pulse or wave in mid acceleration

**proton** · 05-27-2014, 05:02 AM

I dont know how to discribe this well. look intermitent too but more and more often. under mild acceleration from mid trottle, like if I want to accelerate but not pedal to the floor, the power come in form of a wave. Nothing rough, it is like a soft pulse. Like if I was slowly rocking my foot on the pedal (and I'm not). I have a chinese dice and vida and I have no codes. I've tried to monitor the pedal pot, the tcv (IPD) throttle body and MAF without any success to catch something. any suggestion to look at?

**men2be** · 05-27-2014, 05:37 PM

I have experienced the same thing.

**Antherzoll** · 05-27-2014, 05:40 PM

I've noticed a similar issue when I first purchased my XC. On gentle accel on flat or slightly uphill the power delivery from the engine/transmission would rock the car very gently then smooth right out. I'm not sure what cured it, but I replaced all the mounts and did a tranny flush/reset all in the same weekend and haven't experienced the issue since. I've also read that someone else had a similar issue and traced it back to a worn subframe bushing.

I'd try doing the tranny flush/reset first if you haven't done so recently, then maybe give your mounts and control arms a look over.

Good Luck

**proton** · 05-28-2014, 05:02 AM

sorry, maybe I did not explained it well. There is nothing with the balance of the car. It is really in the acceleration effect. My acceleration is not linear but feel like if I was slowly and slightly playing up and down with the gas pedal.

**JRL** · 05-28-2014, 06:08 AM

If you mean slight surging, most will do this especially in the heat (summer)
They run lean.
If you flash the ECU, this usually goes away as it runs a hair richer under a load

MY old S60 AWD 2.4T really did this on the highway in the summer but my (very good) dealer said there was nothing they could do, it was running properly!

**men2be** · 05-28-2014, 06:38 AM

JRL, I think you nailed it! That is exactly when it happens. I will see if the dealer will do it next time in.

Originally Posted by JRL

If you mean slight surging, most will do this especially in the heat (summer)

They run lean.
If you flash the ECU, this usually goes away as it runs a hair richer under a load

MY old S60 AWD 2.4T really did this on the highway in the summer but my (very good) dealer said there was nothing they could do, it was running properly!

**Antherzoll** · 05-28-2014, 08:07 AM

Try the data logging through VIDA if you can and take screenshots of the graph for review. I'd monitor IAT, Boost, MAF, AFR, fuel pressure or any other parameters you think may be causing it.

**Pneubi** · 05-28-2014, 08:38 AM

Same. Fuel filter

**proton** · 05-29-2014, 06:16 AM

Originally Posted by Pneubi

Same. Fuel filter

changed it a few mount ago...volvo genuine

Try the data logging through VIDA if you can and take screenshots of the graph for review. I'd monitor IAT, Boost, MAF, AFR, fuel pressure or any other parameters you think may be causing it.

..and TCV , and Gaz Pedal Pot.... that is exactly what I am doing but to success in "catching" yet

it is not under high load. I'll try to make an image. I'm on the hightway at 100km and just want to slowly raise my speed to 120km. not petal to the floor. just low pression. I fell my car raise it speed by slight wave. again, their is nothing weird like bad noise, clunk or bad hesitation. just not linear acceleration around mid range power. Pedal to the flow, now problem or I can't notice.