Maf diagnosis. Zd30.

[Cobblers_uk]

Hello all i waS wondering if i could get some help. Ive had my terrano since last august and been on yhe road with no issues since october. Done about 6000 miles without any trouble yet it picks the week im on holiday in cornwall to get issues.

I first noticed the issue after stopping at the services on the way down to cornwall after about 150 mile.

Pulling out from the services i had a lack of power. I had to get the revs up over 1500 or so to even pull away without major bog down.

So far with the limited tools i brought ive checked air pipe leaks intercooler looks ok but bypassed and made no difference.

On going through the maf tests in the service manual. The voltage from the data cable on the maf should be 1.6 to 2v. The reading is 2.25 so a little high. Also on testing continuity from the maf plug ground to the engine ground resistance seems high. In the 200k scale im getting a reading of 14 where if i touch the probes i get a readi g of .2. Has anyone got experience of testing rhr maf or had simerlar reading to this while testing one. Thanks for any advice

 

[Cobblers_uk]

Ive managed to get into the ecu now. Ive finished the tests in the manual. The high resistance reading i got earlier was down to a bad connection where i had my meter the maf ground is fine. The last test requires access to the ecm plug so you can test the ouput voltage from the maf. In the manual it says the voltage should be between 1.6v and 2v at idle increasing to approx 4v at 4000 rpm. The manual says the voltage increase should be linear with rpm.

My result was 2.25v at idle going up liner to 3.98v at 3000 rpm then steadily dropping back to 3.48v by 4000 rpm.

The manual says that the maf needs replacing.

Going off my symptoms though im still not convinced.

The voltage is slighty high at tickover so presumably the car would be over fueling but it really has no low down power.

Is there anyway i can trick the turbo into giving full boost all the time? Ive never worked on anything with a variable turbo on it before. I dont have a boost gauge here but it feels like it has no boost and it even sounds louder more like a naturally aspirated than a turbo diesel.

 

[Thomas61]

Hi,
Can't offer much I am afraid except a good luck.

However I am sure I read about one member on here who had power loss and it ended up being a leaf of all things stuck against the maf grill. Maybe as it had been running well before you stopped it could be something as simple as that especially with motorway speeds blowing things around the engine bay.

Take care.

 

[solarman216]

Hi, you seem to have the test gear and know how to use it, Rayf is your man for this as he is not only an electrical engineer but owns a 3lt as well and is well up on it, I have only had one 3 in for work so am not so well up on its idiosyncrasies (would never have got that without the spell checker) however I do have to wonder why it only started playing up after a stop, did you let it idle for a couple of mins before shutting down? if not your turbo may have suffered some heat damage, did you get fuel at the stop? I would not have suspected the Maff at that stage, has it ever been run on anything but Derv? Rick

 

[Cobblers_uk]

No only ever run on diesel that i know of. starting to make a little progress now though i think. Ive ruled out turbo issue now. After checking the output from the boost sensor the voltage is rising with the rpm like it should.

I did notice that the eml light had not come on even though id unplugged thr maf and the boost sensor for test runs.

I turned the ignition on and noticed that my eml light wasnt doin its bulb test. I removed and stripped the clocks and found the leg on the led had been cut.

I didnt have a soldering iron with me but i managed to bodge by trapping the leg and bending the cut off bit over it.

I have read the codes and got 6 i all.

0403 0707 0102 0703 0905 1405.

The maf boost sensor and nats faults i can explain from work ive been doing but the 2 injector pump faults would be what im interested in. Ive cleared the faults for now and ill take it for a drive in a bit see what comes back.

 

[Cobblers_uk]

Ok so the new code i got after clearing is 0707. According to the manual this is either a wiring fault or a pump failure. Its looks like the pumps cost a small fortune so i really hope its just a wiring issue. Has anyone else seen any pump failures on these pumps?

There is people selling transistors on ebay to repair them bust thats just if they are non starters not for power or running issues.

 

[rayf3262]

The IP pulls quite high transient current when adjusting the fueling.
If there are any unsound connections that could limit the peak current available to operate the control sleeve, the IP it will likely throw the code you have.

Check all of the ground connections first, the principal being on top of the O/S inner wing behind the coolant expansion tank, then there are some attached to aluminium engine parts that corrode too.
Don't forget the crimps on the battery connection clamps these can look ok but frequently exhibit higher than desirable resistance.
Then start looking at the IP connector connectors for any signs of corrosion etc...

BTW your maf voltages are not ideal, esp. dropping off at 4K. However I suspect that is not the root cause although probably warrants later attention.

Here's the MAF o/p from my ZD30:http://www.nissan4x4ownersclub.com/forum/showpost.php?p=143546&postcount=79

 

[Cobblers_uk]

Ok thanks for all the advise. Ive done some more tests. The power supply looks good. There is .1v drop from battery voltage while under load. So 14.04v at the battery and 13.92v at the pump connector. I pulled all the connectors and checked they all look clean. I tested and cleaned all the ground points. I also checked continuity of the wiring between the pump connector and the ecm.

After checking the referance voltages from the manual i found one big issue. Wire 33 40 and 52 were all pretty much spot on but wire 53 should be .35v while idling but is 1.15v. I would imagine this is where my issue is coming from the maunal says this is the dzg line but its not clear what this is responsible for.

I may have to bypass the loom first with a new cable from the connector straight to the ecm to rule out a short. Does anyone else have any ideas on what could cause this? Cheers

 

[Cobblers_uk]

So i just downloaded the service manual for the vp44 and ive found that the dzg is the input for the crankshaft speed sensor to the diesel pump not a output from the pump itself maybe this is where my fault lies.

 

[rayf3262]

After checking the referance voltages from the manual i found one big issue. Wire 33 40 and 52 were all pretty much spot on but wire 53 should be .35v while idling but is 1.15v. I would imagine this is where my issue is coming from the maunal says this is the dzg line but its not clear what this is responsible for.

I may have to bypass the loom first with a new cable from the connector straight to the ecm to rule out a short. Does anyone else have any ideas on what could cause this? Cheers

Just saw this on page 75 of the EC manual:
You have 1.15V, so that would appear to be correct.. Where did you see .35V?

 

[Cobblers_uk]

Just saw this on page 75 of the EC manual:
You have 1.15V, so that would appear to be correct.. Where did you see .35V?

I saw this on this list here in the service manual.

 

[Cobblers_uk]

Page 193 of 454 ec in service manual.

 

[Cobblers_uk]

Well i got back off my holiday at the weekend and ive managed to fix the problem although im not 100% sure exactly what caused it. Before i left cornwall i changed the oil and filter and the diesel filter but that made no difference.

When i got home i stripped it some more. I took the rocker cover off and checked the spill pipe for leaks i dryed around the unions and put about 30psi of pressure on the pipe for about a hour but there was no leak. I did notice that the rubber pipe that goes between the head and the ip inlet would easily slide back and too even with the hose clips on so i changed the clips on this

I removed the turbo inlet the turbo looks in good condition and span freely with no play.

I removed the electronic module from the diesel pump and took the cover off but there was no obvious issue so i re installed it.

The throttlebody was removed and cleaned out and i noticed some rub marks on thr vacuum pipes to both the swirl flap and the throttle flap so i shortened them and reconnected.

Once i put it all back together the code cleared and didnt come back the engine is nice and quiet any and it pulls really strong it seems better than its ever been.

Sorry i doesnt really help anyone who gets the issue in the future i would say the most likely problem was the rubber pipes to the swirl flap and throttle flap. it made it sound like a old n/a landrover really loud under load and really gutless. In happy its all sorted now thanks for all the help.

 

[terranosaurusdoug]

Interesting, I will remember this if I ever get a simular problem, cheers :thumb2

 

[Blocky10]

Well done. Glad its running ok now and must say, impressed you managed to do so much faultfinding when on hols! :bow
Another thread for me to bookmark.

Ian

 

[solarman216]

I did notice that the rubber pipe that goes between the head and the ip inlet would easily slide back and too even with the hose clips on so i changed the clips on this
.

If this is the feed to the injector pump I would suggest this was your problem as it could have been drawing air, Rick