I took my 97 sedan (97k miles) to Jiffy Lube for an oil change today, and they suggested I get a Coolant Flush and a Fuel Injection Cleaning. I let them do the Fuel Injection cleaning. I thought it was worth a try.. It seemed to be doing something, as tonnes of carbon came out of my exhaust.

But afterwards, as soon as I started up my car, the Check Engine Light came on. I told the Jiffy Lube guys this and they said it was "normal" - and it would go away within a couple of hours, after the lines finished cleaning themselves out.

Is there any truth to this?? I just had my 90k checkup, and the engine light hasn't been on at all until I had this cleaning done. Should I be worried?