1997 Lumina Service Engine Soon ??????

My 1997 Lumina has done 145k kms (90k miles). This problem started 4 days ago. The Service Engine Light came on and the car started vibrating/shaking. I thought this was coz oil change was due and so changed oil and filter but the problem persisted.

Something funny/crazy is happening. When I am driving at 40KPH and remove my foot from the accelerator, the car continues to accelerate upto 60. As if something is pressing the accelerator. When I was to park, I put the gear in P, apply foot brake and lo and behold, the rpm needle starts to climb.

Has anyone faced similar problem? How do I resolve it? The manual has given a few reasons for the Service Engine Light remaining on. I am trying to eliminate the possibilities one by one. Meanwhile will appreciate help for the experts.

Cheerio.

It sounds like you are misfiring, either due to an spark issue or a bad injector, and the ECM is trying to cope with the power loss by making it up with added throttle opening. You may have a massive vacuum leak causing both problems. Does the motor smooth out when you give it gas? As soon as you open the throttle, a vacuum leak will be overcome, and the misfiring will stop. If it is sucking major air somewhere it shouldn't be, it might act like this. Take a look under the hood and see that no vacuum lines are off. I remember seeing them do this after a pop through the intake if it didn't catch and start once, backfire thru the intake and blow a vacuum line or two off. Then you get the rough idle, and the engine seems to hunt for it's idle speed.

Thanks jeffcoslacker.

I took the car to the mechanic for scan test. The diagnosis pointed to E.G.R. valve (dont know what it means but thats what the mechanic told). It had carbon deposit, so was cleaned. The light is gone and the car does not vibrate anymore. :)