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post #91 of (permalink) Old 06-11-2015
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I agree, Ive read what youve been doing, and youve got the best chance to avoid carbon issues.

As to the trans vs carbon issue.....Ill just say that at GM list prices a trans is $2200 or so plus 8hrs labor. Replacing valves is about 23hrs, plus around $600 per head. Math.
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post #92 of (permalink) Old 06-11-2015
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But the valves don't need replaced because of carbon deposits, do they? I mean they just need cleaned right? Surely that doesn't cost anywhere near $2200!

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post #93 of (permalink) Old 06-11-2015
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But the valves don't need replaced because of carbon deposits, do they? I mean they just need cleaned right? Surely that doesn't cost anywhere near $2200!

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In heavy cases they do if the valve develops a sealing issue and the face(sealing surface) gets damaged.

But replace, or remove to clean, either way its same amount of time.


And of course to take heads off means youll need to replace the head gaskets, head bolts, intake gaskets, cooling system gaskets, exhaust gaskets, valve seals, camshaft cover seals, water pump seals,etc...

Removing the heads to physically clean valve on both banks could easily broach $3000 depending on where you live
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post #94 of (permalink) Old 06-11-2015
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I'm talking about the much more common cleaning method that you previously discussed, which doesn't involve any of that (heads do not have to come off). I would imagine that would method be sufficient in the vast majority of carbon build-up cases.

If you're telling me that it's common to have to spend $3000+ to clean carbon deposits on the intake valves by 100k miles, then I have a huge problem with that! I think that you are referring to fairly extreme cases that are not very common at all. Whereas the 4-speed transmission failures on the non-DI Impalas actually are fairly common - again, at least judging by the failures noted on this forum.

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post #95 of (permalink) Old 06-11-2015
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I'm talking about the much more common cleaning method that you previously discussed, which doesn't involve any of that (heads do not have to come off). I would imagine that would method be sufficient in the vast majority of carbon build-up cases.

If you're telling me that it's common to have to spend $3000+ to clean carbon deposits on the intake valves by 100k miles, then I have a huge problem with that! I think that you are referring to fairly extreme cases that are not very common at all. Whereas the 4-speed transmission failures on the non-DI Impalas actually are fairly common - again, at least judging by the failures noted on this forum.

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No thats not the cleaning I mentioned before, thats worse case scenario buildup. However its likely if you ignore the loss of power thats likely to occur over the course of that much time. Simple fact is valve DO NOT stay clean in these engines

I dont have too many LFXs over 100k yet. Of the ones I service though a high percentage(over half) they have been apart in some level.

I CAN tell you that I see more 90-110k mile valve sealing failure on the 2.4L SIDI trucks than I see failed 4T65s of similar mileage around here these days.

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post #96 of (permalink) Old 06-11-2015
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Ok, thats enough of a hijack. Ill just leave with the fact that I havent had A SINGLE carbon buildup related valve sealing issue in the last 8 years on a port injected engine, I have FOUR vehicles right now with direct injection and carbon related valve sealing concerns.

Whether people choose to believe its an issue or not is up to them.
post #97 of (permalink) Old 06-11-2015
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You almost make it sound like GM cars are getting less reliable instead of more reliable - do you really believe that? I think that the fact that you aren't seeing many LFX's over 100k is a good thing - surely there are many fleet LFX vehicles with over 100k miles now - even personal LFXs are getting up there. You have to remember, you are only seeing the broken cars - there are tons that aren't broken and have never been broken. :-)

I am curious if you think GM cars are more or less reliable than they used to be though (current DI models vs. 10 year old non-DI models, for example) - when they were both 5 years old let's say (DI has been around for at leat 5 years now).

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post #98 of (permalink) Old 06-11-2015
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Without a doubt the SIDI engines are LESS reliable long term then their port injected predecessors. Anyone who claims otherwise is blowing smoke.

Direct injection, variable valve timing, cylinder deactivation, flex fuel, variable lift....none of these features are more reliable than the traditional version of the system they replace, and none of them increase engine longevity or reduce maintenance costs.
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I guess the question is - what is "long term"? I just don't understand why every manufacturer is moving towards direct injection if it is so problematic over what I would consider a reasonable timeframe (100k-150k miles). In my experience, most people don't keep their cars over 150k miles, so if they are generally just as reliable overall up to 150k miles, then I can understand the move towards direct injection. Direct injection gives you more power and better fuel economy, but those gains are minimal. I just don't understand why direct injection is so popular if it's really that problematic.

But that wasn't my question anyway... The question was do you think GM cars are more or less reliable overall than they were 10 years ago (not the engine specifically, but the cars overall). If you truly believe that the cars are generally less reliable now than they were 10 years ago, then that is very problematic, in my opinion. Again, the timeframe that we're talking about here is important too. Why would every car company purposely move towards technology that is more problematic and more expensive for them to warranty over a reasonable "lifetime"? It just doesn't make any sense for a few extra HP and a few more MPG.

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Originally Posted by jtrosky View Post
I guess the question is - what is "long term"?
Long term, anything past warranty, definitely past 5yr/100k. Average age of the US car populatiob is over 11yrs now.
I just don't understand why every manufacturer is moving towards direct injection if it is so problematic over what I would consider a reasonable timeframe (100k-150k miles).
Emissions, power density. plain and simple.
In my experience, most people don't keep their cars over 150k miles, so if they are generally just as reliable overall up to 150k miles, then I can understand the move towards direct injection.
Original owners my not keep them, but the huge majority of cars on the road have over 100k on them
Direct injection gives you more power and better fuel economy, but those gains are minimal. I just don't understand why direct injection is so popular if it's really that problematic.
Because its the only way they can meet regulatory targets.

But that wasn't my question anyway... The question was do you think GM cars are more or less reliable overall than they were 10 years ago (not the engine specifically, but the cars overall). If you truly believe that the cars are generally less reliable now than they were 10 years ago, then that is very problematic, in my opinion.
Hard to say. On the face of it, NO, they arent more reliable. They break more, they have more issues, there are more complaints than there were in 2005. This has the caveat that people now expect more from their vehicles, we live in an ever increasing "I need it free" society, and the cars are simply more complex and have more thing to go wrong. See the threads regarding features feel vehicles are "missing", and things like infotainment functionality and peoples expectations of what a car should do now.

As a society we have forgotten what REALLY used to be involved in owning and operating an automobile, how much it cost to maintain, what characteristics and condition were considered acceptable and how long a vehicle should last with no money spent on it, and how long the manufacturer should be expected to be responsible for taking care of it.

Again, the timeframe that we're talking about here is important too. Why would every car company purposely move towards technology that is more problematic and more expensive for them to warranty over a reasonable "lifetime"? It just doesn't make any sense for a few extra HP and a few more MPG.
It does if you cant continue to sell vehicles because you dont meet the requirements.

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But in terms of the Impala, for example, GM could most certainly meet are regulatory requirements without a DI engine - yet the continue to use DI engines.

Everything I read says that cars today are more reliable than ever. I don't understand where the "discrepancy" is. Again, maybe it all depends on the timeline considered. If my car is completely reliable (no major breakdowns or maintenance expenses) until 125k, I consider that to be a good car. So it all depends on what you consider the normal life span of a vehicle, I guess. Cars definitely seem more "disposable" nowadays.

But in general, people seem to feel that cars today are more reliable now than they were 10 years ago.

If DI is truly that problematic, than maybe GM sees it a win-win - people will either buy a new car sooner or pay delaerships a fortune to maintain them! Plus they can advertise more power and better MPG!

I just haven't seen the general public up in arms about their cars being less reliable - seems the opposite to me. Like I said, I just don't see the issues with the DI Impalas from the owners on this site, or the internet in general. Maybe sine we are car people, maybe we just maintain them better? That may be key too - if maintained properly, maybe they truly are more reliable.... Lots of variables, I guess.
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Think we are done with the current line of discussion. Your point of view is amply clear, I believe Ive made my opinion and observations obvious as well. Clear we both love these cars and thats great.

If you come up with any different questions let me know, I feel this horse is dead.
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Agreed - was a good discussion though - it's always nice to have discussions where we have different views but can still discuss something rationally! Appreciate the info!

It could just be that DI is still to new and the majority of people just haven't run into the issues discussed yet - maybe everyone will truly by up in arms about their vehicle reliability in a few more years! :-)

To the OP - sorry for the HUGE thread-jack!
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post #104 of (permalink) Old 08-18-2016 Thread Starter
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another approx. year has gone past and trip B is up to 30K again. just an arbitrary number i picked. i may let it roll to 60 for next year.

25mpg over the past year is very good. keep in mind summer/winter i idle 30 min a day at lunch and drive somewhat spirited.

2 RSA for sale. 7/32 good tread. berks county PA

166K on 2014 Blue Ray Metallic 2LTZ with 19s and nav. sadly new trans at 140K. Used to own 1995 DCM SS with only 260K!
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