Alfa 164 QV 3.0 24V ignition problems

[dev]

Dear 164 Owners,

I have a nicely and fully restored 1994 QV 3.0 24V. I love this car. I had been using it for some a weeks when symptoms started.

Strong engine noise, pulsating exhaust gas, frequent stall on warm idle

I realized there is no ignition in at least one cylinder on the front cylinder bank (spark plug covered by fuel). I swapped ignition coils with a working cylinder but nothing was changed. Ignition coils are ok. Spark plugs were all new.

After some days the situation was getting worse: the engine did not start. I have checked several potential problems (injectors, fuel pump, fuel pump relay, fuse, fuel pressure regulator, temperature sensor, camshaft angle sensor, idle motor, air flow sensor), but I found all of them ok.

Then I suspected the Motronic ECU. Maybe some defective ignition amplifiers are the sources of the problems or some broken connection. before disassembling the ECU I took try with the diagnostic tool. I connected 12V and a ground to the cable as needed and the surprise arrived: the engine started (but still rough noise idle) . Finally it was clear there were some grounding problems. Without the ground-connected diag. cable the engine couldn't start. Diagnosis: Motroinc has no proper ground.

After some further research I realized that some ground points on the chassis were painted (the car is fully repainted) and weren’t cleaned before connecting ground wires during the assembly. I measured 2-5 Ohm connections which is terrible. I cleaned all the ground points of the paint and reassembled. In this way the Motronic had got proper ground, the engine started but the ignition problems remained and the sound of the engine indicated that more than 1 cylinder fell out (maybe 2-3). It couldn’t start each time.

I disassembled the Motronic ECU looking for broken soldering on the connector or overheated ICs but it seemed to be perfect.

I continued the research with the wiring. Each ignition coil has a 3-pole connector with the following wires: 1 ignition trigger signal, 2 ground, 3 12V. The ignition trigger signal is generated by the Motronic ECU which defines the timing of the ignition on the secondary side of the coil (spark plus).
And this is the most interesting part: I checked the 3 front cylinders and none of them has a trigger signal connection towards the Motronic cable harness. I can’t find the wires on the other end (motronic) of cable harness (I searched them by measurement). The question: is there something between these wires and motronic (relay, fuse? but I really don’t think so) or is it possible that all these wires are torn?
I checked the cable harness along almost all its length and I couldn’t find any damages on it.

Any meaningful help or idea would be greatly appreciated.

[KY2006]

My guess is that one or both of your ignition modules ( Parts No. 60562702) located in the engine bay close to radiator and the air box) are failing. This happened to my QV24 once - one cylinder failed to fire up; swapped the ignition modules and the bad cylinder then moved to another cylinder. Replaced both ignition modules and everything return to normal.

[AlfaWhiz]

Interesting topic, electrical gremlins will be more and more common in our cars after all those years.

Not sure if you have the ignition modules integrated in the ECU or as separate units by the radiator, in such case worth checking.

From what I can tell, in my Q4 wiring was toast to the injectors and coils right above the cylinders. In the area where the wiring goes under the cover of front cylinder bank, insulation was deteriorated and shorting. This was not visible from the outside, just after looking closely at the wiring. Perhaps this will be worth to check.

Hope you will find the root cause soon, fingers crossed!

[dev]

Thank you for the tips. I've already replaced both 0 203 100 227 ignition amplifier modules (beside the air filter box) with used, but the same Bosch modules. Unfortunately no changes. At least 3 cylinders are off.

The only remaining failure source is the engine control unit (0 261 200 663, Motronic M1.7) itself, more precisely the low power iginition amplifier stages in it. Affected pins: 23,24,25,50,51,52

[alfascozia]

Hi There

I have a similar if not the same problem ... wondering if you managed to cure it in the end and importantly what was the cause ?

Thanks