Random misfire on all cylinders

Tiny
LOPYLOBSTER
  • 1999 HONDA CIVIC

Engine Mechanical problem 4 cyl Front Wheel Drive Manual 91000 miles

Ok, my car is throwing codes p0300-p0304 and p1399, they are cylinder misfire 1-4 and random cylinder misfire. I've changed my distributor, spark plugs and wires, pcv valve, fuel filter, o2 sensor, ground wires, valves adjusted, valve cover gasket, compression test came out good, and injectors are firing. But I still keep getting these codes. The Car has no EGR because it's a SI model, and it's all the cylinders misfiring. Not sure where to go from here. Any ideas?

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Wednesday, September 17th, 2008 AT 4:26 PM

2 Replies

Tiny
RASMATAZ
  • MEMBER

A code P0300 may mean that one or more of the following has happened:

If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.E. Spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.K.A. Coil packs). In some cases, the catalytic converter has gone bad.

This can be a mixture issue which can be caused by a bad fuel pump, vacuum leak or a bad map sensor. When a MAP sensor goes out it may or may not trigger a check engine light. Here are some guides and a digram (below) is help you see what's going on.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

and

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

and

https://www.2carpros.com/articles/repair-lean-mixture-codes-p0171-or-p0174-on-some-manufacturers

Diagram (below)

Cheers,

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Friday, September 19th, 2008 AT 10:49 PM
Tiny
LOPYLOBSTER
  • MEMBER

Alrighty, couldn't find a vacuum leak, but you hit it on the money with the MAP sensor I replaced it and the problem was fixed!

I love this site thanks guys!

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Saturday, September 20th, 2008 AT 3:49 AM

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