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post #31 of (permalink) Old 04-30-2019
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Same here - no special procedure when I installed my ported TB either.

They do make a special "DI" topend cleaner for DIY folks... Look up "CRC GDI Intake Valve Cleaner". It's supposed to help clean the intake valves - may take repeated cleanings though. And you should change your oil shortly after. Plenty of videos and instructions out there. Can get the stuff at Advance Auto, Autozone, etc...
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post #32 of (permalink) Old 04-30-2019
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Originally Posted by jtrosky View Post
They do make a special "DI" topend cleaner for DIY folks... Look up "CRC GDI Intake Valve Cleaner". It's supposed to help clean the intake valves - may take repeated cleanings though. And you should change your oil shortly after. Plenty of videos and instructions out there. Can get the stuff at Advance Auto, Autozone, etc...
Seafoam also makes a spray cleaner for this


I throw a bottle through every few oil changes. Haven't had any issues with my 2013 (not that I would have necessarily without it).
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post #33 of (permalink) Old 04-30-2019 Thread Starter
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Originally Posted by jtrosky View Post
Same here - no special procedure when I installed my ported TB either.

They do make a special "DI" topend cleaner for DIY folks... Look up "CRC GDI Intake Valve Cleaner". It's supposed to help clean the intake valves - may take repeated cleanings though. And you should change your oil shortly after. Plenty of videos and instructions out there. Can get the stuff at Advance Auto, Autozone, etc...
Thanks for the replies, a good video here that might help someone

Yes that would be simple enough. With that being said, I can say I am pretty certain carbon buildup is not or was not the problem in this car. There was NO loss of power at all and no symptoms aside from the low rpm hesitation. Like I have posted in this thread a couple times, the car never had any loss of power issue and accelerated just fine once past the slight hiccup that was consistently around 700-800 rpms. Once past the hesitation if you jumped on it, it would run to 65-80 mph just like it always has very quickly. No fuel efficiency loss, car still getting 25.6 or so mpg with mixed driving. No codes either. Would seem like if there had been a carbon buildup issue that there would be some sign, and then still the question is how if that were the case did it seem to resolve itself with no mechanical action taken.

I will pull a couple plugs this weekend and check them out to see how they look.

Still leaning towards thinking this was an issue with the tb motor or something to do with the positioning sensor.
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My 6 year constantly asks why. What adults can learn from 5 and 6 year olds, to listen with your ears and mind open. Hard to learn when you don't listen ......
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post #34 of (permalink) Old 04-30-2019
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Yeah, as most of you know, I still think the whole "valve coking" issue is way over-hyped. I'm sure it's a serious problem on some makes and models, but it really hasn't turned out to be a huge, widespread issue on these Impalas, for whatever reason - at least as far as I can tell. I'm sure the intake valves don't "look" pretty and the carbon does rob you of some small amount of power and efficiency, but it certainly doesn't seem to be as big of a problem as some have made it out to be - especially on well-maintained vehicles using quality oil and fuel.

That being said, I guess it can't hurt to run a can of that cleaner throught the intake every once in a while. Whether or not it makes a noticable difference or not though, I'm not so sure...

Just my two cents - not that anyway asked for it. :-)
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post #35 of (permalink) Old 05-13-2019 Thread Starter
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Bit of an update. Wife had another issue Friday same as had been happening where the car just hesitated briefly. Still no codes. Seems really odd to me that whatever is happening is not tripping anything in the cars computer.

While I was pretty certain the issue was not injector related I have run two treatments of techron fuel injector cleaner through the car in the last two consecutive tanks, that was prior to the most recent issue that happened on Friday.

I pulled two front plugs, they looked ok, but went ahead on and got a new set of bosch iridium plugs to replace the autolite iridium's that have about 60,000 miles on them. May as well go ahead and replace them now, so will replace them sometime this week. Being this problem has become intermittent don't expect changing the plugs to make any difference with regards to the hesitation issue.

A lot going on with kids and end of school year, unless the problem resolves with the new plugs will probably just go ahead and get a new throttle body in the coming weeks, don't see anything else that could be causing the erratic hesitation and not throw any codes in the process.
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My 6 year constantly asks why. What adults can learn from 5 and 6 year olds, to listen with your ears and mind open. Hard to learn when you don't listen ......
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post #36 of (permalink) Old 05-19-2019
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Originally Posted by 12 lt View Post
Thanks. Replaced the pedal today, no change. Wonder if rock auto will accept a return on it, may call or email them?

Guess I will be tearing into the throttle body next.
Just FIY...
And I know this isn't what you want to hear but...
Mechanics code states we don't reinstall old parts if the new part we replaced didn't fix the problem.
We leave it in place and keep the old one as a spare.
If anything you can probably sell it on ebay.
That's what we do, because it is the proper way.
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post #37 of (permalink) Old 05-20-2019
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similar problem

LT12,
I have a similar issue on my 2016 limited, which is the same generation as the 2012 because it is the rental car Limited version they kept making for a few years after the newest gen came out.

From reading the stuff on here about transmission wierdness, I always assumed my issues were related to the computer or the transmission. But now that I have read how similar your issue is to what I am seeing. I don't think I have the technical knowhow or the awareness to determine if the lag is due to engine power at low RPM, like you are saying, or if it is some sort of computer or trans issue that only happens at city speeds/driving and lower RPMs.

Anyone know how to tell if a lag is throttle/engine related versus computer/transmission related?

Hoping you find out what is going on with your wife's care so I can maybe get a hint as to what is going on with my car.

Adding a singature only because I am tired of being shown my incomplete account setup.
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post #38 of (permalink) Old 05-20-2019 Thread Starter
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Quote:
Originally Posted by sidemouse View Post
Just FIY...
And I know this isn't what you want to hear but...
Mechanics code states we don't reinstall old parts if the new part we replaced didn't fix the problem.
We leave it in place and keep the old one as a spare.
If anything you can probably sell it on ebay.
That's what we do, because it is the proper way.
Fwiw I left the new one on the car. I considered putting the old one up on ebay, but will probably just hang on to it. More in the garage my wife calls junk. lol.

Quote:
Originally Posted by VladThe View Post
LT12,
I have a similar issue on my 2016 limited, which is the same generation as the 2012 because it is the rental car Limited version they kept making for a few years after the newest gen came out.

From reading the stuff on here about transmission wierdness, I always assumed my issues were related to the computer or the transmission. But now that I have read how similar your issue is to what I am seeing. I don't think I have the technical knowhow or the awareness to determine if the lag is due to engine power at low RPM, like you are saying, or if it is some sort of computer or trans issue that only happens at city speeds/driving and lower RPMs.

Anyone know how to tell if a lag is throttle/engine related versus computer/transmission related?

Hoping you find out what is going on with your wife's care so I can maybe get a hint as to what is going on with my car.
Issue we are having has never presented as a transmission issue. This happens with the car in neutral as well as in gear. When this very first started it was every time you pressed the gas, it would hesitate in the low rpm range for just a fraction of a second.

Between our 17 year old's graduation and other stuff with our kids and a tune up on the hemi in our durango have not had a chance to get to the plugs yet, but should get to them by this weekend.

Will post an update at some point after the plug change whether it makes a difference or not.

My 6 year constantly asks why. What adults can learn from 5 and 6 year olds, to listen with your ears and mind open. Hard to learn when you don't listen ......
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post #39 of (permalink) Old 05-21-2019
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Quote:
Originally Posted by 12 lt View Post
Issue we are having has never presented as a transmission issue. This happens with the car in neutral as well as in gear. When this very first started it was every time you pressed the gas, it would hesitate in the low rpm range for just a fraction of a second.
Well shoot. It never occurred to me to try the car in neutral to see if it had the lag. Which probably is a good argument for my sticking with letting the shop do all my repairs, and probably even my oil changes.

Adding a singature only because I am tired of being shown my incomplete account setup.
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post #40 of (permalink) Old 05-26-2019
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I will say this...
All high powered engines suffer to a degree from this "lag," even Corvettes.
We are so used to instant gratification, however in the real world it takes actual time to build things up...
When a driver first steps on the gas pedal it sets in motion a series of events, the reason we don't notice much lag in lower end vehicles is it doesn't take that long to go from a few horses to 80 or 100... But in a more powerful car it takes longer because it has to get up to more horsepower, there exists a distinct pause from when we step on the gas pedal until the engine has finally achieved the horsepower the driver had intended to gain because it just takes time to revv up to that...

No, it is not possible for an engine to go from 800 rpm's to 4 thousand instantly, it takes a second even in neutral. Once we add the transmission and the driveshafts and the wheels to the equation it takes even longer for all that power to transfer from the crankshaft through to the wheels. In layman's terms we call this lack of responsiveness "throttle lag."

Further, stock cars straight from the factory aren't designed to take full advantage of their abilities, the manufacturer wants that car to last the owner a long time.
The more we ask from our vehicles, the less reliable they become. Thus the manufacturer may have intentionally not built these Impalas to racing specifications.

Some things that can be done to increase the pedal's responsiveness are to install thicker high performance (8mm Accel or Taylor) spark plug wires.
You may consider replacing the spark plugs at this time, especially if they haven't been done in a long time.
A thin synthetic oil such as 5w-20 will also help reduce friction that may be slowing the engine.
Believe it or not filling each tire to the Max. PSI printed on the sidewall will help as well.
Beyond that a clean air filter, maybe even an aftermarket K&N to help deliver air down the intake faster.

If any one or more of the above isn't there...
The car will lag.
It could even be that the caliper guide pins haven't been lubricated in a long time and the brake pads are mildly 'dragging' on the rotors, for all we know...

Once we're done with the simple stuff unfortunately we're looking at crazy upgrades such as polished intakes and cold air intakes and all sorts of other things that, may be cheaper to reprogram the ECU to a stage 1 or something...

Hope that made sense, what I'm saying is there's probably nothing wrong with the car in that sense.
You want less lag, the first step is always keep up on the maintenance.
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post #41 of (permalink) Old 05-26-2019
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See, let me tell you the very first thing that created "lag" was the throttle "cable."
Did you know in the early days a steel rod linked the gas pedal to the carburetor's butterfly valve, when a driver stepped on it the message to the engine was truly as instant as one can get.
When that valve opened up the engine sucked AIR and that air rushed past jets in effect sucking FUEL in with it!

Then came cables, and these are not as responsive as rods because rods are stiff.

Nowadays we have sensors on the gas pedal that detect when the foot steps on it, send a message to the ECU, the ECU in turn sends a command to the motor inside the throttle body that opens the butterfly valve AND to the fuel injectors to start delivering fuel to the cylinders. One would think electronics are the fastest in delivering the message but have you ever watched this in real life? That butterfly valve opens quickly, but even at top speed the gears can't turn the valve as fast as my foot can mash the pedal to the floorboard. In fact, even at top speed that valve opens some kind of gradually.
The steel rod could deliver the message, if I mashed the pedal to the floor in an instant that rod opened the valve just as quickly.
Carbureted engines always were quicker right off the start, even to this day.
But the older cars also suffered from this throttle lag for different reasons, most of it to do with slack and looseness.

If a U-joint has even a thousandths of an inch of play in it that will create a split second of lag and that is only one piece that must function to deliver power along the way from the gas pedal to the wheels. U-joint, CV joints, all the same thing for the sake of this argument.

It's funny...
Like if you're planning on racing someone else, you actually have to PLAN on hitting that gas pedal ahead of the actual event of accelerating because if you hesitate you will lose.
Throttle lag, the bigger the engine, the more lag the driver will experience and thus the farther ahead of actual acceleration the driver must plan on hitting the gas.
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post #42 of (permalink) Old 05-27-2019 Thread Starter
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Quote:
Originally Posted by sidemouse View Post
I will say this...
All high powered engines suffer to a degree from this "lag," even Corvettes.
We are so used to instant gratification, however in the real world it takes actual time to build things up...
When a driver first steps on the gas pedal it sets in motion a series of events, the reason we don't notice much lag in lower end vehicles is it doesn't take that long to go from a few horses to 80 or 100... But in a more powerful car it takes longer because it has to get up to more horsepower, there exists a distinct pause from when we step on the gas pedal until the engine has finally achieved the horsepower the driver had intended to gain because it just takes time to revv up to that...

No, it is not possible for an engine to go from 800 rpm's to 4 thousand instantly, it takes a second even in neutral. Once we add the transmission and the driveshafts and the wheels to the equation it takes even longer for all that power to transfer from the crankshaft through to the wheels. In layman's terms we call this lack of responsiveness "throttle lag."

Further, stock cars straight from the factory aren't designed to take full advantage of their abilities, the manufacturer wants that car to last the owner a long time.
The more we ask from our vehicles, the less reliable they become. Thus the manufacturer may have intentionally not built these Impalas to racing specifications.

Some things that can be done to increase the pedal's responsiveness are to install thicker high performance (8mm Accel or Taylor) spark plug wires.
You may consider replacing the spark plugs at this time, especially if they haven't been done in a long time.
A thin synthetic oil such as 5w-20 will also help reduce friction that may be slowing the engine.

Believe it or not filling each tire to the Max. PSI printed on the sidewall will help as well.
Beyond that a clean air filter, maybe even an aftermarket K&N to help deliver air down the intake faster.

If any one or more of the above isn't there...
The car will lag.
It could even be that the caliper guide pins haven't been lubricated in a long time and the brake pads are mildly 'dragging' on the rotors, for all we know...

Once we're done with the simple stuff unfortunately we're looking at crazy upgrades such as polished intakes and cold air intakes and all sorts of other things that, may be cheaper to reprogram the ECU to a stage 1 or something...

Hope that made sense, what I'm saying is there's probably nothing wrong with the car in that sense.
You want less lag, the first step is always keep up on the maintenance.
The issue with our car happens in neutral as well as in gear. It is almost like a hiccup or like a dead spot around approximately 7-800 rpm's. Once past that point the car accelerates just fine with no issues at all and has plenty of power. No change in efficiency. The car is not displaying any codes and has no stored codes either.

I just changed the plugs last Wednesday to bosch double iridiums, the autolite iridiums I put in the car around 100 thousand miles had a little over 60 thousand miles on them. The autolite plugs at 60 thousand miles did not look too bad. The lfx engine uses coil packs at each cylinder, there are no plug wires. This car has a k&n filter, was just cleaned within the past 5-6000 miles. So the car has had a complete tuneup within the past 5-6000 miles, throttle body cleaned, maf sensor cleaned, 2 treatments of techron injector cleaner.

Prior to this morning my wife has only driven the car a couple times since the plugs were changed, she said the car has not had any more hesitation issues yet. If or when the next time this problem/issue presents, I will just go ahead on and get a new throttle body and replace it.

My 6 year constantly asks why. What adults can learn from 5 and 6 year olds, to listen with your ears and mind open. Hard to learn when you don't listen ......
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