1997 850 Transmission Downshift Problem

kseyoum · Post by **kseyoum** » 25 Sep 2006, 14:15

Hi All,

My 1997 850 T5 engine stalls intermittently while coasting to a stop because the gear remains stuck on 4th. The engine usually stalls after a long drive (more than half an hour). To remedy the stall, I usually put the gear into neutral when the engines starts hesitating to stall. I then put the gear back into drive and drive on without a stall. Also, at time, shifting from 1st onwards seems a bit jerky. Any ideas as to what is contributing to the sticky 4th gear?

I've been reading this forum about changing the PNP switch, but I do not see the arrow flashing. There has not been any check engine light, or any code to read. Can a code be read even if there is no check engine light on? I had the code read by a regular auto shop, but did not get any code. Do they not have the right tool?

Thanks.

-Kef

95autoturbo · Post by **95autoturbo** » 25 Sep 2006, 17:35

Feel free to add in half a can of "Sea Foam" for transmissions it will not harm, about 6bucks from Napa, I have only heard good things about it and, I do use it on my electronic transmission ....knock on wood!

White850Turbo · Post by **White850Turbo** » 25 Sep 2006, 19:38

Not so sure I'd seafoam it quite yet. Try a drain and fill of some fresh Mobil 1 ATF and see if the problem improves. You'll need about 3.25 quarts for this if you're using the transmission drain plug method.

If that doesn't help at all, then you can try some seafoam, but I'd drain a few ounces of ATF out before putting it in. Too much ATF is just as bad as too little.

Post by **MadeInJapan** » 25 Sep 2006, 19:45

I'm thinking more in terms of the TPS (throttle position sensor) or CPS (camshaft position sensor). Does it only do this on downshifts or are there times it has trouble shifting up too?

kseyoum · Post by **kseyoum** » 26 Sep 2006, 08:16

The stall is always during down shift. When the engine dies, it feels just like leaving a manual transmission on a higher gear and not depressing the clutch. Also, in a stop-and-go traffic, it seems to have difficulty going back to 1st gear from 2nd gear; it's jerky at times. On the other hand, the transmission shifts just fine upwards if you just accelerate regularly, or punch it a bit.

You mentioned "throttle position sensor"; Can this cause intermittent failures; I'll look into this though. You also mentioned "camshaft position sensor"... I had originally thought that this could be the cause of the problem; do you know where it is located? I had replaced one of these on my old 740--it was on top of the flywheel housing, and a 5-minute job.

Any other suggestions? How about the transmission control module? Anything on the transmission that can make it too sticky? I'd rather not put additives at this time without a bit more investigation.

Thanks all for your advice, and looking forward for some more.

bobsnow100 · Post by **bobsnow100** » 26 Sep 2006, 09:50

I'd check the fluid level first. Do it on a warmed up engine. Follow your manual to do it the proper way. Usually engine running,car on level ground, use lint free cloth and wipe off transmission dipstick and put back in and pull out and check
I'd change the fluid first
I'm not sure about your car but most newer cars transmission shifts are done electroniclly though your engine computer. (ECU) maybe volvo dealer needs to reset the computer if this is the case.

kseyoum · Post by **kseyoum** » 27 Sep 2006, 15:05

Thanks for the inputs. The transmission fluid is clean, and was replaced 3months ago. Still open for some ideas. I have not got around to replacing the TPS or CPS yet.

cn2000 · Post by **cn2000** » 27 Sep 2006, 17:34

The symptoms you describe sound like a failing torque converter lock-up solenoid. Try a fluid flush, I think it is unlikely that this is a software problem, but only a transmission guy could confirm that. Ususally the only cure is replacement of the part, some are external, some internal, I'll check for you.

kseyoum · Post by **kseyoum** » 27 Sep 2006, 20:03

Thanks for the inputs!

I'll try a transmission fluid flush as soon as I can. Would putting synthetic ATF help? Milage = 141KMiles. Awaiting more inputs.

Saeed · Post by **Saeed** » 27 Sep 2006, 20:43

Could you please provide me some info regarding the average cost of replacing the torque converter lock-up solenoid? and if it can be replaced by a novice handy man who can perform only external part replacement with minimal mechanical talent?

Regards,
Saeed