Ok so heres the deal yesterday my cel came on I was on my way to work. .. on break went to autozone try to get the codes checked they were busy so I left disconnected my battery to see if any codes would pop up again once I did my drive cycle. ..so today as I ws letting my car warm up to get a soda my cel came back on went back to autozone and got the read. .here are the codes P0301,P0302, P0303, P0306.... the car runs fine and amazing so I'm stumped. ..did anyone ever have this happened only difference I see is my mpg have dropped and only averaging 260 per full tank same driving habits and same gas 91 any info would be great going to start by changing plugs,

 

six speed or automatic?

 

That's what the guy told me when I het home im going to run the codes on my scanner to see if I get the same codes

 

Sorry automatic

 

could be your spark plug, loose perhap goes bad before 105k services. Other thing could be is the EGR valve been clog.

 

Ran my scanner same codes so buying spark plugs as im typing wish me luck

 

How many miles you got on her? Do the obvious first Change your spark plugs and clean your erg ports. If your still misfiring after that check your valve clearance and adjust your valve if needed. On higher mileage cars I have seen loose valve cause misfires

 

Do yourself a favor and get the OEM NGK-IR plugs because the cheap ones can cause coils to burn up. I know they are expensive but it's better than having to buy coil(s)

 

Thats all I get for my honda ngk iridium. ...just changed them cleared my codes so well see if the light pops up again god I hope that's it

 

Been reading around on forums will one bad coil cause several codes to pop up..going to clean my egr valve as well. .. and check my egr ports to see any clogging. ..

 

Sorry didn't see this question 136k on it at the moment...if all else fails going to he doin a valve adjustment

 

I have Misfire cylinder 1, 2, 5, and random
Then it shows P0300, P0301, P0302, P0305 codes pop up. Might try my plugs too. But mine isnt like yours, mine is only when I go wide open throttle. hmmm...

 

One bad coil will not cause multiple misfires.

 

Those plugs are expensive lol. I wouldn't have bought them unless I diagnosed an ignition problem.

If you think an ignition coil is the problem, swap it with a cylinder that isn't misfiring and then clear your codes and see if it comes back on the same cylinder. You can use the same strategy for the spark plugs. Finally, check the connector going into the coils: Measure the VOLTAGE between Pin 3 (BLK/WHT wire) and GND. It should read 12V with respect to GND when the ignition is on. Measure the RESISTANCE between Pin 2 (BLK wire) and GND. It should have continuity 0 Ohms.

The ECM/PCM can be troubleshot to further verify the ignition system operation, but I think it's unlikely to be a problem unless you've been fiddling with stuff down there. I would check the fuel system after verifying the ignition system is alright.

Edit: Oh yes, and clean those EGR passages lol. It's free and should be clean anyway.

 

Thanks for the input guys...I got spark plugs just to see if that was the problem and plus since I got the car 3 months ago I didn't know how long the old ones were on there so it's also reassuring knowing there's new plugs in there. ....started this morning let the car warm up just waiting for a cel to pop up to start further diagnosing...going to clean the egr and ports when i get off work and check all coils...when ibput them back on last night I swapped several around to see if i get any different codes if the cel does pop out

 

So far driven almost 100 miles no cel

 

Did you use anti-seize on the new plugs? What torque spec did you use?

 

13ft lbs and yes anti sieze....sorry for the late response been already 230 miles and no cel light. ...might have been bad spark plugs

 

im having the same problem, car runs fine but bad gas mileage. I've replaced all the coil packs and plugs and erased the codes. CEL still pops on. Will cleaning the EGR valve help or EGR Ports? Would SeaFoam work?

 

how do you check/replace the EGR valve? i've looked in the garage, but the page is pretty old and the scans are on a server that's no longer hosting them

 

Exact same codes I had, except the P0302 code and mine only happened on WOT runs. I returned from the dealer and they erased the memory for the stored codes and reflashed the computer. No issues after several WOT runs.