Well my goldbrick (the 740 B230F, non-turbo) has started backfiring on deceleration. I can rev it fine, but as I back off the throttle I get some black smoke out the exhaust and a loud "ding" from the engine.

I opened the hood and I could reproduce it by manipulating the throttle. It's the sound of one lead pipe hitting another lead pipe. It seems to be coming from the back of the engine, or the exhaust manifold.

Any ideas?

Thanks folks
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1991 740 B230F 140K miles

Check your plugs. If one is black and sooty you may have a leaky injecter. If they're all black your engine temp monitor could be bad causing a permanent rich gas mixture condition. It's the rear one closest to the firewall.

thanks, I'll check this weekend
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1991 740 B230F 140K miles

Last night I looked under the hood and sure enough the cable going to the TPS had come loose. No more backfiring!!
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1991 740 B230F 140K miles

My backfiring was corrected by readjusting the black throttle box so that at rest/idle you hear that "click". See FAQ's. Reset by adjusting screw, they do creep a little. No more bacfiring because the fuel from injectors is curtailed. Hope this helps you. The backfire sound is of course dependent on the shape and condition of your muffler and hangars.

check your motor mounts.

nope...they're fine....

anything else?????????
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1991 740 B230F 140K miles