A small development in my Monaro misery

A small development in my Monaro misery

Author
Discussion

AndiD

Original Poster:

147 posts

166 months

Thursday 27th May 2010
quotequote all
Any mechanically or technically minded people please please please rack your brains to see if you can think of anything that would cause this.

I know I’ve been moaning about my Monaro stalling/cutting out all the time – so far with no luck from Vauxhall or independent garages. (Sorry to keep going on about it!)

However, through trial and error I’ve finally noticed it’s a lot worse when the car/engine bay is hot. When it was really sunny the other day it was doing it all day, then last night I had it sat idling on the drive getting really warm and it did it 4 times in a row.

Essentially – my question is this..

What would cause the immobilser to cut off the fuel when the car/engine bay got hot?

If it's a dodgy wire/connector - where should I be looking? Tried some general poking and wiggling of most of the connectors in the bay.

(btw there’s no hi temp warnings or anything – it’s just normal hot v8 engine temp that’s making it worse) The only fault codes are P1632 NP: IMMOBILSER FUEL DISABLE SIGNAL RECEIVE so what (with the addition of heat) could be causing it.

ANY ideas are very gladly received

woody vt

1,890 posts

215 months

Thursday 27th May 2010
quotequote all
Near room temperature, the electrical resistance of a typical metal increases linearly with rising temperature, while the electrical resistance of a typical semiconductor decreases with rising temperature.

So basically I'm thinking you have either a tiny short which at normal temps is unable to conduct well enough to allow the short to produce the Immob fuel signal but does when the engine bay is hot (broken component in the BCM perhaps though this is unlikely)

OR

A damaged conductor somewhere in a loom that is barely making the circuit (frayed and broken strands reducing the cross sectional area) which at low temps is able to conduct well enough for a stable circuit but at high temps (when the engine is hot) the resistance of said conductor increases causing a voltage drop and a now unstable circuit which then goes on the cause the BCM to issue the immob fuel signal.



Just a theory but makes sense to me. Had this happen recently on an aircraft I was working on. Relatively minor snag but a fault we I "chased" for some time.

AndiD

Original Poster:

147 posts

166 months

Thursday 27th May 2010
quotequote all
Another development!

Had a good long chat with Chris at Picador who's been speaking to the tech guys who had one in doing the same a few years ago.. turned out when they replaced the ECU it solved it.

I'm going have a look at it this evening and check/clean all the connections, but don't want to mess around with it too much. Has anyone removed those 3 huge connectors on the heat sink? Is it ok to pull them off and put them back?

MadMaxHSV

1,814 posts

197 months

Thursday 27th May 2010
quotequote all
AndiD said:
Another development!

Had a good long chat with Chris at Picador who's been speaking to the tech guys who had one in doing the same a few years ago.. turned out when they replaced the ECU it solved it.

I'm going have a look at it this evening and check/clean all the connections, but don't want to mess around with it too much. Has anyone removed those 3 huge connectors on the heat sink? Is it ok to pull them off and put them back?
Disconnect the battery first, but should be fine to pull and plugs and replace.

the_ferret82

25,627 posts

183 months

Thursday 27th May 2010
quotequote all
MadMaxHSV said:
AndiD said:
Another development!

Had a good long chat with Chris at Picador who's been speaking to the tech guys who had one in doing the same a few years ago.. turned out when they replaced the ECU it solved it.

I'm going have a look at it this evening and check/clean all the connections, but don't want to mess around with it too much. Has anyone removed those 3 huge connectors on the heat sink? Is it ok to pull them off and put them back?
Disconnect the battery first, but should be fine to pull and plugs and replace.
yep what he said. disconnect the battery wait times mins and then unplug check all connections for dirt / corrosion and then refit and press hard.

AndiD

Original Poster:

147 posts

166 months

Thursday 27th May 2010
quotequote all
I love you guys

the_ferret82

25,627 posts

183 months

Thursday 27th May 2010
quotequote all
AndiD said:
I love you guys smile
we hope you mean biblically wink

there is many people on here with lots of car and technical knowledge and we are always happy to help.

AndiD

Original Poster:

147 posts

166 months

Thursday 27th May 2010
quotequote all
Good clean man love obviously

Worse case scenario.. anyone know how much a new ECU use? I'm guessing a lot..

the_ferret82

25,627 posts

183 months

Thursday 27th May 2010
quotequote all
AndiD said:
Good clean man love obviously wink

Worse case scenario.. anyone know how much a new ECU use? I'm guessing a lot..
a far few quid yes.. would not like to guess how much.

you might be able to get a second hand one as long as its the right model.

do you have any mods on your car?

AndiD

Original Poster:

147 posts

166 months

Thursday 27th May 2010
quotequote all
hmm.. I suppose one from Ravers breakers might be OK as long as it's the same year and not damaged..

My only mods are a Powerflow exhaust that came on the car. (sounds good but might change for a Wortec if I hear one in the flesh and it sounds a lot better)

global-i

366 posts

215 months

Thursday 27th May 2010
quotequote all
Have you tried posting the same question on the LS1GTO.com/forums, or the LS1.com.au/forum, there are many more Monaro / GTOs over there than here.
If it is a heat related issue they may have seen it before.

AndiD

Original Poster:

147 posts

166 months

Thursday 27th May 2010
quotequote all
global-i said:
Have you tried posting the same question on the LS1GTO.com/forums, or the LS1.com.au/forum, there are many more Monaro / GTOs over there than here.
If it is a heat related issue they may have seen it before.


Good idea.. I'll give it a go.. thanks

the_ferret82

25,627 posts

183 months

Thursday 27th May 2010
quotequote all
AndiD said:
hmm.. I suppose one from Ravers breakers might be OK as long as it's the same year and not damaged..

My only mods are a Powerflow exhaust that came on the car. (sounds good but might change for a Wortec if I hear one in the flesh and it sounds a lot better)
if its had a remap you will loose this if you change the ECU

SimonV8ster

12,543 posts

227 months

Thursday 27th May 2010
quotequote all
Have you given Monkfish a ring ?

AndiD

Original Poster:

147 posts

166 months

Thursday 27th May 2010
quotequote all
SimonV8ster said:
Have you given Monkfish a ring ?


Spoke to them a few days ago and they said they'd have to have it in for a while to investigate.. but because the problem is so bad it's not ideal to drive it all the way from Leeds to MK when it's cutting out on the motorway.

I'm going to have to book it in anyway if these ideas don't sort it over the weekend. I'll get them to fit a new ECU and code it all up for me and hopefully that'll fix it.

AndiD

Original Poster:

147 posts

166 months

Friday 28th May 2010
quotequote all
Checked all the ECU connections last night and it's all like brand new so that's not the problem. Wiggled every cable I can see in the engine and that's not doing it either. I've been searching online for a list of all the LS2 sensors and where they're located but can't find anything yet. As a last ditch attempt before I just put it in the garage for a few weeks before Monkfish can fit me in, can anyone think of any sensors that could be dodgy and would get worse with heat?

2woody

919 posts

209 months

Friday 28th May 2010
quotequote all
don't rush off and buy an ECU....

Mine did exactly the same - cured by a new crank position sensor.

as the sensor ages, the internal winding resistance breaks down, causing an entirely random engine stopping, related to engine temperature. other web forums are alight with tales of pouring cold water over the sensor at which point it comes back to life. Also related is heat damage to the wiring that leads to the sensor, as it passes the exhaust manifold.

cured by a new sensor for about 30 quid as far as I remember. Mind you, it's a sod to fit as it's above the starter - mine took a good couple of hours to do.

Just to double-check. The failure mode on mine was that the vehicle would occasionally stop when driving - just cutting out, sometimes twice a day, but sometimes every other week. Once left for 20 minutes, it would come back to life and run as normal. Never happens when cold, and happens more often if the car is (ahem) excercised. Mo "mill" light illumination.


Edited by 2woody on Friday 28th May 11:25

IanLWarrington

385 posts

166 months

Friday 28th May 2010
quotequote all
Although a very different car, I had a similar symptom on my Vectra 2.6 a couple of years ago - wasn't cutting out while driving but would struggtle to start with a hot engine - was intermittent and Vauxhall weren't particularly interested, offering no suggestion - until, on one particularly hot day, it wouldn't start at all and the RAC had to get me home!

I was, as you would imagine, not happy and Vauxhall took it in to diagnose - and it turned out to be the crank sensor then - don't know how much though as it was replaced under warranty I had no more problems after that so, assuming that it is the same thing, I hope this helps you.

At the roadside I seem to recall that the RAC guy established that there was no fuel being pumped (he put it down to a faulty pump) - which is why it wouldn't start of course!

Regards

Ian

AndiD

Original Poster:

147 posts

166 months

Friday 28th May 2010
quotequote all
2woody said:
don't rush off and buy an ECU....

Mine did exactly the same - cured by a new crank position sensor.

as the sensor ages, the internal winding resistance breaks down, causing an entirely random engine stopping, related to engine temperature. other web forums are alight with tales of pouring cold water over the sensor at which point it comes back to life. Also related is heat damage to the wiring that leads to the sensor, as it passes the exhaust manifold.

cured by a new sensor for about 30 quid as far as I remember. Mind you, it's a sod to fit as it's above the starter - mine took a good couple of hours to do.

Just to double-check. The failure mode on mine was that the vehicle would occasionally stop when driving - just cutting out, sometimes twice a day, but sometimes every other week. Once left for 20 minutes, it would come back to life and run as normal. Never happens when cold, and happens more often if the car is (ahem) excercised. Mo "mill" light illumination.


Edited by 2woody on Friday 28th May 11:25


I'll have a look at that this evening.. any chance you can describe exactly where this is located, as I'm not mega-tech minded. The only thing is it always re-starts instantly - you don;t have to wait any length of time - just turn the key back and forth and it starts fine again.. if it was a dodgy sensor would I have to wait for a while before it re-started?

ringram

14,700 posts

247 months

Friday 28th May 2010
quotequote all
Does it throw a code?
Sometimes there will be codes in there without a MIL as mentioned.
Best to get it somewhere with a scan tool etc.