Rough idle - cylinder 1 and 6 misfire HELP

[austindavies935]

Where do I start? It originally had a cylinder 1 and 6 misfire check engine light and had a rough idle when cold. Then a couple weeks later it turned into a high idle but no check engine light or rough idle. I replaced the coils and IAC and no difference. Then I got a performance catback and it made the high idle even higher. I cleaned the throttle body and no difference. I did a blowby check by opening the oil filler cap and putting my hand over the hole. Zero blowby.

Then i learned about disconnecting the battery for 20 mins. Did that and now my high idle has turned into a low and rough idle when warm. Check engine light came back on and is still saying cylinder 1 and 7 misfire. Its also backfiring out the exhaust when letting off gas when rolling (sounds good tho lol)

I'm confused because when under hard acceleration the car has plenty of power and no issues. Just has issues idling. When cold its fine and idles at 1k rpm but slightly shakey. When its warm it'll bounce between 500 and 700 and it shakes the car. There's zero issues on hard acceleration.

Also unsure if this is related but I swear there's like an air noise or knocking noise coming from under the car? Sounds like around the catalytic converters. It does have high flow cats. Its absolutely not coming from the engine tho.

The guy who installed my catback said at the downstream 02 sensor there was a very small hole but it shouldn't affect anything as its downstream.

Where do I start??? Injectors first or plugs? Has new coils, IAC, cleaned throttle body.

Just want a smooth idle

 

[Noobz347]

I would start by pulling codes.

 

[austindavies935]

I would start by pulling codes.

I took to autozone and they said cylinder 1 and 6 misfire. Pretty sure thats p0301 and p0306 ?

 

[Noobz347]

I will look those up. In the meantime, you should get on Amazon and order an OBD2 Code reader.

There are other with more/less/different/more features etc..., but I believe this one covers all system for your year:

Amazon.com

Without a reader, it is tough to troubleshoot from here. Normally, I would have you move the coil packs to different positions and see if the misfire follows those coil packs.


So... I fear we are at an impasse. See if you can get your hands on a reader even if it's borrowed.

 

[austindavies935]

I will look those up. In the meantime, you should get on Amazon and order an OBD2 Code reader.

There are other with more/less/different/more features etc..., but I believe this one covers all system for your year:

Amazon.com

Without a reader, it is tough to troubleshoot from here. Normally, I would have you move the coil packs to different positions and see if the misfire follows those coil packs.


So... I fear we are at an impasse. See if you can get your hands on a reader even if it's borrowed.

Not sure if you read the whole post. But I replaced the coils and its still cylinder 1 and 6 misfire so its not the coils. Also the autozone guy used his obd2 scanner and like I said the codes said cylinder 1 and 6 misfire

 

[Noobz347]

You still need a way to actively scan codes.

When I look up your codes, the troubleshooting steps are as follows:

• Always start with the coil and plug swap. It's free and eliminates the most common cause.
• Check COP boot for carbon tracking or cracking. Use dielectric grease on reassembly.
• Scan freeze frame data to see when the misfire happens (idle vs. load).
• If misfire occurs at idle only, consider vacuum leak or low compression.
• If misfire happens under load, suspect coil or fuel injector.

You've swapped the coil packs, did you pull codes again after the replacement --or-- before?


Other things you can try:

Check for vacuum leaks (can of ether/brake cleaner/etc...)
Pull and read the plugs to see what's going on there.
Pull and clean/inspect fuel injectors (I would actually send these off or take them somewhere local to get cleaned and flow tested).

Once you do any of these things though, you're still going to need a way to scan if you're doing your own maintenance.

 

[austindavies935]

Pulled codes both before and after.

And damn i hope I don't have low compression. I did a blowby test and there's zero blowby

 

[Noobz347]

I'm inclined to think that you have some worn parts, or gaskets, or hoses, and not a physical engine issue.

How many miles you have on the car? I mean, it's an SN so, I'm guessing close to or over 100K. Have the injectors ever been out of the car?


Soooooooooo much gas out there.

 

[austindavies935]

I'm inclined to think that you have some worn parts, or gaskets, or hoses, and not a physical engine issue.

How many miles you have on the car? I mean, it's an SN so, I'm guessing close to or over 100K. Have the injectors ever been out of the car?


Soooooooooo much gas out there.

Its in the 130ks. Odometer quit working last week on me. The previous owner did mention it had bad fuel in it at some point but unsure if that was fixed

 

[Noobz347]

I will leave this here:

Order Fuel Injector Service |

injectorrepair.com

There may be an outfit that's local to you.

 

[austindavies935]

Wouldn't it be better to just replace all of them with new ones? If I take these out of the engine and send them off I won't be able to use the car

 

[Noobz347]

Wouldn't it be better to just replace all of them with new ones? If I take these out of the engine and send them off I won't be able to use the car

If you choose to do that, I won't try and talk you out of it. However, they might be expensive --and-- if you order a set I would order them pre-tested with flow sheets to ensure that each one is within 3% of the other seven.

Also (and I should have mentioned this before):

You can move the injectors around and see if the misfire follows the injector.

The danger here is running into pintle and o-rings that are bad. You could get it apart and not have on-hand what you need to put it back together.

It still relies on the ability to re-check for codes.

And for God's sake, do not buy an budget garbage injectors off of Amaxon, etc... You need Bosch and I think yours are EV1 but you should double check.

 

[gkomo]

Smoke machine available? Vacuum leak?