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:unsure: I have a SC400 that is running ruff; have already replaced both catalytic converters, spark plugs, wires etc....this happened all of a sudden at a stop light, this was 3 weeks ago, it's been in the shop all this time. It has no power and after it runs for 6 to 12 minutes the cats and pipes are glowing red....Any suggestions. I hate to see my shop bill for this one.
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:unsure: I have a SC400 that is running ruff; have already replaced both catalytic converters, spark plugs, wires etc....this happened all of a sudden at a stop light, this was 3 weeks ago, it's been in the shop all this time. It has no power and after it runs for 6 to 12 minutes the cats and pipes are glowing red....Any suggestions. I hate to see my shop bill for this one.

Check the ignition coil, there are two coils on your sc400.

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What's causing the cats to become glowing red is that raw unburned fuel is getting into the cats because it's not being burned. This obviously means that you don't have a good spark. I'd also look at the coils because I'm betting that one of them is bad. Pull each plug and check for it's condition. If it's soaked in fuel then you know that plug isn't firing.

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It sounds to me like your timing is retarded. You may have blown the computer or one of the sensors.

If the ignition timing on a car is retarded, then less power is made because the air/fuel mixture doesn't completely combust during the compression/combustion cycle. The flame front completely combusts after the piston has started its power stroke. This results in a loss of power.

The unburned gasoline then burns in your exhaust manifold and catalytic converter, heating them up (even to a bright red color).

I suggest you check your timing with a timing light to see if this is the problem.

Also you can connect a vacuum gage to your intake manifold with a T fitting and monitor the vacuum at idle. Normal is around 18-22 inches of mercury. If the timing is retarded, you will get a low, steady reading on the gage (i.e. around 14 - 16 inches of mercury.

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:unsure: I have a SC400 that is running ruff; have already replaced both catalytic converters, spark plugs, wires etc....this happened all of a sudden at a stop light, this was 3 weeks ago, it's been in the shop all this time. It has no power and after it runs for 6 to 12 minutes the cats and pipes are glowing red....Any suggestions. I hate to see my shop bill for this one.

the same thing happened to my sc400. the driver side plug wire coming from the coil had broken & half the cylinders were getting no spark. the cats glowed red & melted after very little time( 2 miles driving). i had to replace the cats & plug wires to fix the problem( the cats directly after exhaust manifolds)

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ok just swapped coils with my LS and sure enough the secondary coil was out. as soon as i changed it the car ran a bit rough at first because it had to burn off the extra fuel but i revved it for a bit and the smoke cleared but as soon as i started i could tell and it purrs like a kitten again!!

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