Hi all, I'm after a little bit of help, with testing the MAP/IAT.

only recently bought my defender TD5 2003 yr. It needs a fair bit of work, the first thing i've found is that the engine was seriously sluggish, I tested the (MAF) mass air flow sensor, confirmed 12V supply and earth good, but the feedback was only 1Volt at idle and 1.1V when revving the engine, which i had read should be 2V idle rising to 5V with acceleration. Changed it out and she now goes well.... that was easy phew!..

the next issue is that the engine hesitates when accelerating, so before I look any deeper I want to test the (AAP) ambient air pressure sensor, in the air intake housing, but can't find any data on what the feedback Voltage should be at different ambient pressures. I only have a multimeter to test with. I'm assuming that I will see a change in voltage with air temperature, but also a change in voltage between engine idle and revving the engine, due to a change in pressure in the air inlet box as it will be sucking air. Don't suppose anyone has tested one with a multimeter and can offer typical voltage feedback?

the other thing I need to test is the MAP/IAT mass air pressure/inlet air temperature sensor, again can anyone offer typical feedback voltages at idle and revving the engine, based on known ambient temperatures?... I appreciate its not that simple, but this is only way I can test without using a diagnostic tool.

cheers all!

A regular issue which can cause rough running on the Td5 engine is oil in the injector harness, as you probably know it's a common rail system using electrically operated injectors. Pull the red plug out of the ECU and check for oil ingress.
If that's the case, a replacement injector harness will be required and the oil left in the harness between the engine and the ECU will have to be allowed to drain out and then cleaned up; it can take quite a while. Check also the ECU itself to make sure that no oil has worked its way into the case, if so that will have to be cleaned out too. You can use small amounts of solvent such as IPA or brake cleaner to assist in cleaning.

thanks for the advice I will check this out... much appreciated

Worth getting Hawkeye or Nanocomm

I think your right...

i've just tested the sensor in the air filter box, pt. no. MKH100820L, and its working, whether its working correctly is a differant matter... looking on a few sites this sensor is described as the AAP, and with 3 wires, live feed/earth/feedback..... in my haynes manual its called inlet air tempertaure sensor, 4 wire device, which has two feedbacks, pressure and temp... (same as MAP/IAT in inlet manifold).. anyway poppoed it out of teh air filter box lid and cleaned it..... tested with multimeter with ignition on, engine off...
got 5.2V feed
3.7V, feedback on temp (found a chart that reckons this is about 8degC),
0V on pressure
0V on earth.
then tested on idle and got same as above plus, 4.2V feedabck on pressure...

i then moved on to checking the MAP, again 4 wire device, took it out and it was gunged up, so cleaned it, it has temp sensor, and small hole which presumably it pressure sensor... anyway struggled to back probe it to get voltage reading as i was usign a paper clip and couldnt be sure it was actually contacting.... so i put it back in and went for a drive and its no longer hesitaitng when i accelerate... so a good clean seemed to help...

bottom line.... much to the pain in my wallet, i think i need to invest in a hawkeye... i'm also thinking i should strip off the turbo and EGR to check condition and wear...

So did you check the injector loom for oil, or did you just dive into trying to work out what the sensors are saying armed with nothing more than a DVM and a copy of the Haynes book of fairy stories?

only had time for quick look... hopefully get chance ove the weekend to check for any oil through loom... i had planned to test the MAP & AAP with vaccum pump... just to confirm a voltage change against pressure... but i've ordered a hawkeye this afternoon, so will see what it tells me...

cleaning the MAP has made a noticialbe difference.... and the delay has now gone. The plan now is strip the turbo and EGR off and check the wastegate... just to make sure everrthing is clear and free, and seals are good..etc... i will check harness as well.. i see the harness connector is at front of engine, if oil can bleed through loom, does it show oil in the connector?

looking forward to messing about with the hawkeye.. i've ordered from MM 4x4, already had a call from them saying it on back order and will be mid october, to befair they did ring me straight away... decent price from them though, so will wait..

thanks

Take a look at this webpage:-
http://www.discovery2.co.uk/Injector_harness.html
OK, it's a Discovery, but it is a Td5 engine. From it you can see where the oil turns up. It doesn't run down the outside on the wiring harness, it actually runs along the wires inside the insulation by capillary action, so you won't see the oil until you pull the plug on the ECU. Before you go any further, I would suggest that you do check it. You can always play with the new toys at your pleasure later.

Because the ECU is a long way from the cylinder head on a Defender it would take a while for the oil to get there. Best place to check for oil contamination is the multiplug where the loom goes into the cylinder head. At the front, on the driver's side (on a RHD).

i understand its capiliary action down the cores that you were refering to, which is why i was thinking you would see tell tale signs of oil in the wiring loom connectors before the ECU... thanks for advice chaps... sounds like an easy thing to check... so will look at that next

much appreciated

rockjunky said:

only had time for quick look... hopefully get chance ove the weekend to check for any oil through loom... i had planned to test the MAP & AAP with vaccum pump... just to confirm a voltage change against pressure... but i've ordered a hawkeye this afternoon, so will see what it tells me...

cleaning the MAP has made a noticialbe difference.... and the delay has now gone. The plan now is strip the turbo and EGR off and check the wastegate... just to make sure everrthing is clear and free, and seals are good..etc... i will check harness as well.. i see the harness connector is at front of engine, if oil can bleed through loom, does it show oil in the connector?

looking forward to messing about with the hawkeye.. i've ordered from MM 4x4, already had a call from them saying it on back order and will be mid october, to befair they did ring me straight away... decent price from them though, so will wait..

thanks

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I picked up some nuts from there today for my rear ACE ram