I have a 97 xlt that starting making a popping noise every now and then,very irregularly.Over the past 2mths it got worse.Sometimes loud sometimes not so loud, mostly under load. Up hills or with weight is worse. WE started thinking converter, but computer check showed up nothing, we thought exhaust but they said no. Took to for d dealer ,2 mechanics took it for a drive didnt do it for about 15km, then started,they hadnt heard anything like it, we replaced the plugs{again} and leads, no change. It now does it pretty constantly but still not tht consistantly, please help, somebody. You cant get a manual, in all 6 mechanics later and i am desperate. Any ideas would be appreciated.