limp mode??

[Rickie3]

Yesterday I installed a EGR blanking plate, and I also removed the the MAF sensor and gave it a good spray of carby cleaner and re-fitted, anyway went for a drive and my bus ran sweet as, oh yea its a 2000 GU wagon with the 3Litre direct injection donk, anyway today went down the town and on my way home the engine went into limp mode and crept up the hill, so I backed right off the throttle and hit the throttle again and away she went back to full power, would fitting the blanking plate have anything to do with it going to the limp state? before I actually did the plate ive had a small issue like a flat spot when I put the gas down what causes this flat spot? any help appreciated

[mudski]

If you don't have a dawes valve installed the EGR plate will be causing the issues I reckon. Also carby cleaner is not the best thing for cleaning the maf. Supercheap and the likes actually sell a maf cleaner. Remove the EGR plate and see what happens.

[the evil twin]

EGR faults in a CRD won't trigger limp mode, they just latch the check engine light and store a "P04nn" fault code.

Dunno about the pre '07 ZD30's like yours, but I would have thought it a tad odd. If you had flat spots before it could be throttle/engine sensor related.

Mudski's right tho, you could try taking the block out if it's easy enough (it's a huge PIA in a CRD)

[Mud Gecko]

When you block the EGR it raises the MAF voltage by around 0.2V to 0.4V. This is why you are suddenly getting limp mode, you can either lower your max boost or get a voltage modifier to trick the ecu.

[the evil twin]

When you block the EGR it raises the MAF voltage by around 0.2V to 0.4V. This is why you are suddenly getting limp mode, you can either lower your max boost or get a voltage modifier to trick the ecu.

OKaaaay, I'll bite.
If thats the case, why doesn't everyone need a "voltage modifier" ?

[kevin07]

OKaaaay, I'll bite.
If thats the case, why doesn't everyone need a "voltage modifier" ?

silence I kill you

[the evil twin]

silence I kill you

ROFL... hiya mate,

I'm curious is all. It could be another Di thing that us CRD jock's thankfully don't encounter.

[Covo71]

Hi mate, I have done most of the NADS over the last couple of weeks. When I put plate in a drive around to see what happens it went for a few days and then started to go in to limp. Installed Dawes and needle valve and all is ok again.

[threedogs]

When you block the EGR it raises the MAF voltage by around 0.2V to 0.4V. This is why you are suddenly getting limp mode, you can either lower your max boost or get a voltage modifier to trick the ecu.
I cant see how blocking an exhaust recycling pipe your MAF receives extra volts ??

[Mud Gecko]

I have a Di, according to the Nissan manual, MAF voltage should be 1.6v-2.0v. With a blocked EGR and no modifier, MAF voltage at idle is 2.2v-2.3v. Without my modifier and running 18psi of boost I will get limp mode at 2500rpm and just under 3000rpm @ WOT in 3rd and 4th. Limp mode is a combination of high boost and high MAF voltage. Usually if you go over 3.98v under 3000rpm you'll get limp.

With my modifier, I have tuned my MAFv at idle to 1.7v-1.8v. I no longer have that "fuely" smell at idle and I can tune out limp mode by raising or lowering the MAF voltage around those limp points.

If you don't believe me there is plenty of info on the "other" site, lots of guys doing it now.

[threedogs]

not doubting just needed some clarification, I run 19psi max boost and mine never goes into limp mode.
The longer we have these motors seems the more we find out about them.
Whats a voltage modifier look like out of interest and is it a big mod or fairly simply.
I have my ECU-Talk in view when I drive I'll see what readings the MAF says

[Mud Gecko]

Mate if you don't get limp mode that's great! I wouldn't worry about it then. But for those that do you'll need this-

http://www.jaycar.com.au/productView.asp?ID=KC5490

and this-

http://www.jaycar.com.au/productView.asp?ID=KC5386

and a degree in electronics to put it all together lol

or check out this thread- http://www.patrol4x4.com/forum/zd30-di-engine-3-litre-71/jaycar-digital-voltage-modifier-102192/

[Rickie3]

I just went out and removed the blanking plate and put back in the original gasket, and test drove it has stopped the limp mode issue and appears to be running spot on

[threedogs]

I have a Di, according to the Nissan manual, MAF voltage should be 1.6v-2.0v. With a blocked EGR and no modifier, MAF voltage at idle is 2.2v-2.3v. Without my modifier and running 18psi of boost I will get limp mode at 2500rpm and just under 3000rpm @ WOT in 3rd and 4th. Limp mode is a combination of high boost and high MAF voltage. Usually if you go over 3.98v under 3000rpm you'll get limp.

With my modifier, I have tuned my MAFv at idle to 1.7v-1.8v. I no longer have that "fuely" smell at idle and I can tune out limp mode by raising or lowering the MAF voltage around those limp points.


If you don't believe me there is plenty of info on the "other" site, lots of guys doing it now.

My MAF reads up to 3.9 and a bit driving along normally, with no limp

[BillsGU]

Mate if you don't get limp mode that's great! I wouldn't worry about it then. But for those that do you'll need this-

http://www.jaycar.com.au/productView.asp?ID=KC5490

and this-

http://www.jaycar.com.au/productView.asp?ID=KC5386

and a degree in electronics to put it all together lol

or check out this thread- http://www.patrol4x4.com/forum/zd30-di-engine-3-litre-71/jaycar-digital-voltage-modifier-102192/

Sounds good. Never knew it existed.

[the evil twin]

Well, I bow to popular opinion but something doesn't gel to me.
I think you are effectively detuning the engine by reducing fuel

If a MAF is serviceable and its temperature and airflow output voltages are "in spec" then they are proportional to the airflow.

If you "reduce" the voltage then the ECU is being told "you are getting less air".

Anyway, no biggee. I'm guess I'm lucky mine runs fine with out the need for a modifier

[Lemo79]

Well, I bow to popular opinion but something doesn't gel to me.
I think you are effectively detuning the engine by reducing fuel

If a MAF is serviceable and its temperature and airflow output voltages are "in spec" then they are proportional to the airflow.

If you "reduce" the voltage then the ECU is being told "you are getting less air".

Anyway, no biggee. I'm guess I'm lucky mine runs fine with out the need for a modifier

And I think that is where the problem is, when we block EGR more air is dragged past the MAF increasing the the voltage hence increasing the fuel. Restoring the correct voltage ensures the correct amount of fuel and not an increased amount of fuel.
It would also make wonder though if the ECU has two fuel maps, EGR open and EGR closed. In which case by modifying the voltage it upsets the fuel mapping at times when the EGR is supposed to be closed, eg off idle and not at cruise.

Just my thoughts?

Lemo.

[the evil twin]

And I think that is where the problem is, when we block EGR more air is dragged past the MAF increasing the the voltage hence increasing the fuel. Restoring the correct voltage ensures the correct amount of fuel and not an increased amount of fuel.
It would also make wonder though if the ECU has two fuel maps, EGR open and EGR closed. In which case by modifying the voltage it upsets the fuel mapping at times when the EGR is supposed to be closed, eg off idle and not at cruise.

Just my thoughts?

Lemo.

That is where it doesn't quite work with me as well.
I think it is a hide the symptom versus cure the problem but Pffft, both will stop a limp mode.
I guess it is only needed for MAF's that have a 'higher' output for a given airflow.

I want more air so my ECU and Chip can feed more fuel so I get more herbs.
The MAF sensor is saying you are now getting more air so have more fuel.
I modify the signal to say you are getting less air.
The ECU then takes fuel so I get less grunt.

... and to make it more complicated the EGR valve control is different between the Di and CRD
AFAIK CRD's aren't an "open/close" valve, they are a stepper motor.

Anyway, the OP has a Di so I'll bow out and stop confusing the issue with my CRD gibberish. :clownredpuff:

[BillsGU]

ET - Just kicking around some thoughts. With the ERG unblocked the engine would be getting air from two sources (the normal air intake and the air supplied via the EGR). The ECU would supply fuel proportional to this amount of air. The only metered portion is via the normal air intake, where the MAF senses the amount of fresh air supplied. I would imagine that the ECU would compensate for the air that is also supplied via the EGR.

When the EGR is blocked the ECU would not know that this amount of air is now shut off and the engine would be getting less air than it should have for the amount of fuel supplied. This device would allow the adjustment of the correct air / fuel ratio by making the ECU think there is less air entering the engine than there actually is.

Does this makes sense ...................................... ?

[Mud Gecko]

That is where it doesn't quite work with me as well.
I think it is a hide the symptom versus cure the problem but Pffft, both will stop a limp mode.
I guess it is only needed for MAF's that have a 'higher' output for a given airflow.

I want more air so my ECU and Chip can feed more fuel so I get more herbs.
The MAF sensor is saying you are now getting more air so have more fuel.
I modify the signal to say you are getting less air.
The ECU then takes fuel so I get less grunt.

You are correct. I don't have a chip. I only reduce MAF voltage at idle, above idle I actually increase the voltage thus increasing fuel (sort of a poor mans chip :) ). I only need to reduce the voltage at particular points in the upper rev range when I get limp, it can be a surprisingly small amount that makes all the difference.

If you don't have issues with limp mode then I wouldn't worry about it. It seems these cars each have their own idiosyncrasies...

[Lemo79]

I guess the fact that CRD's monitor flow through the EGR (hence the error code when it's blocked) is what makes them able to compensate the boost correctly and also not hit limp when the EGR is blocked, and would mean their fuel mapping isn't effected by the block. But like ET said that's enough of the gibberish from me as well.

Lemo.

[kevin07]

that is where it doesn't quite work with me as well.
I think it is a hide the symptom versus cure the problem but pffft, both will stop a limp mode.
I guess it is only needed for maf's that have a 'higher' output for a given airflow.

I want more air so my ecu and chip can feed more fuel so i get more herbs.
The maf sensor is saying you are now getting more air so have more fuel.
I modify the signal to say you are getting less air.
The ecu then takes fuel so i get less grunt.

... And to make it more complicated the egr valve control is different between the di and crd
afaik crd's aren't an "open/close" valve, they are a stepper motor.

Anyway, the op has a di so i'll bow out and stop confusing the issue with my crd gibberish. :clownredpuff:
now silence i kill you

[Rickie3]

I went for a 100 k drive and about 80 k in my bus started experiencing limp mode again, back off the throttle completely and gas back on again it comes right for a bit then goes back to limp, should I have disconnected the battery when I took the blanking out and put the original gasket back in?

[Mud Gecko]

Do you have pyro/boost gauges?

[Rickie3]

No not at present

[Mud Gecko]

Hard to say what happening mate. Is it happening under power or cruising? Do you have dawes/needle valve?

[threedogs]

they say disconnecting the battery for 20min or more will re set the ECU

[Rickie3]

No Dawes valve as I've put engine back to stock, it does it when cruising at 100kmh, I had no issues until I cleaned the maf

[threedogs]

so cruising at 100 it just goes into limp mode for no reason. I say cruising to

[Mud Gecko]

I know its a pain mate but get NADs done, you'll kick yourself for not doing it sooner. Makes the ZD drive heaps better.

[Rickie3]

Yes limp for no reason, NADs? What's that? I've been kicked in mine a few times over the years

[Mud Gecko]

Nissan Anti Detonation System. Boost/EGT gauge, Dawes/Needle valve, EGR plate and a catchcan. Could also include ECUtalk, glowplug timer and a MAF voltage modifier.

If you know someone with the same model Nissan you could swap MAFs to see if that's what is causing your limp mode.

[threedogs]

as above you take the thinking away from the ECU by installing a manual boost controller.
You can monitor any changes by looking at your boost and EGT gauges,
I must do Mod for any Di ZD30, and Cr for that matter