Ok so I purchased this car about a year ago and it had 198000 miles on it. I have not driven it that much in the year... car currently has 203000 miles on it. I recently changed the oil and filter put in mobil 1 5w-30 and a mobil 1 oil filter. Also cleaned the K&N filter as it was pretty nasty... car has a SLP Lid and TSP Rumbler Catback and some sort of Shift Kit that was in the car when I purchased it. Other than that it is stock... Car does have high mileage so I know this could probably be a number of things but was hoping I could get some help finding out what it is... okay heres whats going on:

On idle the car idles REALLY rough the longer you leave it in idle. It starts out fine but after about 5-10 mins it starts shaking my seat a bit while sitting in it... also I notice that the lights on the cluster are also surging brighter and then dimmer when this is going on. Also when putting it into reverse after its been sitting in idle for a while it almost seems as if it wants to die but never does.... just slowing rpms kick back up... Another thing happened last night.... speedometer needle at idle is bouncing up and down from 0 to 15 mph constantly... also noticed oil pressure gauge was sitting at 25lbs... never has been that low before usually lowest is 35-40 range.... Got in the car this morning to come to work and at cold start oil pressure is at 60lbs... dropped down to 35-40 again like normal on the way to work... car still idles rough but hasnt died on me yet.... just kinda trying to figure out all these crazy things.... my voltage reads steady in the 13-14 range even when all this surging in lights etc is happening... so any suggestions thoughts would help... thanks...

also oil level is fine in car.... checked this morning...

 

the surging light is voltage regulator in the alternator,so you need a new alternator. same thing was happen to me when i went into reverse all the lights got dim like it was going to die

 

Have both the Battery and Alternator checked. I had a battery issue last year where the inside part of the terminal rotted out and I would get intermitten issues like this.

 

okay sounds like i'll get both tested... my question does that have anything to do with why my oil pressure guage was reading so low?? thats the biggest thing that worries me is that it dropped down that low...

 

it could be just a bad gauge or sending unit. thats a lot of miles for everything to stay perfect. hook up a scan gauge or tuning software where u can actually read the oil pressure. my truck had a bad gauge in the dash where it stuck on full pressure all the time even off. it could be very simple, if not it might have blow by or the motor is actually taking a dump which could also explain the surge at idle and stuff. if it doesnt shake at first but then does, oil could be making it past the rings down the piston wall.


check the pressure first and the alternator. then you could go from there.