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Cadillac Repair/Backfires going down highway
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Question
1987 Cadillac Sedan In park step on it and it is good backfires at high RPM. When you drive and ease into it it acts like it has no power. Have replaced the rotor, coil and cap. Could it be the catalytic converter collapsing?
Hello,
The problem could be numerous things, but your description of the symptoms could be consistent with a plugged catalytic converter.
To isolate the problem, what we used to do is disconnect the exhaust system at the manilfold. If you do so and donut gaskets are required, make sure you buy them before you partake on this adventure. If you don't use them, you should be able to return if you don't need them.
Test drive the car making sure you have the exhaust tied up good with steel wire. Careful, the engine will be noisy, but if the cat is bad, you will notice an instant difference on acceleration with no acceleration problems. Then if that was the problem, go to an exhaust store like Midas, Merlin or Carex and have the converter changed.
Another way that might show up for you that may be a little easier is drive the car at night. Park the car, let the engine run and look under the car at the cat. If it is cherry red, you know the cat is bad.
I do not recommend driving the car a lot if this is the problem, because under the right conditions, an overheated cat can cause the jute and the carpeting to smoke and start the car on fire. This is an extreme scenario, but it can happen.
Good Luck!
Rob
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Rob Painter
Expertise
Alarm system questions cannot be answered on this forum. These systems are not what I can answer. Without being physically at the vehicle and not knowing what kind of electrical service has been done on the vehicle, there is no possible way to give an accurate answer over the internet. My expertise is in Ignition/key based anti-theft systems. These issues include GM VATS (resistor chip in key blade) PASSLOCK (MRD)-ignition lock rotation based, no special ignition key and the PKIII Transponder (computer chip in key) systems. These systems are not alarm based and are integral with the starting of the engine. This is why I cannot diagnose alarm problems without physically looking at the vehicle: Alarm systems are a completely different annimal than ignition key/lock based anti-theft system. Many alarm questions come from vehicles 10 years old, and since older, many hands that had been involved over the years.I am an expert in all GM factory (ignition/key based)systems. Alarm system questions pose to many situations beyond my knowledge as to what has been done to the vehicle over the years. Some guy may have actually wired the stereo into the alarm system. Who knows? Over my past 30 years in vehicle wiring repair, I have seen unbelievable wiring disaters done by guys that consider themselves "mechanics." I have seen stereos and alarms intalled using surgical tape. I have seen modules burn up, un-fused circuits, wiring jambed between the doors and even lamp cord used for a starter kill. To answer alarm questions over the internet without examining the vehicle is like asking; What does it take to remove a dent?
Experience
Education/Credentials-ASE certified. 11 years with a GM dealer and 17 years with a repair facility dealing with only the repair of theft recovered vehicles.
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