Help

[MidShip]

I just came into a 93 MR2. I started the car and idled fine. But when revved up it backfires when the turbo starts to spool. Like it hits a rev limiter or something. Need Help please.

[Wally]

That's generally caused by a hot lean mixture. But other things to look at are:

colder plugs;
excessive carbon buildup on exhaust valves;
ignition retard on boost;
valve timing.

Check your fuel regulator is seeing a the rise in plenum pressure. If a MAP is fitted make sure it is also seeing plenum pressure.

[tech4america]

It definitely lost its HP.

Do a compression test, then and ignition test and finally an ignition test ...

[Wolfe]

werd on the hot lean mixture, I have never run across the problem but I have heard that before, if you have lost hp though I would check for the simple stupp first before spending any money on it(aka boost leaks, althought they would not cause the backfiring)

[JoeThaMan]

Might check and see if you have any boost leaks. if you have a boost leak it could run overly reach and cause backfiring or run too rich for the plugs to ignite the air/fuel mixture. As a starting point, though, I would make sure it has all the maintenance done, ie plugs, wires, filters, pcv, etc, then start to diagnose the problem.