pump circuit was bad and someone hotwired the fuel pump. We removed all of that mess and installed a used ECU so that it would be right and safe.

As I mentioned before, this is likely going to be a matter of chasing power and ground wires. You just have to decide if spending money to diagnose and fix the problem is worth doing or just get another car.

I really don't want to sound like a gloom and doom person, but I have been dealing with cars long enough that this sounds like one of those very extensive time-consuming tasks just to find the fault. I do not condone throwing parts at anything unless the item is inexpensive and part of the normal maintenance anyway.