General: 70: - Misfiring when hot

Funman.60 · Jul 9th, 2009, 10:33

Hi and help!

2lt 10 valve V70 1998 148,000 miles

On a hot day the car starts in the morning no problem, but once hot starts to misfire on acceleration. having stopped goes very lumpy, but even worst when trying to reverse the car it will stall, and to start again will have to turn over for about 10 turns and then will be ok for awhile.

Took car to my local Volvo garage checked codes, nothing registered.

I had changed the plugs previousley to this, it seemed to improve it for awhile, but back to its old self.
I also added injection cleaner which seemed to help for awhile.

I feel it could be a fuel problem, but don't really know.

Any advise would be helpful, (redundancy means not a lot of money so can't just tell garage to fix it).

GavinC · Jul 9th, 2009, 15:14

What a hassle!

Fuel... air... spark...

Are you absolutely sure correct spark plugs are fitted? For example, if they are not the correct temperature plugs for your engine specification they may not perform well and so 'break down' across the engine's temperature range.

Visually check that no air is getting in where it shouldn't. Such as a split in the induction tubing or a hole in a vacuum line... or a vacuum line that has detached. I also start the engine and listen for a hiss and/or a changed engine note while gently squeezing induction tubing and wriggling vacuum lines just a little. (NB.While carefully watching out for DANGEROUS belts, pulleys, high voltage sparks etc... ie. No fingers, hands, neckties in the way...)

Could be ignition wiring breaking down... but not very likely, though others are welcome to say different.

Wonder whether it is engine Coolant Temperature Sensor... but as far as I know they manifest cold start and cold running problems when they fail. But perhaps they can also fail t'other way?? (ANYONE COMMENT?)

When my car exhibited misfiring - and only when hot under load/acceleration, I found it was a failing coil pack - just one out of six. Having been told that failing coil packs are sometimes difficult to test for, I took a guess after running the checks above and bought one new coil pack. Doddle to fit. Fixed and fine thousands of miles later!

ANYONE MORE QUALIFIED/EXPERIENCED/KNOWLEDGEABLE THAN I AM AGREE/DISAGREE/ADD TO THIS so 'Funman' can have... more fun and less hassle?

Chris_Rogers · Jul 9th, 2009, 16:49

What is the engine temperature gauge reading when the engine is hot?

If it's not at 3 o/clock then I'd suspect the Coolant Temperature Sensor.

Funman.60 · Jul 11th, 2009, 15:34

Chris/Gavin

New plugs from motor factors seemed to know what he was talking about, but willing to get new set from volvo and try.

Temp gauge reading 3 o,clock (perhaps little higher but not much).

Had to fit the large pipe from the air filter (the corrigated one) as old pipe was split, no difference, but bit dusty in there.

Can't hear any hissing noises.

Willing to try coil pack, any hints for fitting?

Would it be worth trying new leads, or perhaps better to trying one thing at a time.

Ta for help

Chris_Rogers · Jul 11th, 2009, 16:56

"Took car to my local Volvo garage checked codes, nothing registered."

What did they use? a generic OBDII code reader is no good for ths car.

You can make a DIY code reader like this:

http://www.volvoforums.org.uk/showthread.php?t=46943

KBB · Jul 11th, 2009, 19:39

Change rotor arm and distributor cap. They are not listed as service items and are often overlooked

Jul 9th, 2009, 10:33	#1
Funman.60 New Member Last Online: Sep 15th, 2009 21:29 Join Date: Jul 2009 Location: St Martin du Limet	Misfiring when hot Hi and help! 2lt 10 valve V70 1998 148,000 miles On a hot day the car starts in the morning no problem, but once hot starts to misfire on acceleration. having stopped goes very lumpy, but even worst when trying to reverse the car it will stall, and to start again will have to turn over for about 10 turns and then will be ok for awhile. Took car to my local Volvo garage checked codes, nothing registered. I had changed the plugs previousley to this, it seemed to improve it for awhile, but back to its old self. I also added injection cleaner which seemed to help for awhile. I feel it could be a fuel problem, but don't really know. Any advise would be helpful, (redundancy means not a lot of money so can't just tell garage to fix it).

Jul 11th, 2009, 15:34	#4
Funman.60 New Member Last Online: Sep 15th, 2009 21:29 Join Date: Jul 2009 Location: St Martin du Limet	V70 Misfire when hot Chris/Gavin New plugs from motor factors seemed to know what he was talking about, but willing to get new set from volvo and try. Temp gauge reading 3 o,clock (perhaps little higher but not much). Had to fit the large pipe from the air filter (the corrigated one) as old pipe was split, no difference, but bit dusty in there. Can't hear any hissing noises. Willing to try coil pack, any hints for fitting? Would it be worth trying new leads, or perhaps better to trying one thing at a time. Ta for help

Jul 9th, 2009, 15:14	#2
GavinC GavinC Last Online: Oct 13th, 2012 18:51 Join Date: Dec 2003 Location: Harrogate	What a hassle! Fuel... air... spark... Are you absolutely sure correct spark plugs are fitted? For example, if they are not the correct temperature plugs for your engine specification they may not perform well and so 'break down' across the engine's temperature range. Visually check that no air is getting in where it shouldn't. Such as a split in the induction tubing or a hole in a vacuum line... or a vacuum line that has detached. I also start the engine and listen for a hiss and/or a changed engine note while gently squeezing induction tubing and wriggling vacuum lines just a little. (NB.While carefully watching out for DANGEROUS belts, pulleys, high voltage sparks etc... ie. No fingers, hands, neckties in the way...) Could be ignition wiring breaking down... but not very likely, though others are welcome to say different. Wonder whether it is engine Coolant Temperature Sensor... but as far as I know they manifest cold start and cold running problems when they fail. But perhaps they can also fail t'other way?? (ANYONE COMMENT?) When my car exhibited misfiring - and only when hot under load/acceleration, I found it was a failing coil pack - just one out of six. Having been told that failing coil packs are sometimes difficult to test for, I took a guess after running the checks above and bought one new coil pack. Doddle to fit. Fixed and fine thousands of miles later! ANYONE MORE QUALIFIED/EXPERIENCED/KNOWLEDGEABLE THAN I AM AGREE/DISAGREE/ADD TO THIS so 'Funman' can have... more fun and less hassle?

Jul 9th, 2009, 16:49	#3
Chris_Rogers VOC Member Last Online: Apr 10th, 2017 16:55 Join Date: Jan 1970 Location: South Kent Coast	What is the engine temperature gauge reading when the engine is hot? If it's not at 3 o/clock then I'd suspect the Coolant Temperature Sensor.

Jul 11th, 2009, 16:56	#5
Chris_Rogers VOC Member Last Online: Apr 10th, 2017 16:55 Join Date: Jan 1970 Location: South Kent Coast	"Took car to my local Volvo garage checked codes, nothing registered." What did they use? a generic OBDII code reader is no good for ths car. You can make a DIY code reader like this: http://www.volvoforums.org.uk/showthread.php?t=46943

Jul 11th, 2009, 19:39	#6
KBB Master Tech Last Online: May 18th, 2020 10:57 Join Date: Dec 2006 Location: On Contract Dubai Automotve Technical Academy	Change rotor arm and distributor cap. They are not listed as service items and are often overlooked

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