Q: high rpm when starting car, then idles very rough. Also lack of power accelerating at times while driving

asked by on October 25, 2016

At random when starting car, engine revs high to 2000 rpm several times, then drops to 1000 and idles very rough. while driving at times either on highway or side road, the car goes into limp mode and pressing accelerator gets no response. Starting happening after driving across country in summer after about 8,000 miles. engine light was already on at start of trip. ETM was replaced and software upgraded in july 2015 at volvo dealer by previous owner. After towing to mechanic, car working fine, who then referred to volvo dealer Now at volvo dealer for several days, they are unable to get the car to replicate symptoms above, told me they have to keep trying until symptoms show in order to locate problem. Fault codes are 951F, Accelerator pedal position sensor; 903F Throttle position;902B Communication with throttle unit faulty signal; 2210 rear heated O2 sensor. Not sure where to go from here, thank you for your time.

My car has 110716 miles.
My car has an automatic transmission.

Throttle Position Sensor Replacement $129.21 - $646.10 Get a Quote
Oxygen Sensor Replacement $108.80 - $869.59 Get a Quote

These codes all point to the operation of the throttle position sensor. The throttle position sensor is a sensor used to monitor the throttle position relative to your foot on the gas pedal. The sensor is usually located on the butterfly spindle/shaft so that it can directly monitor the position of the throttle. The ECU then makes the direction to supply more or less fuel to the motor. When this sensor is not working properly, this can cause intermittent responses when pressing the gas pedal. The last code related to the O2 sensor relates to the oxygen sensor behind the catalytic converter which monitors the exhaust gases after they leave the catalytic converter. This essentially reports whether or not the catalytic converter has done it’s job correctly or not. When this is faulty, this may cause inaccurate signals to be relayed to the ECU which then causes inaccurate amounts of fuel to be supplied to the motor causing the rough idling and poor running condition you describe.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

What others are asking

Throttle position sensor going out

If your vehicles throttle position sensor has gone bad then the vehicle may be put into reduced power mode. In reduced power mode the vehicle will not drive over a certain RPM and engine speed. Usually, a Check Engine light...

Gas pedal won't work

The adjustable pedal mechanism sensor may be defective, require replacement, and have the codes cleared. Ford had a bulletin that covered this problem in 2005, and offered a free replacement of this sensor. This bulletin is no longer active, but...

transmission not changing gears

The internal transmission shifting mechanism of the valve body to the forward clutches is not working, or the forward sprag clutches are broken. Only a transmission pressure test would be able confirm if the problem is in the valve body...

My cars ac drains heavily, sometimes inside the car if its been on, theres high low-side pressure and poor cooling

It sounds like you may have a faulty AC Compressor or potentially a leak in the AC lines somewhere. Car air conditioners work on a simple principle of heat transfer, relying on the fact that heat will always transfer from...

Master cylinder losing fluid and I can't find leak.

It is possible that your brake fluid could be leaking into the power brake booster. This is the big round container that the master cylinder is bolted to. The brake booster operates off of the vacuum created by the engine...

Crack on engine head gasket

Generally, a failed head gasket will leave evidence in one of four areas. The oil needs to be checked for a milky residue -- as this would indicate coolant leaking into the oil. The coolant needs to be checked to...

My Dodge Ram 1500 4.7 stalling at stops sometimes

To pinpoint the cause, a diagnostic decision tree is used by mechanics and all components on that "tree" must be directly tested. As components are ruled in or out during that testing, one just proceeds along the tree. That is...

Battery dies if the car sat for over 20 hours

Batteries that drain overnight are common. Usually when this occurs, there is a parasitic drain on one of the car's systems. When this occurs it drains the battery down over time. Batteries that are drained down repeatedly can cause them...

I accidentally put expired motor oil in my car, will it damage my engine?

Hey there, thanks for writing in about your 2002 Subaru Outback. I don't think you should have any worries. As long as the oil did not have any contamination from water then it should be okay to use the expired...

Related articles

Does An Automatic Transmission Have a Clutch?
Most of the time we think of a clutch in the context of a manual transmission. An automatic transmission does have...
The Best Used Cars to Buy if You Live Close to the Ocean
If If you live close to the ocean, your vehicle is going to be far more vulnerable to rust than if you lived further inland. And the fact is, when it comes to resisting rust, not all vehicles are created...
The Best Used Cars to Buy If You Live in a Cold Climate
If If you live in a cold climate, likely one of your biggest concerns when you are considering which used vehicle you should buy is how well it will perform in snowy, icy conditions. We have evaluated a number...