997.1 3RS Unstable Idle and loss of power/throttle response
 

Dear all,

I have been having this issue for a while. My car's idle would hunt and won't come to a stable idle. Also my gas pedal has zero response after the first 40-50% of pedal travel. It just happens suddenly. The first time this happened was about a month ago. My car would have the unstable idle as well as loss of response after 50% of pedal travel. Also I couldn't rev the car past 4k rpm. One afternoon, the car even sounds like it's misfiring when idling. And also when there was once where the car stalled when I was trying to downshift from 4th to 3rd. As soon as I stepped on the clutch and moved the shifter out of 4th, the car died. I had the car in the shop and had a fuel pump changed and pulse sensor changed. After that the car drove absolutely fine until today. The unstable idle suddenly came up again. Now when I step on the gas, the first 30-40% of the pedal travel seems perfectly normal. However once past that, it seems as though there is zero response. The car wouldn't accelerate like it normally would.

The shop ran the computer and no fault codes are present. Any one can chime in? Car is gonna go in the shop tomorrow again. But I honestly don't think they have a clue on what is wrong. Any advice/suggestions would be greatly appreciated.

Thanks in advance.

Art

Plug or coil pack issue??? Have they checked those... Won't necessarily throw codes if not rite...

It could be a faulty throttle position sensor.
I would run a diagnostic even though they're no codes present. Use an OBD2 scanner with Live data capabilities and read your Short and Long fuel trims so we can see how your car is running : Normal,Rich or Lean. You can also test your TPS using the scanner : at Idle the TPS is usually showing about 5% opening and it should gradually go higher to 100% opening as you're pressing the accelerator pedal towards WOT(Wide Open Throttle).
Also your throttle body might be gunked up and in need of cleaning,just as well as the injectors...
Testing your fuel pressure doesn't hurt either...
A vacuum leak can be responsible for this behavior...
The MAF(Mass Air Flow sensor) is probably the NO1 enemy. Disconnect it and drive the car and if you can't reproduce the problem you've found your culprit. Even the MAF can be tested with the scanner.
There's a few things...but like I said,in order not to go on a wild goose chase,I would check the fuel trims to make sure the mixture is good.


P.S. I should've thought about this : you're not in the US so you probably are not using OBD2...

MAF

Agree that the MAF and TPS (throttle position sensor) are possible culprits. Maybe a bad oxygen sensor or a bad connection to the sensor.

Disconnect the MAF and drive and see what happens...

how old is the gas in the tank?

Thank u all for the inputs. Really appreciate it.


The funny thing is when I started the car and drove it to the shop, the car drove completely normal again. It's killing me...!!!!

The gas tank is the original one from the car. The car is a 2007 997.1 3rs

MAF is very likely, cheap enough online but you can try and clean with IPA.

Check vacuum hoses are connected and not split.

Sounds life maf. Exact same behavior I had coming back from a track weekend. No cel either. Replaced maf- problem solved. Mike

Thanks again for the inputs! Will have shop replace MAF and see what happens!

Update:

After changing out the throttle position sensor, maf sensor, and spark plugs, the car seems to be running fine! But keeping my fingers crossed......

Thanks for the input guys!