Cruise control shuts off and engine speed reduces/surges a few times

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MEMBER
2000 VOLVO XC70
2.4L
5 CYL
AUTOMATIC
181,000 MILES

Car on cruise control at 50 mph, cruise control shuts off and engine speed reduces/surges a few times.
Does this with or without cruise control engaged a few more times at speeds between 50 and 60. I think car was going uphill each time.
Engine is fine for the next 30 miles til it is shut down for the night.

All 5 engine coils were replaced about 4 years ago, at approximately the same time.

Gas tank almost full, using same gas station as always.

Thanks.

6 Replies

JIS001

MECHANIC
3,408 POSTS

If you have a surge at cruising speed with no check engine light on, then the most likely fault will be the turbo control valve. The solenoid is attached to the air filter housing with 3 ports which are color coded red, yellow, and blue. The solenoid is most likely sticking causing the surge.

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Sunday, December 22nd, 2019 AT 4:21 PM

TABLETALK

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15 POSTS

Can I continue to drive vehicle safely? Will car simply stop running if it gets worse?
Can my local mechanic determine if a TCV is needed, and how does he do that? A scan?
Check engine light hasn't come on so far.
If I can put car on jack stands, is the replacement easy for an average non-mechanic with some tools?

Thanks again for your help.

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Monday, December 23rd, 2019 AT 2:42 AM

STEVE W.

MECHANIC
12,997 POSTS

Continuing to drive it will make it act like it has been, it shouldn't just stop running unless it gets much worse. The valve is a solenoid attached to the air filter housing under the hood. No need to jack up the vehicle to change it. Just remove the solenoid, remove each hose and swap them to the new part and you are done. Very easy to do.

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Wednesday, December 25th, 2019 AT 4:47 AM

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I found it. Thanks. Now, should I replace the hoses? They are showing wear at the bends.
Or, can I just cut off the ends of the hoses and re-attach them?

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Saturday, December 28th, 2019 AT 1:27 AM

STEVE W.

MECHANIC
12,997 POSTS

I would probably replace them is they are getting crumbly, IE you rub them and get black on your hands or they start shedding. I would also check the other hoses for the same.