Urgent: temp sensor quiz

V480t · Post by **V480t** » Sat Feb 28, 2004 12:11 pm

Hello again,
I made some cleaning on my engine(idle valve ,throtle valve, etc.)
And iÂ´ve always had problems starting the engine when cold.
But now the engine has much more dificulty to start and runs realy bad and only if i put my pedal on the acel.Even though i canÂ´t drive the car like this.
And now quiz:
-I supposed that the cold dtart problem was related with the coolant temp sensor(the one in the front right of engine) so, i asked the price to volvo and its 70 euros

, but i found a store of electrical stuff that sold me exactly the same sensor for 10 euros.

The real quiz:with the sensor wiring connected the car runs bad and makes a lot of smoke.With the wiring disconnected works like a new car for about 20 seconds and then stalls(fail safe?).
So is the problem related with the sensor or not?

volvofox · Post by **volvofox** » Sat Feb 28, 2004 12:34 pm

guess so... I have the same problem. Mind you there has to be a good ground connection (see electrical schedule) it are actually two sensors in one, both are grounded over the block

My problem also started with cleaning the throttle housing. Be aware that the throttle house valve sensor must engage in rest (click!) also look at the wires, remove the rubber from the connector, and look (mine had burn traces)

If no luck its schedule and multimeter time....

best is to go to a volvo garage or volvo specialist, and have an ECU readout: it will tell you were it hurts...

V480t · Post by **V480t** » Sat Feb 28, 2004 12:53 pm

What shoul i look for?the readings seems ok.the throtle is fine(clicking) and with the sensor disconnected the idle valve works fine.the connectors of the sensor go to the injectors and to the ecu, so what in hell can be wrong?shoud i measure something on the ecu?
the problem now is that the car wont run so its difficult to go to a volvo garage because i donÂ´t want the car to be repaired there(bad previous experience).Please help because im getting mad.
The car ran fine before the cleaning(only bad on cold start) but now is a lot worse...

volvofox · Post by **volvofox** » Sat Feb 28, 2004 1:05 pm

did you readjust the bypass screw on the throttle housing ? maybe it gets to much air at start... is the tiny hole inside the throttle housing still open ?

than see if you can measure the resistance towards the ground (the block) on both sensor pinns. Place em here. anyone with VADIS can verify. (I knew the data, but forgotten em, I don't have vadis)Maybe an idea to make a good extra ground cable near /at this sensor to the negative plug of the battery...

V480t · Post by **V480t** » Sat Feb 28, 2004 1:11 pm

Bypass screw?is it the screw on the side of the throtle housing?is the tiny hole inside the throttle housing still open ? What do u mean with this?
If there was some misadjustment wouldnÂ´t this happen without the sensor?

volvofox · Post by **volvofox** » Sat Feb 28, 2004 1:20 pm

V480t wrote:Bypass screw?is it the screw on the side of the throtle housing?is the tiny hole inside the throttle housing still open ? What do u mean with this?
If there was some misadjustment wouldnÂ´t this happen without the sensor?

I had to adjust this bypass screw (yes on the side of the housing) that lets air around/pass the valve... logically, the dirt you took away seals the valve, so there is now more air around it. (the dirt has gone). As cleaning it, I also saw a tiny needle hole, that I smeared close, and had to punch open with a needle. Don't use agressive thinks, or rough sand paper in the throttle housing..

as the double sensor is removed the ecu gets different data... so starts different Maybe it "thinks" the engine is hot than, and the extra air at the cleaned housing is ony wellcome ... sore something like that.) As I said I did not solve this problem too yet. ... but make sure the fundamental things like the bypass and the needle hole are ok !

V480t · Post by **V480t** » Sat Feb 28, 2004 1:27 pm

i donÂ´t know what u mean with a valve inside the throtle housing, i can only see a butterfly that opens and closes and a few holes around the entrance of the throtle.where is located that tiny needle hole?Also i didnÂ´t take too much dirt off.(maybe some mechanic cleaned it before...)

volvofox · Post by **volvofox** » Sat Feb 28, 2004 2:49 pm

what this board can do to you.... I just have made a thick cable from the negative plug on the battery to a m6 hole around the corner from the engine (ECU) sensor, and also to the throtlle valve housing.

the car starts fine now (lets wait with cheering if this trend sets)

why ?

well I assume as you take loose the throtlle valve housing U use the gaskets and use some lockbond on the screws. If You look at the schedule, one can see that one lead in the throlle valve sensor and valvepositionsensor (all in one) have a grond connection..... Now there was not much of a ground connection. (the housing was practically insulated) so I made an eye connector under a screw of it.

First thing i did was a ground to the sensor in the block. I had ground trouble in the extra gauges a while a go, this made me think ground on the block was getting worst (all the original straps are there, but mights be oxidated) the double sensor uses ground from near the sparkplugs. they produce lots of magnetic field and take away a lot of ground. There was a M6 hole available nearby, just around the corner, and srrewed a bolt inside with teethed washer and a eyecable connector.

I cannot tell wich solution of the both helped the most, but I am sure they did. Hope it helps also for any of you with the same problem.

V480t · Post by **V480t** » Tue Mar 02, 2004 12:37 am

My only sin is loving this car...

Anyway the car is running again.The idle valve was not sealed and i donÂ´t know very well how to seal it(now is sealed with glue stripe).Even though itÂ´s well sealed and i dink the car is exactly the same,the cold start problem.Thanx VolvoFox iÂ´ll check for that ground connection.

volvofox · Post by **volvofox** » Tue Mar 02, 2004 12:46 am

this problem fools me over and over. its because its not consistent, i mean its doesn't always occur. so if i change something like grounding the valve housing its starts ok, I think i have solved the problem, but then after some days it all comes back. very, very odd. I will get some help on this one

V480t · Post by **V480t** » Tue Mar 02, 2004 7:31 pm

I checked the ground connections and they seem fine.Do u think that even in this case i should put more ground connections?how can i ground the idle valve?

thanx