2000 civic stock d16y8, 166k

If the engine is cold, the engine sometimes fails to start. It will crank and crank but it will not start until I crack the throttle open. When I get it to start, it misfires like crazy under 1500rpms, but over 1500rpms it acts normal. It will not idle at all during this time. After 30 seconds of sitting OR driving, it will idle and act perfectly fine.

The only code I am throwing is "catalyst efficiency low", bad cat or 2nd o2 sensor i guess. It HAS thrown misfire codes for cylinders 1-4, but that code is not currently in the list.

I have tried nearly everything I think, here's everything I've replaced.

new iacv
set valve lash
air filter
fuel filter
plugs
wires
cap
rotor

What else can I check? could it be dirty injectors? fuel pump? I've replaced all the spark stuff and the iacv so i'm thinking fuel, where do I start?

 

If you suspect the injectors, then try using fuel injector cleaner. It's cheap at any auto parts store.

 

sounds like its building up fuel pressure

 

if it's building up fuel pressure, what part is failing to do its job? fuel pump?

I've used techron a few times, no change.

 

try running that fuel injector cleaner, then try gas treatment, maybe you have bad gas. You have the right ECU? Stock p2p? if its chipped maybe it was chipped wrong

 

stock ecu, this has been happening since april when I bought the car. it is not bad gas.

I'll run some cleaner and ****, but i don't expect results. any more ideas?

 

bump

 

clean your intake manifold

 

bump, filled the gas tank half way and put a bottle of techron in it. I doubt that will fix, anyone had this problem before?

it's happening more and more often, only after the car sits for an hour or more, runs like utter **** for 30 seconds, must hold the gas, then it clears up and runs perfect.

 

anybody? should i get my injectors cleaned, replace the fuel pump, could a clogged cat be the culprit?

 

sometimes it doesn't fully happen, the car starts but runs rough for about 30 seconds as always. it is happening more and more lately.

 

Have you done a compression check?

From my own personal experience.. I had low compression and the engine had to warm up before it would run right.

 

That would suck, but I guess it's worth a shot. i'll borrow my friend's compression checker and take a look.

 

compression results:

1- 210
2- 210
3- 215
4- 215

Pretty good I'd guess, good thing i don't need a rebuild or a head gasket.

back to square whatever, put some new pluggies in because the old ones looked a little tired, the car is running a tad smoother but that's it. still doesn't like cold starts.

 

A plugged cat can be diagnosed at home with a vacuum gauge. An exhaust place can check it with a back pressure tester. The second o2 sensor is checking if the cat converter is functioning as it should. If it is partially plugged - it probably isn't working.

 

Maybe a plugged cat. I have the same problem. Do a leak down check...no compression and see what happens. I know i have some blow-by....aka, failing rings.

y8 also

 

maybe i'll buy an egay test pipe and see what happens. i'm getting exhaust soon so we'll get a good look at that cat.

I'm also going to get my injectors cleaned.