lxdriver

A while back I got the P0420 code, turns out my catalytic had a huge crack in it causing the code, I replaced with a brand new one and the code went away. A few months later now, I got the same code again but I very highly doubt the cat went out again. Now sometime last year a mechanic told me that the car was running too rich which got me thinking that one of the fuel injectors are bad. The injectors are easy to change (found a how-to online its basically a few bolts and wiggling them out, but how can I determine if one, or more, is/are bad and which ones in specific?

B_Swapped93

I've rarely heard/seen injectors "go bad" it's more then likely something else causing the car to run rich have you looked at the plugs to confirm this ?. 2nd have a look at the cat you never know...

NameGoesHere

To test the fuel injectors, while the car is running, just unplug one at a time, if the injector is good, the car rpms should change drastically, if it does change much it might be faulty (most likely they only get clogged, which a fuel injector cleaner would fix).

But I think since you are getting the code, it would be a problem with the cat.
What cat did you replace it with? Possible a aftermarket one could crap out very quickly.
Does you car get unusually bad gas mileage? Or run rough?

B_Swapped93

No that's NOT how you test an injector....you do a pulse test with a noid light to confirm it's firing as it should. and to go further you check for continuity at the ECU with a test light.

NameGoesHere

Yeah I know there are more ways to test the injectors more precisely. The way you say, isn't that just checking the timing of the injector spraying?
But you can do the method I mentioned. Much faster to see if that injector is not functioning correctly.
Of course I ment unplug the electrical connection and not the injector itself in case you thought I that's what I said haha.

B_Swapped93

yes it just confirms that is pulsing(firing) as it should. if one wasn't working(fifing) that would cause a notable misfire in that cylinder and unplugging them would help find which one the misfire was in

NameGoesHere

Yeah, I know it's mainly to determine which cylinder has a misfire. Haha, was just thinking that trying that might also see which fuel injector is not functioning properly as well, since that one cylinder is not getting enough fuel (clogged or whatnot) that maybe unplugging the injector would not show much difference because that cylinder would already be combusting unefficiently, sorta nearing a misfire, but not as severe.
I might be wrong or I might be on to something haha.

But OOOOOHHHHH.. I misread the original post, was sleepy when I read it (sleepy right now too lol) I thought he said too lean, now I see it says too rich...so that rules out clogged injectors. Fuel injectors can leak, but usually just get clogged if they are the problem so I doubt they are the cause. If they are bad somehow and need replacement, they cost quite a bit.

So now that I re-read and know I misread it wrong the first time.
And I see that the mechanic that said it was running rich mentioned that was last year.

The part making it to run rich might be the cause, but that is not what the code is saying. The code is saying the cat is bad. If you are running really rich, then your cat could foul up fast in those few months since the replacement. You probably could get away with just cleaning it out. But that still does not get rid of the part causing the car to run rich, so you need to fix that or the cat will clog up again.
But if you hear rattling, like pebbles jumping around, inside the cat, there is a chance a aftermarket cat wore out very quickly and is breaking into pieces inside causing clogging as well.

I have some questions to better pin point the problem.
Does your car run and idle rough? Get bad gas mileage? Any black smoke from exhaust? Is the exhaust louder than normal (possible loose piping at cat?)? Any rattle noises coming from the cat?

B_Swapped93

OP still needs to state if his plugs are black from running rich

NameGoesHere

Haha, yeah doesn't seem he has checked back yet.

Hey B_Swapped93, I am still new, under the Trial User status, am I able to post threads yet?

You seem to really know your stuff, maybe you can help me out.

Too tired right now to get into too much detail but,
I have a problem with a stock 2000 civic ex y8 (stock manual trans) jerking very hard (whole car rocks back and forth) in the first two gears. Code said it was the IACV, but we replaced it with a brand new one and a gasket, it got a little better, but still violent jerking. It does it when driving in both gears, and also when down shifting into 1st or 2nd. It's not our driving that is causing this.

Car idles and runs very smooth. No noises from the transmission or anything. Motor mounts seem fine. Clutch was said to have been changed a not long ago, no grinds or slippage, seems fine. The code for the IACV still comes on after resetting it. I think there must still be a part related to the IAC system causing this, but I don't really know the parts involved.

Any idea what I can check into?

I'm gonna sleep for a bit so I will catch up later.
Thanks in advance.

B_Swapped93

Yes you can.

as for your problem I would check off the basics first: Last full ignition sys tune up ? is mechanical timing on , check that the TPS is to spec, jack the front of the car up and inspect the suspension components. and make a sepate thread you'll get help from others including me

tony_2018

Check your engine and tranny mounts to be sure they are not worn out or ripped. When does the jerking happen, at what speed/rpm?

OP are you using the correct injectors? What yr is your civic?

NameGoesHere

Sorry for the late response.

Will make a thread later on today.
What is a spate thread?? You mean spare thread?

Had full tune up not too long ago, runs and idles very smooth, no sputtering.
Pretty sure the mounts are fine on the engine.
Will need to check the other stuff out when I have some time.

The jerking is like how the rocks back and forth hard when you almost stall the car. But that jerking motion happens constantly through most of 1st and 2nd gear. Haven't really looked at the rpms it acts up on, but I know it jerks through most of the gear/rpms. So as you can imagine it's not so fun to drive. Even tried shifting at high rpms and it still jerks in the first 2 gears.

But yeah, I will check some of the things out and report back with more info. But that might not be until tomorrow, I'm busy all day today.

Thanks for the help guys.


EDIT:
We bought the car with this symptom. Previous owner said it did this many times before. He would clean the IACV and it would be fine again, then eventually I guess the IACV cleaning just wouldn't cut it anymore. The code says it's the IACV so we bought it thinking that was what was causing it. I had doubts, but the guy seemed honest. Maybe he wasn't or maybe he was, but there just might be another part related to the system (the IACV code comes back even after replacing with a new one) that is faulty.

lxdriver

Checking back in guys haha. Well I bought the cat new this april from autozone cuz I had my smog check due already. It was fine for like 2 months and then the code came again. My civic is a sedan 2000 manual tranny. The current injectors idk if they are factory oem or replaced by the previows owner. The cat I just eye balled it kinda quick and it seemed fine so idk what else it could be. If say for example the injectors were clogged, would a simple fuel injector clean do the trick?

Mmac

I used a stethoscope to hear the fuel injector solenoids clicking (activating) and just happened to be listening to #4 cyl when it quit for a few seconds. Motor jumped and ran rough. Replaced with used injector ($10) and problem solved. 2000 civic dx. Very elusive problem but persevered.