Help! Stalling engine

[CMF_detach8]

Hey all, its been about three weeks since I've gotten my car back from the workshop from a top overhaul. Now my engine stalls. I've not gotten to re soldering my throttle body but I did try cleaning my idle valve. The symptoms are quite weird and the old mantra goes "if it ain't broke, don't fix it" so I won't touch the TB until I can determine it's faulty.

Here's how I reproduce the stall (about 50% success rate) on my 1996 K11 (auto transmission).

1. Drive around until engine is warm. This reduces my idling to about 600rpm with gears engaged.
2. With air conditioning switched ON, drive around and come to a stop, e.g. at a traffic junction.
3. Just as the car is about to stop (engine rpm should be around 1k at this point), switch off A/C.
4. The engine rpm will quickly drop below 500rpm mark and cut off.

I've tried the ECU flash code readouts, even drove around with it. Here's the readings:

* ECU flash codes in mode 1 reads 5 long + 5 short.
* ECU in mode 2 flashes constantly with about 0.5s pause at 2krpm
* ECU in mode 2, A/C off, gears engaged (very low idle RPM) gives very quick flashes.
* ECU in mode 2, cruising gives consistent flashes. I realise it doesn't flash when accelerating (running lean i suppose?)

Some observations on my engine idle speeds
* Cold start idle rpm is approx 1k.
* Warm engine gives an idle rpm approx 750 (3/4 mark).
* With gears engaged and NO A/C gives idle rpm approx 600.
* With gears engaged + A/C gives idle rpm approx 750.

Sometimes I can feel the engine stalling. When the A/C happens to cut out at the same time I'm coming to a stop, my brake pedal will drop lower and a sudden strong braking force is felt.

My FC is also pretty bad. I'm doing approx 10/11 km/l on my K11. I am a slow driver and don't usually exceed 3k rpm on the throttle. I use Mobil 95. 98 seems to give worse FC.

Any advise is much appreciated. THis has been bugging me ever since. :-(

 

[CMF_detach8]

Just to add on... it does not always happen unless i get so unlucky the A/C cuts out at the right time, but it gets really frustrating when it happens!

I also realized the A/C thing (don't know what it is) attached on the firewall is not original nissan. Would that be a culprit?

I don't get this problem with A/C switched off.

 

[CMF_kevin]

Hi detach8,

I had this very problem. After alot of hassle i pin pointed the problem to the distributor and now it is 100%. if you replace the spark plugs, does this fix the fault for about a day and then it goes back to being the way it was? Because that is what happened to me and it worked out that the distributor was sending too much voltage to the spark plugs and they were failing to produce a good spark and sometimes not even spark. For the sake of replacing the spak plugs i would do this first and see if it fixes it for a bit, if it dos then a new distributor is needed.

Hope this Helps

 

[CMF_detach8]

Hey kevin thanks for the tip. I do notice some clicking noise when the engine hits about 3k rpm, could it be a cylinder failing to spark causing the noise? my distributor seems to have a loose piece of rubber coming off...