1995 2.0 16V Cav MIL and causes

[Cavalier342]

I've never touched an ecotec myself, but yes the engine ECU is behind the driver's kick panel under the dash, easy enough to get to.

Regarding the sensor, it should be somewhere around the thermostat housing..

[tom50]

There appears to be a sensor with blue plug near to the head at the same side as the gearbox ?

[Cavalier342]

Someone will have to confirm that but they are located in different places on different engines. As I said, on the 8 valvers, it's on the cambelt side. On the V6's it's at the gearbox side on a coolant bridge along with the other sensors. Should be a 2-pin plug, although someone will say for definite if that's it or not.

[tom50]

Both the small brass ( with spade connector) and the blue two pin temp sensors are next to each other, under the coil pack, I for testing purposes unplugged the blu two pin one, and started the engine, and the mil stayed on , re connected it and re started and it went off after a few seconds

[thegriffin]

Heynes says "in the end of the thermostat housing
on the inlet manifold side of the engine"

[tom50]

the plug looks like this one, which is next to a smaller brass type that a spade connector slides onto both under the coil pack both screw into the head

And the thermostat housing would appear to be at the front left (timing belt side) connected to that is the top rad hose, like on the 8v 1.8 engines

[thegriffin]

That looks like the one you want.The one with a
single spade is for the gauge.
I think Heynes has got it wrong with the location.

[tom50]

Unless I'm wrong, But if i am why have they made the housing for the top rad hose removable ie two bolts holding it to the head ? doesn't make much sense, unless they expect the the part that is inside the rubber house to corrode away? or for when the head is removed for skimming ect following the head gasket or even worse a failure of the timing belt ,But that wouldn't be worth pursuing ,unless a known good SH replacement head complete with valves can be sourced for a reasonable fee,

Well assuming that i located the correct temp sensor i could replace this , but how do i know that it's faulty , as when unplugged the mil comes on and stays lit, doesn't that indicate that it's working , of course it may be working but not correctly , possibly damaged by the old alternator over charging, but would that cause the run on? any way to test the sensor ?

[Cavalier342]

It's cheap enough to eliminate mate, I'd just go ahead and replace it. Had to replace them on both my C18NZ and C25XE, simple enough to do. If you haven't got a deep reach socket bit, a pair of mole grips would suffice.

[tom50]

I will replace it,Is it better to get a genuine vaux one or will a OE one do which should be available from most motor factors ? Been scrutinising this run on a bit more, and it does appear that as the temp rises the engine starts to run on slightly, add that to how a temp sensor works ie the resistance gets lower the hotter the temp, i think /hope this cheap easy to swap sensor is the culprit,

And for a few days now no MIL when driving, but it has gone days/ weeks without illuminating before now in the past year, maybe longer than that, but the ways it affects normal driving do appear to be getting more cause for concern , I'm starting to think of having both crank and can sensors replaced instead of trying to diagnose it further at most it would probably cost me £50-£75 labour and whatever the sensors cost me , or i could just let the garage supply them, then if it won't go the onus is on them to sort it,

[tom50]

After going out for a decent run in the car motorway speeds of course, engine warm/normal running temp which is anywhere from just above the blue to half way,( but just above the blue band on gauge) after one or 2 engine stalls at traffic lights, the idle speed increased to around 1200-1300rpm, sometimes it would remain at that same speed or it would reduce slowly till the normal 750-800rpm, then just die, (no run on) also again no MIL throttle position sensor ?

[tom50]

Just got off the phone from the vauxhall dealers, they want nearly £100 for a crank sensor, as they have to order them as no longer stockedm I ain't going to pay that for a £30 sensor

[Cavalier342]

Sounds about right...

[tom50]

Well i can confirm that replacing the Ecu temp sensor( genuine vauxhall part ) hasn't stopped the running on, but it may have made a difference to the idling (engine suddenly cutting out) issue, but a bit too early to be sure, the mil came on today (prior to swapping temp sensor using a 21mm deep socket ) but without the usual dip in power or it stalling if left to idle, the only noticeable effect was a lack of power when pulling off from a standing start, it felt/sounded like it was misfiring as you gave it gas the light remained on, until i stopped to change the temp sensor, so around 5mins

[sribobby]

Hows it revving now? Is it going past 4500rpm? I got a genuine crank sensor for £35. Wouldn't be getting one from Vauxhall

[tom50]

When the mil came on yesterday, it didn't appear to be limited to 4500rpm, but it has done this before, sometimes it will limit the rpm other times it doesn't as weird as that sounds ? i think hopefully i can get a crank sensor for £45.00 approx,(Siemens ) according to the sales person i spoke to is only one listed for my car, but they differ in the "number of lugs", on the plug i assume? if the cable that runs over the cam cover from the front of the engine to underneath the air filter pipe to the MAF sensor is the crank sensor cable it has it's white shielding exposed as some of the black pvc casing has cracked and fallen off (which maybe the underlying cause)

[sribobby]

Yip siemens is good. If the wire is exposed it will play up in the rain with water splashing round it. As said earlier lambda sensors cause poor running/idling aswell and don't always give the rite code

[sribobby]

Should be a 3 pin plug for the crankshaft. think omega and calibra r compatible.

[tom50]

changing the Lambda sensor,would be a lovely job on an old cavalier not,I doubt anyone would want to be replacing front pipes knowing that it's very likely that several of the studs will snap even with some heat applied , and require drilling out been there and done that before,

[ilovedmymantas]

I've had similar symptoms on my last ecotec and the intermittent problem turned out to be the lambda sensor.
This is a very easy fix. Jack the car at o/s/f, this gives underneath access to the sensor. Cut the wire at sensor, this lets you get a deep socket on to break the 'heat' weld with as much leverage as you need to ease it undone. feed new sensor down from engine bay, tighten with open spanner( shifter if you have to), attach plug, job done. Nothing else needs to be touched
iirc paperclip test showed lambda/voltage high.
Would be worth doing paperclip test for a 'second opinion'- may not be as detailed but you'll get your info from 'the horses mouth' rather than from a second set of software

[tom50]

I had visions of the old one,not coming out without damaging/striping the threads , then having to mess about changing the front pipe and associated grief freeing off /snapping exhaust studs that hold it to the manifold, i could try the paper clip test, there is only one code stored so far i assume, Did your problems include the engine running on once it was running at normal temps ?

[ilovedmymantas]

I had visions of the old one,not coming out without damaging/striping the threads , then having to mess about changing the front pipe and associated grief freeing off /snapping exhaust studs that hold it to the manifold, i could try the paper clip test, there is only one code stored so far i assume, Did your problems include the engine running on once it was running at normal temps ?

Although I did have it running on at one point the problem with the lambda gave me too lean a mix. Around the same time I replaced the icv ( a £20 pattern one is fine). This was causing me to cut out at junctions & turns, rough idle etc. I always have a spare icv cleaned & ready to bolt on, usually swapping somewhere between 8-10 months when needed.
I noticed the sheathing on the crank sensor was cracked & broken away. I cut a 10" bit of hose, split it along its length, filled with blue hylomar and slid it down the sheath. All good in the final 3 yrs I had that car
may be icv but I suspect lambda. I tried several places to get one. The ones you wire yourself aren't suitable, I think the cheapest I could get was around £60 but as soon as it was changed, no more limp-home mode. icv was next
Hope you get sorted soon, ecotec's a good engine despite what you may hear

[tom50]

Just an update, Sometime after running the car as it was, the Head gasket failed, water in the oil , after it losing small amounts of water over time without any obvious clues as to why i thought water pump or thermostat housing,ect,
Fortunately, i caught it straight away in the winter, so no overheating and warping the head, So the head gasket replaced, and the water pump and timing belt kit fitted, icv and throttle body stripped & cleaned whilst head was off ,
At first no EML at all, idling fixed no longer cut out, but after a short journey i did loose all power (no throttle) until i pushed the pedal down hard a few times, then normal service resumed, my thoughts where TPS?
Do this was only occasional, hasn't happened in the past 6 months or so, the run on the issue is there but not all the time only when the engine is warming up but not hot, the EML has recently started illuminating within the 1st min of starting the engine and it stays on, with reduced power, unless it revs it and quickly turn the ignition off and on again, the EML doesn't or hasn't come on whilst driving, like it did before, so i guess it's back on the code reader, hopefully, this time it will provide the correct diagnosis either that or put up with it
Oh, and under 12mths ago it passed the emissions test with flying colours , though if this has any significance or not i don't know, and whilst i was pricing up a front pipe i found that the lambda sensor had been replaced in 2008, a year before i bought the car

[Robsey]

Apologies if I am telling you what you know already.

A point touched upon briefly was the lambda allowing the car to run lean.

If this happens, the engine should get hotter than intended.
This extra heat can cause running on or dieseling.

The way to look for a hot ignition is the condition of the plug electrodes.

Plugs that are too hot can look whitened, scaley deposits or melted electrode. Suggesting lean mixture.

Normal plugs will have cream / beige colouring from normal fuel additives.
Just right.

Black sooty plugs = too rich a mixture / fuel enrichment issue.
Sooty plugs can also cause difficult hot starting.

Black oily plugs = severe piston ring or valve guide / seal issue.

A faulty lambda could cause either the white lean electrodes or the rich black sooty electrodes.

[tom50]

Well, the M.O.T emissions test it flew through it, although that i don't think would be conclusive, the run on the issue was occurring before i had the Head gasket and timing belt kit & w/pump replaced, the spark plugs where ok back then (even though the cam cover gasket had failed and the plug recesses where full of engine oil, but EML would light randomly whilst it was being driven mainly, I'm hoping it won't be the lambda sensor, due to the cost of not only the replacement sensor but the new front pipe that it will also likely require & gaskets