Rough idle, three misfires

2001 HONDA CIVIC

165,000 MILES • 1.7L • 4 CYL • 2WD • AUTOMATIC

BUSINESSFRED

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First I checked compression with wide open throttle.
175 , 175 , 170 , 175
1 2 3 4

The misfire codes are:

P0300
P0301
P0302
P0303

So far I have:

Swapped coils and installed new spark plugs.

Swapped the ELD Relay (because the misfire is most present when I'm in drive).

Cleaned the IACV + Throttle body.

Ran fuel injector cleaner through gas tank.

I bought 3 fuel injectors but have yet to install . I want to do some troubleshooting first.

Is there specific way I can check my current injectors?

I'm also leaning towards changing out the intake manifold gasket , exhaust manifold gasket and throttle body gasket
.

I would also like to identify the 3 relays behind the glove box.

There is a black , blue and brown relay . I understand one or two of these relays are PGM- FI relays .

Jan 27, 2020 at 1:46 PM

SCGRANTURISMO

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Hello,

I would recommend changing the intake manifold gasket and checking for vacuum leaks. Here is a link below explaining the process:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

As far as checking out the fuel injectors it's a pretty easy and straight forward. Put your Digital Multi-meter [DMM] in Ohms and check the resistance across the two pins. The reading should be between 10 - 20 ohms. Check them once when they are warmed up and then again when they are cold. When they fail it will happen when they get warm. They are basically on/off solenoids that when they get are failing will short the internal coils when they warm up. Please get back to us with what you find out.

Thanks,
Alex
2CarPros

Jan 27, 2020 at 7:49 PM

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I have two replacement gaskets.
Neither of them look to be the same as the one that was removed.

Mine doesn't have EGR and I assume that's what the small holes in the new gasket are for .

Which one of these would be the correct one to replace it with ?

Image (Click to enlarge)

Jan 28, 2020 at 1:10 PM

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Should these ports be blocked off or should the new gasket allow air flow through these ports?

Image (Click to enlarge)

Jan 28, 2020 at 1:12 PM

SCGRANTURISMO

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Hello again,

I would use the middle gasket. The ports you are referring to look like coolant ports. They go with the channels in the bottom of the intake manifold. It looks like the other holes are where the fuel injectors go and all the other holes are bolt holes. Please let us know how it turns out.

Thanks,
Alex
2CarPros

Jan 28, 2020 at 8:14 PM

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I found out that the middle one was for a D17A2 vtec model.

And the bottom one is for a D17A7 CNG model.

So I've ordered a new one that looks exactly like the one that came out.

I called Honda and provided my VIN to find the correct part number.

I did unplug the upper ECT sensor and my idle smoothed out , could this sensor or the other ECT sensor affect idle somehow ?

Jan 28, 2020 at 10:54 PM

SCGRANTURISMO

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Hello again,

Believe it or not, yes. The engine temperature is one of the sensor inputs that the Powertrain Control Module[PCM] uses to adjust the ignition timing. In the diagrams down below I have included a picture of the ECT for the PCM. Is this the location of the ECT you are referring too?

Thanks,
Alex
2CarPros

Jan 29, 2020 at 8:01 AM

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I didn't receive a diagram or picture in your last reply.

That's very interesting ! originally I thought the timing was off .

Another symptom I had before I began to troubleshoot was an extended crank at start up .

Jan 29, 2020 at 5:28 PM

SCGRANTURISMO

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Hello again,

I'm so sorry about that. Here is the picture in the diagrams down below. This engine is an interference engine, so I don't think it's jumped time. There would be serious damage as the valves would hit the pistons and the engine would just turn over freely with no resistance or not turn over at all because the valves would be bent.

Thanks,
Alex
2CarPros

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Jan 29, 2020 at 7:55 PM

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I've replaced the intake manifold gasket, no major difference.

But I'm looking to purchase a ECT now as it definitely allows me to idle better and not shake when it's disconnected.

I think this will be the last thing I try before adjusting the valve lashes.

Do you have any instructions on this procedure?

Feb 1, 2020 at 9:43 PM

SCGRANTURISMO

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Hello,

I have included in the diagrams down below the instructions for the removal and installation of the ECT on your vehicle, as well as how to do valve lash adjustments on your engine's valves. I hope that these help and let us know how everything turns out.

Thanks,
Alex
2CarPros

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Feb 2, 2020 at 6:27 PM

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Great information ! I've already replaced the ECT earlier and I must say that the car feels great .

I'm going to try it out and see if the issue is fixed . So far so good though , never knew that the ECT could cause so many issues.

Next step will be the valve adjustments if needed.

Feb 2, 2020 at 11:49 PM

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Update : I got rid of 1 misfire.

P0301 / P0303 remain.
P0302 misfire is resolved .

The car was bogging down - when I disconnected the (new) ECT Sensor , it smoothed out.

So I reconnected it , and didn't have to do that again for the rest of the drive.

After that I got a P0118 for the ECT.

Could a short in the wiring be causing this issue with the sensor ?

Feb 3, 2020 at 12:34 PM

SCGRANTURISMO

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Hello again,

Absolutely. The sensor could be brand new and working perfectly, but if the electrical connector or the wires are messed up then the signal still will not it to the Power-train Control Module[PCM]. In the diagrams down below I have included the engine management wiring diagrams with the ECT circuit highlighted for you as well as guides with known automotive electrical system failures and a guide on how to find unwanted resistance in an automotive electrical circuit via the voltage drop method. You will need a Digital Multi-meter[DMM] to go through these guides, so here is a link explaining how to use a DMM below:

https://www.2carpros.com/articles/how-to-use-a-voltmeter

Please go through these guides and get back to us with what you find out.

Thanks,
Alex
2CarPros

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Feb 4, 2020 at 12:28 AM

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I performed the valve lash adjustment .
I found that the clearances were all very tight.

Some were as tight as .006 when it should've been at .009.
Only found 1 of the 4 to be in spec on the intake side only and the rest were all out of spec including the exhaust side.

So far my idle has improved dramatically.
The misfires seem to have also been resolved as the DTCs have not returned.

I did get a shake going from park to drive after being parked for about a minute with the engine running. But i'm impressed by the change that the valve lash adjustment has accomplished so far.

Feb 20, 2020 at 10:42 PM

SCGRANTURISMO

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Hello again,

I am glad to hear that. How far the valves open up makes all the difference in the world. They are what let's the air/fuel mixture in and takes the exhaust out, so they are at the heart of how an engine runs.

Thanks,
Alex
2CarPros

Feb 22, 2020 at 6:32 PM

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Alex thank you so much , the misfires have been resolved .

Feb 25, 2020 at 10:11 PM