Help please on bad starting on xmv6si

[paulxmski]

Hi,

When I start my recently purchased 1990 xm v6si I have to place my foot on the accelerator i.e apply light pressure to get it to start otherwise it fires and dies. Then it ticks over at low revs about 800. When I press the accelerator it will not go above 2000 revs and dies back. If I try and drive it from cold it hunts or chugs as the engine dies then cuts in again. It has been suggested that this may be an HT problem, although I wonder if it might be the cold idle valve playing up.

I must point out that there is a Trafficmaster device installed the power for which is taken directly off the battery and the connector box is nylon tied to the heatsink plate of the ignition module so there might be a problem there.

When the car has thoroughly warmed up and the ignition has been switched off for a while the problem disappears until alarmingly at some random point in the journey the engine can cut out with no power at all at the accelerator pedal and then it cuts back in at low speed. This happened on the M5 and when it cut back in at about 40 mph it shot into first screaming then back up the box alarming!!
Help!!!

[noz]

paulxmski,

I don't have any experience of the V6 but I think your first diagnosis is correct. A duff idle valve or cold start valve if it has one would give the initial symptoms.

As for the random cutting out, thats another story. If it's connected to the first problem then I haven't a clue. If it's a standalone problem then any number of bad electrical comnnections could cause the problem.

Hairline cracks on the distributor cap (does it have one?) would cause this. As the engine heats up and the moisture in the cracks evaporates the problem seems to disappear. However leave it overnight and the moisture creeps back into the cracks again causing random shorts and loss of sparks. Similarly cracks in the rotor arm causes the same symptoms.

A new set of spark plugs might not be a bad idea. How are they looking? Is there a brown ring on the porecelain just where it meets the metal base?

Is the Trafficmaster a retrofit or original? If it's original it's not likely to be the problem. Even if retrofitted, It would have to be giving of a serious amount of heat to affect the ignition module which gives off heat itself.

Let me know how you get on.

Cheers

noz 8)

Hi Noz,
Thanks very much for the advice. When I examined the battery I found loose terminals. First the pos terminal was very loose. Then the neg was marginally loose and hadn't been pushed fully down the cone of the terminal. I coppereased them and put in a copper shim to give the pos terminal some grip. I have driven it since and I did not experience the sudden cut out as before although I haven't been very far so maybe deluded. I will look at the sparkplugs and distributor/rotor arm later today Sat24/01/04. Can anyone tell me where the idle valve, cold start sensor/valve are on the XM mk1 V6 12valve please? [/img]

Hi Noz,
Thanks very much for the advice. When I examined the battery I found loose terminals. First the pos terminal was very loose. Then the neg was marginally loose and hadn't been pushed fully down the cone of the terminal. I coppereased them and put in a copper shim to give the pos terminal some grip. I have driven it since and I did not experience the sudden cut out as before although I haven't been very far so maybe deluded. I will look at the sparkplugs and distributor/rotor arm later today Sat24/01/04. Can anyone tell me where the idle valve, cold start sensor/valve are on the XM mk1 V6 12valve please?

[noz]

paulxmski,

I hope the loose terminals solves your problem but I have to say it seems unlikely. If the terminals become 'disconnected' the alternator would keep all the other electrics going. Can't quite see the logic which would cause this to make the engine conk out. However, it would depend on the exact wiring scheme to determine it for sure.

As for the cold idle valve, if your engine is the ES9J4 then the 'idling regulation electrovalve' is located beside the throttle butterfly. It should have two tubes, one connecting it to either side of the butterfly and a cable.

A simple quick fix (albeit temporary) for the hairline cracks is a squirt of 'cold start'. It is a spray can of a substance which is drawn into the cracks and displaces the water. The spray is non-conductive and hence stops the sparks going astray. There's no substitute, however, for a new set of spark plugs.

Let me know how you get on.

cheers

noz 8)

[Reply from David Evans CCC Citroenian]

Can I suggest you check the distributor cap? I had very similar symptoms and it turned out to be dirt and condensation in the DC, which is at the front of the car and right behind the radiator, as I recall.

The throttle potentiometer which sends signals to the ECU should be checked.

All earth points need checking, cleaning and modifying - i.e. ring bolt terminals bolted to clean metal using existing studs.

Check ALL multi-pin connector blocks - there's lots of 'em

Best wishes.

Hi noz & David Evans,

Finally found my way back here after trawling the cookies since I hadn't bookmarked it

The cutting out does seem to have stopped since I coppereased and tightened the terminals, although I have only done two 56 mile journeys in it since. Thanks for the advice about the cold start valve, plugs and distributor. Now that the weather is improving I will be giving these a close inspection since I still haven't fixed the chugging problem.

My previous car, a V6sei was knocked out for a month until I looked in the distributor and discovered it had a pool of HLM in it, and I had been advised by the very nice AA man with the electrical tester that it was the ignition module. Incidentally I took several ignition modules that I acquired after that to a local workshop that had a testing kit (they always handed them back to me nice and warm) and each time they said "no mate it's no good!". When the car was going again I put each one in the car and they all ran with no problems whatsoever!

With regards to multi-pin connectors there is a receipt from about 1999 (which is only about 7,000 miles ago because the car was laid up in a garage for a number of years) for the connectors which are under the LHM reservoir. I believe these are pretty central to starting the car but I don't know why/how?

Since I received the car's history folder last week I have found that it has had a block treatment applied to it after having the heads done. Goodness knows what that might mean.
On the plus side virtually every component in the engine bay has been replaced and all fairly recently (within the last 5,000 miles).

I will report back with more news later.

[paulxmski]

Still can't isolate this problem. Followed everybodies advice and checked all ignition components which appear to be ok. Many components according to the history file which I received in Mar are newish like 2-4k miles. Seems to be a sensor problem but I don't know which sensor is where and perhaps more importantly their associated relays :oops: I thought it might be the a/c cutting in and causing back emf on the ecu but last weekend I eliminated this.
Last week I removed the cover in-front of the ECU box revealing four sensors. I swapped these over for the ones in my other XM (engine ok otherwise u/s). This didn't make a difference One thing that did seem to help, to some extent anyway, is that when it cut out after driving a number of miles with it running ok and then cutting down to chugging mode, unplugging these relays and plugging them back in again seems to stop the incessant cutting out. I'm not sure, but maybe it clears some condition in the ecu.
It has been suggested it may be dropping into limp home mode, but I believe you can do upto 50mph but with my problem 10 -20 is max as it wont rev above 2000 but on a hill above 1000 which prevents it moving up the gears.

(note to Russek's ed) I looked in Russek's xm book but diagrams are unlabelled so when it shows a detail drawing of a portion of the engine bay it doesn't give a clue what area you are looking at. One might expect something like the following label for a diagram about dismantling the engine: a detail view of items to be disconnected looking at the underside of the battery tray from engine topside or items to be disconnected near battery tray viewed from underneath front, but no labels therefore senseless diagram which requires a considerable amount of wasted time just to figure out something that a few words would make clear!
Still a diagram is better than nothing but definitely not a 1000 words if not accompanied by a few pointers. :evil:

[noz]

Paulxmski,

Sorry to hear you've still got problems. Whereabouts in the country are you?

I'll put my thinking cap on but it's a difficult one to diagnose remotely.

Does the problem seem related to temperature at all? ie does it happen when she's cold?

It would be worth getting a pen and paper out, logging all the resistances/voltages for all the appropriate sensors when she's cold and then when in the middle of achugging episode. It could be that a sensor checks out when cold but after running a little while develops an intermittent break.

Have you had the car plugged into the Lexia to read the fault codes? Do you have a friendly local agent that would do it for you? My local agent does it for nothing because all I want is the results, I don't ask them to fix anything. Even so, they have a standard charge of £20 for the service if you pay for it.

cheers

noz 8)