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Low RPM, Rough idle, 4 or 5 cylinder and backfire from exhaust

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PROBLEMS:

Low RPM: it stays at 500 RPM and then goes down to almost 0 (car feels like it’s going to stall) and then goes up to 500. I recently change my battery so I had reset the ECU, after reset the RPM goes up to 1200, and next day goes back to 500 to 0 cycles again. I also clean my throttle body but nothing improves.

Rough idle: just rough… :frown:

4 or 5 cylinder: the car feels weak as if I am only running on 4 or 5 cylinder. (Engine light not on and no error code from ECU)


Backfire from exhaust: pretty much any RPM and any speed backfire comes and goes. At first I thought maybe one of my cat is bad, because it only happens with driver side’s exhaust (No black smoke)

Spark plug? Injector? Coil? Timing belt?


thanks in advance
 
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Backfiring is usually caused by unburned fuel entering the exhaust. That would lead me to believe that at least one cylinder is not firing. Check coil packs and plugs.

good luck
 
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What year? Have you recently washed the engine/engine bay? Out for a drive in a bad rain storm? Pull the coils, and BEFORE you rem ove the plugs, have a look in the plug bores for water. Then test each component.

HTH,
LarryB
 
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Larry Bastanza said:
What year? Have you recently washed the engine/engine bay? Out for a drive in a bad rain storm? Pull the coils, and BEFORE you rem ove the plugs, have a look in the plug bores for water. Then test each component.

HTH,
LarryB


95, I clean my engine/engine bay without water. Recently drove in rain (light rain) one of the coil is bad and spark plug #1, #3 and #5 got water on it. I suspect that body shop wash my car with hose spray directly into my side vent. So far this is the only explanation I can come up with. :frown:
 
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How about letting the car idle and pull one coil connector at a time? When the cylinder that is not fire is found, the idle will not change. I'm not sure if you can do any damage to the coil pack this way, but I have done it on other distributor type cars without a problem. Very easy to find a dead cylinder that way.

Good luck!!
 
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