I have had this problem for a long while and I cannot pin down the root cause. It only happens when it is cool outisde ( lower than 50-60 degrees )

When I first start the car, it runs fine, revs nice and high and drops down fairly quickly. It seems to run fine for 30 seconds or so, and then it happens. It will start to miss sometimes so badly that it almost stalls, but it typically chugs along for a little bit and then seems to correct itself. After that there is an occasional misfire, but that goes away when it warms. It only really happens on a cold engine that has been sitting all night.

My typical drive is to take local streets for a mile and then get on the highway. Usually by then the car is running pretty well. When I jump quickly onto a higher speed road, the car will miss, even when revving higher and accelerating to highway speed.

I have replaced a boatload of parts (o2 sensors with denso, cat from bosal, ignitor,coil, cap, rotor, wires, plugs, valves adjusted, coolant replaced and bled as best I could, even my throttle body is from a lower mileage car that was running fine)

Thanks for the help. Please help me fix this before it goes away with the warmer weather.

The car also gets decent mileage ( about 26MPG )

Auto, 4cyl vtec

 

Might test the ECT sensor. You might think about pulling it and test it in water of the proper temp...a few ice cubes should sim a cold start.

 

Thanks Poorman212.

I had actually purchased a replacement temp sensor from autoworks. I was going to install it, but it looked nothing like the part I took out. It was right by the upper radiator hose on the engine side, right where the thermostat is. I may have pulled the wrong part!!

My replacement part had a small 1/4" or so prong that extended from teh sensor, where the stock one had a flat surface about the size of a dime. The electrical connector side was the same

Does anyone know if that is the same sensor?

Thanks

 

Let me just clarify the 4 different "sensors" for water temperature.

First, the thermostat isn't at the upper radiator hose. Follow the LOWER hose back towards the firewall. Thermostat housing is sorta below the throttle-body.

Mounted in the thermostat housing is a fan switch that controls the fans while the engine is running. I think that one's called "fan-switch A".

Now follow the upper radiator hose to the engine. In that nozzle (bolted to the head) is another fan switch "B". That one has authority to run one fan, only after you turn off the engine.

Screwed into the end of the head, roughly below the distributor, are 2 more temperature sensors...
The one with only one wire is for the dashboard temperature gauge.
The one with a 2-wire clip is the water-temperature sensor for the fuel-injection ECU.

 

Jim, that description should go into the DIY or something,,,,,It is the best I've seen in a while. Sorry, to the OP, I call the ECT (engine coolant temp-for the ecu) the two wire one under the dist. Jim explained it way better than I did. Also please TEST before replacing.

 

Maybe I'll do a summary or something about the fan-control systems over the years. Do you know about the older ones? For awhile back in th 80s they just had one fan switch in the radiator? Or maybe I'm confused...

 

I have to be honest. I have not checked the operation of the temperature sensor and the problems that I had last winter are starting to return. I guess now with around 195K miles, the car will start and run rough right from the start. When warm it runs great and has no problems at all. When it starts idling rough I can usually give it a little gas and it evens out. Eventually it starts to sputter and will have noticeable problems trying to accelerate if I drive before it is warm.

I stumbled upon something that pointed toward valve adjustment being a possible issue. I did adjust the valves and if this could be a cause, I probably did it in the summer and never noticed any issues.

I need to get at the leaking valve cover gasket anyway, so I was thinking about checking the valve clearances. can valve clearances cause this very rough cold idle? I wonder if i screwed this up or if my manual has the proper settings??

 

If the cover has to come off, it doesn't take too much to check the valve adjustment....I personally don't think that is the issue.

The "lower" mileage tb, did it come with the FITV?

 

thanks poorman212. I have my doubts that my problems will be resolved with a valve adjustment also. Worth a shot.

The FITV was on the newer throttle body. That was a big reason for changing the throttle body. I snapped off the connector pipe on my FITV when I was trying to get the original hose off to replace with a new Honda hose. I pulled the newer throttle body entirely, so even the MAP sensor was replaced. Getting a newer throttle body with less wear was a bonus.

This problem is getting old....

 

I just finished up with replacing timing belts and ignition wires. Car runs great except when cold. Same problem as always. runs fine at 1300 rpm for less than a minute, the a misfire here and there, then some overall rough running and finally it runs smoothly when warm.

I put my inductive tach on the wires and for just about all of them, the light would show that there was intermittent firing when the car ran rough. Seems to definitely be ignition, but why does it run well when ice cold???

Is there anything that makes sense for these conditions that would cause random misfire shortly after starting on a cold start. This thread talks about the fuel-injection ECU's temp sensor, but I could not find a deep large socket to remove this and test. I am 100% sure that it is ignition and not fuel.

Also another strange thing was a loud ticking noise coming from a part that has a couple of vacuum lines and is to the right of the cruise control diaphram... or whatever that is with the cruise control cable coming out. It gets vacuum from the throttle body and is OEM denso, but I am not sure what it is. I will try to pull a part number tomorrow.

thanks