CarTalk.com Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Help

my 2007 3.2 s80, 75 K miles, will not respond to accelerator for the first 1-2 miles after a cold start, then runs fine, no check engine light has shown. Per shop recommendation switched to 92 octane x3tanks, then replaced fuel sensor for $650, neither solved. Any help?

How do you drive 1-2 miles without any response to the accelerator? Must take an awful long time.

Your accelerator is not connected to the throttle body. The gas pedal is more accurately a throttle position sensor and is a pedal with a variable resistor attached to it. The a set of wires goes to the computer telling the PCM what position the pedal is in. From there, the computer sends a voltage to a motor attached to the throttle body to move the throttle plate.

There is an outside chance that either the throttle motor or the throttle position sensor is not working when cold, but that is really long odds in your case. The computer gets information from a number of other sensors before determining how much voltage to send to the throttle motor and I’m guessing that one of those sensors is sending false information to the computer.

I doubt the computer itself is at fault, but it could be. The trick is to figure out which sensor is sending the bad info and why. Your dealer would most likely have seen this before, or have access to corporate knowledge about this situation (in the form of a TSB) and know what sensor to repair or replace.

Thank you Keith. Guess I’ll surrender my fate to the dealer rather than my local Swedish repair shop, who until this I’ve had good luck with. They have suggested O2 sensors next but will not assure of solution

+1 for keith because I believe it’s the TPS.

All of the “drive by wire” have multiple position sensors for the pedal and they all have to agree or you get very limited throttle response. Plus a failure of this unit should set a malfunction code and turn on your check engine light.

If you have access to a scan tool that can show live data, it might be useful to see what the computer thinks the throttle is doing when you step on the gas. “Lazy” oxygen sensors can be detected this way too, as can other sensors that are not bad enough to cause your check engine light to be illuminated, but still are returning screwy information to the ECU. It sounds like the shop you’re using are skilled at changing parts but lacking in the troubleshooting department. You have already spent $650 on a sensor you may not have needed. I would find someone that can diagnose the problem instead of just throwing parts at it.

The OP can count this as one more vote for the TPS being the problem.

Additionally, a mechanic whose solution is “try 3 tanks of premium gas” with a vehicle that was designed to run on regular is…a mechanic whose competence/expertise I would question.

The gas pedal is more accurately a throttle position sensor...

On my Insight, this is called an “accelerator pedal position (APP) sensor.” The TPS is where it’s always been, on the throttle body.

I thank all for responses, wish I would have started here instead of the shop. I have limited car knowledge. If is is any kind of a sensor issue does it make sense that the problem ceases after the car has been running a very brief period? Does a vacuum leak make sense as Keith’s second response suggested?

First, you need to answer Kieth’s question…how are you driving 1-2 miles with no throttle response? What happens if you let it idle for 5 minutes before driving?

A vacuum leak will usually cause a high idle speed, it’s the same as opening the throttle a little bit, but is will also cause fuel/air mix issues as the MAF sensor (mass airflow) will be bypassed and so all air entering the manifold will not be accounted for. That almost always gives you a check engine light unless the leak is very very small.

Because this is a cold engine issue, I would be inclined to look for one of the coolant temperature sensors to be giving false data. You need a mechanic that can look at the live data stream, otherwise your mechanic is just guessing.

And again, how do your drive 1-2 miles without the throttle working?

Edit: My thanks to insightful for the technical correction.

Very cautiously! There is a very limited initial response. Then after a several second delay, the engine suddenly kicks in as expected. I have tried a long warm up with no change. Nor does ambient temperature make a difference. After closer to 1 mile of driving than 2 the car runs normally

So, if you start it cold, and “jazz” the throttle, no normal revving? Even “jazzing” it for several minutes? But drive 1 mile and it’s fine??

Has the throttle body been checked for gunk buildup behind the throttle plate? It may just need a throttle body cleaning.

I will pay closer attention to the idling/revving behavior when I leave work tonight. The shop invoice did not indicate any action regarding the throttle plate.

@VDCdriver. The manual 2007 Volvo S80 recommends 91 octane or. Though 87 octane is listed as the bare minimum.

"Octane rating
Volvo engines are designed to achieve rated horsepower, torque, and fuel economy performance using premium 91 octane fuel.

Volvo recommends premium for best performance, but using 87 octane or above will not affect engine reliability.

In demanding driving conditions, such as operating the vehicle in hot weather, towing a trailer, or driving for extended periods at higher altitudes than normal, it may be advisable to switch to higher octane fuel (91 or higher) or to change gasoline brands to fully utilize your engine’s capacity, and for the smoothest possible operation. "

I

^
In that case, then the OP has been practicing false economy by running the car on regular grade gasoline, and the mechanic should have advised exclusive use of 91 octane gas, rather than just 3 tankfuls.