I've got standard equipped a 95 Civic EX (1.6l D16Z6) that has recently started misbehaving. I do most of my own tune-up work--valves, plugs, timing, & oil. 110K miles.

About a year ago, when I was putting the valve cover back on, I noticed that the breather hose that clamps to the valve cover was cracked. I drove it anyways (probably not smartest thing to do), and it was OK, but it did hesitate just a little at low RPMs (<2200) at cold and hot. On Friday, it got noticibly worse overnight. The check engine light never came on.

On Saturday, I check the the valve lash, & replaced plugs (forgot to look at them closely--they were a little black, but I don't think the electrodes were fouled--will check when I get home this evening). I also changed the oil & filter, air filter, adjusted the timing and replaced the cracked breather hose. I also scraped off some old RTV at the corners of the valve cover, but did not put new RTV in it's place.

The car ran great, and I drove it 3 times over the weekend for maybe about 10 min at a shot. I also added gas and fuel injector cleaner. I did some reading and pinched the PCV valve hose--I can't be sure I heard a click the 1st time or two because I wasn't sure what I should be listening for. When I pulled the valve out and covered the bottom, it clicked and the RPMs took a dive, but the car continued to run.

This morning, the car ran fine until the 10 minute mark where it picked up all the old habits again--rough and hesitant until about 2800RPM. I drove it some more at lunch today and again, it's fine until it's been running for ~10 minutes. Again, I'm not seeing a check engine light.

I'm planning on checking for vacuum leaks this evening (did a search and found the carb cleaner trick) and I feel pretty confident that I'll need to put some RTV on the valve cover, and I picked up a PCV valve at lunch.

Is there any reason to think that it might not be a vacuum issue? If I still have the problem tomorrow, what else can I look into without special tools/gages? I guess I should replace the plug wires at this point as well...

TIA,
Ty

 

Does it do it at a certain RPM, just a stutter, goofy idle? Awesome info, but we need more.
I'm thinking it's probably the tps. I'm going through the same thing. Mine was the tps and only did it at certain rpms, and at idle. Basically anything under 10% throttle.

 

The car would start stuttering as it warmed up but only when the engine was under load (and then at any throttle position). At first it would clear at 2500RPM, then 3000, then 3500 when it was fully warm.

I got home last night and checked the old plugs--they were normal. Ceramic was a little yellowed, the electrodes were charcoal colored, but definitely not sooty.

Put grey RTV (liquid gasket) on the corners of the valve cover, and R/R both the sparkplug wires and the PCV valve. The PCV valve was definitely gunky with oil and when shook, it felt/sounded nothing like the new one that went into its place.

Problem solved!