1994 Volvo 850 stalls, slow restart...with a wrinkle

Hi everyone,

I have a '94 Volvo 850 and a while ago it started stalling. It has a bit of a rough idle that has improved a little with non-ethanol fuel and fuel injector cleaner. I honestly don't know if that is related to the main problem.

The main problem is the stalling. Sometimes, it will just stall when I'm stopped at a light. Sometimes, it will stall when I'm going 30 miles an hour. Sometimes, it will stall when I'm going 70 miles an hour. Typically, when it stalls at slower speeds or at the light, it just dies straight away. When it dies at higher speeds, the first thing I notice is "hitch" or a "bump" sensation at which point the engine stops responding to depression of the accelerator pedal. The engine continues to run for a few seconds as I roll along. The tachometer slowly falls and then the engine dies.

There was a time when I could throw it into neutral and get it started again before coming to a complete stop from highway speed, but those days are gone. It seems that it is taking longer and longer to get it restarted. The car has to have the key in the off position for a minimum of 10-15 seconds before it will even have a chance to restart. Lately, after about 30 seconds to a minute it will restart very briefly and then immediately die. If I'm patient and wait a bit longer it will restart like normal, but it seems more likely to die again if I don't wait a generous amount of time.

This problem seems to very rarely occur during long trips, but I can't tell if that is relevant or just secondary to the fact that I take I take relatively few long trips. Of course, if it were completely random it should occur more often during these 5 hour trips since it seems to happen so often on the shorter trips.

It's been to the mechanic at least twice for this problem. The mechanics say that the car is not displaying any "codes." They replaced the fuel filter the first time without improvement. The second time, it was in for other things too and they were unable to "recreate" the stalling despite driving it for 40 miles. They said that without any codes or being able to recreate the stall, they didn't want to just "do something."

I've read some posts from people with similar cars and problems. Seems like the things that come up most often are the fuel pump, fuel relay, and oxygen sensor. However, only the fuel pump and fuel relay seem to be mentioned when there are no codes. Is that at all accurate? Do the symptoms the car is having seem more compatible with the fuel relay or the fuel pump or something else entirely. I haven't tried to "listen" for the fuel pump when it happens before, would that be likely to help?

Thanks a ton for any help.

Pid

pidgas wrote:
> Hi everyone,
>

> The main problem is the stalling. Sometimes, it will just stall when
> I'm stopped at a light. Sometimes, it will stall when I'm going 30
> miles an hour. Sometimes, it will stall when I'm going 70 miles an
> hour. Typically, when it stalls at slower speeds or at the light, it
> just dies straight away. When it dies at higher speeds, the first
> thing I notice is "hitch" or a "bump" sensation at which point the
> engine stops responding to depression of the accelerator pedal. The
> engine continues to run for a few seconds as I roll along. The
> tachometer slowly falls and then the engine dies.
>

That sounds exactly like what my 740 did. I don't know how similar the
engines are, and I actually doubt they are similar enough for this to be the
cause of your problem, but.....mine was caused by the auxiliary air valve
pipe, right on top of the inlet manifold, working itself loose. Check yer
pipes!

Si