What's wrong with my car?
 

I have a 99 SE Maxima (97k miles) and I always fill up my gas using premium. This might just be a coincidence, but the last 2 times that I used regular/plus, my CEL came on a few days later and I noticed that when I pressed on the gas, the acceleration was not smooth. The car felt very shakey in the low rpms but got a little better in the higher rpms. It also felt like there was a lot of hesitation during the acceleration. It almost felt as if the clutch was slipping badly or something was wrong with the air intake.

I was unable to get the CEL code because after I filled up my tank with premium again, the light went away after a few days. The first time this happened was a couple months ago when I filled up with regular. I had the same issues and the CEL came on, but a a week later I filled up with premium and a few days later the light went away and everything was fine.

My car seems to be fine now, the acceleration is smooth and I don't notice any hesitation. I don't think it has to do with the type of gas I used and probably was just a coincidence. Any ideas? I'm confused :confused:

Thanks in advance!

the lower octane was probably setting off your knock sensor... stick to 89 octane or higher. i believe the manual calls for at least 91??

i always get premium just to be safe.

Check for codes (hidden ones),now....even if CEL is off..

:sprint:

may be time to change your knock sensor

Always use premium, it is better for your car and it is still cheaper then regular because you end up getting better gas milage which makes up for the 20 cent deiffernece per gallon.

Check your codes from Autozone for free. I have a 99 GLE (with 171000) and i have had no problems since i started using Permium.

Cheap gas will cause the knock sensor to retard your timing, costing you performance. It should not cause a CEL or shaking. Poor performance might make it doggy enough to lurch if your motor mounts are worn.

Not quite, engine knock and ping will cause the KS to retard timing. Most cars run fine on regular. Engine knock (ping) can be caused by a number of things, including but not always related to low octane.

Knock and ping will not set a CEL, a faulty KS will not set it either. What you describe sounds like a misfire. Check for any stored fault codes, they can be stored without the light on. I would suspect a coil pack is getting weak as the 99's are known for it.

Yeah, have the computer codes read. You may have a ghost code (pending code) hiding in there. Come back when you find out what it is.

If you haven't done much maintenance on your car do the following:

Fuel filter, spark plugs, run some seafoam through your intake manifold, run some seafoam in a tank of gas, and also check your coil packs. All the info on how to do the above can be found on this site.

:sprint: