Do not clean your TB! Since I cleaned mine, my idle sits at 950, my engine revs surge when I let off the throttle very badly! It's more of a jerking feeling, like someone took a quick stab at the throttle. I have done the reset soooo many times. When it works, the idle RPMs drop to 600ish, but upon restart are back to ~900.

 

Well, I have similar mods, and i've noticed my car does the same thing, it is pretty harsh, that I the car jerks. I have a smooth idle.. when the car is warmed up but if I turn off my car, and immediately turn it back on, sometimes it will stall. Just ordered a new set of spark plugs, I'm at 50k, but the previous owner had a exhaust on fora while, and ever since I've put a intake, its just gotten worse. Bought a Osiris ecu management, hopefully this fixes the G along with giving it more power.

 

i cleaned my throttle body but left the wires connected. no issues whatsoever

i just want to get fixed the problem that the OP and I are having

 

As long as your car is in gear, the RPM's are above a certain point(1500 RPM's), and you have your foot completely off the gas with the engine fully warmed up... the fuel cut feature will engage as you coast for a second or so. It's called DCFC(Deceleration Fuel Cut) in most vehicles.

You can read about it in the FSM... it's on page EC-28 and is described as Fuel Cut Control(at no load or high engine speed) on our cars. If you have a Scangauge® or some other real-time OBD-II scanning tool, you can actively see when the fuel cut kicks in. I do this all the time in my Tacoma, and you can feel it once it kicks in after you get accustomed to the gauge indicating when it happens.

The braking force of the engine while the fuel cut is active is negligible on our cars... or at least it is when the system is running as intended on a healthy VQ motor.

 

Thanks a ton, this is great to know! In this case, OP, if you're above 1500RPMs on the highway and you let off the gas, does the deceleration happen as you've described? If so you can rule out anything having to do with fuel, spark, etc.

It sounds like your TB needs more cleaning, or perhaps some of the gunk got into the moving parts of the valve. When I cleaned mine i totally disconnected it, but did NOT touch the valve. I just sprayed the TB cleaner everywhere it was dirty. Used almost the whole can because i couldn't touch the valve, but it worked! Make sure all the fluid drains out, you don't want that stuff sitting in the TB and drying. When you reset, have you tried just unplugging the battery, pumping the brakes to discharge the capacitors, then reconnecting the car?

I also heard the airflow sensor can get dirty and cause throttle related issues. Guys I am not saying I know the answer, but hopefully some others can suggest how to rule out my ideas and get to the bottom of your issues!

Another thought! If you are driving on the highway, lift off the gas, quickly clutch in and put the car in neutral, does the engine RPM drop like a rock? If it drops slowly, the issue may not be lying in the engine, but instead in the transmission! If it does drop quickly, you will know it is your engine, not your transmission. If you need a comparison, let me know and I'll take a vid on my phone tonight of how fast my needle drops (fing slowly...stupid "dualmass" flywheel..)

 

i will go out later and investigate how fast my revs drop with the clutch in and/or in neutral. although i feel like i would have noticed that before if it was dropping quickly

 

To put it in perspective, my rpms rise to near redline within a second in neutral, but fall to idle over about 3-4 seconds. I am estimating...but this is how it feels to me. It would be best to do this while driving, to more accurately simulate the situation you are experiencing. In otherwords, don't do this in your driveway, head out onto a road and clutch in when you're at 30 mph or something. If RPMs do drop at a normal rate but you are still decelerating aggressively, then your slow down must indicate some wear or issue in or past the transmission (brakes, wheel bearings, axels, diff, etc).

If this is the case, to test if its the brakes, turn on a cold car, accelerate into the street, get up to 30, and let the gas out, eventually coasting to a stop not using the brakes at all. Go out and compare the left and right, front and rear brakes to each other. If one or more are hot, you found your issue. Be careful surfaces might be hot. I don't think bad wheel bearings would necessarily cause enough heat to be detected, but they should make noise.

Another question, does it happen to the same degree in each gear, or is it less noticeable at higher gears?

 

70 MPH @ 4th Gear. Let of Gas. Oh my car is decelerating really fast.

 

at 70 MPH in 4th gear, you will be feeling some deceleration, that's normal in a manual. If you think its severe, clutch in while this is happening, does the deceleration stop?

 

Sorry to interrupt, but I have been having the exact same problem.
Car decelerates quickly in the first 3 gears (automatic transmission), but on the highway (high speed and gears) acts normal. At the same time, I can also feel a repetitive deep vibration under my feet that seems related to my speed (frequency decreases with speed), which i though at first was related to a wheel bearing problem. This vibration is also only present at lower speeds
Finally, when i start the car and in park gear, i can feel slight shakings, idle rpm is at 2000
I need help! I am no professional in ECUs and especially infiniti

 

Any updates on this one? Anyone ever figure out a sure fix?

 

What are your rpm's sitting at normally? Not sure exactly what part of the thread you're talking about but the OP had a high idle.

 

High idle here as well. Did an engine swap (rev-up to rev-up, 6MT to 6MT) and it bounces between 1000 and 2500 at idle. Also surges when letting off the gas and hitting the gas while driving.

After some more reading it seems I need to do the idle re-learn. I tried it once, but it didn’t take. Going to try it again when I get to work tomorrow and it’s warmed up.

 

Anytime you unplug the throttle you have to relearn the throttle closed position. You also need to relearn the idle air volume, you should probably also reset the ECM to get a new baseline for the LTFT.

Steps are all in the FSM, section EC - Engine Controls, look under "basic service procedures" it's near the front.

 

Cleric, you're the man. I appreciate all the help!

Now I've got to go find the FSM.