Hunting engine possibly connected with brakes? Topic is solved

ashleyg82v702001 · Post by **ashleyg82v702001** » 26 Jul 2020, 09:16

Hello, I'm very new to volvo bought my v70 2.4l 2001 a month ago,
I was well aware it needed some attention and have set out on the path of saving my new baby. It's done just 56, 500 miles and looks almost showroom condition, however the front suspension and brakes were a little neglected all bushes were shot, disks were shot and springs were poor. this has been done. Once it was all back together and brake lines were replaced it was time to bleed it has started hunting. It seems to run OK until you depress the brakes for the first time after starting then if revs between 700 - 940 revs at idle occasionally dropping below and stalling.

The only other thing I have done is replace pre cat oxy sensor that was not heating.

Any ideas?
I'm a little stumped.

Thanks for your help

Post by **misha** » 26 Jul 2020, 09:57

If the o2 sensor is aftermarket and not OEM...it's bad right out of the box.
These cars will not run properly,or not run at all,on aftermarket sensors.

ashleyg82v702001 · Post by **ashleyg82v702001** » 26 Jul 2020, 13:24

Well I've re-fitted the old sensor apart from failed heat it has cured the hunt.... Thankyou

Post by **misha** » 26 Jul 2020, 13:59

Remember....every time you need to replace sensor(o2,maf,ect...etc) you need to remove negative battery cable for 15-30min in order to reset fuel trims.

About o2 sensor....write down Bosch or Denso numbers from it('01 should have Denso management)and buy o2 sensor with exactly the same numbers and from the same manufacturer(brand).
Aftermarket replacements simply doesn't work on these cars because they have out of spec. values.

ashleyg82v702001 · Post by **ashleyg82v702001** » 27 Jul 2020, 07:27

It was replaced with a denso sensor with the same part number..

Post by **misha** » 27 Jul 2020, 13:36

Take it back...it's obvious that it's bad right out of the box...or you didn't reset fuel trims after new sensor replacement.

How do you know that heater on o2 is bad?
Did you read the codes?
Mileage is pretty low for o2 sensor failure.

ashleyg82v702001 · Post by **ashleyg82v702001** » 27 Jul 2020, 13:58

My original o2 is coding resistance is 0 on the heater, new one has no code but hunts and stalls

Post by **misha** » 27 Jul 2020, 15:18

With sensor connected or disconnected?
Resistance should be checked when sensor is disconnected.
If you checked resistance with sensor connected,you could damage ecu.

You really need to scan for codes.

ashleyg82v702001 · Post by **ashleyg82v702001** » 27 Jul 2020, 21:18

It's OK the resistance measurement was given by my diagnostic tool under the live monitor function