The Nissan Path

Hey guys,

I have a 2004 R50 VQ35DE engine, and I'm having an issue that is driving me totally crazy and I don't know what else to do... issue is: very slight/minor hesitation/misfire at idle...

Conditions of the issue: can happen when the car is cold or hot (doesn't matter), sometimes is more noticeable than others... it only happens at idle.. car behaves perfectly under any other condition... no change on fuel consumption or power loss...no check engine or stored codes... no recent changes to the car... the issue happened after a long trip (around 180 miles). When we arrived to the destination, I started to notice that... before that everything was perfect... engine has only 86.000 miles since new (very low mileage and no abuse of the car).

Since the issue appeared a couple of months ago, the following maintenance/changes have been done to the car trying to solve the issue:


- Oil change (Mobil 1 5w30 fully synthetic)
- New OEM oil filter
- New OEM air filter
- New spark plugs (OEM PLFR5A-11)
- New ignition coils (all 6 of them)
- New crank sensor
- New MAF sensor
- Complete cleanup of intake manifold, including testing and cleanup of injectors
- PCV valve replacement
- Idle re-learn procedure
- New OEM fuel filter

Again, car works perfectly fine under any circumstance except idle. No vacuum leaks (reading is steady at 18 inHG). Emissions test passed succesfully. No smoke. Alternator working as expected (6 months old battery)

I'm out of ideas on what else to do to solve the issue and I'm really getting frustrated as none of the changes have helped or making the issue worse, and the ECU doesn't seem to be worried about it (no CEL).

Anyone with a similar issue/experience? Any suggestion or input?

Thanks in advance and sorry about the long post...

Regards,

Luis

It would be helpful to get a scantool look at the fuel trim and MAS input. You could try cleaning the MAS hotwire. Camshaft position sensors can sometimes become faulty and not always throw a code, but I'd hate to see you spend more money replace them and not have it fix the problem. Viewing the spark patterns on an oscilloscope would also be helpful, of course, most DIY'ers don't usually have access to that kind of equipment. You could also try cleaning up the EGI grounds, which wouldn't cost anything. On the VQ40DE, they are on the front timing cover on the driver's side, but I'm not sure if they are in the same place on the VQ35DE? There would be two 10MM head bolts with a number of black wires going to them.

smj999smj wrote:It would be helpful to get a scantool look at the fuel trim and MAS input. You could try cleaning the MAS hotwire. Camshaft position sensors can sometimes become faulty and not always throw a code, but I'd hate to see you spend more money replace them and not have it fix the problem. Viewing the spark patterns on an oscilloscope would also be helpful, of course, most DIY'ers don't usually have access to that kind of equipment. You could also try cleaning up the EGI grounds, which wouldn't cost anything. On the VQ40DE, they are on the front timing cover on the driver's side, but I'm not sure if they are in the same place on the VQ35DE? There would be two 10MM head bolts with a number of black wires going to them.

Thanks for the quick reply... I'll take a look at the grounds.... and yes, although I also hate to waste money without any certainty, given the circumstances, I think at this point in time, I can risk a bit and replace the cam sensors and see if that helps at all...

Stick with genuine Nissan, Hitachi, NTK or Denso sensors. Some of the other brands are a bit hit and miss.

smj999smj wrote:Stick with genuine Nissan, Hitachi, NTK or Denso sensors. Some of the other brands are a bit hit and miss.

Noted on that!!!

Quick Update:

Checked the grounds and even added a ground kit... unfortunately, issue remains the same...

On the other hand with the additional grounds a feel a faster and stronger start and better throttle response...

I also took out the o2 sensors, cleaned them up but made no difference on the issue...


Up next: will replace the cam sensors.. I actually took them out to clean them... they didn't look that bad but will give it a try...

Will keep you posted....

I remember i had a brand new '04 Z in the past.

It had a slight stumble at idle.
A lean misfire as it were.

Dealer said it was normal.
Seems a lot of VQ35des of the time have it.

Was a healthy car that later made 370/411 hp at the wheels with an aftermarket supercharger ( depending on the pulley)

Yes, the VQ40DE is the same way; they always idle a little rough. It's built-in at the factory!

Hehe well.. my internal DIY refuses to accept this LOL...

While I wait for the cam sensors to arrive home... do you guys think the VVL solenoids can somehow be the culprit on this case?

I couldn't really say without actually experiencing what the vehicle is doing for myself. Typically, when there is an issue with the variable timing, a code will trigger.

It seems like you are spending a lot of money on an issue that just might not be one...

palmerwmd wrote:It seems like you are spending a lot of money on an issue that just might not be one...

There's got to be something wrong... how could you explain that during 15 years (86.000 miles) car behaved correctly and all of a sudden, this starts happening? There's got to be something wrong causing this!

r50pathcr wrote:

palmerwmd wrote:It seems like you are spending a lot of money on an issue that just might not be one...

There's got to be something wrong... how could you explain that during 15 years (86.000 miles) car behaved correctly and all of a sudden, this starts happening? There's got to be something wrong causing this!

Well with that history thats something else. I had a VQ35 that did have a slight stumble/misfire literally off the showroom floor.

You already hit all the usual suspect (and so probably saved yourself a lot of future breakdowns)

Ok so... sad update on this topic...

New cam sensors didn't fix the issue....

So at this point I'm totally out of ideas... nothing seems to solve the issue...

I'm literally willing to pay for solutions!!!! Don't know what else to do

Well, Im not an expert but another area to check is

If you always put gas in the same gas station, try another one. They could have a problem in their tanks or filters and maybe the gas has a poor quality there.

or your intank fuel pump filter its clogged and its having problem maintining gas pressure.