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Matt
Matt, Mechanical Engineer
Category: Volvo
Satisfied Customers: 20588
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I own a VOLVO 850 2.5lt,r auto, none turbo, 1996, with

Customer Question

I own a VOLVO 850 2.5lt,r auto, none turbo, 1996, with 170,000 miles on the clock. It has not missed a heart beat in the seven years I have had her, with regular services. however on sunday I broke down 3 times.I called the breakdown service,they found a breather pipe had came adrift, they did other checks, nothing was found so I started the car and got on my way, 30 miles later it cut out again on the M25 in heavy slow traffic, I called the breakdown again, 45 mins later they arrived, he asked me to turn it over and she started first time like nothing had happened, he did a diagnostic check and found no fault on the read out, again i got on my way. Ten miles later on the A3 it cut out again, 1 hour later the breakdown service arrived, he checked her out did a diagnostic test and again no faults are shown, he asked me to turn her over, she started 1st time again, I was on my way again, this time with the breakdown behind me, 8 miles later I was Home, He did say that when i pulled away there was smoke from the exhaust. On monday I asked my local garage to have a look at her, i have known him for 25 years, he did another diagnostic check and no faults where found, he checked the leads, valves, breather pipes ect they all seem to be ok. So what can be the cause of her cutting out, no faults being found and when she cooled down starts fine.
Submitted: 2 months ago.
Category: Volvo
Expert:  Matt replied 2 months ago.

Hello

This sounds like an electrical actuator or sensor at fault .Usually when you can cycle the ignition key on / off and then restart the engine and the fault is gone temporarily this indicates that this is an electrical component causing this issue.

This could be a wiring issue as things tend to expand when hot and its possible a poor or partial electrical connection is being pushed apart on one of the major sensors so check the connection plug and wiring to the following;

Airflow meter

Crank position sensor

Cam position sensor

O2 sensor

Throttle position sensor

unplug each in turn and use some switch / contact cleaner spray on the pins to ensure its all grease / dirt free

Also worth checking the connections to the fuel pump for the same reason - unplug each in turn and give them a good squirt of switch / contact cleaner - Not WD40

and also unplug and inspect the main power relays and fuses for signs of overheating or corroded terminals - so the ones for the ECU and the fuel pump

And also unplug the wiring loom connections in the engine bay one at time and inspect for corroded or recessed pins.

Check the resistance of the spark plug leads ( 13-15Kohm / metre) and replace if any doubt or high resistance - Also replace the spark plugs if any of them fail this checklist:

http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqread.asp

Expert:  Matt replied 2 months ago.

Hi

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