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Hello all, looking for help troubleshooting a miss under load on a 2000 Honda Civic SI. The car has 250000 miles, and had a significant overhaul at 200000 miles (rings, headwork, timing belt, water pump…). I still need to adjust the valves from this work.

I was having an issue where the car would die warming up in my driveway after about 10 minutes. Sometimes on rainy days the car would miss and sputter like the distributer cap had water in it, then later it happened a couple time when it was dry. It would smooth out after 10 minutes of hell. I found help pointing to the IAC valve and cleaned it up, and found a couple of sparks from the plug wires that I corrected. The car stopped dying warming up and I didn't have any problems for a month.

For the last 3 days, the car runs great, except it will miss under a slight load a few times until the speed of the car matches the rpms of the motor. It does not matter if the engine is cold, or well warmed up If I give it gas, it will miss intermittently until there is balance again. It feels safe to drive, as long as I don't need to get there in a hurry.

I suck at troubleshooting if this is fuel, electrical, or timing to blame. Does anyone have some good suggestions to try. I appreciate your input.

SR

 
Rep Power: 517

I dunno about the dying issue, but the other sounds like spark....

Load induced misfire usually seems to be ignition related. Somewhere in the ignition system, spark is finding an easier path to ground than getting to the end of the spark plug inside the cylinder.

Got a check engine light on? Got a specific cylinder misfire code you can concentrate on? That could help narrow it down a lot.

Correct NGK or DENSO plugs? Correct gap?



If the plug wires are the type that have a rubber boot on the tip of a plastic tube, they can leak spark between the boot and tube. They can leak spark right through the side of the tube too.

Danger! I do this, I ain't skeered.....With the engine running, I will lift up the plug wire off the plug but not all the way out of the hole, and look down inside. Usually you can see if the spark is coming out of the end of the wire or if it's coming out the side of the wire.
(If this test kills the ignition coil, then the coil was already bad and needed replaced. Better to fail now than to be stranded somewhere at the worst possible time.)

I've found better examples than this but not today LOL





Ooh found one
Pinhole burned thru the tube, spark leak:




Then I might pull the plugs and look for arc trails on the outside like this:




If you do find this, you MUST replace the affected plugs AND wires at the same time. If you don't, one bad part will ruin the new part.



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No water in the plug tubes?

Cap is good, no carbon tracking?

Lightly mist some water onto the distributor cap area while the car is running. If it stumbles or even hiccups at all, that's a problem that needs fixed.

 
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Thanks zone, you have some good suggestions for me to follow. I unfortunately think ala chicken little with things I know just enough to be dangerous with. I do use NGK plugs, gapped correctly. and the plug wires should in the time to replace phase. I did see some sparks hitting the motor because I did not put the guides back on after doing some work (again the motor wasn't missing under load at this time), and in the dark I could not see this happening after they were reinstalled. After doing this cleaning the IACV did the missing seem to start.

Do you have recommendation for plug wires other than OEM?

I did have a misfire CEL on up until a week ago, it would usually on cylinder 1 or 3, but for the first time in awhile the CEL is off. Crazy how when the CEL was on the car ran good, now that it is off it is not running right.

I appreciate the quick response, and will look closely at the wires and plugs Saturday.

Take care,

 
Rep Power: 517

Not really, many aftermarkets from the parts stores are hit and miss. Some work good, some are crap as soon as you try to plug them in.

The blue NGK wires were good though.

HTH