MG EFi running problems

[Ricky]

Hi all,

Lastnight I ventured out to pick up my latest "present" (as Mum put it!) from the scrapyard she goes to on her travels, which just happened to be a pretty tidy Targa Red '86 EFi, complete with cheese graters. However, whilst the body is in excellent order needing only a good polish, the engine and electrics are, well, knackered! It broke down on the way home on the motorway, which is why I'm writing now, as the AA man has fitted a new rotor arm which he thinks has cured it but I know differently!

It seems fine when cold, when it actually gets going! It takes a good few attempts to start it, where it just coughs and splutters, and eventually springs into life. It then idles as if it is cold pretty normally, around the 1500-2000 mark. When it warms up is when the problems begin - the idle becomes lumpy, it has an obvious misfire until about 2-2500 rpm and sometimes it will just carry on misifring all the time. On the motorway lastnight it actually stopped - it hasn't pulled that trick since.

I fear it would be simple, if things were standard. However to supplement the Lucas "Prince of Darkness" (thank you Clarkson) electrics, there is something far more hideous..... 80's immobiliser circuitry! It has a relay attacthed to the negative side of the battery, which kills the power to the whole car when switched, as well as an ominous white box that lives on the bulkhead - I have no idea what it does.....! Also, it has what appears to be the Crankshaft position sensor hanging loose in the engine bay just above the gearbox, and it looks wired in, but I have been told that the car would not run at all if this were the case??

All in all, if anyone knows where to start, I'd be most grateful!

TIA,

Ricky.

[tony]

Hi all,



It seems fine when cold, when it actually gets going! It takes a good few attempts to start it, where it just coughs and splutters, and eventually springs into life. It then idles as if it is cold pretty normally, around the 1500-2000 mark. When it warms up is when the problems begin - the idle becomes lumpy, it has an obvious misfire until about 2-2500 rpm and sometimes it will just carry on misifring all the time. On the motorway lastnight it actually stopped - it hasn't pulled that trick since.


to start with a full sevice and a change of the plug leads will be a good start
the crank angle sensor may need taking out and cleaning , a change of the temp sensor would be a very good bet too , make sure you get the right one tho there is two fitted one for the ecu and one for temp gauge

I fear it would be simple, if things were standard. However to supplement the Lucas "Prince of Darkness" (thank you Clarkson) electrics, there is something far more hideous..... 80's immobiliser circuitry! It has a relay attacthed to the negative side of the battery, which kills the power to the whole car when switched, as well as an ominous white box that lives on the bulkhead - I have no idea what it does.....! Also, it has what appears to be the Crankshaft position sensor hanging loose in the engine bay just above the gearbox, and it looks wired in, but I have been told that the car would not run at all if this were the case??

if your not sure about the immobiliser thats fitted and you think its giving you problems , the best thing to do is strip it out and fit a new one that you know how it works, mostly tho its will be a bad connection somewhere , thats the 1st place to try ,
the c.a.s may be flopping about but if the car is a runner it must be connected. theres a clip/bracket near the speedo cable/sensor. that will be missing , not a big job to replace it , but its realy fiddley

All in all, if anyone knows where to start, I'd be most grateful!

TIA,

Ricky.

[Dave]

1. Strip out that alarm..
2. Get that crank shaft sensor fitted properly...
3. Swap the temperature sender fitted in the coolant elbow - one from a K, M or T series engine will do. In fact, i've got a spare one you can have when I come for the tow bar.

Dave

[Ricky]

A bit more digging has revealed a few more things.....

1) It does actually have a crank sensor in the correct location, the one that looks wired in actually isn't, it is just flopping around on a bracket mounted to the gearbox.

2) The temp. gauge does function, I thought that if it was a temp. sensor problem then I would have no reading or an intermittent one, it usually sits just under halfway when warm. However, I have a sneaking suspicion that there is a couple of spare ones in the boot, it seems that you wouldn't be the first one to suspect it.....!

3) I am beginning to suspect the coil, as I cannot find any mention in the Haynes manual of either the Maestro or Montego having a Ducellier coil fitted, it always seems to be either Lucas or Bosch. I thought Ducellier was a make confined to the French cars.....? Not only that, but the coil has changed location in my engine bay, not living on the bulkhead but on the suspension turret, almost under the air ducting....? Where I think my coil should live, there is the aforementioned ominous white box.....!

Oh, and Dave, re the towbar, name your day and either I'll take it off for you and you can come into work and pick it up off of me, or in the unlikely event I'm actually off then you can come over and study the state that is currently my own personal Austin-Rover dealership! :laugh:

Ricky.

[Dave]

Hi Ricky,

The coil sounds like its in the correct place, way down under the air ducting just above the gearbox... The exact spec of the coil shouldn't matter too much, if it looks about the right size I wouldn't worry - though it could still be knackered! Get a beefy one from a Rover 800 or similar.

Dave

[G Force]

3) I am beginning to suspect the coil, as I cannot find any mention in the Haynes manual of either the Maestro or Montego having a Ducellier coil fitted, it always seems to be either Lucas or Bosch. I thought Ducellier was a make confined to the French carsRicky.

Hi it is not unusual to see a Ducellier coil, but it is important to have the correct type of coil. An easy way to check is measure the resistance of the primary windings, disconnect all the wires on the coil and with the meter measure the resistance between the two low tension + & - terminals the resistance should be between 0.85 - 0.95 of an ohm if it is a constant energy / programmed ignition coil.

As for the misfire have you considered the usual suspects like the HT leads, the crank sensor has to be in place and connected otherwise it would not start at all. Recheck the wires you found and check the connecter plug is clean dry and secure.

Is the petrol ok if it has been stood a while?

Cheers Gary :)

[Ricky]

Well, my incessant fiddling and farting (with the engine!) has thrown up yet another anomaly: if I disconnect the vacuum from the back of the fuel pressure regulator, and plug it so that no vacuum can escape from the inlet manifold, the running of the car when hot improves so much it is almost normal! I took it up the road earlier, and it only misfired the once - what could possibly be causing this? I did fiddle with the coil, and also a suspect HT lead, but neither made much of a difference...

My (wildly innaccurate!) finger of suspicion is now pointing at either the fuel temp switch or the pressure regulator, both of which are fortunately easily replaceable, or is it a simple case of tweaking a screw to calm the mixture down a bit?

Many thanks for your help so far, this has really been stressing me out, I thought I might have to admit defeat and scrap this one! :horror:

Ricky.

[tony]

My (wildly innaccurate!) finger of suspicion is now pointing at either the fuel temp switch or the pressure regulator, both of which are fortunately easily replaceable, or is it a simple case of tweaking a screw to calm the mixture down a bit?

Ricky.

The fuel temp switch only operates if the fuel is 90c or hotter, normally its contacts remain open

The pressure regulator keeps the system pressurized and only lets excess fuel back to the tank. Replace it but don’t tweak it unless you have a pressure gauge connected up

[G Force]

Hi, disconnecting and plugging the pipe to the fuel pressure regulator has the affect of richening the mixture on idle & light throttle, but not wider throttle openings. This could suggest that the injectors need cleaning.

I would still fit new ht leads as they are not too expensive and cause many probs if faulty.

Cheers Gary :)

[Fast Guy]

Take your crank position sensor out and try looking at the wires themselves where they go into the back of the plug. I had a running problem for years with my monty turbo which turned out to be these 2 wires. One was broken the other had 1 strand intact, so they were obviously makeing and breaking the ignition circuit every so often and causing a hell of a misfire, even complete cutting out sometimes.
I found it by grabbing the wiring loom and moving it about when the engine was running ok. It eventually started running rough the nearer I got to this sensor on the loom,

[Ricky]

Well, having thought I was getting somewhere with the fuel pressure regulator, it then decided to pull its stopping trick on me about 50 yards from home, it coughed and spluttered more than usual and then wouldn't run on any more than two cylinders at most..... it hasn't started since! Admittedly partially due to the flat battery, which was me trying to start it when temporarily deceased, but it doesn't even seem to have any sign of life at all..... no coughing, no spluttering, nothing! The AA man changed the rotor arm on the motorway, which made it go again then, surely it doesn't need another rotor arm already? Where else should I be looking?

Thanks,

Ricky.

[E_T_V]

What do the spark plugs look like? They can tell you a fair amount about the running of your engine.

Here are a couple of examples and in brackets the things I'd be thinking about looking at.

If they are oily then you have a big bill coming
If they are white/glazed then it isn't getting enough fuel (fuel filter, fuel pump or fuel pressure regulator?)
If they are black then it is gettting too much fuel (ECU temperature sensor or fuel pressure regulator)
If they are sort of a brownish grey then everything seems to be fine in there
If they are wet with petrol then you have a HT or ignition timing problem (HT leads or crank sensor)

[Beaker]

I see you have't sorted your engine probs out from the classfieds :sad:

[Fast Guy]

1) It does actually have a crank sensor in the correct location, the one that looks wired in actually isn't, it is just flopping around on a bracket mounted to the gearbox.

Ricky.

It sounds like it's previously suffered from the same fault my montego did and I would check for it again just to be safe. Pull back the cover and check the wires going from the harness into the back of the crank sensor plug. They can break and when the engine is running they can disrupt the signal to the ecu. If you can get hold of a decent plug chop, the one (two) off the car and replace it.

[e692wtt]

This happened on my Monty 1.6, the wires came out of the plug to the crank Sensor. The connection is now made with 4 block connectors and 2 pieces of wire and it works fine (just needs checking regularly as any faults here cause very odd running indeed, or the car just stops dead).

Hint: if you connect the wires wrong the engine won't start, so it's easy to sort out.

Thing is, the wiring to the harness seemes to be shielded so you've got to cut the shielding back (not fun, it's copper mesh) to get enough wire to make the connections.

Got my monty back on the road in '99 though. :) Got to be worth a try?