Volvo V50 hesitation

[hiccy18]

Last roll of the dice here but thought I'd ask:

My partner has an '06 V50 1.8 petrol that in March started stumbling and refusing to accelerate reliably; she sometimes reported the traction control light coming on too. The garage recommended changing the coil packs, which wasn't my first choice, but we tried it to no avail. When lockdown was eased the garage changed the solenoids for the inlet manifold which seemed to be worth trying but still no improvement. An auto electrician inspected it and diagnosed an ABS pump fault; the garage said given the age it was not worth fixing.

Due to lockdown the car has sat unused and now her ladyship is using my car for commuting so in a fit of furlough frustration and boredom I took the car out for a run today with the following symptoms:

• The car hesitates, stumbles and occasionally the anti-skid light comes on
• After a few miles the ABS and anti-skid lights come on permanently
• The hesitation then vanishes and the car drives great (although assuming no ABS)

Could this be an ABS pump problem or is there something else (cheaper?) causing the issue?

[GreenV8S]

Fault codes?

[hiccy18]

Ah I missed that bit out, sorry:

None

PITA

[GreenV8S]

I would suspect a dodgy wheel speed sensor or wiring to it. Proving that might be tricky though, if the problem is intermittent. The ideal solution would be an expensive OBD scanner which supports the wheel speed sensor PIDs. Maybe you could pick it up with a storage scope. The El Cheapo option would be an analog volt meter connected to backprobes on the relevant ECU pins, and a passenger to watch it while you drive. If the problem is happening so consistently, you may find there's no sensor input or the input is intermittent.

[oakdale]

I don't think a faulty ABS sensor or wiring fault would cause this but an implausible signal from a sensor could, I think the sensors pick up the signal from the wheel bearings one these, so try disconnecting each wheel ABS sensor lead in turn to see if it eliminates the problem.

Doing this will put the ABS light on but will stop the system from getting a nonsense signal if that's where the problem (faulty wheel bearing) lies.

[oakdale]

Thinking about this further, disconnecting any of the sensors will probably disable the ABS system so you really need to have it checked with a scope, but disabling the system will prove if that's where the fault lies.

Have you checked the obvious like tyre pressures and size?

[hiccy18]

Thank you chaps for your input, very much appreciated. Next dry day I'll get the wheels off for a visual inspection and see what I can work out with a multimeter. Tyre sizes are correct but will check the the pressures with a gauge rather than my foot.