Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

RPM revs up and down non-stop and now check engine lite. 1998 EX v6

The car was not started for about a week and this morning when I turned the car on the RPM start high at 1k and then after a minute it just went to 1.7k and would rev between 1.2k and 1.7k. I let the temp of the car raise and then did a little revving myself. The idle went to 1k again with temp gauge about 25%. I put the car in drive and started driving and in about 5 minutes the check engine lite came on. I pulled the car to the side and turned it off to check the oil. The oil was fine and after about 3-5 minutes I started the car back up. The idle is fine now between 500 - 700 but the check engine lite stayed on. I drove about 9 miles with the check engine lite. Before the check engine lite the drive idle was at 1k - 1.2k. So, what is going on with my car? thanks!

The illuminated Check Engine light (CEL) means that the car’s OBD2 system has stored a trouble code (or two, or three…). Go to Auto Zone, Advance Auto Parts, O’Reilly, or another parts retailer that will read the stored trouble codes free-of-charge, then come back to this thread to report those codes.

Incidentally, the Check Engine Light has absolutely nothing to do with the level of oil in your engine, so please don’t rely on that light to tell you when you need to add oil. Similarly, do not rely on the Oil Pressure Warning Light to inform you of a low oil level. You should check the dipstick frequently, especially if your car consumes some oil between oil changes.

Thanks for a quick response. I was wondering if you could tell me why the RPM acted the way it? I am at work right now so when I start my car again on my way back I will stop by kragens to see if they can check the code for my car. I am still curious about the RPM and wonder if it will do that again in the evening when I start my car again? Thanks again for the quick response and I will post again with the code.

There are a number of things that cause this. That’s why the code is the first step. It very well might point right to it or at least say where to start. Otherwise its all just “well, it could be this…or it could be that…or it could be…”

From prior experience I would suspect a sticky thermostat, which keeps the engine from fully warming up.

…or a dodgy IAC, or a vacuum leak, or…

The IAC was the first thing that jumped into my mind too, but I also would emphasize that the first step should be to check for stored fault codes.

VDC’s point about the CEL not being indicative of oil lebvel was a good one.

I’d like to add that the oil light is not there to tell you the oil is low either. It’s there to tell you that the oil is SO low that the engine has lost its oil pressure…and your engine is now in "phase two… self destruction imminent) mode. Your dipstick is there to tell yo the oil is low and needs to have more added BEFORE it gets to “phase two… self destruction mminent”. Check your dipstick regularly. I do.

I congratulate you on pulling over, shutting down, and checking the only thing you knew to check. If something catastrophic does happen, this action will save your engine. You did the right thing.

That CEL (check engine light) is just a kid in class waving her hand trying to get you attention because she has the answer. You need to have the codes read. Some places will read them for FREE. Try Autozone or Advanced Auto Parts. Get the exact code (like P0123) not just their translation into English and post it back here.

Thanks! I try to listen to car talk as much as possible (when ever I have time). Okay, so I went to a local mechanic and he check the code foe me for free. The code came up PO505/P0505 (not sure if that was zero or caps ‘O’). The code description were multiples (I found this while Goggling the code for 1998 accord: P0505 ICS Malfunction) but the mechanic says that he will change the coolant sensor and clean the throttle body valve for $150. His explanation was that the sensor and the throttle should be changed but he will just clean it since the throttle will be too expensive. What do you guys think? He asked me to come by tomorrow morning with cold engine so it will be easier and faster for him to do the job.