Terri49 New Member 4 Member For: 11m 29d Posted 16/01/24 05:22 AM Share Posted 16/01/24 05:22 AM Hey, when I am driving on high speeds my rpm starts to fluctuate especially with incline. In addition I get the cod p0420. Recently I changed the o2 sensors and I also did a service including the air filter, ignition coils, oil filter, fuel filter and valve cover gasket. Does anyone has idea what could cause the engine speed to fluctuate? Link to comment Share on other sites More sharing options...
hjtrbo Bronze Donating Members 320 Member For: 13y 11m 11d Posted 16/01/24 08:58 AM Share Posted 16/01/24 08:58 AM Time to beat the francis flog at his own game... Hey there! It sounds like you've done quite a bit of work on your car already. The fluctuating RPM and the P0420 code can be indicative of a few potential issues. Here are some things to consider: Catalytic Converter: The P0420 code is often related to catalytic converter efficiency. Even though you've changed the O2 sensors, it might be worth checking the condition of the catalytic converter itself. A failing converter can cause RPM fluctuations and trigger this code. Exhaust Leaks: Check for any exhaust leaks, especially near the O2 sensors. Leaks can lead to incorrect sensor readings and impact engine performance. Vacuum Leaks: Vacuum leaks can cause RPM fluctuations. Inspect all vacuum hoses and connections for any cracks or disconnections. Throttle Body and Idle Air Control Valve (IAC): A dirty or malfunctioning throttle body or IAC valve can result in unstable idle speeds. Consider cleaning these components and inspecting for proper functionality. Mass Air Flow (MAF) Sensor: A faulty MAF sensor can affect air-fuel mixture, leading to RPM variations. Ensure the MAF sensor is clean and functioning correctly. Fuel System: Check the fuel injectors for clogs or issues. A fuel system cleaner might be beneficial. Ignition System: While you've addressed ignition coils, also check spark plugs and wires. A weak spark can cause RPM fluctuations. Transmission Issues: If the RPM fluctuations are related to changes in speed and incline, it's worth checking the transmission for any issues. Ensure the fluid is at the correct level and in good condition. Remember to double-check your work to make sure everything is properly installed and tightened. If the issue persists, considering a professional diagnostic scan or seeking advice from a mechanic might be the next step. Good luck, and I hope you find the solution soon! ZF, BTR or manual? And that cat code needs to be addressed 1 Link to comment Share on other sites More sharing options...
Terri49 New Member 4 Member For: 11m 29d Posted 18/01/24 10:57 PM Author Share Posted 18/01/24 10:57 PM My cat is brand new. And because of the fact that I only have those fluctuations when I am in 4th gear or higher it might be the transmission. I have a 6sp automatic one but I don’t know which one. Link to comment Share on other sites More sharing options...
k31th less WHY; more WOT Site Developer 29,072 Member For: 16y 8m 20d Gender: Male Location: Melbourne Posted 18/01/24 11:13 PM Share Posted 18/01/24 11:13 PM There's only one 6sp auto in a falcon/territory and that's the ZF 6HP26. Link to comment Share on other sites More sharing options...
Puffwagon Puff Gold Donating Members 16,000 Member For: 9y 11m 1d Gender: Male Location: South Australia Posted 19/01/24 12:30 AM Share Posted 19/01/24 12:30 AM AWD Territory has ZF 6HP26X Link to comment Share on other sites More sharing options...
k31th less WHY; more WOT Site Developer 29,072 Member For: 16y 8m 20d Gender: Male Location: Melbourne Posted 19/01/24 12:32 AM Share Posted 19/01/24 12:32 AM that's good news glad there's something else out there... Link to comment Share on other sites More sharing options...
Puffwagon Puff Gold Donating Members 16,000 Member For: 9y 11m 1d Gender: Male Location: South Australia Posted 19/01/24 12:43 AM Share Posted 19/01/24 12:43 AM I suppose I should add something useful to the thread other than being a pedantic carnt. You need to log the vehicle to see what it is doing when it's fluctuating. It could be the converter locking and unlocking. Not a lot of point speculating on what or why when the first step is logging/scanning. Link to comment Share on other sites More sharing options...
hjtrbo Bronze Donating Members 320 Member For: 13y 11m 11d Posted 19/01/24 11:42 AM Share Posted 19/01/24 11:42 AM 4th or higher huh. I got $$$ on something... But you know, gotta watch out for the pedantic carnts around here 🙃. ^^^ What puff said. Link to comment Share on other sites More sharing options...
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