New to the forum but I've had a problem lately with my 99 Si. I'm getting a CEL code of misfire 1, 2, 3, and 4 also multiple misfires. I've replace the distributor with an oem replace, adjusted valves (none were loose), cleaned injectors, replace fuel filter, and sprayed IAC valve (idle was still rough after this). Idle is rough, engine shakes when accelerating but this all only happens when at normal operating temp. When cold idle is fine and not flucuating, but once warm it runs horrible! Please help lost what to do next!! Quick note when I turn on the heat or give it a little gas and hold the RPM around 1500 the misfire smooths out!

 

I have been having the same problem with my 96 cx hatch. I assumed it was because it was such high mileage, but when I did the same things you mentioned above it continued. Except with one crazy twist that now magically the CEL has turned off and nothing seems wrong...? Then when I least expect it, it happens again. Almost like my car is on its period or something...

 

^Your primary O2 sensor is possibly faulty. Does the problem go away if you unplug it?

 

My 2000 civic si is doing the same thing. I did everything I could and still no change. My local Honda Dealership has had it now for (4) days and they dont know what the problem is. Did you do anything to your car before the misfiring began?

 

I haven't tried that yet, I have tried everything except this, is the primary the sensor at the end of the headers? Should I just unplug it and monitor its progress? I'm believing it is also O2 due to gas mileage just being **** and it smells like raw gas on heavy acceleration sometimes.

 

What exactly have you tried? And have you tried the o2 sensor as they suggested?

 

By definition, the primary sensor is before the cat and the secondary is after.

The diagram below may help.

Unplug it and drive the car to see if the performance problems disappear.

 

Great diagram, will remove tomorrow and will see how it turns out? Will report back to the forum, anything else I need to do others than unplug it?

 

Nope.

1. Unplug the primary O2 sensor connector.

2. Drive car to warm up engine.

3. Continue driving to see whether problem is eliminated or not.

 

Ok great thanks ill be sure to try that and let you know tomorrow

 

Have I change plug wires and spark plugs? Mayb bad gas? I've had a bad plug wire go bad on my Honda and it could cause the other spark plugs wire to misfire when one is bad. I say check plug wires with the spark plug connected first. Take one out one by one first (with car turned on) with the spark plug connected and put wher the end of the spark plug end near the valve cover bolt. If u see spark then the plug wire/spark plug is good, if u don't see no spark them replace plug wire/spark plug if no spark is seen.

Try that out and see

 

Also if u see spark turn the car off and screw the spark plug back in and do the same to the other plug wires/ spark plug as u did the first one.

 

i have replaced both wires and plugs, always with Denso, i have to constantly change the plugs due to the tips gather white carbon on the end of them due to extremely rich run. The worst is when it is all warm, up until that point it feels great then it just goes down hill

 

Ther are 4 plug wires. So two were bad?

 

When all 4 plugs were removed they were equally white tipped

 

Have u checked to see if ur burning coolant or losing coolant or engine running hot?

Could b a lot of things.... Headgasket, bad fuel injectors, bad fuel pump, bad ignition coil, bad plug wires, bad spark plug

Mayb ur timing belt jumped a tooth and could cause it too.

 

Engine isn't running hot and coolant is all intact; I don't believe it's head gasket because the oil isn't milky, I also assumed injectors, bought a rebuilt kit and rebuilt all the injectors. Bought brand new distributor so the ignition coil can't be the cause. New plugs and new wires also. I can surely buy a timing light and monitor the spark that way but it doesn't explain the reason it only does it when it's normal operating temp. Very stumped on what to do other than try the o2 sensor tonight, let me know if y'all know any other ideas! Thanks

 

If it anything I've posted then I'm stumped too. Hopefully anyone else on here can chime in and help the guy out.

If u do find the problem please let us know

 

Has anyone done a compression and leak down test?

 

Will def keep everyone informed, and compression 145 all the way around

 

Compression 145 all the way around

 

is that with the throttle open? that is extremely low for any gauge.

 

And/or cold engine?

 

Open throttle? Wet compression test, I did it cold, disconnected spark, hooked up gauge cranked it over and got 135-145psi on all 4 cylinders

 

The throttle plate should be wide open (WOT) for the compression test.

When possible, it's also best to do the test when the engine is warmed up.