What sensors are these?

[gothy]

Hey guys what sensors are these?

Would they cause the car to stall if they are loose? Or shorting out?

They are found on the left of the throttle body plenum on a 172.

The black wiring housing that runs up the left side of the engine, that holds the wiring for these two sensors, could be the problem?

 

[st3ve]

Top one is MAP sensor, bottom is for the carbon canister.

 

[Chip-mk1]

Top one is map sensor which provides the main engine load value to the ecu so it knows how to fuel and spark the engine, the bottom one is not a sensor it is the dephasor solenoid which activates the variable cam timing.

If the map sensor signal is incorrect for any reason, the engine wont run well if at all.

 

[gothy]

Ah ok, so the map sensor may be the cause for my problems.

would it throw up a fault code?

I have the regular issue people have been complaining about, but the seems to be no definitive fix.
It stalls as its coasting upto junctions, stalls in neutral, in gear, clutch down or up.
also I have trouble starting it up, sometimes 11 times to get it to catch.

Also it does have an occasional misfire, feels like its lost a cylinder or two, then you can't apply any power, so when you slow down enough it stalls. But it fires back up just fine following that.

would that MAP sensor cause those running problems?


ive had replaced,
plugs and leads
Rear lambda sensor
Coolant temp sensor
Cleaned throttle bobody


none of these seem to fix the problem so far.

 

[jjones82]

The cold start issue sounds like the TDC sensor to me, have you tried cleaning that?
Also the rear lambda shouldnt affect the running its the front one that you have to worry about, have you tried swapping them over?

 

[Chip-mk1]

Do you have an RS Tuner or similar to read codes with? Not every fault puts the light on.

 

[gothy]

Yes I told my mechanic about the lambda sensors and he said, when they plugged it in it only said the rear one was faulty.
but he wouldn't listen when I told him about the front one causing problems.
i think I'm going to put it on the ramps my dad has, and swap the lambda sensors over tomorrow, and go for a drive.

oh yes I've had the tDC sensor cleaned too, thanks.

this suggests he's got something to plug it into, his son who also works there is an ex Renault mechanic.

Cheers so far, I will check tomorrow and report back.

 

[MG cup]

Phase one or 2. Im guessing ph2 from your profile. That stalling coming upto junctions sounds like a TPS or ICV on a traditional throttle body. The ph2 not having a ICV I would think your FBW throttle body is playing funny buggers. Cleaning a CPS sensor won't do much unless there's grease or likes built up on the end( unlikely) they are cheap to replace and cause starting issues. I've replaced 5 between my mum and sisters 1.2 clio's. There that bad for them, my mum knows how to diagnose them lol.

 

[gothy]

I couldn't get the lambda sensors to budge with the clearance I had to work under the car.
but I unplugged the battery for 15 mins to reset the ecu.
It seemed to have an effect on the starting, first flick of the key, however it doesn't always start after stalling now which it still does.

Ok I've had the car plugged in to Renault clip.
I've had the following faults come up.

* 3rd cylinder injection fault - not the wording, i think it pointed to injector.
* downstream lambda sensor - already been replaced by my mechanic although it was a second hand part, which i wasnt happy about, also he may not have been able to reset the code, so it might be working.
* manifold absolute pressure sensor. - map sensor. - this is what I think may be the problem, as above moving the wiring housing, causes it to stall. The sensor itself may be ok.

So I'm thinking MAP sensor is dodgy, or the wiring harness that trails down the side of the engine may be earthing out, see in the above photo, it has electrical tape holding the wiring together, is that standard?
Perhaps injector 3 could be causing the misfire.
Or would a faulty map cause misfiring.

the Renault mechanic reset the codes, drove it and no new codes showed up.

however it still misfired on the way home, so that would have caused a new fault code to log I'm sure.

I asked the Renault tech, if when I was unplugging each cylinders fuel injector wiring one by one that would have thrown the 3rd cylinder fault code up, he said it would bring them all up.
and since they weren't all up, I can only assume that what I did the other day had no effect on the readings.


Where do I go from here?