'99 Civic Si - Check Engine light questions

[RonJ]

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.

You should probably post this problem on an Acura forum.

When P0505 is thrown, you have a high idle problem. While this is happening, what happens to the idle speed if you unplug the IACV or use your finger to block the hole in the throttle leading to the IACV? If the idle speed drops, then test the TPS and ECT sensor, as well as their connectors and wires.

 

[skyclimber]

I tried that before, but I find out in the Acura forum, there is not as much help I can get.
When the P0505 code is throw, it is hard to unplug the connector because I am driving. But that is a good suggestion to try. Next time, I will park it aside and unplug and give it a try.
So let's say it drop if I unplug, then what would you suspect?

 

[RonJ]

If unplugging the IACV or blocking the IACV port with your finger drops the high idle speed (1500 rpm), then this tells you that high idle is mediated by the IACV (rather than for example from a vacuum or intake air leak), likely indicating that the ECU is telling the IACV to raise the idle speed. Given that the TPS and ECT sensors provide key inputs to the ECU for idle speed control, your next step would be to test the TPS and ECT sensors. These tests will be a tricky, however, given that P0505 is intermittent. Test results are only valid when the high idle problem is occurring.

 

[skyclimber]

I dont think I have a ECT sensor.
I have a TPS and MAP sensors.
I replaced both already and they do not seems to be the problem.
I also cleaned the throttle body, replace the gasket.
IACV is replaced with a used one, but have the same problem.
And that happens starting winter.
I have the same problem last year, I found out one wire from the PCV value is shorted and it stuck open.
That problem is now fixed.
The problem goes away for 1 year and now it comes back in the winter.
I think it got to have something to do with the cold.

Oh, by the way, when the guy change oil for me, he sprayed water high pressure from under the car. Can that cost the problem.
I have the gasket of the catalytic converter broken before. After I replaced the gasket,
I have code P0420, I replaced the catalytic converter and the code P0420 does not comes back up now.
But I now have the code P0505. When I have the P0420, when the MIL comes on, the car does not hesitate.

I was thinking may be the seal lube for the gakset killed the O2 sensor. But you said the O2 sensor would not cause the hestitation. So I am out of ideas. If there's vaccuum leak, is the idle high problem going to show up all the time? Or is it going to be intermittent?

By the way, thank you so much for your help. I really appreciate it. I need to have emission test in 2 months. I really am worried.

 

[RonJ]

I'm pretty sure your engine has an ECT sensor. Check your service manual.

For the TPS sensor, the problem could be the wires or even the ECU. Check the wires for a short or open. Have you measured whether the ECU supplies proper reference voltage to the TPS and that the TPS outputs the correct voltages at closed and wide open throttle?

 

[skyclimber]

I checed my service manual, but I cannot find anything about the ECT sensor.
Is it suppose to be in conjuction with the throttle body?
I take apart the TPS, TB and IACV many times, and I only see the TPS and MAP there.
You can check out the manual here
http://www.2shared.com/file/3007261/a50e5e7d/97-00_Acura_EL_Manual.html

When I install the TPS, i measured the volatge and alter it to spec before I tighen it.
So I think the TPS adjustment should be fine. I got this problem before I replaced the TPS. So I think the problem is not the TPS. But it could be the wire being intermittent.

Speaking of ECU, I also replaced that before ( 1year ago) and it did not solve the hestiation problem.

I think some problem is hidden in my car. 1 year ago when I fixed the shorted PCV valve problem, it was well for a year. But when winter comes, it just do it again. Usually when P0505 comes on, the car should not hestitate, right? I think it is someithing else, may be something really simple that I was missing.

Let's assumpt something is intermittent (just like my speaker on the front). When I turn off the car and turn it back on again, the current temporary solved the problem.

The question here is that why when I remove the backup fuse for a long time, then the problem will go away for a much longer time that using my OBDII to reset the error code?

Could it be the learning mode that delay the problem?

Let's say it is the wire of the IACV, can it cause that problem?
When it intermittently disconnect, then the MIL will be on.

 

[RonJ]

I can't download the manual here at work, but I will when I get home this evening. That should help me guide you with specific troubleshooting for your car.

In the Cooling System section (Water Pump) of your service manual, you should see a diagram showing the location of your ECT sensor. Below you can see a similar page from the 96-00 Civic service manual. In this case, the 2-wire ECT sensor screws into the block below the distributor.

 

[skyclimber]

When you mention it, I remember I replaced the thermostat with original honda parts.
How do I check the ECT sensor?
My radiator fan turns on though, does that mean the ECT may be intermittent?

I will unplug the IACV if it gives me trouble when I drive in the weekend and see how is the idle.
Do I need to remove the distributor in order to see that?

 

[RonJ]

I looked at your service manual, and the ECT sensor is located in the same location as is shown in the diagram I posted.

Your engine has three temp sensors:
(1) The 2-wire ECT fan switch located on the thermostat housing.
(2) The 1-wire temp sender unit located below the distributor.
(3) The 2-wire ECT sensor located below the distributor (see diagram).

You need to test (3) and its plug and wires. You also need to test input and output voltages at the TPS.

 

[RonJ]

This is taken directly from the service manual for your car:

 

[paulx022]

When you mention it, I remember I replaced the thermostat with original honda parts.
How do I check the ECT sensor?
My radiator fan turns on though, does that mean the ECT may be intermittent?

I will unplug the IACV if it gives me trouble when I drive in the weekend and see how is the idle.
Do I need to remove the distributor in order to see that?

f**kin thread jack to the max.

 

[skyclimber]

I've tried all those trouble shoot of P0505 from the manual.
Although I am 80% sure there is no vacuum leak, I cannot vertify.

How do I test the ECT?
do I measure the voltage when it is on?
I will check it tomorrow and see if I can reach it without removing the distributor.

By the way, I just got some data from my ODBII.
When the car is warm and with no MIL on.
calc load % 61.5
coolant (0F) 180
MAP 7.1
IGN ADV 16
IAT (0F) 68
ABSLT TPS 8.6
O2S11 the value change from 0.175 to 0.855 in cycle. (Is this normal?)
O2S12 0.605 - 1.015


When I just start the car:
O2S11 the value change from 0.175 to 0.855 in cycle.
O2S12 1.275 constant

Will try more troubleshoot tomorrow.

 

[RonJ]

I've tried all those trouble shoot of P0505 from the manual.

What did the troubleshooting tell you? It's only yields useful information when you have the high idle problem.

 

[skyclimber]

I am getting this for a reference when I get the data from the high idle.
By the way, is the varying voltage of the primary O2 sensor normal?

For the ECT sensor, I am thinking to tamper out 2 wires from the connector to measure the voltage and see how the V-T relationship is like.

Thank you so much for your support. I my self like troubleshooting too.
I hate it when I change a part without knowing if that is the problem.
Everything is just too expensive from Honda.

 

[skyclimber]

f**kin thread jack to the max.

I am sorry if I jack the thread, but I got the same code. That is how I find this post in the first place.
P0420 - "Catalyst System Efficiency Below Threshold (Bank 1)"
P0505 - "Idle Air Control System"


Besides, anyone in the future if they have the same problem and find this post, it is going to help them troubleshoot. I think it is constructive.

 

[RonJ]

For the ECT sensor, I am thinking to tamper out 2 wires from the connector to measure the voltage and see how the V-T relationship is like.

When the engine is hot and you have the idle/P0505 problem,

1) Unplug the ECT sensor and then measure resistance across the two sensor terminals. It should 200-400 Ohms.

2) Turn the key to ON(II). In the unplugged ECT sensor connector, the Red/Wht wire terminal should have 5V when either the engine or the Grn/Blk wire terminal is used for ground.

 

[skyclimber]

Today I was driviing the car and the problem did not show up.
But I went to someone who has the honda OBDII.
He checked the ECT sensor and all O2 sensors and they are normal.
But he found out that the spark plug I am using is the platinum one.
He saw my engine need to use the regular one. The tempoerature range is different.
So I went over to Honda and got the regular NGK ones. They are not expensive in Honda $4.85 each (I was suprised). I will not get the cheap version of the NGK from now on.
I also get the gas filter for $29.95. They are all replaced.
I find out something was wrong with my non OEM gas filter on the car.
The hold on the screw on top of the gas filter was not aligned properly.
I guess you can never trust the mechanics. The best way is to do it yourself.
Now I feel my car has more power with less push on the gas pedal (May be just my bias).

My ignition cables are not the original ones too.
But I do not want to replace them at this point because they are $88 for the set!

I will see if my engine hestitation comes back together with the P0505.

I will unplug the IACV and report back here if the code comes back on.