Car is a 2007 G35S 6MT Sedan.

It has what seems like a slightly delayed (about 1 second) throttle release when driving. Meaning, when I let off the gas pedal completely it takes about a second before it appears the throttle is fully closed and you can feel the engine braking.

I just had Infiniti check it out under warranty and their experienced tech could feel what I was talking about but thought it *could be* normal... they checked it out anyways and upgraded the ECU, which didn't fix anything.

What bugs me is they think it might be normal but because they've barely ever even seen another 6MT at this dealer it seems they don't want to say definitively.

Now, I've owned lots of Nissans ('97 Maxima SE 5MT, '01 Maxima, '02 Maxima, '08 Rogue) and driven a bunch more... never have I had a throttle hesitation when RELEASING the throttle like this.

First, is this normal for a G?

Second, I had my mechanic look the car over and he attached some diagnostic tools and saw that the voltage readings between the throttle body sensors were different and he's fairly confident that should never be the case; thus the problem could be that the throttle bodies are out of sync.

The dealer just reprogrammed the ECU so they would have just applied all the re-learning procedures and the problem still exists, so if the voltages should be identical (which would make sense) then are the throttle bodies bad?

I've got just three months left on my basic warranty and if there's an issue with the throttle bodies then I want it fixed before that's up

 

If the voltages are only very slightly different then that's probably okay. They not gonna be exact all the time.

Did this issue occur only lately or was it present since you acquired the car?

 

I understand that they won't be exactly the same .. I'm trying to remember the actual voltage readings, but lets say they were supposed to be about 12V, the difference would be like 11.4V vs. 11.9V, or a similar ratio.

What I would expect is that they should be much closer, like 11.85 vs 11.9; but I could be wrong.

I've had the car for under two weeks and it's a rather subtle thing to feel that I didn't notice right away.. but starts to bug you on regular commutes when you are travelling at constant speed (foot on pedal slightly, take off.. 1s delay, engine brakes, tap gas lightly, delay, engine brakes 1s later..) It just can't be normal.

 

I see.
Either way, the operation of the throttle body shouldn't differ between AT and MT transmissions. The technician should know this and even if they don't have a MT car to compare that shouldn't make any difference.
If you want the engine to brake in the 5AT/7AT cars just place the shifter in M mode and the car should engine brake instantly any time you're in low gear/high rev and take your foot off the throttle. There shouldn't be any delay.

Now, have you tested the TB voltages while driving? Perhaps both TB's are staying open for a second after letting off the throttle which is causing this issue. If that was the case then you'd know this because the voltage would stay high on both TB's for that period of time.

I need to look at the FSM when I get home and see what the values should be at each pedal position.

 

If you could point me to the relevant info in the FSM (I have a copy in PDF form) I'll visit my mechanic, compare the voltage readings to what they should be in various conditions .. and if they're off (which I suspect they are) I'll have some ammunition to give the dealer to potentially get them replaced.

I greatly appreciate any help!

 

Should be in Engine Mechanical, if not then probably Engine Control.

 

So I'm reading in engine control... I believe i found the correct section(s)

First question is (from page EC-369) what is a DTC.. I'm guessing diagnostic trouble code. If my assumption is correct, this is not a normal check engine/MIL light type code.. or is it?

FYI, I have no check engine light, or stored codes

Second, there's a manual procedure listed to check for DTC outlines (ON 1s, 1st gear, 3s, off, 10s .. etc etc), I don't personally have the diagnostic equipment, so if I were to do this myself in my driveway... is there a way for me to check the DTC code after performing this manual procedure?

Next, more specifically on EC-373 there is a chart which shows the ECM terminals 30/31 (TP 1 bank1/2) and 34/35 (TP 2 bank1/2) with fully released/depressed pedal voltage readings.. Can I accurately diagnose these readings with a multimeter or should I just wait and visit my mechanic who has the tools to hook up to properly monitor this?

I guess my real question is.. when you get a chance to peek at the FSM, do you think its possible for me to do any meaningful diagnosis w/ a multimeter at home, or can I only rely on tools designed to monitor this type of data?

 

DTC is diagnostic trouble code. You shouldn't worry about this unless you're getting a CEL or a code when you scan the ECU.

Anyhow, I'd let the shop hook up the Consult scanner and check the TB voltages while driving the car to see how the TB's respond to your input, particularly when you let off the throttle. Use the voltage data in the FSM to see what the voltage range should be while you drive and see if the voltages drop as soon as you release the pedal or if there is any delay.

BTW, next time you go to your mechanic check and see what the voltage difference between the TB's is.

 

Alright I'll have to quit my meddling for the weekend and visit my mechanic on monday/tuesday.

I'll come back with any relevant info/questions if there is any.

Thanks

 

i can't speak much for the issue but as far as the warranty you have already reported it and brought it in and they should be investigating it. at this point even if you leave the standard warranty time frame they should still take care of this issue for free since it was previously reported.