infiniti i30 engine a it lacking in power

My trusted Maxima decided to crap out a few days before our planned road trip (MAF gone bad?). I probably don't have time to diagnose/fix the issue before the trip.

I may need to use my wife's car for the trip. It is a 99 Infiniti i30. The ONLY issue that bother's me a bit and makes me a little hesitant is the engine. Comparing to my Maxima (while it was operating normally :), the engine has a sutble vibration under load. I can feel it in the gas paddle when I accelerate.

I put in new spark plugs, changed engine oil, replaced air filter, no change. I don't know the status of the coil packs. It idles fine. Could a dirty MAF sensor cause the sympton? HP should be very similar to my maxima, but it just doesn't seem as responsive with the suble vibration. (the engine makes a deep humming sound under load and this is when the vibration occurs). The engine oil seems slightly overfilled, could that have caused it?

A mechanic test drove the car while diagnose a different problem, and said the engine is fine. So it's probably not too out of spec, but it doesn't feel quite right. It does make long trip slightly less enjoyable as I find myself let go of the gas, and press it again to see if I can reduce the hum..

I was going to delay diagnose this until a bit later, but the maxima craping out moved up the priority a bit.

Thanks!

Raymond

Reply to
nospam.auto
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If all thats wrong with the Maxima is the MAF, why not swap the one from the i30 onto it & see if it fixes the problem? You can always put it back on the the I30 when you get back from the trip.

Reply to
e.meyer

yes I could. But if In the process I mess up the Infiniti as well, then I am really screwed. At least now it's an OK backup.

I am going to clean the MAF and see how it goes...

Raymond

Reply to
nospam.auto

Ok I found out the oil level in the engine is too high. I forgot to check it after I did my last oil change. I gave the shop 5 QTs of

5w30, and the stupid guy probably dumped the whole thing in it as he didn't return me the half bottle. (my car takes 4.25 QT)

With the correct oil level, and driving this car more, I think I have a better description of this problem.

At RPM 1000-2000 (about 40-50 miles, when the engines shifts gears and the engine drops to 1.5k RPM from 2k+ RPM), There's a subtle hum from the engine. This can be felt both in the gas peddle, and the sound of the engine. The hum can also be felt during initial acceleration from a stop, but it goes away pretty fast as the car picks up speed.

At normal highway crusing speed at 2.5k RPM, even under load with 5 people in the car and some cargo, it runs fine and I don't feel a lack of power, the engine is also quiet, just like my Maxima. Perhaps the slight lack of power I felt was due to the incorrect oil level.

What would be the cause of this hum at 1.5k RPM? Do I need an engine tune up?

The car has 70K on it, has 5w30 synthetic oil. I changed the spark plugs a month ago with OEM plugs and new air filter. (and that's about all I know how to do. ;) The hum was there when I first bought the car

2 month ago, the maintenance I did improved performance but the hum never went away.

This car is known for its ignition coil failures (I replaced all 6 on my Maxima and this car is the same year, but half the miles, and I believe is still running on the original coils). Could a coil that's not working in top condition cause this?

Raymond

Reply to
nospam.auto

How many miles are on the car and is it a manual tranny that has been driven in an, um, enthusiastic manner? My first thought is a weak engine mount allowing a little more of the engine's natural vibration to be transmitted to the chassis where it is resonating. This is only a guess however and really with a description like you give one would have to drive/hear the car to make a diagnosis with any degree of certainty. Not that your description was poor but that kind of noise could be any number of things.

nate

Reply to
N8N

The car has about 75k on it. It is a 99 infiniti i30. It's an automatic transmission. I don't know how it's driven by the previous owner. My guess is average driving. It's mostly local street level driving by the parents, hence the low miles.

Raymond

Reply to
nospam.auto

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