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My 1996 Honda accord with 200k miles has started acting up.

After a long vacation, I came back and the engine would seriously stutter at all speeds, especially on acceleration. I assumed it was fuel delivery, so I put some fuel injection cleaner in a fresh tank and took a quick look at the air filter. Everything seemed fine. Then it stalled and refused to start in an intersection about a month ago, that was fun.

I had it towed into my mechanic who changed the oil, replaced the valve cover gasket, replaced the spark plugs and cleaned the throttle body. The massive stuttering and stalling stopped for a bit, but now it's back again in a much more mild form and only at stoplights.

The engine will hover at around 750 rpm, and every few seconds dip below for an instant and stutter. It reminds me of turning down the choke too fast on a carbureted motor.

I've switched gas stations and upped to 89. I brought it back in a couple weeks ago to have my mechanic look it over again and he couldn't find anything wrong.

Any suggestions on how to debug which part might be causing this and how I can fix it?


Solved:

The cat was falling apart. Breathing in wasn't the biggest issue. Breathing out was.

When the pieces of the honeycomb rattled around underneath it would prevent exhaust and suddenly start working again. Hence erratic behavior. I guess I forgot to mention the sound of rustling leaves under my car (before fall even hit). That was my destroyed cat.

I had a few faulty O2 sensors in the past couple years which likely led to my Cat's demise.

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2 Answers 2

I've seen something similar to this before. It sounds odd, but try taking a spray bottle filled with water, start your engine, and heavily mist all around your spark plug wires (get EVERYWHERE around the wires) and see if the engine begins to stutter more than usual. I noticed from your profile that you live in the state of New York. Being close to the Atlantic, I'd assume you get some fairly cold, wet days.

If so, then at least it's a cheap fix. Just buy some new wires, plug them in (carefully, making sure they're in the correct order), and it shouldn't bother you again (at least until the new ones wear out).

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That's how I found that I had a cracked distributor cap. Water spray bottle is a very handy diagnostic tool! :-) –  Brian Knoblauch Nov 8 '11 at 13:10
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It's definitely the first thing I turn to when things stutter. I'd rather pay $2 for a squirt bottle than pay a mechanic $60 for them to use theirs. I also find that it commonly does find the problem. –  Sivvy Nov 8 '11 at 16:04
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if you're only having idling problems, and no problems while driving, that's usually an air/fuel ratio issue, and can often be traced to the idle air control valve or a vacuum leak. The IACV opens to allow more air into the engine while the throttle plate is closed.

Prior to removing the IAC, take a spray bottle and mist water on your vacuum hoses and pay attention to how the engine reacts. If the engine shudders more than usual when misting water over a given hose or connection, you may well have found your problem, and can fix it for cheap.

Failing that, if you can find it, remove the IAC, check the quality of the gasket, and the condition of the IAC internally.

Fill the IAC with gasoline or throttle body cleaner and let it sit for 10+ minutes, then wipe it out with some q-tips and/or paper towels. If the gasket is not in good shape (though generally it's a good idea to replace it every time you remove the IAC, sometimes you can get away with leaving it there), replace that now. clean the electrical connections to your IAC and coat them with dieelctric grease at this time.

Once that's all cleaned up, and the throttle body is clean, reassemble it and see what you're getting, with any luck you'll have a more even idle, and the IAC was just full of crud.

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The cat was falling apart. Breathing in wasn't the biggest issue. Breathing out was. –  ZMorek Sep 7 '11 at 15:47
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