I am having ongoing problems with the truck miss firing and rough running. Timing is ok, replaced cap and rotor,coil. It still starts rough,idles rough and misses when at cruising speed,although it seems...
Misfire is a common driveability problem that may or may not be easy to diagnose, depending on the cause. A misfiring cylinder in a four-cylinder engine is, pardon the pun, hard to miss. The loss of 25% of the engine's power output is the equivalent of a horse trying to run on three legs. The engine may shake so badly at idle that it causes vibrations that can be felt in the steering wheel and throughout the vehicle. The engine also may be hard to start and may even stall at idle, depending on the accessory load (air conditioning, headlights and electric rear defroster, for example).
When misfire occurs, performance suffers along with fuel economy, emissions and idle quality. And, when a misfiring vehicle is subjected to an emissions test, it will usually fail because of the unusually high levels of hydrocarbons (HC) in the exhaust.
What causes a cylinder to misfire? Basically, it's one of three things: loss of spark; the air/fuel mixture is too far out of balance to ignite; or loss of compression. Loss of spark includes anything that prevents coil voltage from jumping the electrode gap at the end of the spark plug. Causes include worn, fouled or damaged spark plugs, bad spark plug wires or even a cracked distributor cap. A weak coil or excessive rotor gas inside a distributor would affect all cylinders, not just a single cylinder.
"Lean misfire" can occur when the air/fuel mixture is too lean (not enough gasoline in the mixture) to burn. This can be caused by a dirty, clogged or inoperative fuel injector; air leaks; or low fuel pressure because of a weak pump, restricted filter or leaky pressure regulator. Low fuel pressure would affect all cylinders rather than an individual cylinder, as would most air leaks. A leaky EGR valve can also have the same effect as an air leak.
Loss of compression means the cylinder loses most of its air/fuel mixture before it can be ignited. The most likely causes here are a leaky (burned) exhaust valve or a blown head gasket. If two adjacent cylinders are misfiring, it's likely the head gasket between them has failed. Also, if an engine is overheating or losing coolant, it's likely the head gasket is the culprit.
Intermittent misfires are the worst kind to diagnose because the misfire comes and goes depending on engine load or operating conditions. They seem to occur for no apparent reason. The engine may only misfire and run rough when cold but then smooth out as it warms up. Or, it may start and idle fine but then misfire or hesitate when it comes under load. Also, it may run fine most of the time but suddenly misfire or cut out for no apparent reason. Intermittent misfires can be a real challenge to diagnose, so let's start with a steady misfire in one cylinder before moving on to intermittent misfires.
Hope this help.
Thank you, I am having it towed in today and I will let you know how it goes.
engine light is on I had the store run a scan; it showed #3 & #4 cylinder not firing when at idle. Engine runs fine at cruising speed. This is a 2000 dodge caravan se 3.3. What could be wrong? I suspect that I have a malfunctioning BCM, would that cause engine problems?
I wanted to update everyone on my solution after havingit repaired. I had it towed in and it was determined it was a bad wire connecting the PCM. Repairs were relatively inexpensive ($181) and has been fixed for about 4 weeks and seems to be running fine.
I am having a similar problem with the exception of the fuel out of the exhaust. I am getting misfire on #1 and #4 cylinders. I already had to replace the front cylinder head (2,4 & 6) due to a burnt valve exhaust valve. I had this problem before the replacement and still now. It has all new plugs, wires and a new ignition coil. And, it also has a new pcm. So, if you could send me more info on this wiring problem, maybe I can get this beast a rolling again. And as a side note, when I was troubleshooting the problem the radiator has gone to leaking now. Ugh!
Loud muffler/exhaust. No engine lights on. Was driving this morning and all of a sudden a strong smoke smell. Turned heat down to low and smell got better. Any suggestions?
stopped at gas station and filled up. started the car and it didn't want to run. all cylinders are not firing and smell fuel bad.
2001 check engine light on ran check said pug 3 repaced plug but not coil 112000 miles just purchased used of curse
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