I have a 2009 Nissan Infiniti G37. The car went into limp mode. I took it to a repair shop. They charge $130 for a diagnostic fee. They called me back and said spark plugs need changing and a fuel induction cleaning needs to be done. Total cost = $930 (including the diagnostic fee). Does this sound ok in your opinion? I know there are overhead and labor costs. Is this fair or does it seem a little excessive? Thanks for any and all input.
Without knowing the actual codes obtained can not be answered,
Spark plugs may be due, usually around 80-100,000 miles.
Fuel induction cleaning, I don’t know.
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The diagnostic cost is acceptable. It probably needs the spark plugs changed after 13 years. If you have a direct injection engine and it runs rough, you might need the throttle body and injectors cleaned (induction service). Given the limp mode, you very well might need the induction service. $930 at a dealer seems reasonable.
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You can always get a second opinion somewhere else, even one that drops the diagnostic fee if repairs are performed.
130.00 for a diagnostic fee is low for some areas and we have no idea where you are or what kind of shop you are using . As Mr. Barky says you might call and ask other shops what they charge for those services . But more than likely they will want a diagnostic fee also So if you have had good service from this shop before just let them do it .
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I think it is a little on the high end, but not unreasonable. The intake manifold has to be removed to replace the spark plugs but that is not a difficult job. The intake manifold gasket can be reused but most shops would rather replace it then take a chance on a call back.
I don’t think this engine has direct injection so unless there is other evidence, I suspect that the induction cleaning is not necessary.
The car went into limp mode. It might be worth it to get the induction service done anyway to clean the fuel delivery system and avoid a call back. The car is 13 years old.
The bigger question to me than cost is accuracy of the diagnosis. Why did you pick this shop? Do you trust them?
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I think @texas above raises a valid concern. Seems sort of unlikely that a new set of spark plugs and an air-path cleaning is what it takes to solve a problem that causes limp mode. I suppose such a thing might be possible if spark plugs have been in there far more miles than manufacturer recommends. How many miles on these spark plugs?
As far as the $930 to replace the spark plugs and the induction cleaning, seems a little on the high side of what I’d expect, but not totally unreasonable either. The cost depends greatly on the car’s configuration and the shop’s hourly rate, and I don’t know either. For that job on my Corolla I’d guess about $350 at a shop that charges $125 per hour.
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It’s an extremely bad idea to reuse the gasket
A lot of guys get themselves into trouble, as that gasket won’t seat that well afterwards, and the customer may come back upset, because the MIL is illuminated due to P0171 and P0174
I wouldn’t even reuse the gasket on my personal vehicles, if I was taking off the intake
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I don’t see an issue with the cost but I agree with texases about the accuracy of the diagnosis. It comes across as a bit suspect to me.
Maybe you should ask them if they are 100% certain on that issue and get it in writing from them (in advance) that they are going to waive any and all charges if they turn out to be wrong. If they balk then it may be time to get another opinion.
As for reusing gaskets I would never do that even on one of my own vehicles.The thought of a POed customer and a money eating comeback is not very palatable.
Thanks for all the replies. I was sick and could not get back to update. I love this forum. 
It also turned out they had to replace a bad ignition coil. I think that was the main cause of the limp mode. Here is a screenshot of the receipt. Please tell me what you think. This is the second ignition coil that has been replaced. If this happens again, how hard is it to diagnose and replace the ignition coil yourself?
Yes, the spark plugs were really fouled. They needed to be replaced. Thanks for your response.
Then you should have been given the option to replace the remaining 4 at this time. It’s like one of those bathroom light fixtures that has 6 bulbs. I installed them all at the same time, then years later they burn out one after another. I would have said something like this:
“Look ADP41, you car has 6 of these igntion coils. They all work under the same conditions and are the same age. 2 of them have failed now, and every time one goes bad your car runs terrible and we have to charge you $125 to figure out which one it is. Would you like to just replace all of them now and be done with it?”
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No experience w/your car, but on some modern car designs if drivetrain computer detects that spark plug is not firing robustly, it may increase the firing voltage in response. That would make the engine run better, and produce less emissions, but could also damage the coil. Probably best for your pocketbook to replace the spark plugs more frequently. A set of spark plugs considerably less expensive than a set of coils. As mentioned above, for maximum reliability might be a good idea to replace the remaining coils as well. Their spark plugs likely had same problems.
As far as the P&L cost, looks about what I’d expect. The fuel induction service might not have been needed, but the cost was pretty reasonable, so that’s a quibble.
The key here is " might not have been needed" if it wasn’t $211 is more than a “quible”
Plugs and coils may be the symptom rather than the cause. You say the plugs were “really fouled”.
I might ask with what were they fouled? Oil?
If the plugs are fouling that bad then new plugs and coils may be headed down the same road as the now replaced ones. And if the plugs are fouling badly that leads to questions about the catalytic converter and O2 sensors.
Thanks asemaster. The coils at autozone and advanced auto are $ 115.99 X 4 = $463.96 for the 4 remaining coils alone.
Yes, that can be a lot of money. But remember, unless you can do the work yourself, every time your car runs rough and the shop checks it out, they will charge you a diagnostic fee and labor to replace the part. So then your bill is the $125 (or more) diag and maybe .3 hours (at $140/hr?) to replace a coil and plug. Plus the cost of the parts.
As a mechanic, I don’t want you to save a few bucks now just to have it cost you hundreds more in the long run, and I want to fix the car completely the first time it’s in. We hate to see a car come back time and again for a problem we could have fixed the first time.
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