S90 2 years of shifting problem

lindy8_man · Post by **lindy8_man** » 01 Jan 2013, 21:37

Fix the vacuum leak. It is surprising what faulty vacuum can do. Just had a "Charcoal Cannister" "Large LEak" code. I hunted and hunted for that leak with no success. There was a very small hose under the engine that was dry rotted, and caused my leak. $10 fix for a long time hunting...

As for the other info, When was your last radiator flush? Burnt fluid can cause crazy shifitng. I had a similar slip going on with mine, and a flush with a secondary fluid cooler did wonders! I replaced the radiator two years ago with a metal one. I wasn't sure that the cooler was doing a great job because I kept burning through my tranny oil. Tranny was replaced four years ago now. so I added the air cooler. No more slipping on acceleration (at about 30 mph for mine).

vova · Post by **vova** » 01 Jan 2013, 22:36

If it does this only when tramsmission warms up. Here is what i think:.. Once tramsmission warms up temp sensor sends OK to use lock up, it locks up too soon, RMP tanks and it down shifts before shifitng back to previous gear. Can i disconnect lock up solenoid?? if problem is with a lock up solenoid then outdoor temp effect makes sense i guess.

also if i floor gas pedal it shifts fine but i cant be driving like manic. If it shifts fine before warming up then vacuum leak may not a problem.

lindy8_man · Post by **lindy8_man** » 03 Jan 2013, 23:56

My recommendation is to find and fix the vacuum leak first. The trouble with a "charcoal Cannister leak" is that it could be anywhere on that evap system. As I described in my previous post. Your ECM is going to interpret that "leak" in a particular way. Your ECM and your TCM are very complexly connected. Cause and effect is not so easy to prove. You could have a shorted sensor. those 12 volts gotta go somewhere. You know this is a problem. It could be the cause... Start there!

Second. Flush that fluid! and I don't mean a drain and fill. Burnt fluid can cause poor shifitng. What may be slightly burnt to you could be crispy sludge to your Volvo's system. Dex III (if I remember correctly) is not that expensive.You can get a case of it good and cheap online! There are some great tutorials for do it yourself tranny flushes. Save yourself 80 bucks! You know you need to do it... Go there next!

If these things you know you need done do not solve the problem, then it makes sense to start looking elsewhere.

lindy8_man · Post by **lindy8_man** » 04 Jan 2013, 00:05

Also remember evap system settings change as the engine warms up. If I recall, it is supposed to draw the vapor from the charcoal cannister after warm up... or is it before? doesn't matter. The whole darn thing is electric/vacuum.

vova · Post by **vova** » 04 Jan 2013, 13:33

Ok.
please tell me what happens once engine warms up and it starts drawing vaccum from canister and there is a large leak present? what happens next in this process?

lindy8_man · Post by **lindy8_man** » 04 Jan 2013, 20:28

Why Wait? Why Hesitate on these jobs? You have been driving the tranny like that for two years.

To answer your question, the ECM is controlling the cannister. When the car gets to 120 degrees, the ECM removes the ground from the purge valve allowing the vacuum to pull the vapors into the intake manifold. It is a Bi level purge system there are two sources of vacuum that remove the vapor from the cannister. The PCV is your source at idle, and I believe the throttle body is your source at speed. you could have multiple opportunities for leaks and failures. the purge valve could have failed, the hoses could have dryrotted and seals could have failed. Many of the lines are a nylon tube that you don't have to worry about. but there are sections of rubber hose that are not clamped and could be leaking. Your intake manifold should be looking for that vacuum to exist. Any leak/failure from manifold and PCV back to fuel tank/Gas cap/and Access seals to the tank caould cause your "cannister leak." During "certain conditions", the ECM may ground the purge valve to control fuel mix calibrations. If your problem with your tranny is electrical there are multiple systems involved with the Evap Cannister. Yes it is vacuum... But it is controlled by 12 volts here and there.

vova · Post by **vova** » 04 Jan 2013, 22:51

Thanks very educational,
so if there is a Large leak present then once car is warmed up it draws pure air from canister instead of gas vapors and therefore provides lean combustion? am i correct? lean mixture wants to kill engine therefore makes rmp to tank and creates a feeling of dawnshifting. Am i making any sense?
Why engine works steady at speeds above 15-20 mph, highway speeds?

thanks

lindy8_man · Post by **lindy8_man** » 05 Jan 2013, 12:08

Remember that the ECM is taking all this in and is trying to compensate. When the vacuum is present at the manifold or PCV a leak would cause the Vacuum to be less powerful than the ECM is expecting. That can cause all kinds of wacky things. As you said, If you floor it, the mixture would be rich.... less compensation by ECM.

Crawl under the car under the driver's seat and check between the cannister (I think I remember that ours is not round) and the fuel tank. There should be a two nylon hoses connected by a rubber hose. It comes off easy. I'll bet this is where one of your leaks are. There are a few other links like that at the other end. You can test your purge valve easy enough. Then check your Nylon hoses for any torn spots. I think there was also an issue with the O rings on the quick connectors. You would need to go through and check all those. Does New York test gas caps for emissions control? Your gas cap could have failed. Then the Last place I would look for that leak is in your trunk. There is an access port going throughthe floor into the tank. It is a big round plastic disk with a seal onit. That could be leaking.

vova · Post by **vova** » 05 Jan 2013, 12:23

I ll check lines and canister. I did replace valve a few weeks ago but nothing changed.
Why there is no problem at speeds above 15-20 mph? is this because of throttle plate being opened wide enough to create proper mixture?

i ll check all lines and i ll also put voltmeter on the valve to see if it openes at the the same time when car warms up and shifting problem starts just to see if all 3 things come to play at the same time.

shifting issue became worse within 2 years so did vacuum leak, 2 years ago it was a small leak as per code now code shows as a large leak. so it all could be related.

lindy8_man · Post by **lindy8_man** » 06 Jan 2013, 17:05

I would think the ECM has gone through all the steps to compensate for whatever funky input the leak is causing. The Bi level is also switching idle to speed... One more layer of complexity... So by the time you reach 30 the ECM has compensated.

Try acceleration to 20. When it shifts funny, try to accel to 25 and hold it. After a little while accelerate again past 30. From 25 to 30 was it shifting normally? I'm expecting that lag is ECM trying to compensate for funny signals due to that leak. Especially if the two got worse together... Seems like a strong correlation don't you think?

S90 2 years of shifting problem

Re: S90 2 years of shifting problem