high rpm......bad?

[spike4073]

hi, my volvo 340 dl 1.4 cvt is stuck in low gear ratio at the moment, the fault has been traced to faulty tacho (am awaiting replacement)

in the mean time im stuck with it reving its nuts off round 3000 rpm when traveling at 30/35 mph.. 4500/5000 rpm when traveling 50 mph

so my question is this:

if i spend approx 1 hour in the slow lane of the motorway at 50/60 mph with the car reving like this will it kill my engine?? and if not are there any potential problems with driving it while revs are so high?? or is she just going to be noisy and burn through a lot of fuel?

i ask because i have to do a fair bit of driving over the next few days with some motorway journeys and im worried my engine is going to explode :S

any input greatly apreciated

[volvodspec]

a B14 can take the revs, just make sure the engine is on running temp before you drive off and keep an eye on the coolant temp.

however, this problem you have is very rarely caused by the tacho; are you sure it's diagnosed correctly???
if the fault really is in the tacho, disconnect the yellow/green wire off the EMV, this should let the revs go down quite a bit but not as much as it is supposed to be because the tacho either gives an output on kickdown OR gear up, not both but anyway; that should make driving a little bit more pleasant

if the rpm's don't cange after disconnecting that yellow/green wire on the EMV then the fault isn't electric, but in the vacuum system. if disconneting te wire helps, but plugging it in after the new tacho is placed doesn't help either then both tacho's are fine and there's a electrical problem in the kickdown/low gear hold/brake pressure switch- circuit. for all of these problems i get a full diagnostics test uploaded in the next few days; i'm busy today but should be touching up the last details tomorrow.

[spike4073]

well the guy who diagnosed it admitted to not knowing a lot about cvts but he followed the green book that i downloaded from here and printed out for him and he tells me that as best he can tell, the tacho has failed as however high you rev the car the voltage always stays on the low ratio side of the emv and never switches to the overdrive side,

he tells me that when he disconnects the wires from the low ratio side of the emv the revs still dont drop so he recommended replacing both tacho and emv to be sure that the fault isnt with either of them and basicly prey that this fixes the problem lol

does it sound to you as if he is thinking along the right lines???

buggered if i know what to do, ive got new tacho and emv lined up so i guess we will see

[volvodspec]

for me this is the first time i'm actually reading the green books on the subject and now i understand why it's no wonder most of you V3M guys are struggling with CVT-faults the only usefull page in the entire faults/diagnostics section of the manual is page 29. as far as getting a correct diagnose correctly and relatively fast (faster than with that green book, trust me on that!) you'll be much better off with what i'm translating/writing atm.

^^ DONE!, check this out: http://www.volvo300mania.com/forum-uk/v ... =6&t=12314

oh and reading your description it can be a combination of things and not nescasarely emv or tacho, with the engine running idle; pull off the thicker hose that goes to the gearbox; does it start to suck immediatly even if you don't have the wires connected?

[spike4073]

no, it doesnt suck at all with or without wires connected, i think thats why i was told to replace both tacho and emv .... from having a quick look myself the green book seems to say the same thing but i have no idea,

all i know from my own amature attempts to figure this out is that there is always voltage at the kickdown side of the emv and it never switches to the change up side,,

but to be honest from what i can work out the valve has something wrong with it,,, it never "sucks" at you mention in your posts, and i do think theres something going wrong in the tacho,, i opened it up and noticed that the transistor you point out in your post has already been replaced by someone before i got this car?,,,


ive taken this to a local electrical guy who soldered in a new one for me this morning,,, no change tho

banging my head against a wall atm

[volvodspec]

i think one of the 3 switches on the "kickdown" side of the EMV is active, i've copied a bit of info from the manual

Important info before we proceed
Beware that the electrical system switches the kickdown OR gear-up side of the EMV, it will never activate both at the same time. While knowing that, electrically the kickdown-circuit gets priority over gear up, hence why the kickdown circuit can be activated while the car is driving under “ gear up” conditions and you activate the kickdown circuit for overtaking or using the gearbox as a engine brake in the mountains. In short words; if the EMV is electrically activated on the kickdown side, you will never get vacuum OR voltage on the coil of the gear-up side of the EMV.


if you take a look at the "checking the electrical system" part:
Now we check a few connections of the 8-pin connector, note the angular sides to make sure you take the right pin!

- Connection 6: switched earth of the kickdown circuit (resistance measurement, ideal is 0Ω)

i believe you don't measure 0Ω there but infinite, in that case one of the 3 switches is indeed active.

to find out wich is,
Besides mounting new switches if one of these are broken, you can also rule them out electrically as a temporary solution. For the brake pressure switch, interconnect the yellow and red wire with another wire. For the kickdown switch, go inside to the switch at the top of the accelerator pedal (remove black isolation panel under dashboard to get there if present), connect the yellow/green wire to an earth.
do that and check where the resistance becomes 0Ω again.

[spike4073]

hi, thanks for your quick anser,

ive just checked resistance at terminal 6 on the tacho ot reads 0 "no resistance"

what do you think this means?

[volvodspec]

that will probably mean that replacing tacho and emv won't help curing your problem, but just to be sure; we'll run through it again

- term 6 is no resistance? does that change when you apply the brakes hard; give full throttle (not with engine running!) and with the low gear hold switch??
- no voltage on yellow/green wire with ignition on?
- no voltage on yellow/green wire with low gear hold switch on?
- car at idle, hose B off the emv; doesn't suck?
- car at idle, hose B off the EMV; doesn't suck with low gear hold switch on?

what about the "checking the vacuum system" chapter in the manual http://www.volvo300mania.com/forum-uk/v ... =6&t=12314
do you get result 1 or something else?

[spike4073]

ive just finished checking all of those things:

resistance remains at 0 with brakes applied hard, when giving full throttle and with low gear hold on.

voltage at yellow/green wire remains present whatever i do.

at idle hose b doesnt appear to suck with or without low gear hold applied

vacuum system check: i get result 1


so what do you think could be the problem if not the tacho or emv?

[volvodspec]

if the voltage stays on it's continuously activating kickdown.

but, with this in mind; and hose B off the EMV it should start to suck instantly once you start the engine; if not there's also a valve broken inside the EMV (easy to check; take the thing off the strut mount; 2 bolts. then unscrew it with the 3 small screws at one coil's end to take a look at the valves)

have you tried/checked this bit?
Electrical check of the tachometric relay outputs
There is a possibility the tachometric relay can stick on an internal relay, put the tachometric relay back to the 8-pin connector and do a volts measurement to the B side on the yellow/green(+) and brown (-) wire. Again apply the 3 switches the same as above and this time each coil needs to reach 12V and instantly drop if you release the switch. If it stays 12V for a while or doesn’t respond open the tachometric relay and note the big relay at the middle, carefully check the larger solder pieces for cracks around the pin and if necessary solder them again.

[spike4073]

ive already checked the solders inside the tacho... all good altho i noticed that the transistor thingy had been replaced at some point.... hoping that this had simply failed i had the guy at my local electrical shop replace it (this made no difference)

ive also checked the rubber bits inside the emv ... all appear good ... none cracked or broken off.....

im stumped,, when i dissconnect the yellow/green wire from the emv in an attempt to effectivly switch off kick-down the revs are still high? (no difference)


one guy i spoke to did mention that my drive belts may need tentioning? ... could this cause the problems im having?

[volvodspec]

the big relay controls the kickdown side of the EMV
and the transistor and a few other parts control the gear-up side of the EMV. so yes its quite possible that it has been replaced and probably doesn't cause the problems you have now

slack drive belts can make the revs a bit higher, but the revs you describe aren't likely to be caused by slack belts.

is the thinner plastic hose connected to connection A of the EMV (just another extra check, you never know )?
if you pull both hose A and B off the EMV, does the car drive different from what it is now?
if you have it in idle, select D and hold the selector button down; does the car need more revs to take off from a standstill or is it the same?

[spike4073]

lol, yes a is the thinner hose,

no removing them makes no difference to how it drives.

if i keep the selector button held down it wont take off at all........ untill i release the selector button..... i thought thats how that bit should work?

clutch engages at around 1500

now what? lol.....

[volvodspec]

yep that's how it's supposed to work. it was a quick test to check if the EMV gets enough vacuum to make the gearbox work. but if the clutch engages at 1500rpm you'll need to take a look at the clutch airgap and adjust that to correct spec

as far as the high rpm's; measure the resistance on coil B; this should be around 33Ω, if it's infinite or 0Ω then the coil is broken
also, as the tacho continuously switches 12V to this coil the relay inside the tacho is stuck/broken

[macplaxton]

if i keep the selector button held down it wont take off at all........ untill i release the selector button..... i thought thats how that bit should work?

It will if you give it enough welly. All it does is delay the engagement, so it won't engage until about 2000rpm.

Without pressing the button, it should engage a lot lower than 1500rpm.

Going back to the belts, slack ones will lower the gearing. Adjust them properly (I seem to remember they were only done on a guestimate before).