Requesting a helping hand in determining an acceleration problem. I suspect the problem is either the acceleration pedal or throttle body.

Problem: When the engine is warm and the car is at a complete stop, it takes approximately 1/3 throttle to get the car moving; moving at granny acceleration speed. After a couple of seconds the engine responds with acceptable, but less than normal, acceleration. When the engine is cold (running for less than 5 minutes) throttle response is normal and acceleration is good.

Observation: With the engine warm, stationary, and in park, slightly pressing on the acceleration pedal results in increasing RPM, but the increased RPM tends to creep-up well after the pedal remains in the newly fixed position. Example: engine at 1,000 RPM; press and hold throttle, engine speeds to 1,500 RPM then slowly creeps to 2,500 RPM and the holds at 2,500 RPM.

I did follow directions for resetting the ECU. It did not help. Age of the fuel filter is unknown. It needs to be replaced as the car sat unused for a couple of years before I purchased it.

Vehicle is an early 2004.

 

You need to perform the Throttle body reset correctly . . . List of resettable Crossfire features - CrossfireForum - The Chrysler Crossfire and SRT6 Resource

Daniel

 

I think not, look for a code that has been set. Why waste time guessing?

 

I think some realistic diagnostics are in order here. The ECU and other modules in these cars simply do not respond well to filthy or low voltage. I'd be cleaning the battery posts, battery cable clamps, etc.
I'd be considering a new battery. (Any who says, "Have the battery tested" should be ignored).

I'd then measure the fuel rail pressure, in fact, I think I'd do that first - there is no reason to be guessing about the pump or filter when it's as easy to measure fuel pressure as it is tire pressure. The engine has NO SENSOR to tell the ECU what the fuel pressure is, pressure is assumed and if it is too high or too low, the ECU has little to detect that with, other than the O2 sensors.

I'd wonder about the throttle body as well, but fuel pressure is vital and is very easy to measure.

 

Thanks for the replies and assist, it is much appreciated.

Throttle body reset: I did this twice before starting this thread. Once with the key in the off position and once with the key removed. Now I have done it two more times. I have also plugged-in an OBD2 scan tool. The scan tool is set to display throttle opening as a percentage.

Today’s road test: Ran the throttle reset procedure prior to the test. The car ran fantastic for 15 minutes and the OBD2 scan tool showed expected throttle position percentages after a few minutes of driving. Around 15 minutes into the drive, throttle response became sluggish. The scan tool readout confirmed that throttle position was responding sluggishly to throttle pedal input. Pulled to the side of the road and re-ran the throttle reset procedure. Once again the car ran fantastic.

Fuel pressure: The scan tool was not reporting fuel pressure. Pizzaguy, thank you for stating there is no fuel pressure sensor. This saved me time and trouble with locating and testing a non existent sensor. Got my fuel pressure testing tool out. It is for old-school carburetors. Time to upgrade the tool collection.

Electrical: Looks like I’ll be spending time in this area. The car and battery sat for two years. When I saw the car the battery was dead and had been dead for an extended time; it probably suffers from sulfation. The electrical system is probably accurately described by the statement “…filthy or low voltage.”

 

Let’s close this. The issue has been resolved. A new battery did not correct the problem. The CEL did come on. The code was P0123. A new throttle pedal was ordered and installed. Since the installation of the new pedal there have been no throttle related problems.

The pedal is Mercedes, for a 2003 SLK 320. Part number 170-300-02-04.

Again, thanks for the assist.

 

Thanks for posting back about your solution. Wish everyone would do that!


.

 

I would like to add, thanks for posting the part number as that is really helpful and a great time saver for me.

 

My XF have this intermitent problem but it never ever coded . It happened only one time in the 4,900 KM i did to date in 2021 and still no code . Each time all i have to do is a throttle reset and the problem go away This intermitent problem have been present since I bought this car in November 2012. I did the 74mm Throttle body upgrade on my NA many years ago and the problem did follow with no change .

No code = hard to diagnostic most of the time . . . and some time all their is to do is wait fot the problem to become permanent .

For now, I live with it as a part of her personality

Daniel

 

Interesting... I had this same issue last weekend... but only after i played with the traction control button.... no throttle response... shut the car off...restarted it.... all seemed well...

 

I have the same issue. I guess I don't understand on a throttle peddle could cause the problem. Could you please elaborate?
Thank you very much
Randy

 

The throttle pedal is electronic, no throttle cable just wires.

 

Onehundred80 is right. Similar to a volume **** on a radio. Turn it one way and the radio volume goes up, the other way and volume goes down. No cable, just wires and electrical magic.

 

Thank you for explaining this to me. I didn't realize the throttle control was electronic. I appreciate you guys.
Randy

 

Changed out the throttle pedal and it's working fairly well. The only thing I am noticing is my Crossfire feels like it wants to stall after stopping when I start to take off.

 

Acting like it may stall when coming to a stop and when starting to take off may be the Mass Air Flow sensor (MAF). My suggestion is to check wiring leading to it and especially the connector for corrosion. Cleaning the MAF sensor may also help. Note: check at the auto parts store for the correct cleaner to use.

 

Thanks.... I will check it out on Monday.
Randy

 

Thanks for the solution to my stalling when coming to a stop. I had changed out the throttle pedal and thought that fixed my issues. I ended up buying some CRC products and cleaned the throttle body and the air sensor. It totally solved my issues. My Crossfire runs so smooth now and I have noticed an uptick in my performance and gas mileage. Thanks for all the great suggestions and help.