'98 V70 T5 occasionally cuts uut when not under load.
 

'98 V70 T5 occasionally cuts out when not under load.

When idling, or when rolling (i.e under momentum, without needing propulsion), on a few occasions it has just died*. Starts again no problem. Sometimes I think I feel it briefly 'hesitate' when under load.

Warm engine, no other glitches.

Any ideas?

Thanks!

*Disconcerting in the middle of a 3-point turn (steering and brakes).

Possible coolant temperature sensor
 

Maybe ETS possibly giving wrong engine temperature but would recommend a full code scan and check live data to make sure temperature that the ECU gives are close to the actual temperature

Thanks for the notions there, andrewc1267.

Not familiar with ETS. I found this description: "Electronic Throttle System (ETS) including the Electronic Throttle Module (ETM) and Throttle Body, including position sensor and actuator", but I don't see how that could that be "giving wrong engine temperature"... Would you kindly confirm what ETS means in this context, please?

Recently (since this issue first showed) had a code scan and there was nothing showing there, but I'll try to verify the temperature as [per ECU.

Cheers

Just to add...before you replace anything remove and thoroughly clean the Idle Air Control Valve as it may be sticking due to carbon deposits therefore not compensating for the load being applied. I'll hazard a guess you had the air con on at the same time? Couple that with the load from the power steering pump and the IACV has its work cut out for itself.

Also, whilst you're in the area, clean the throttle housing and its butterfly valve for good measure.

ETS - engine temperature sensor.

Never heard that before, it's usually considered to mean Electronic Throttle System. I think you mean CTS =Coolant Temperature Sensor, the sensor that sits under the thermostat housing on these engines. This is easy enough to test, and cheap enough to replace, though a bit fiddly to get at.

Thanks for the contributions there, chaps.

Would like to point out that the otherwise the car starts and runs really well. I did a cylinder head job on it, completed late last year (burnt-out exhaust valve, resulting in replacing all exhaust valves), so I had a chance to inspect the throttle body etc. Could see no carbon deposits or general muck. I replaced the PCV. (All emissions are now spot on, and mpg is up by at least 25%).

I also replaced the coolant temperature sensor (thanks, Luxobarge), using a decent non-Volvo part (I gave up waiting for an original from Volvo), and can't recall any other Engine Temperature Sensor (thanks, ITSv40), but would be glad to be enlightened as to where, exactly, that may be located. The dash temperature dial shows running temp exactly normal.

I had wondered about some sort of idle control, so Baffler's Idle Air Control Valve sounds interesting. My initial search for more info indicates that (of course) the throttle kit changed in '99 (mine's a '98), and as I reply, I haven't yet found a good description of such on a '98 V70 T5.

Baffler - I've only finally (crossed fingers) got the air-con working in the last fortnight, and had observed this glitch occurring before that, but we've certainly got the weather right now to test whether having it on makes a difference! The last time the engine conked out when moving, I was doing a slow-speed turn, with the air-con on...

It does appear to cut out when moving at average speeds, but picks up again without intervention.

The only other immediate process I have in mind is to use contact cleaner spray on all the engine management connectors I can find.

Anyway, if anyone can link to (or has) a picture of where the Idle Air Control Valve actually is on a '98 V70 T5 (or the 'non-coolant' Engine Temperature Sensor), I'd be pleased to see it.

Thanks for taking an interest!

If yours is a '98 model then its a pre ME7 (ie its a non-electronic throttle body).

In which case the idle air controller is located just in front of the intake manifold near the throttle body - there is a good write up of cleaning the IAC here - https://www.matthewsvolvosite.com/fo...ic.php?t=47533

BTW I'm only aware of the single coolant temperature sensor on these - the one located under the thermostat.

HTH

If yours is pre-ME7 then it'll have a conventional distributor and rotor - these are well worth checking, to make sure the contacts are in good condition, clean and free of oil. I've had occasional problems with this, well worth keeping an eye on as mine never threw a code.

As above - only one coolant/engine temperature sensor on these.

I've just been through this with my 2.4 170 auto... random stalling at low speed and when pulling away, sometimes instant restart, sometimes took a few attempts. Eventually it died outright and couldnt be restarted. Luckily it was on the driveway at the time.

It was a dead 'main engine system relay' (fuse no.1) in my below video. These are just generic Volvo relays you can get on ebay for few quid.

+ YouTube Video