Hello everyone! First time 350z owner and poster in this group, guys I just bought an Automatic 04 touring convertible with 145k miles for 5200$ from private individual. Now I test drove the car before I bought it of course and noticed no major issues and no engine lights Etc…
HOWEVER… I noticed quickly after buying it that when the car is in drive but at a complete stop AKA idling, it is inconsistent but it will shake / pull for a second every 10 to 20 seconds. The RPMs dip a little immediately after this shake/pull. Also, it ONLY does it in DRIVE. I noticed turning on the AC makes it worse, and that it does it less when Air knob is OFF. Its very aggravating since Im already stuck with car and I have to fix it.
P.s. car runs amazing/shifts excellently, starts up easily every time with NO engine lights. Thanks so much for reading this!
Sounds like a typical idle air control valve issue. Remove the valve and clean it good with carburetor cleaner. While you are at it clean the intake as well. Search youtube for some examples. There are tons of them.
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Thank you so much for replying, so you dont think its major? That makes me feel much better… im very amateur at car mechanics but i know how to use Youtube and will do exactly like you said. Thanks again
The AIC valve is responsible for the control of the idle… HOWEVER what you are describing here sounds to me much more like an intermittent engine misfire. The AIC valve is suspect when you’re engines idle speed is not correct…this would be noticeable in Park and when you start the engine cold…the engine rpm’s should be higher when cold and then slowly transition to a slower engine rpm when warmed up… If it cannot do this then the AIC is suspect. But you are describing an engine misfire…and intermittent one at that. So I would leave your AIC alone for now…
The reason you notice this more when you are in Drive and at a stop is because you added a load to the engine and it is allowing you to notice the misfire more so than at idle and Park with no load…turning on the A/C is yet more load on the engine…and thus…you notice a degree even more.
A VERY very common cause of this issue is when the valve cover gasket leaks INTO the well of the spark plug. The plug well fills up with engine oil and will short to ground that ignition coil…which will cause a misfire… and very often a misfire with NO engine light…because technically the ignition coil is working it is just being shorted to ground and many engine ecu’s do not make this distinction and illuminate the engine light. This type of valve cover gasket leak is common and shows no other outward signs of leaking…you will only notice it when you have an engine misfire and go to change your spark plugs.
So, look into this… I have repaired many many vehicles with this situation… no engine light and an intermittent misfire. I strongly recommend you change your spark plugs…while doing this…you will also be checking for a valve cover gasket that is leaking into the plug wells. I cannot count how many vehicles where this was the easy solution…but it is a large number.
Let us know what you get…
Blackbird Out
The first thing I do after I buy a used car is change plugs. This idle problem has many possibilities, but so far you have been given the first places to check. These recommendations cost you nothing so far, because you should be doing them on this car anyways whether you had problems or not. If you’ve never changed plugs before, you should you tube that also. The most common mistake for beginners is forgetting to clean spark plugs and wells before removing plugs.
Not properly gapping and over tightening is another problem for beginners.
I’ve had numerous people tell me that plugs are pre gapped and not to worry about it. I can tell you from common sense and experience this is not true. My first proof was doing plugs in an old V8 van. They made changes to the engine half way through the year. Plug gap was different on each half of year. And not just a few, but quite a few times the pre gapped plugs were not correct for application. Always have and always will check gap.
Thank you guys so much for the lengthy and detailed responses. Im very much a beginner and I know it sounds easy to you guys but iv never changed spark plugs and know nothing about this “gap” stuff and over tigbtening… im worried ill screw it up but if I youtube it i can probably pull it off.
But are you guys basically saying changing the spark plugs should fix this and then i can quit worrying about it?
Changing the spark plugs could fix this. The only way to tell if it should or will fix it is to have the ability to be physically present to make a confident diagnosis. But on the positive side, if you change the plugs, and it doesn’t fix the problem, you didn’t waste any time or money because in this situation they need to be replaced regardless.
Sorry to be my old school butthead self but I consider any Datsun/Nissan Z car with automatic transmission an abomination.
Concur with the comment above, sounds more like a misfire problem than the idle air control (IAC). If you can get this to occur at a shop then they could fiddle with the IAC to see if it makes any difference, so while I think that’s not the problem, since it is easy to check that’s probably the place to start.
If it is a misfire , that’s usually caused by a problem w/one of these
- spark
- air/fuel mixture
- compression
A basic tune-up would be where to start for those, checking for diagnostic codes in the engine computer memory, new plugs, new engine air filter, new fuel filter, basic ignition system test, fuel pressure test, valve clearance (if applicable), and compression test. Once you have done all that, either the problem will be fixed, or you’ll be well on the way to getting it fixed.
The recommendation here btw is to always pay your own mechanic to do a pre-purchase inspection before buying a used car. That will often catch this sort of problem.
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Okay guys iv decided im going to start with simply changing the spark plugs and see if that fixes it. Im going to try to do it myself. If it doesnt fix it, then im going to have to pay a shop money to figure it out because I work and go to school and dont have time for this. Thanks everybody
Try to get the diagnostic codes read out as well. Might be the reason you were looking for to buy an inexpensive obd2 code reader. The codes are easy enough to get, and could provide important clues. Replacing the spark plugs is like an oil change, if done properly, will only help, never hurt.
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Well sure enough I was on the highway and past 80 miles an hour and it triggered an engine light and then it went away at the lower speeds only to return again when I went 80 plus. I’m going to get the plugs changed within a week and hope for the best thanks