Sudden onset misfire mystery

[Laird Scooby]

Just did a search to verify the new type of injector as being 156045 and fond these on ebay :

https://www.ebay.co.uk/itm/235162729508

It gets better as not only are they cheaper than the French offering but if you enter the code "BUYBETTER20" at the checkout, you get a further 20% off and they also do price breaks for buying more than 1, buying 4 = £31.16 each, presumably (but check) the code will reduce this further.

[Foeux]

Originally Posted by Laird Scooby

Just did a search to verify the new type of injector as being 156045 and fond these on ebay :

https://www.ebay.co.uk/itm/235162729508

It gets better as not only are they cheaper than the French offering but if you enter the code "BUYBETTER20" at the checkout, you get a further 20% off and they also do price breaks for buying more than 1, buying 4 = £31.16 each, presumably (but check) the code will reduce this further.

Back of the net.

Let's see where this gets us.

Until then, my daily has to be a 1962 Land Rover - not a good look for a 'reliable' volvo to be outworked by something that should have been dead in 1963!

[Foeux]

UPDATE

The car seems to be fixed... I would ask anyone that reads this to touch wood, cross themselves or whatever other superstitious thing you like doing, but, it works.

Here's what I did, one by one, in this order to see what was broken and to see what made the difference:

1. Spray manifold with water (one branch cold)
   
2. Compression test (12.5bar a cylinder)
   
3. No oil in coolant, no coolant in oil
   
4. New plugs (£14.01)- didn't fix anything
   
5. New Leads (£40.56) - didn't fix anything
   
6. New cap (£41.39) and arm (£24.75) - Big difference but still misfiring a bit
   
7. Disconnected battery, reconnected next day, still misfiring
   
8. Made a gauge to measure injector output - cyl 3 producing 37.5% of the fuel of the other 3. Swapped injectors and seemingly they produced same amount of fuel but still ran rough
   
9. Removed and resealed exhaust - sounded healthier but ran rough
   
10. Cleaned out and dried fuel rail for new injectors
    
11. 4x new Bosch injectors (£99.71) Better still and improved with driving - was it 're-learning' itself? Still struggled to accelerate in gear, wouldn't do more than 80mph on a test track.
    
12. Drove the next day and felt like it had 'healed' a bit. Had a 'stumble' or hesitation just above idle then revved freely.
    
13. Replaced coil (£0.00) - no change
    
14. Replaced ignition amplifier (£0.00) - stumble gone
    
15. Idle control valve (0.00 - no drop in revs once you roll to a stop out of gear. it was dropping to 500 rpm then picking back up to idle speed.

Remaining issue - possible exhaust manifold leak

Overall result - car seems to be back to full power.

Total cost to fix: £220.42
Total time to fix: 4 hours in bits here and there

Thanks to everyone that helped and hopefully this is a good way to end the thread.

I don't know what made the car throw a wobbly but it did. The two things that made the biggest difference were Distributor cap and injectors. I think it could have been a multi-faceted problem associated with age. Nevertheless it has made the car run again and that;s the important thing.

[Moomoo]

Let’s hope there is ongoing cause for rejoicing!🤞👍🧐

Thanks for the thread.

Andrew.

[Laird Scooby]

Glad to hear it's all sorted, having followed the thread since inception, i would point the finger at the injectors and/or fuel rail.

The cap/rotor would have given a minor improvement on any engine given the condition you described for those items but doubtful they'd have completely destroyed the running. Worth holding on to the old cap and rotor as a "known good spare set" just in case.

[Foeux]

Originally Posted by Laird Scooby

Glad to hear it's all sorted, having followed the thread since inception, i would point the finger at the injectors and/or fuel rail.

The cap/rotor would have given a minor improvement on any engine given the condition you described for those items but doubtful they'd have completely destroyed the running. Worth holding on to the old cap and rotor as a "known good spare set" just in case.

I am very grateful for the help and advice. A forum member gave me a load of spares he no longer needs which was very generous.

In doing the tests and buying the bits and puzzling it all out, it became.abundantly clear how easily a 940 not owned by an enthusiast could just be thrown in the bin for letting the side down or being difficult.

Glad it lives.

[Laird Scooby]

You're not wrong, many older cars of all makes and models get canned due to simple faults causing seemingly insurmountable problems.

A methodical approach and logical thought while not testing often leads to a quick and simple solution.