tzi ignition fault

[velosolex50]

1990 1.9 Tzi, motronic 3.1, no cat
Couple of weeks ago, had a brief misfire that cleared after a few seconds. Felt like 2 cyls.
Just coming home earlier today, suddenly went onto 2 cylinders & has stayed that way (still enough go to get up the hill fortunately). Investigation at home shows sparkless cylinders 2&3. Tested the double coil, its fine on both parts. So, the big question, is it the ignition module (£80 odd from Citroen) or the main motronic ECU (GOK how much)? I tried a module saved from my old 19trs, but it was different & didn't work at all. Reluctant to shell out for a new module in case its something else.........Anyone got any suggestions eg how to test the module, or measure ECU output etc?
Any assistance gratefully received!
Huw

[Jaba]

It could be the HT coil, the ignition module, the wiring between these items and to the ECU, which could also conceivably be faulty. Check the pins inside all the connectors for damage as well.
If you could somehow reverse the connections to or from the ig/module and then see if plugs 1 + 4 are dead this would rule out the HT coil.

The HT coil can measure out ok but leak HT to earth in use. It is usually the ignition module I have to say. Time to get your digital meter out and have look at the circuits for the two sides of the module by comparing the readings while the engine is running.

[velosolex50]

I've checked that both sides of the coil give a spark when energised using jumper leads. I don't know how to check if the loss of pulse for 2&3 is from the ecu or the module. Connections all seem ok. On a slightly brighter note, Vehicle Electrics Online has good prices for modules, 12 quid for most BXs, 27 for mine, of course...

[Geoffrey Gould]

Hello have had the same thing running on 2 all of a sudden for a short time and then OK for a couple of days, then running on 2 all the time, it was the coil. I have been informed by someone in the know that coil failure is not at all unknown, really when you consider where it is mounted then it is no great wonder really. Heat,vibration are killers. Cured on another Citroen by mounting the coil on the bulkhead.
Cheers.
Geoff.

[velosolex50]

Hmmm, Interesting. Come to think of it there has been some high rpm roughness for a long time which may or may not be coil related. Still, I got a spark both sides on test, but it then still only ran on 2.
Not been a good couple of weeks for the car, the ABS light is now on most of the time, the steering rack needs a new end joint, the starter circuitry is playing up (serious on an auto)& 2 days ago the drivers door window fell out of its mechanism! Perhaps it's trying to tell me something. A shame it's getting creaky, it is such a lovely car. Perhaps someone can sell me a low mileage/rust free/auto/aircon/estate to replace it.......but probably not I suspect. Thanks for your thoughts so far.
Huw

[Geoffrey Gould]

Hi as a small add-on I have just had a thought, what was the spark like, fat , blue and with a real crack because anything less is suspect. The spark may have enough umph in the open air with no compression to deal with but can be extinguished when faced with firing under compression. Been there,done that and have been caught out before.
Have a look.
More thoughts to follow may be.
Cheers.
Geoff.

[Geoffrey Gould]

Hi said I might be back, I had a coil lurking and have found it. It's a Bosch with the following numbers on the side.
BAE. 04.
0 - 221 - 503 - 422.


The HT coil connections, looking at the coil from the end with the 4 pin socket are marked.

top left 14.
top right 32.
bottom left 41.
bottom right 23.

measurement in K ohms.( K = thousand.)

32 to 23 = 13.25K
14 to 41 = 13.23K.

4 pin socket marked 1 2 3 4. small numbers inside socket.
1 - 2 = 1.0 ohm.
1 - 3 = 0.5 ohm.
1 - 4 = 0.5 ohm.

I hope this may be of some help.

Cheers.
Geoff.

[Geoffrey Gould]

Hi back again. I have re read this a couple of times, would you be kind enough to clarify something for me please, it could be me being pedantic, I think that's the word.
I have tested the coil and have a spark at both ends. well there are Two Coils thus 4 ends and that means 4 sparks, see where I am going? 1 coil down 2 cylinders missing.
I will go and get my coat. White for the use of.
Cheers.
Geoff.

[velosolex50]

Vile weather out there, so car is staying dead for a while. To clarify, the coil is a double arrangement, each half firing two plugs simultaneously, i.e wasted spark. I checked that each half gave a spark when energised directly from the battery & momentarily earthed---but admittedly I only looked for one spark from each. They did look symmetrical though, unlike when fired by the ignition system when there was no spark from one half. Itching to get out there & get it sorted, but don't want to get blown into the sea! Will keep you posted.
Huw

[Geoffrey Gould]

OK I think I can see where you are coming from. I know about the wasted spark principle, each coil, of which there are two coils, ( completely separate from each other.) has a plug at either end thus each coil has to provide 2 simultaneous sparks.
I was wondering if one of the coils had gone down and could not provide 2 'simultaneous' sparks , not just one spark at one end.
The old way I used to use was to put something like a panel pin in the end of each lead and slide each lead into about 2" of clear plastic tube. 4 short lengths of HT cable each with a pin also in one end, slid into each end of the clear plastic tube thus forming a visible spark gap. The remaining ends of the short pieces of HT lead goes to the plugs of course.
Gets interesting when you have proven that there are 4 sparks and it still runs on 2. Head gasket blown in between two adjacent cylinders. Sorry you didn't want to hear that I am sure.
I hope the weather clears up for you soon.
Cheers.
Geoff.

[velosolex50]

1.7 td AUTO I see.....very interesting. Is it good? I converted a 1.9 tgd to auto a few years ago, and it was a bit too slow for comfort in modern traffic. Also wrecked the economy, down to 40 or less. I have often wondered why the TDs never got the official auto option when they would presumably have been a bit quicker. After all, the same box handles the GTi power without any trouble. My wife has a zx1.9 diesel auto, and that seems even slower than my conversion was.......but as we don't have huge high speed roundabouts or dual carriageways here it's just about ok. Nice car if you are patient, managed to overtake a cyclist today!
Regards
Huw

[docchevron]

I'd plump with the coil aswell, sounds fairly typical of intermittant coil failure.

The TD was never offered with an autobox because the box wasn't strong enough to take the torque of the turbo lump. A standard box with a turbo engine strapped to it lasts, er, not long.
In the test case here it lasted 199 miles IIRC.
The box in dads (Geoffs) car was built for purpose, cost alot of money and is a fricking hoot. It's one of a very few number of auto cars I've driven that I really like.

[mat_fenwick]

The car in question was also subject to an arsonist attack and subsequent rebuild, Chris is probabaly too modest to say what a good job he did but you can judge for yourself here.

[Way2go]

The box in dads (Geoffs) car was built for purpose, cost alot of money and is a fricking hoot.

Did you manage to improve the 3rd to 4th change up point too?

[velosolex50]

I was going to ask the same thing..........4th from 30 up would be v useful.