Diagnosing MAF sensor wiring

[ninchi]

2001 Defender TD5 10p for reference.

My Nanocom is logging an error related to the airflow circuit. The airflow data shows 4.0 at ignition second position (engine not running), and 0.0 when engine running in all phases.

Testing the MAF connector with a multimeter shows about 200mV when off, and open low when running. This leads me to think it's a fuse/relay/ECU problem rather than the sensor itself.

Tracing the wiring diagram, looks like I have a couple of candidates:

* check ECU connector for oil
* check glow plug relay/fuse which looks like it switches the MAF sensor +ve via header 0294?
* check the EGR wiring and modulator, which carries the +ve from the ECU

It had an EGR delete before I bought it, and I only just got the Nanocom so it's quite possibly had this problem since I bought it.

I am hoping sorting this MAF sensor will help me with my hot-idle smoke problem.

Any suggestions, corrections?

194085

194086

tia

[AK83]

If I recall correctly, the MAF can be 'deleted' on a 10P with egr delete, as that is it's only purpose.

ie. I doubt that the MAF will be causing your hot idle issue.

[shack]

If I recall correctly, the MAF can be 'deleted' on a 10P with egr delete, as that is it's only purpose.

ie. I doubt that the MAF will be causing your hot idle issue.

Correct.

Post up a recording log and I'll take a look.

[ninchi]

Post up a recording log and I'll take a look.

I'll have a crack at that, thanks.

[ninchi]

Post up a recording log and I'll take a look.

@thanks, attached two fairly short recordings. One starting cold, driving until warm, then parking. The second starting warm and driving home.

194243 194244

[shack]

@thanks, attached two fairly short recordings. One starting cold, driving until warm, then parking. The second starting warm and driving home.

194243 194244I'll take a look tomorrow, can you explain your hot idle smoke issue in a bit more detail please?

[ninchi]

can you explain your hot idle smoke issue in a bit more detail please?

Yep. She's a 2001 10p TD5, 302,000km on the original head with an EGR delete before I bought it. Headgasket was replaced (coolant in oil, now fixed) and injectors were serviced (JLR washers and o-rings) about 300,000 km. Been running well since, including a big day 4wding. She holds oil well, loses a bit of coolant (3/4 overflow bottle per tank, local driving) which seems to be through the core plug under the exhaust manifold but only when cold (long trips she loses almost no coolant, but loses a bit every trip with local driving). The heater core was also disconnected from the cooling system when purchased, I haven't investigated why.

The last tank of fuel she has been smoking white/grey diesel-smelling smoke while idling at the lights/carparks, but only while hot (>65c measured by a watchdog on the head). It's usually a noticeable and antisocial puff when I take off, but sometimes a constant puffing. It doesn't do it while cold, and doesn't (noticeably) while cruising.

I recently got a nanocom and that showed me that the MAF sensor was inop, so I was heading down that route as I though it might be throwing fuelling off or into defaults which might be unsuitable for a 25 year old engine. I've had several 10p owners tell me that theirs runs rough with the MAF disconnected. The injector harness was replaced with a sealed one when the injectors were done, but I haven't pulled the ECU connector to check for old oil. I'll do that today.

It could be something as simple as she just needs a decent highway run to clean her out, as this last tank has been all short trips. But if there's anything else noticeable in the logs, much appreciated.

Attached pics of ECU. Cleaned with cotton buds soaked in CRC contact cleaner and reassembled.

194246194247

[shack]

Apologies, ran out of steam for today.

Oil in the ECU plug can certainly cause strange running, if you aren't going into any water you can remove the seal on the plug and that will let the oil drain quicker without having to keep removing the plug.

[shack]

I can't see anything wrong in those logs other than maybe the cylinder balance figures deviating forget from zero than you would like, that could be caused by oil in the ECU plug.

So if it improves when it drains out a bit.

Did you use a good quality replacement injector loom?

I'd suggest the 10p owners telling you the car runs better with the MAF working is wishful thinking.

Maybe try borrowing a good one and see if that makes any difference, or if it actually works as you could have a wiring issue as you stated.

It's pretty normal for them to fail like yours appears to have though.

[ninchi]

Thanks. I took it for a highway and beach run yesterday and it felt better after the ECU clean, I guess time and a bunch of short trips will tell if the smoke is improved. It could even have been a bad tank of fuel, as I refilled before the trip yesterday.

The harness was pre-sealed by M.R. Automotive who have a good reputation so I'd be confident it's fine. They're big on genuine/OEM parts.