1995 2.0 16V Cav MIL and causes

[tom50]

Hi, i have i think more than one problem with this car and it's doing my nut in not being able to find the cause and repair it, The MIL (amber engine lamp) will come on whilst driving , i can be on a motorway doing 70+mph and suddenly it will come on, there is usually a loss of power just prior to the lamp illuminating , or i can be at a road junction start to set off and engine dies and then doesn't want to start again , a mate who has a garage put it on his solus plus diagnostic scanner, it on the first occasion gave a low voltage fault to the MAF but now produces a crank sensor ,incorrect rpm fault code

But whatever the underlying cause is i think it's getting worse

The second issue i have only appeared after i had a replacement alternator fitted , since then the engine will sometimes try to keep running after i switch off the ignition it only does this when the engine is warm/hot so after a run out, sometimes after it does this it wont start, starter turns but it doesn't attempt to fire my thoughts are a faulty ignition switch , either that or the old alt did some damage before it was changed as it started over charging lights would go really bright when revs increased, and it blew the battery lamp in the dash

If anyone can help it would be appreciated

[thegriffin]

Did you have an engine fault before the alternator was
changed ?

[tom50]

Yes the engine fault (MIL) was happening before the old alternator decided to start overcharging i have in the past tried a replacement MAF unit, but after a short time it made things worse of failed, it was a cheap one off ebay, so not a genuine vauxhall part , there have been periods of time when the engine has idled and run under load without a hiccup,

[Robsey]

The obvious question, is -

Have you tried flashing up the codes using the famous paper clip test?

If the MIL / EML lights up for more than four or five seconds, then a code should be stored.

[tom50]

Not tried the paperclip test no, because got a mate who is a mechanic to plug his snap on Solus plus scan tool in to it and see what fault codes it had stored and famous crank sensor RPM signal (crankshaft sensor) Incorrect signal & Air Flow Sensor (AFS)Low voltage was all it had stored after iirc over a week of running, and around 300miles travelled

But currently i am disconnecting the battery as i ain't using it everyday, and the battery maybe on it's way out, as it seems unable to cope with the parasitic drain and cold temps, the parasitic drain i measured to be around 300ma but not sure if that included the alarm /immobiliser as the multimeter was inline between the earth of battery and earth lead, I didn't want to blow the fuse in the multimeter when locking the door, i may have to do it again with the central locking disabled (fuse pulled )

[thegriffin]

It's funny you say the battery is suspect because I
was to suggest you change it for a known good one.
If faulty they can intermittently go open circuit leading
to high voltages.
Also check the connections and the earthing .
I'd only buy OEM sensors as I've had problems with
pattern ones before.
Otherwise I'd get the boffins to do a proper diagnostic
before changing any more sensors.

[tom50]

The car has been running on the original MAF sensor since i changed it back, could it be the idle control valve,blocked breather? as it does sometimes cut out when idling usually only after the engine is at normal temps, and is sometimes slow to return to normal 750-800rpm

My problem is my mate is nearly always busy, and obviously doesn't want to spend time on my old banger for mates rates, i was debating on cleaning or replacing the idle control valve and the bit it attaches to, things like this are a pain in a** to pinpoint and the isn't no sense buying parts that aren't needed , the proper airflow sensor (Siemens branded ) is around £80.00 i wouldn't want to buying one of those unless i was sure it would cure it

[planetc]

If a maf sensor is faulty they usually run better disconnected.

[thegriffin]

I wouldn't recommend cleaning the idle valve.The
last time I did that it wouldn't work at all !
Sensors are expensive that's why I suggested a proper
diagnostic.
You can buy good quality ones from Autovaux.
Why not buy a scanner ?They aren't that expensive
but you might not get a definitive answer
Sounds like your car is going into limp mode and
running rich hence poor idle/hot starting.
You haven't said if the MIL clears itself.

[tom50]

In does clear it's self some times , but some times like when in traffic i will dip the clutch switch of the ignition until engine stops, then back on again & clutch out engine runs ok until the mil comes on again, although only yesterday the engine nearly failed to restart again, i have also noticed yesterday that the exhaust gases smelt like rotten eggs , (mil ) on, restarted engine normal smell again
As for buying a scanner , like you say along with my mate who has already scanned it, the codes don't always point you in the right direction

When the mil comes on sometimes it runs ok but other times it runs rough missing when i accelerate, and also limits the rpm to around 4000rpm So driving it at the moment isn't a good experience, closely guarding the throttle with my right foot when at lights or give-ways, and of course when you get behind the 20mph dawdler who is oblivious to everything around them

So far i have avoided taking the car to a vaux dealer as i doubt they would be able to correctly pinpoint the underlying causes, but then there is the costs involved, the car isn't worth spending lots of money on at the end of the day

[thegriffin]

It's curious that the light doesn't come on and stay on.
The smelly exhaust is usually caused by sulphur in the
fuel burning off the cat but modern fuels are low
sulphur .
I'd check your exhaust isn't blocked to eliminate that.
It happened to me last year when all the wadding
decided to block the tailpipe .
Spending on an old car is always a problem .

[tom50]

Exhaust middle and rear silencers are less than 12mths old and don't appear blocked plenty of gases coming out whilst driving /idle (I have also had the rear silencer spit out it's wadding in the past ) but this in my case didn't block the exhaust .it just got louder and louder as the tailpipe parted company with the silencer too on the motorway most probably

The mil did stay on yesterday , but as it was running like a bag of excrement , i dipped the clutch and turned ignition off briefly after it came on, so i had normal driving power ect,
Today the mil hasn't come on whilst driving around, i have also replaced the battery , but in testing i let the engine idle for a while it cut out once only in 15mins (no mil) prior to this, it started ok,

I let it Idle some more until temp was quarter of the way up from the cold section, switched off ignition key removed in my hand away from ignition, engine continued to run on in a rough fashion,pinking and spluttering during this time i observed the radio still had power and was showing the radio stn,
only once whilst it continued to run on did it display "code" indicating it had briefly lost power , finally after around 15-20seconds maybe a little longer ,it stopped radio off too, tried to start it straight away, starter winding over fast but no attempt to start, i depressed the throttle as it did this i could hear it popping like misfiring but it still made no real attempt to start

[sribobby]

The 4500 rpm limit and popping noise is nearly always crank shaft sensor, although it could be camshaft sensor or the wiring to it aswell. Mine seems to play up the hotter the engine gets. Don't buy cheap crankshaft sensors, I tried 3 and car wouldn't even start!

[tom50]

Another thing that i've found when the engine starts it's run on nonsense if i drop the clutch and stick in cog with handbrake on thus stopping the engine rotating, it starts off the key, where as if i allow it to do it's own thing it fails to start, until i disconnect the battery or wait say 30mins (or possibly the locking of doors and arming the alarm system ) whilst i go and have a brew ect ? i still think ignition switch on the run on problem,as i cant see how else it's getting power from the battery /alt ?

As for the crank sensor, i was planning getting one from vauxhall dealer, as i don't think they are that expensive

[thegriffin]

It seems your car runs ok until it warms up.
Bearing in mind they are now 20years old if it
were my car I'd change both the cam & crank
sensors for peace of mind & to eliminate them.
I've bought them & oxygen sensors from Autovaux
for my Vectra & have found them good quality & value.
You might also consider the water temp sensor too
if it's separate from the gauge.
Let us know how you get on.

[tom50]

I was talking with a mechanic in the pub about the run on, and said that i thought it was down to the ignition switch, he wasn't convinced he said if it was the switch it would run on every time, not only once the engine is upto normal operating temp, he asked if it was overheating ,

I explained that if i leave it to idle the temp will reach the quarter or half way mark and then the fan will cut in, it cools then stops again
So still no further along on that front, unless the sensors are the culprit of the run on as well as the stalling and mil coming on,

But i guess it's a case of process of elimination , Just one thing could there be something wrong with the alternator that could be causing this run on , although everyone i have asked doesn't think that could be the cause, is it a possibility ?

[thegriffin]

Can't see how an alternator can cause an engine to run
on.
It's usually caused by fuel in a hot combustion chamber
and the engine "dieselling " without a spark.This is
unusual with fuel injection but maybe because your
car is in "limp home " mode and running rich.

[planetc]

Beginning to wonder about the possibility of a sticking injector? It's certainly rather an odd set of symptoms

[Robsey]

Dieselling (running on) would indicate a hot engine...

Hmm - sticking injector - it would have to be stuck in a position within it's travel to allow just enough fuel to flow without racing the engine.

Difficult hot starting reminds me of running far too rich resulting in heavy soot deposits on the plugs.
I had this many years ago...
I was convinced it was the MAF sensor, but it turned out to be the oxygen sensor, even though I did not get the expected code -
I was getting code 15 (MAF I think), whereas I would have expected code 13.

By the way, I have had a code 13 many years earlier, and this usually only set the EML when gassing over 60 mph on the motorway, and would usually go off again within 30 seconds.
Probably sluggish switching action between rich and lean and back again.

My money is on the Oxygen / Lambda sensor...

[Robsey]

Regarding temperature sensor..
There are usually two.
One on the back of the engine near to the alternator for the engine ecu.
connector is a blue rectangular item.

One on the thermostat housing (front of the engine) for the gauge.
Connector is a female spade / Lucar connector.

It is the one at the back that would affect engine running...

[sribobby]

When I fitted a cheap crankshaft sensor in my ecotec it used to keep turning over afteri switched ignition off. It would never start though, just popped and banged a bit

[thegriffin]

If the ECU temp sensor is on the back of the engine
you definitely want to check that and the wiring as you
have changed the alternator.

[tom50]

ECU temp sensor ? never heard of it, where is it located and what does it look like, BTW i didn't replace the alt personally,

[Cavalier342]

On the 8 valvers, I believe it's the blue plug sensor which is located between the thermostat housing and the alternator. That's the one that tells the engine ECU the temperature so that it adjusts the fuel mixture accordingly.

[tom50]

Ok, mine is a 16V ecotec , and i think the ECU is located inside the vehicle , looking a pictures of alternators there i think is only two connections on them ,