Volvo 940 LPT - Engine missing, cutting out - empomire

My 940 has an intermittent fault, dodgy starting, then runs OK, until about 20 miles later it will start missing at 2500 revs, and the tacho misses also. If I can get up to 3000 it will sometimes be OK, but can cut the ignition completely, tacho to zero although the engine is still turning, if I lift off the throttle the engine fires up and the tacho comes up again. One hot day crawling about town it got so bad I couldn't get over about 1200 revs, had a job to get along, stopped for ten munutes and then back to what passes for normal, OK up to 2500 revs.I can cruise on light throttle openings but floor it and it misses/cuts out immediately. Not much fun towing a trailer uphill. Went to the main dealer diagnostic but nothing found, and now they won't respond to my phone calls. As you may imagine this is frustrating and I would scrap it if I hadn't just fitted a new clutch.

Volvo 940 LPT - Engine missing, cutting out - lordwoody

Specific and good Volvo advice can be found here.......>

http://www.volvoforums.org.uk

Volvo 940 LPT - Engine missing, cutting out - empomire

Yes, thanks, on there also but no results.

Volvo 940 LPT - Engine missing, cutting out - elekie&a/c doctor

I would check the distributor cap and rotor arm for corrosion and cracks.

Volvo 940 LPT - Engine missing, cutting out - empomire

Would a rotor/distributor problem cause the tacho to show zero when the engine is rotating?

Where does the tacho derive its info?

Volvo 940 LPT - Engine missing, cutting out - Cyd

Start at the dizzy as Leckie says. The cap can 'look' fine but i fact be faulty.

Also check out the coil - I once had a very similar sounding problem that turned out to be the coil.

The main HT lead from the coil to the dizzy also does four times as much work as the others and if the coil is body mounted is subject to vibration, so check here too.

Volvo 940 LPT - Engine missing, cutting out - injection doc
From memory these have a crank sensor running off the flywheel and you mention you have just had a new clutch ! I would look at the crank sensor with a view to changing or get the garage to scope it to see if its breaking down when hot ! I suspect it is !
These also have an ignition module that could be an issue ! Make sure if you change the amplifier buy a quality unit !

Edited by injection doc on 16/09/2013 at 22:59

Volvo 940 LPT - Engine missing, cutting out - empomire

Thanks, fault was there before the clutch change, they did the diagnostic but found nothing. I will have a grope around in the morning.

Volvo 940 LPT - Engine missing, cutting out - empomire

for what its worth I removed the flywheel sensor, the insulation was badly degraded, the third uninsulated core exposed, and the white wire was kinked, it parted at the slightest pull. Temporarily repaired, new one coming, £35.

 

Value my car