MAF erratic readings

Hey GRAEME PARKER-WILLIAMS,

Are you experiencing a fluctuating idle also? If it is hunting at idle, ie the engine revs are fluctuating i would advise first checking for intake leaks.

Here is a guide in the link below that will run you through the process:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

I would also advise cleaning your MAF sensor, here is another guide for this process:

https://www.2carpros.com/articles/mass-air-flow-service

Let us know is you have any further questions and what you find after either of these processes.

Regards, Joe

Hey GRAEME PARKER-WILLIAMS,

What scan tool are you using to check the MAF reading?

Just to rule out an issue with the live data you are getting with the scan tool I would say try and borrow another scan tool to check against to verify.

With the readings you are getting you should be experiencing an unstable idle.

If it checks out then the next step would be to check for air leaks as in the guide in my previous message.

Regards, Joe

Hey GRAEME PARKER-WILLIAMS,

Please do try a different scan tool and let us know.

If you can access a vacuum gauge I would advise checking what readings you get. Does the needle on the vacuum gauge fluctuate?

Also what are you getting from the MAP sensor live date, does this also fluctuate?

Regards, Joe

Hey GRAEME PARKER-WILLIAMS,

Just to rule is out have you checked you intake for obvious damage/restriction?

Follow all of the intake pipe work and check for anything loose or damaged.

Checked the engine air filter?

I would also check the entire air intake for signs of oil leaks. An oil leak around the air intake system can point to a boost leak.

Regards, Joe

Hey GRAEME PARKER-WILLIAMS,

Can you please remove and clean the MAP sensor?

I do not have the information for your specific vehicle but a quick search online should show you the position on the intake.

It is likely that oil residue has clogged the transducer on the MAP and is causing it to not respond to the changes in pressure.

Let us know what you find.

Regards, Joe

Hey GRAEME PARKER-WILLIAMS,

This points to a potential blockage in the DPF. It could also be an issue with EGR valve sticking.

Can you please unplug the EGR valve and see if the MAF readings even out?

Regards, Joe

Hey GRAEME PARKER-WILLIAMS,

I would advise removal and cleaning of the EGR valve.

The EGR being stuck open slightly could be causing the fluctuations in the intake that you are seeing.

Let us know what you find.

Regards, Joe

Hey GRAEME PARKER-WILLIAMS,

Perfect, let us know what you find there.

If you could send us a picture of the condition of your EGR valve that would be great.

You do not need to do a reset after replacing the MAF.

Resetting the long term fuel trim will make it quicker for the relearn to happen but it is not necessary.

Deleting the fault codes is a good idea so you can retest to ensure the fault is clear.

Regards, Joe

Hey GRAEME PARKER-WILLIAMS,

If you clear down the fault codes and drive it do you now have any codes present?

Can you get any data for the soot loading of the DPF on your scanner?

How does the vehicle drive now? Are you still experiencing a lack of power?

What is the general use of this vehicle ie. Is it mainly used for short journeys?
Shorter journeys will increase the speed at which the DPF fills with soot.
If it is trying to regenerate it may be pointing to the DPF being loaded.
You may be able to force a regeneration if your scanner has the function or driving the vehicle on longer highway journeys may give it enough time to regenerate.

Regards, Joe

Hey GRAEME PARKER-WILLIAMS,

Please do keep us updated with the information from a different scan tool.

If you have a lack of power and the DPF is attempting to regenerate that often it sounds like the DPF being clogged due to the short drive cycles may be the problem.

Ash accumulates in the DPF if driven on short journeys too often and it can decrease the life of the DPF. Really a diesel vehicle with a DPF should only be used if it will do regular long trips. That or more regular DPF regeneration will be necessary.

Can you force a regeneration using you scan tool?

How dirty was the MAP sensor when you removed it?

Another problem with modern vehicles with DPF's running a lot of EGR to reduce emissions can be coking up of the intake. Especially on vehicles driving shorter journeys.
You generally would see alot of build up when you removed the EGR valve in these cases.

Your vehicle also may have a variable intake or fitted with swirl flaps.
It is not uncommon for the actuators on these to fail on if they are vacuum actuated vacuum pipes leaking. Excessive carbon build up can also cause the flaps to stick.

Again sorry I do not have the specifics for your vehicle but I would advise ensuring the actuator for the swirl flaps/intake works correctly if fitted.

Regards, Joe