arielscar Posted August 31, 2007 Share Posted August 31, 2007 While this topic appears here regularly, there is no consensus on cause, no doubt because a number of things can bring it on. I am second owner of a very nice and well cared for SC400 - at 105K, I began to get a hesitation in low rpm acceleration and at highway speeds after letting up on accelerator and attempting to resume speed, but was very smooth at constant rpms. I put together a parts stash to address this, starting with plugs, wires, coils and distributor rotors & caps. The missing got gradually worse, and I stopped driving it until I had time to address it - then, while starting it up I got a loud and loose sounding rattle that I assumed was coming from a shelled out cat. Wrong! When we got it apart, both rotors were cracked and broken with pieces of them loose inside the rotor caps and other peices had been ground into a fine powder! And, all ingition parts had obviuosly never been replaced, which we did. I'm frankly surprised that it could run at all, especially with such minor symtoms. The old plugs looked very clean, and all the other parts that we replaced looked ok, but we didn't measure coil output. Anyway, it runs like a champ now, but I think I will replace the timing belt and water pump next chance I get. Quote Link to comment Share on other sites More sharing options...
pwonder Posted August 31, 2007 Share Posted August 31, 2007 While this topic appears here regularly, there is no consensus on cause, no doubt because a number of things can bring it on. I am second owner of a very nice and well cared for SC400 - at 105K, I began to get a hesitation in low rpm acceleration and at highway speeds after letting up on accelerator and attempting to resume speed, but was very smooth at constant rpms. I put together a parts stash to address this, starting with plugs, wires, coils and distributor rotors & caps. The missing got gradually worse, and I stopped driving it until I had time to address it - then, while starting it up I got a loud and loose sounding rattle that I assumed was coming from a shelled out cat. Wrong! When we got it apart, both rotors were cracked and broken with pieces of them loose inside the rotor caps and other peices had been ground into a fine powder! And, all ingition parts had obviuosly never been replaced, which we did. I'm frankly surprised that it could run at all, especially with such minor symtoms. The old plugs looked very clean, and all the other parts that we replaced looked ok, but we didn't measure coil output. Anyway, it runs like a champ now, but I think I will replace the timing belt and water pump next chance I get. SOMEONE HELP PLEASE!!!!! I just bought a 92 sc400, and im having that same problem when Im cruising between the speeds of 40 - 60mph and let off the accelerator im getting that hesitation and when i resume accelerating im getting a clunk. Anything under 40 mph its fine. What could it be? Quote Link to comment Share on other sites More sharing options...
jzz30 Posted September 2, 2007 Share Posted September 2, 2007 why dont you check what the first guy did first. then work from there. Quote Link to comment Share on other sites More sharing options...
RICK323 Posted September 18, 2007 Share Posted September 18, 2007 While this topic appears here regularly, there is no consensus on cause, no doubt because a number of things can bring it on. I am second owner of a very nice and well cared for SC400 - at 105K, I began to get a hesitation in low rpm acceleration and at highway speeds after letting up on accelerator and attempting to resume speed, but was very smooth at constant rpms. I put together a parts stash to address this, starting with plugs, wires, coils and distributor rotors & caps. The missing got gradually worse, and I stopped driving it until I had time to address it - then, while starting it up I got a loud and loose sounding rattle that I assumed was coming from a shelled out cat. Wrong! When we got it apart, both rotors were cracked and broken with pieces of them loose inside the rotor caps and other peices had been ground into a fine powder! And, all ingition parts had obviuosly never been replaced, which we did. I'm frankly surprised that it could run at all, especially with such minor symtoms. The old plugs looked very clean, and all the other parts that we replaced looked ok, but we didn't measure coil output. Anyway, it runs like a champ now, but I think I will replace the timing belt and water pump next chance I get. SOMEONE HELP PLEASE!!!!! I just bought a 92 sc400, and im having that same problem when Im cruising between the speeds of 40 - 60mph and let off the accelerator im getting that hesitation and when i resume accelerating im getting a clunk. Anything under 40 mph its fine. What could it be? Quote Link to comment Share on other sites More sharing options...
arielscar Posted October 6, 2007 Author Share Posted October 6, 2007 An update: I have now completed the rest of the maintenance - a new timing belt, pulleys, tensioner, cam shaft seals, water pump, thermostat and serpentine belt. Replaced oil with synthetic. Runs like a brand new car, very smooth all the way through the power curve. This weekend I'm replacing the Transmission mount. Should last for another 100K!! Quote Link to comment Share on other sites More sharing options...
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