General: 70: - surge and popping

jack taylor · Jul 30th, 2019, 01:25

Hi, I have a 1998 V70, 2.5, 20v petrol. When starting the revs surge to 2,500rpm and then die down to about 850rpm. Thereafter tick-over is lumpy between 650 and 850rpm. When I blip the throttle to about 3,000rpm the revs drop but before tick-over speed there is popping from the exhaust. On the move the engine is fine and gives no problems. I had something very similar some time ago but for the life of me I cant remember the remedy.
I would welcome opinions as to the possible cause. many thanks jack.

turboboy · Jul 30th, 2019, 08:03

Does this happen when the engine is cold or every time, even when up to running temp?

jack taylor · Jul 30th, 2019, 15:30

Hi turboboy, thanks for your reply. this happens every time whether hot or cold.

volvo again · Jul 30th, 2019, 15:36

The way the engine is revving could be the idle control valve but I don't think this would cause popping in the exhaust which sounds like the timing is out.
Another possibility may be the cam position sensor

jack taylor · Jul 30th, 2019, 20:29

Hi volvo again, many thanks. This has happened before and I think my mechanic fitted a new valve/sensor which I know was only about £30 to £40.00. I just wish I could remember exactly what was done. The fix was quick and cheap I do know that.
Could the popping be an air leak. fuel mixture is ok I think as consumption has not altered.
Tick over is rough as though the engine is rich and popping could possibly be too much fuel. Could that be right or am I talking out of my rear.

volvo again · Jul 31st, 2019, 08:04

Popping in the exhaust on deceleration is caused by the detonation of unburned fuel in the exhaust pipe. ... Exhaust leaks can cause decel pop, make sure the exhaust is sealed completely at the motor, and at any other connections.

jack taylor · Jul 31st, 2019, 14:47

Hi volvo again, many thanks for that. The exhaust note is louder than usual so I shall get the exhaust system checked. I have looked through my ebay purchases and in oct 2017 I purchased an Oxygen Lambda Sensor. Could that be the cause of the present problems. It probably came from China as I only paid £57.00. Thanks again jack.

jack taylor · Aug 1st, 2019, 13:59

Given the symptoms could the cause be the oxygen lambda sensor or the idle control valve or possibly both. thanks

Jul 30th, 2019, 01:25	#1
jack taylor Master Member Last Online: May 15th, 2022 15:53 Join Date: Jan 2008 Location: Torrenueva, Costa del Sol	surge and popping Hi, I have a 1998 V70, 2.5, 20v petrol. When starting the revs surge to 2,500rpm and then die down to about 850rpm. Thereafter tick-over is lumpy between 650 and 850rpm. When I blip the throttle to about 3,000rpm the revs drop but before tick-over speed there is popping from the exhaust. On the move the engine is fine and gives no problems. I had something very similar some time ago but for the life of me I cant remember the remedy. I would welcome opinions as to the possible cause. many thanks jack.

Jul 30th, 2019, 08:03	#2
turboboy Master Member Last Online: Dec 15th, 2023 08:44 Join Date: Dec 2003 Location: Twickenham	Does this happen when the engine is cold or every time, even when up to running temp? __________________ Turboboy Current: 1998 Volvo V70 2.3 T5 Auto. Previous: 2000 Volvo V40 T4; 1981/2 265 (x2); 1988 740 Turbo Estate.

Jul 30th, 2019, 15:30	#3
jack taylor Master Member Last Online: May 15th, 2022 15:53 Join Date: Jan 2008 Location: Torrenueva, Costa del Sol	Hi turboboy, thanks for your reply. this happens every time whether hot or cold.

Jul 30th, 2019, 15:36	#4
volvo again Master Member Last Online: Apr 23rd, 2024 17:46 Join Date: Jun 2018 Location: Presteigne, mid Wales	The way the engine is revving could be the idle control valve but I don't think this would cause popping in the exhaust which sounds like the timing is out. Another possibility may be the cam position sensor

Jul 30th, 2019, 20:29	#5
jack taylor Master Member Last Online: May 15th, 2022 15:53 Join Date: Jan 2008 Location: Torrenueva, Costa del Sol	Hi volvo again, many thanks. This has happened before and I think my mechanic fitted a new valve/sensor which I know was only about £30 to £40.00. I just wish I could remember exactly what was done. The fix was quick and cheap I do know that. Could the popping be an air leak. fuel mixture is ok I think as consumption has not altered. Tick over is rough as though the engine is rich and popping could possibly be too much fuel. Could that be right or am I talking out of my rear.

Jul 31st, 2019, 08:04	#6
volvo again Master Member Last Online: Apr 23rd, 2024 17:46 Join Date: Jun 2018 Location: Presteigne, mid Wales	Popping in the exhaust on deceleration is caused by the detonation of unburned fuel in the exhaust pipe. ... Exhaust leaks can cause decel pop, make sure the exhaust is sealed completely at the motor, and at any other connections.

Jul 31st, 2019, 14:47	#7
jack taylor Master Member Last Online: May 15th, 2022 15:53 Join Date: Jan 2008 Location: Torrenueva, Costa del Sol	Hi volvo again, many thanks for that. The exhaust note is louder than usual so I shall get the exhaust system checked. I have looked through my ebay purchases and in oct 2017 I purchased an Oxygen Lambda Sensor. Could that be the cause of the present problems. It probably came from China as I only paid £57.00. Thanks again jack.

Aug 1st, 2019, 13:59	#8
jack taylor Master Member Last Online: May 15th, 2022 15:53 Join Date: Jan 2008 Location: Torrenueva, Costa del Sol	Given the symptoms could the cause be the oxygen lambda sensor or the idle control valve or possibly both. thanks

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