854 auto jerks while driving

[n8t50]

Need some help diagnosing an issue with my 96 854 T5 auto. It is doing something that I call "false shifting", where the car will lurch, like it is shifting hard, but won't actually shift. If I restart the car, it goes away temporarily. After about a 9hr drive, the engine RPMs start to fluctuate, especially at an idle. Over time, it will also get worse (more frequent, and sometimes harder, sometimes it will jerk constantly for 30 some seconds), to the point where the car is almost undrivable. I replaced the PNP switch, but that hasn't helped. I'm assuming this is a transmission issue.

 

Edit: I'm considering an issue with the ECM, because when I plug into the OBDII, I can't connect with the ECM.

[jefhon]

dunno re: your ECM issue.

however, your main issue there sounds like 1+ sensors failing.  i've had same/similar symptoms and it was sensors so just check or test your sensors but you should know that there are a butt ton of them on these.  

here is a list of the ones that i know for sure about from 1st hand experience & R/R but do not consider this list comprehensive by any means:

throttle sensor, camshaft sensor, crankshaft sensor, 3 speed or RPM sensors on the tranny, & there's more.

also: the Volvo diagnostic manual uses a few differrent terms for sensors that appear to measure the same thing:  speed, RPM, engine speed, etc.  just an FYI b/c there are at least 4 different "engine speed sensors" that i know of. 

ok then.  so i have also found that once 1 of these sensors goes most or all of them will need replaced around the same time.  i know this isn't what one wants to hear but it makes sense & is generally true.  

so there you go.  i hope this helps but i can guarantee you that i had the exact same symptoms--still having actually  & have 3 "speed/RPM" sensors to replace on my tranny--and it is usually or always 1 or more of these sensors causing it.  

 

good luck! 

p.s.  I highly recommend fcpeuro dot com for most or all of your volvo needs.  i don't work for them i just know them well & recommend them.  i also highly recommend going with OEM/Volvo parts whenever possible because aftermarket parts usually fail sooner, sometimes don't fit exactly right, etc.  others that aren't full of crap on here will tell the same. this makes sense also when you consider that going with aftermarket parts costs you more in time & energy since they fail or don't fit more often.  ok then...best wishes.