G35 idle issue

[mb32]

The idle on my '06 G35 has been uneven. While stopped at a traffic light I can feel the idle stumble briefly before smoothing out. The other day while starting the car after it had been sitting outside at work all day, the idle was surging up and down for a few seconds before it eventually stabilized.

I've read that cleaning the throttle body and MAF will help, but I am leery of touching the throttle body and causing more issues. I've found the manual relearn process but it sounds finicky to get right. Is it possible to clean without having to do an idle relearn?

 

[slacktide_bitog]

CRC has an awesome MAF cleaner that works great!

Try spraying teh MAF with the CRC stuff first

 

[The Critic]

If the throttle bodies are that dirty, there is no chance that you will be able to complete a cleaning without having to perform a relearn.

The 03-06s can be quite problematic when it comes to relearning the idle. We have had to replace throttle bodies, update software and even replace ECMs.

The only advice I can give is to clean them as little as possible and do not wipe off the "paste" that is on the edge of the throttle plate. You will see what I mean when you go to clean the throttle bodies.

Good luck.

 

[mb32]

Originally Posted by The Critic
If the throttle bodies are that dirty, there is no chance that you will be able to complete a cleaning without having to perform a relearn.

The 03-06s can be quite problematic when it comes to relearning the idle. We have had to replace throttle bodies, update software and even replace ECMs.

The only advice I can give is to clean them as little as possible and do not wipe off the "paste" that is on the edge of the throttle plate. You will see what I mean when you go to clean the throttle bodies.

Good luck.


Yikes, that is no good. I'm guessing a new throttle body is $$$.

I'm going to spray the throttle plate and not move the plate at all. Hopefully the throttle cleaner will dissolve the buildup without issue.

Am I safe to clean the MAF separately with MAF cleaner?

 

[CBR.worm]

Is there any pattern to the stumble - ie, every 25-30 seconds it drops for a moment and then recovers? Is there ever any excessive gas smell in the cabin? Both with no CEL or recorded codes?

 

[mb32]

Originally Posted by CBR.worm
Is there any pattern to the stumble - ie, every 25-30 seconds it drops for a moment and then recovers? Is there ever any excessive gas smell in the cabin? Both with no CEL or recorded codes?


No CEL. Have not yet scanned for codes.

The car will stumble every 15-20 seconds while idling. You can definitely feel it as the car shakes momentarily.

 

[mb32]

I went ahead and cleaned the throttle plate and MAF sensor.

I sprayed around the throttle plate several times but did not touch or move the plate. The car is noticeably more responsive and the transmission kicks down without hesitation.

However, at idle, I am still getting the occasional stumble. A new throttle assembly is about $250 CAD (Hitachi). I don't really want to go that route unless I really have to, but I also don't want to have a bunch of hassle and drivability issues if I clean the throttle plate more extensively.

 

[WhizkidTN]

Originally Posted by mb32
I went ahead and cleaned the throttle plate and MAF sensor.

I sprayed around the throttle plate several times but did not touch or move the plate. The car is noticeably more responsive and the transmission kicks down without hesitation.

However, at idle, I am still getting the occasional stumble. A new throttle assembly is about $250 CAD (Hitachi). I don't really want to go that route unless I really have to, but I also don't want to have a bunch of hassle and drivability issues if I clean the throttle plate more extensively.


Assuming your plugs are fine as well as your plug wires/coils, I would move the throttle plate open and with a shop rag (not a paper towel) soaked in Throttle Body cleaner, clean the back side, both edges and throat of the throttle body as far as you can go. This normally takes several times to get it really clean. Next up, I would put a bottle of Red Line SI-1 fuel system cleaner in a full tank of Top Tier gas (Shell/Exxon/Costco) and where possible over the driving range of the full tank, get on it (i.e., "The Italian Tune-up"). Doing the above has worked wonders for me in the past on various cars of mine that ran rough.

 

[Hall]

Originally Posted by The Critic
The 03-06s can be quite problematic when it comes to relearning the idle. We have had to replace throttle bodies, update software and even replace ECMs.

I think updated ECM software is the key. People have had throttle bodies replaced by dealers and they typically update the software as well and in the end, it's all "fixed" but others have only had the s/w updated and it works too. I have an '08 and either it has the newer s/w from the factory or something else is updated/improved as people generally don't have any trouble with these years. I didn't when I cleaned mine.

I would suggest getting an ODBII adapter and NDIS app (Android only though). The paid version (like $5-6) has a function for doing an idle relearn. One button solution vs doing the tricky "pedal dance".

 

[bbhero]

Originally Posted by WhizkidTN
Originally Posted by mb32
I went ahead and cleaned the throttle plate and MAF sensor.

I sprayed around the throttle plate several times but did not touch or move the plate. The car is noticeably more responsive and the transmission kicks down without hesitation.

However, at idle, I am still getting the occasional stumble. A new throttle assembly is about $250 CAD (Hitachi). I don't really want to go that route unless I really have to, but I also don't want to have a bunch of hassle and drivability issues if I clean the throttle plate more extensively.


Assuming your plugs are fine as well as your plug wires/coils, I would move the throttle plate open and with a shop rag (not a paper towel) soaked in Throttle Body cleaner, clean the back side, both edges and throat of the throttle body as far as you can go. This normally takes several times to get it really clean. Next up, I would put a bottle of Red Line SI-1 fuel system cleaner in a full tank of Top Tier gas (Shell/Exxon/Costco) and where possible over the driving range of the full tank, get on it (i.e., "The Italian Tune-up"). Doing the above has worked wonders for me in the past on various cars of mine that ran rough.



^^^^^^^

I agree with this.... Assuming plugs, coils and fuel are ok.... Makes sense to me.

I have 252k miles on my car and never have cleaned the MAF... Only changed plugs two times. Running Exxon, Shell or Sunoco 93... My car idles perfectly, and runs very good under high rpm.

 

[CBR.worm]

I would be hesitant to replace the throttle body unless you know it is the problem. I have had a couple of different idle quality issues on my G35 - one was a bad MAF, and one was a marginal evap purge valve. Neither set a code, the only way to figure it out was to watch real-time data at idle.

 

[mb32]

I had some time this morning so I went ahead and plugged in my Innova OBD2 reader in. There is a pending code for the ambient air temp sensor (P0113 sensor circuit high).

I am not sure if this would be causing the issue I am experiencing, but I would like to troubleshoot further. I am also now noticing when cruising at around 70 km/h with the car in overdrive, I can feel a definite surging and unevenness in the idle, almost like the car is going in and out of overdrive. I can get live data from the OBD2 reader but I am not quite sure how to interpret the data. The TPS % was jumping between 5.4 and 5.8 while cruising at 70 km/h.

With the car idling at operating temperature the TPS % was 1.9. When I lean into the throttle and bring the revs up to around 2000 RPM, I can feel a definite stumble.

I have not yet cleaned the throttle yet, but am planning to this weekend.