'99 Civic Si - Check Engine light questions

[reichbc]

First, I want to apologize if this is in the wrong section - i searched for a similar topic to no avail.

Second, it's good that there are boards like this. I just recently (7 hours ago) bought my Civic from a buddy, and could use the community assistance.

Third, this is the very FIRST civic I have owned, and when I bought it, the guy was explaining stuff about it that I didn't understand. I will learn more eventually, but it basically boils down to this... he said "...and this thing is an AEM cold air intake..." and i replied, "Well, what does that do?"

On to the questions... The check engine light is on. I used my OBDII tester to determine the codes, and it's giving me two.

P0420 - "Catalyst System Efficiency Below Threshold (Bank 1)"
P0505 - "Idle Air Control System"

What do these two descriptions relate to on the car, and what would be my best course of action?

-Brandon

 

[XpL0d3r]

man!

P0420 is an o2 sensor code. Good chance it may be unplugged or bad.
P0505 is a problem with the idle air control valve. it's common that these need to be cleaned, and is no more than two bolts and a plug. It could even just be unplugged.

Search around on the boards or even on google for cleaning the IACV, and as far as the o2 sensor goes, they're fairly pricy, but replacing would be the best option.

Hope ya stick around on the boards here!

 

[reichbc]

Thanks, Xploder. I plan to stick around for the life of my Civic.

Now, this O2 sensor... which one is it specifically / where is it on a civic... in the intake? cause the key word was catalytic and i know there is a catalytic converter... related?

forgive my newness. ha

 

[00_jdm_em1]

your o2 sensor is in your exhaust, you have one in the header, and one on the cat, or it is that ay in my case, I have a 00 Si, more commonly referred to as an EM1, even though most 96-00' are called ek's, the Si is truly an EM1, regardless, pull the IACV off, its on the back of the intake manifold, 2 bolts and a plug are the only things you will need to remove, dont worry about the lines running to it, use a pick or something of that nature to pull the screen out and clean it thorougly, put it all back together and before starting it either un hook the ground for a few seconds on the battery, or unplug the ecu, this will clear the codes, but once this far the battery should have already been un-hooked when you started working on your car, and the codes would have already been cleared, start it up, see what codes it throws again, If still an IACV you either have a broken or loose wire, or the IACV is bad and needs to be replaced, as far as the o2 senso goes, run to your local parts store and buy a can of seafoam, follow the directions on the can, your car will smoke lke crazy but this is normal, if it doesnt help the o2 sensor, at least it gives your motor a good cleaning, i use it in my car just before every oil change, once you read the directions on the can you will understand why.... hopes this help,,, keep us updated, and since your now an EM1 owner, you should check out EM1CREW.com..

 

[RonJ]

Unfortunately ($$$), P0420 generally indicates a bad catalytic converter (cat), though first rule out an exhaust leak before replacing. Usually a bad cat is caused by running rich or engine misfiring, so make sure the plugs, wires, cap, and rotor are in good shape and the ignition timing is set to spec before replacing the cat.

There are multiple possible causes for P0505, and a bad IACV is only one of them. Do you have a high, low, or fluctuating idle problem?

 

[reichbc]

RonJ, I went to the local Honda dealership with the error codes... he said the cat was probably bad. Mentioned that an error code for the specified sensors is different than one for the cat.

I think it's just a "difficult" idling problem, if i can say that. sometimes it idles high, sometimes low, sometimes it does its little revving thing. One thing i noticed though is that it takes a good 10 to 15 cranks for it to catch on a cold start. I usually have to hold the gas a bit to get it to flow, otherwise it just sputters itself out.

 

[RonJ]

RonJ, I went to the local Honda dealership with the error codes... he said the cat was probably bad. Mentioned that an error code for the specified sensors is different than one for the cat.

Again, a cat has a long life until it is subjected to unburnt fuel in the exhaust, a condition that melts the catalytic substrate. So before you install a new cat, give the engine an ignition system tune up. Otherwise, the new cat will soon be dead and you will again need a new one ($$$).

I think it's just a "difficult" idling problem, if i can say that. sometimes it idles high, sometimes low, sometimes it does its little revving thing. One thing i noticed though is that it takes a good 10 to 15 cranks for it to catch on a cold start. I usually have to hold the gas a bit to get it to flow, otherwise it just sputters itself out.

Sounds mostly like a low idle problem. If you unplug the IACV, does the idle speed drop? If so, start by cleaning the IACV and the adjusting the idle speed.

Do you have a USDM (B16a2) 99 Si?

 

[vertech0]

when my IACV went on my '99 si, it would idol up and down when i stopped and sometimes "bounce" between 1.5 and 2.5. once i replaced it though, it was fine. Also, i too had the same issue, once i replaced my o2 sensor though, i got a new code almost immediately after for the catalytic converter.

 

[reichbc]

RonJ, yes, it is a b16a2. I looked at your ICV settings pages (printed out too, thank you) and I will see if this is something i can do within an hour or so.

Last night, driving in the snow, it started acting up. It seemed as though a slight touch of gas didnt give it any power, however pushing a tiny bit more made my wheels spin. Almost slid into a car!

 

[RonJ]

Last night, driving in the snow, it started acting up. It seemed as though a slight touch of gas didnt give it any power, however pushing a tiny bit more made my wheels spin. Almost slid into a car!

If what I suggested earlier does not fix the problem, then you may want to measure voltages (@ closed throttle [~0.5V] & @ WOT [~4.5V]) output by the TPS, which when faulty, can also throw P0505.

 

[reichbc]

measure voltages (@ closed throttle [~0.5V] & @ WOT [~4.5V]) output by the TPS

lol.... remember, RonJ, Honda newbie here. Don't have much experience with engine jargon as it is, on top of this being my first Honda.

Edit: scratch that. I thought it out. (assuming TPS means throttle position sensor)

I would love to measure the voltages off the throttle pos. sensor... However, this is a cable throttle. If it was a throttle-by-wire, i would convert it to cable anyway. I don't like the idea of wires controlling my fuel flow.

 

[reichbc]

So this thing is the little bastard that's causing all my troubles?

 

[RonJ]

lol.... remember, RonJ, Honda newbie here. Don't have much experience with engine jargon as it is, on top of this being my first Honda.

Edit: scratch that. I thought it out. (assuming TPS means throttle position sensor)

I would love to measure the voltages off the throttle pos. sensor... However, this is a cable throttle. If it was a throttle-by-wire, i would convert it to cable anyway. I don't like the idea of wires controlling my fuel flow.

TPS = Throttle Position Sensor
WOT = Wide Open Throttle

The TPS voltage tests I mentioned are not very difficult. I or others here could describe how to do the tests using a digital multimeter.

Ironically, your gas pedal controls air intake not fuel flow. And even though movement of the throttle plate is controlled by a cable from the "gas" pedal, information about the position of the throttle plate is sent to the ECU (computer) electronically from the TPS located on the throttle body. So whether you like it or not, your fuel flow is determined in part electronically by signals from the TPS.

 

[RonJ]

So this thing is the little bastard that's causing all my troubles?

That's the IACV and, if bad, it can cause P0505. However, it's only one of the possible causes.

 

[reichbc]

Alright. See, told you I knew nothing. Hehe. Learn something new every day.

I just cleaned this thing out a little bit... looks like i get to go stick it back on the car and see what it does

 

[skyclimber]

My car have the same problem.
I replaced the catalytic converter with no help.
I notice when the MIL comes on, the engine hestitation starts.
It got to have something to do with the open loop mode.
Some said the primary O2 sensory can be the cause.
But does that not give you another code instead of P0505?
My emission test is coming. I will have to get this fixed...
HOw much is the original Honda O2 sensor?
Are the primiary and secondary sensor the same?

 

[RonJ]

A bad O2 sensor WON'T throw P0505.

 

[skyclimber]

A bad O2 sensor WON'T throw P0505.

Oh, it won't?
I have replaced my IACV, and there is no idling high problem. Only when the MIL comes on with P0505 will the car start hestitating. So what else can it be?

You think it is vaccuum leak? But it is not idling high and it only hestitation in the open loop.

 

[RonJ]

Oh, it won't?
I have replaced my IACV, and there is no idling high problem. Only when the MIL comes on with P0505 will the car start hestitating. So what else can it be?

You think it is vaccuum leak? But it is not idling high and it only hestitation in the open loop.

What car, year, and engine? Any mods?

When your warm engine is idling without any load, the idle speed should be rock steady at ~670-700 rpm, depending on the engine. When P0505 is thrown, are there any idle problems (low idle, fluctuating idle)?

Open loop is when for example the engine is cold. Is this what you mean?

 

[skyclimber]

My car is Acura 1.6EL 2000.
I think it is same as Civic Si
It is manual.
Normally, my car has an idle of around 800-1000 rpm steady.
Once in a while, the check engine light will be on. (May be every few days, and it is getting more frequency every time after I reset. But if I remove the backup fuse, it will takes longer for the problem to comes back.)
When the MIL is on, the idle immediately go to around 1500rpm. And the car will start hestitate.
If I turn off the key and start the car again, while the MIL is still on, the idle high and hestitate problem goes away for a while before it comes back again.