Rattling exhaust - not SCV

Hi all

I have a funny issue with my exhaust. It basically rattles in cycles. The idle runs smooth for a while, let's say 30 seconds, and then the exhaust starts rattling heavily and half the car shakes. It is definitely noticeable from inside the car.

Not sure if I can call this a rough idle...either way it is definitely not the SCV as I changed this one a while ago, replaced it with a brand new one.

Any thoughts? I have a 2007 Spanish D40 diesel.

Dr. OzLov

It's really difficult to come up with an easy answer for this.

How's the EGR? Does it still flow?

Is the MAFS clean?

If you remove the PCV from the intake (remember to block the connection to the intake before starting the car) do you get smoke, or lots of flow, out of the PCV hose at idle?

ok, here we go

EGR blocked with a tiny hole in the middle, just so it does not stuff up any sensors or the ECU.

MAFs was cleaned several times, the issue still persisted.

Two weekends ago fitted an oil catch can following your advice but that hasn't improved that issue either. I will check that with PCV over the next few days.

Cheers!

2007 definitely does not a need a hole in the EGR..

Have you done an idle relearn (or even pulled the battery terminals off, press the brake a few times then reconnect - it will do the same thing)

checked all fuel connections are tight from your filter to your SCV?

Ditto on the EGR hole. No flow sensor = no need to fool the system, it can be blanked off completely.

Any amount of EGR at idle will affect the idle performance. Idle literally means "about as slow as the engine can go without making it stagger or stall". For a 4-cylinder 4-stroke motor that's around the 750rpm mark. If you're getting EGR in there at all, the level of available oxygen diminishes and that compromises the combustion.

It is possible that your EGR valve is jammed, or is intermittently jamming in the open position causing this problem. Fully blocking the EGR will rectify that. Don't replace the EGR valve unless the electronics in the valve fail (because that will not only throw a CEL, it might result in limp mode).

This may not be the problem - as I said at the start, this is a weird one. It could be electrical - but let's deal with the more obvious (and still inexpensive/free) things first.

Thanks gents.

So to clarify:
- check the hoses from filter to scv
- block EGR completely
- report back with results

Correct?

Also - Do an ECU reset.. This will relearn the pump too.

Only time my idled rough / idle hunt was when the SCV had shit itself.

Even run some DIESEL PURGE through it.. This smoothed out my idle and injectors.

Sorry forgot to mention, yes I did reset the ECU several times...was changing my clock spring.

And I regularly use Liqui Moly. So all done.

I know what you are talking about re SCV....my one is not even 6 months old...this current rough idle is different from the one my old SCV was causing.

OK. Do you have any other "symptoms"? Down on power? sluggish? high fuel usage?

To idle, an ICE needs Fuel and Air. If your o2 sensors are screwy, then they could be feeding back wrong AFR and the ECU pulling fuel and making it idle rougher. Especially as it's not instant, but 30 seconds or so sat idle. So, check for an exhaust leak around the O2 sensors in the exhaust. Make sure your exhaust flanges are nice and tight.

I've had replace my 02 sensor - but they are not really a common fail item. I think the previous owner was at fault for that one. But, they are only a sensor - and will fail.

Just another option.

^ quite uncommon for them to fail but yes, fail they can. I'm not sure what the "wait" time before the ECU tries to self-test the HO2S is either. It could be 30 seconds, the manual isn't specific on that.

Intermittent problems are usually electrical in nature. Since there's been work done on and around the fuel/air system it's an obvious first place to look, but also consider cleaning the primary vehicle connections (battery terminals and connections to starter/engine body plus ECU earth) and checking that the battery is still holding enough charge.

Brand new battery gents!

It's not really intermittent, is it? If he lets the car idle for 30 seconds or more, it goes into a rough and ready idle state.

That to me says "sensor" more than earth fault.

Do the Nissans go into OPEN LOOP mode when accelerating, and then back to closed loop for idle (OPEN LOOP = no use of O2 sensor.. Closed Loop = o2 sensor used for all fueling except WOT) or are they in CLOSED LOOP all the time (except for initial startup)

Experiment. Pull the Throttlebody intake piping off (the rubber that comes from the output of the intercooler) and just let it idle with at Atmosphere. See if there is any change to it's idle state.

Hello everyone
DroZlov did you solve the idle problem with your nav?
Mine is 2008 year with 150.000klms on the clock and i have exactly the same symptoms as yours!
Changed scv but the idle got just a little better.
Also my nav doesn't have much pulling power when loaded or when i try to start stopped on a hill.
When i turn the lights on the idle problem is worse and window switch down even worse ,
Does yours does this or its the same with lights on and window switch down?
Anyone any idea why this might be happening no code no nothing
Struggling with this problem almost 8months now
Thanks in advance and sorry for my english not my native language

Greetings!, I'd check/clean all earth points particularly the ecu and also the condition of the battery and both the terminals. No need to be embarrased about your english either it's actually very good.

Thanks for your quick reply
I have reseted ecu several times including hard reset by disconnecting the battery
And the battery itself is in top condition same goes for the poles
I just ordered some liqui moly purge as i suspect that the problem might be from the injectors but i got no black smoke either which as i read is one of the main symptoms if you have a dirty or faulty injector

DrOzLov said:

Brand new battery gents!

Click to expand...

Appears to be the fix.

kouloutouros said:

Thanks for your quick reply
I have reseted ecu several times including hard reset by disconnecting the battery
And the battery itself is in top condition same goes for the poles
I just ordered some liqui moly purge as i suspect that the problem might be from the injectors but i got no black smoke either which as i read is one of the main symptoms if you have a dirty or faulty injector

Click to expand...

Everyone should use Liquid Moly it is very good indeed. I'd still check all your earths, it does sound more of an electrical issue but the YD25 is always full of suprises.

happy john said:

..... but the YD25 is always full of suprises.

Click to expand...

Never a truer word written

A lack of power could point squarely at the turbocharger too. The control solenoid (attached to the intercooler's intake), any of the hosing, the actuator, the vac pump, the brake booster (vac loss = poor brakes = lack of control of turbocharger too) - all of these can prevent the turbocharger being controlled correctly.

Also consider cleaning the throttle body and if you can get your hands on the machine that does it, the intake manifold's innards too.

Old.Tony said:

A lack of power could point squarely at the turbocharger too. The control solenoid (attached to the intercooler's intake), any of the hosing, the actuator, the vac pump, the brake booster (vac loss = poor brakes = lack of control of turbocharger too) - all of these can prevent the turbocharger being controlled correctly.

Also consider cleaning the throttle body and if you can get your hands on the machine that does it, the intake manifold's innards too.

Click to expand...

My friend old tony
the lack of power is only when i start the car from a stop or when i drive with very low speed and rpm and it comes with a bit of a rattling which i think is from the injectors or when it is loaded it lacks of pulling power(only from a stop).
At high rpm -over 2500- the car drives great with plenty of power
Can it be the injector on the first cylinder as i think that the first cylinder is responsible for the pulling power of the car?
Is it possible to have an injector problem without an error code?
For the record egr is blanked and maf is clean and intake manifold clean as well