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Throttle Lag

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Old 05-25-2017, 03:42 AM
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Throttle Lag

Since I bought my '07 AT two months ago, I've had an issue with throttle lag.

Around a month ago, I asked the mechanic at the body shop (needed body work after a fender bender) if he had any idea why the car was hesitating when the accelerator was depressed more than (very roughly) 50%. I tried to show him while in park, but the problem didn't manifest itself. After that, he took my car for a drive and there was no problem.

Since then, the car has been having issues with throttle lag that can be temporarily fixed by fully depressing the pedal twice in park, but the fix doesn't last for long at all and my neighbours (block of apartments) probably don't appreciate my method of fixing the problem. The lag is at its worst when trying to accelerate while already at speed.

I've also had a high idle recently. 1800RPM at startup. It goes down after 30 seconds.

I'm not very mechanically inclined, but what I've read in other threads on this site and elsewhere suggest an ECU reset. I read the self reset instructions that are posted here and on other sites, but I'm worried about causing a more serious problem if I screw it up.

I should probably take the car to a mechanic, but I'd like to hear other people's ideas first.
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Fastmodz (08-07-2017)
Old 06-01-2017, 12:47 AM
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Not sure exactly what problem you have, or what you mean by throttle lag, but from what I've read it appears a hesitation when stepping on the throttle (ex. light throttle application to ~50%+) is normal. The car does what I call the 'snorting bull' routine. It first hesitates losing all power for a split second before then charging -- likely due to a delay in the electronic throttle body.

As far as your high startup idle, that's normal, mine actually idles at 2000rpm initial, before quickly dropping to around 700-800rpm whern fully warm.

What you can do very quickly and easily is perform an ECU reset, I did it on mine and it made another hesitation I was having at very low engine speeds go away. I'd also like to know when to change spark plugs. I think mine are still original.
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Old 06-02-2017, 10:57 AM
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Throttle bodies may need to be cleaned. They get pretty gunky and "stick" sometimes. Have to pull it off to look behind them though, they usually "look" clean if you only remove the intake hoses and look at the outside.

The ECU reset and idle relearn procedures won't mess anything up. If anything, the procedure just won't complete if you mess up a step. I prefer using NissanDataScan app on my phone with a bluetooth dongle though, much easier than that fancy pedal dance.
Old 08-04-2017, 09:45 PM
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Quote:
Originally Posted by LoSt180 View Post
Throttle bodies may need to be cleaned. They get pretty gunky and "stick" sometimes. Have to pull it off to look behind them though, they usually "look" clean if you only remove the intake hoses and look at the outside.

The ECU reset and idle relearn procedures won't mess anything up. If anything, the procedure just won't complete if you mess up a step. I prefer using NissanDataScan app on my phone with a bluetooth dongle though, much easier than that fancy pedal dance.
I would be very weary of suggesting a TB clean with all the issues out there.

This is a last resort type of thing in my book, would check other things first.
Old 08-05-2017, 12:13 PM
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Serge, about your "snorting bull" routine. That is indicative of a vacuum leak small enough to not trip the check engine light but bad enough to force the vehicle to pull back the timing, serious fuel adjustment, etc. Check all fittings with a can of throttle body cleaner, if its sucking air the TB cleaner will drop the engine rpms when ingested.

Last edited by [email protected]; 08-05-2017 at 12:27 PM.
Old 08-07-2017, 12:43 AM
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I finally got my car looked at by professionals after the oil pressure light came on yesterday.

The throttle lag was an ECU problem. The guy reset it and it now accelerates much more smoothly, rather than doing nothing and then revving wildly to redline. I'm just a bit worried that the relearn procedure will not work as planned since the local roads are too congested for fast driving.

As for the oil pressure, the oil was a bit low but I had to drive 130km with the warning yesterday. The oil was topped up and the warning deleted. I'm guessing it was also an ECU problem, as I got home without hearing any weird noises or overheating. A mechanic said the 35c (95f) humid weather we've been experiencing can cause weird issues like that.

I would have asked more questions, but there was a language barrier and they only charged me $25 USD. The mechanic drove the car and was clearly happy enough with it after he'd reset the computer.
Old 08-07-2017, 11:06 AM
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If you're having oil consumption issues you might try a different type of oil, for example my rev up motor will consume 2 quarts of mobile1 full synthetic oil per 3k miles (!!!YIKES!!!), but only 1/4 quart per 3k miles if I use the factory nissan conventional oil. Glad you're getting the problem fixed, I wouldn't be too concerned with trying to get the vehicle fast, it's a constantly learning computer.

As for the language barrier, if you have a smart phone try the Google Translate app, it's quick, automatic, language packs can be downloaded to the device for VERY fast translation (as fast as you can talk into the phone) and it's worked great for me, have to use it all the time.
Old 08-07-2017, 02:50 PM
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Serge, about your "snorting bull" routine. That is indicative of a vacuum leak small enough to not trip the check engine light but bad enough to force the vehicle to pull back the timing, serious fuel adjustment, etc. Check all fittings with a can of throttle body cleaner, if its sucking air the TB cleaner will drop the engine rpms when ingested.
Thanks will check the hoses, I should also say this behavior (split second loss of all power when stepping on accelerator) has calmed down a lot lately and sometimes does not happen at all. Ive got a wifi obd2 scanner on the way so I hope timing and/or knock count is one of the parameters I can display in real time on my smart phone.

I also just purchased some Castrol Edge Synthetic supposed to be capable of 24000km and a mobile one extended life filter. I'm pretty sure the car up to this point has always had regular dino oil as the previous owner had free lifetime oil changes from the dealership. Hoping it doesn't all leak out by the time 20K comes around.

Last edited by Serge Mullen; 08-07-2017 at 02:55 PM.
Old 08-07-2017, 02:55 PM
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I use the Android app Torque Pro, one of the options is a graphing/logging mode. You can pick which sensors to display, start logging, make a few runs to reproduce the issue, then go over the data safely at home without having to try to watch it real-time, it's a great piece of software.
Old 08-07-2017, 03:00 PM
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Quote:
Originally Posted by sjwtriggerer View Post
I finally got my car looked at by professionals after the oil pressure light came on yesterday.

The throttle lag was an ECU problem. The guy reset it and it now accelerates much more smoothly, rather than doing nothing and then revving wildly to redline. I'm just a bit worried that the relearn procedure will not work as planned since the local roads are too congested for fast driving.

As for the oil pressure, the oil was a bit low but I had to drive 130km with the warning yesterday. The oil was topped up and the warning deleted. I'm guessing it was also an ECU problem, as I got home without hearing any weird noises or overheating. A mechanic said the 35c (95f) humid weather we've been experiencing can cause weird issues like that.

I would have asked more questions, but there was a language barrier and they only charged me $25 USD. The mechanic drove the car and was clearly happy enough with it after he'd reset the computer.
Good that a simple ecu reset made most of your symptoms go away. It seems like these cars can get temperamental or thrown out of whack from time to time so it's good that a simple reset can clear it. Also never drive more than a short distance with a low oil warning light. Check the dipstick and top it up asap, no need to wait for a mechanic to do that.
Old 08-07-2017, 03:08 PM
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Quote:
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I use the Android app Torque Pro, one of the options is a graphing/logging mode. You can pick which sensors to display, start logging, make a few runs to reproduce the issue, then go over the data safely at home without having to try to watch it real-time, it's a great piece of software.
Yes I watched a couple.videos of the torque app awhile back, very cool for sure.

Did your car have any interesting or odd issues that you were able to see/remedy?
Old 08-07-2017, 03:14 PM
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I was trying to isolate a low rpm, light throttle engine ping. Eventually decided that it was just in need of a ECU reset since everything checked out. I thought for sure I was getting a bad signal from the intake air temp sensor but that wasn't the case.

I did notice that intake air temps are extremely high on this vehicle (+30-40 over ambient when idling) so I'm looking into various products to wrap the intake pipe to reduce heat soak.
Old 08-07-2017, 03:31 PM
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I was trying to isolate a low rpm, light throttle engine ping. Eventually decided that it was just in need of a ECU reset since everything checked out. I thought for sure I was getting a bad signal from the intake air temp sensor but that wasn't the case.

I did notice that intake air temps are extremely high on this vehicle (+30-40 over ambient when idling) so I'm looking into various products to wrap the intake pipe to reduce heat soak.
I can imagine under hood temps will spike when stopped. Hopefully its designed to channel hot air out of the engine bay when moving back to near ambient.
Old 08-11-2017, 06:36 AM
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I wouldn't be too concerned with trying to get the vehicle fast, it's a constantly learning computer.
I was told that the car would take a month to 'relearn' my driving style. That was about all the guy could explain. I am not knowledgeable about the mechanical side of cars, but I read here that the ECU will make various adjustments to how the car responds to my inputs, based on how I drive shortly after the reset. I assumed this meant I should step on the gas whenever realistic in order to improve throttle response in the long term, but are you saying it isn't that important? I ask because your advice differs from what I read, but you give the impression that you really know what you're talking about.
Old 08-11-2017, 10:23 AM
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Well that's not EXACTLY true. The computer doesn't care at all about your input, all it cares about is fuel trims and timing. There is a base set of logic in the ROM(preset ideal conditions from the factory) and the ecu can trim a limited amount of injector pulse width based on actual engine conditions. This is all accomplished through the short term fuel trim (STFT) and over time it develops an adapted logic based on the input parameters and modifies the long term fuel trim (LTFT). The knock sensor then controls timing advance by retarding timing a preset degree for every knock, it then advances timing again for every successful non-knock cycle to it's upper limit.

The "learned" behavior is simply the exact conditions your motor sees, for example let's say your air filter is very dirty, the fuel map is compensated to adjust for lack of air compared to the preset conditions. The map is adjusted at every point to compensate and over time this modifies the ltft so the engine isn't having to constantly -% the fuel with stft.

Now you change your air filter, the ltft is still expecting less air but suddenly there is a lot more of it so the stft trims +% fuel to compensate if your ecu was reset during a really bad air filter the ltft may never be able to fully compensate for the extra air based on the +/-% limits of the adaptive logic, it would ALWAYS require extra trim from the stft to maintain proper air fuel ratio.

These are extreme situations obviously but they do happen, things like vacuum leaks, failing sensors, lower compression, old spark plugs, etc all affect the adaptive logic. And it's better for the ecu to re-learn the exact conditions of the motor from time to time rather than always relying on the stft and knock sensors to keep stuff in check.

I don't have an exact time frame for you on how long it takes the logic to go through a full refresh cycle, it's not measured in time like months, it's measured in ecu cycles so it depends on how much it's actually driven. By end end of one day of driving there has already been gross changes to the logic and a week later you're probably very close to no ltfm trim changes being made, again I've never tested this nor seen the actual written logic for the ecu.

Hope this helps.

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