okay, so to start, i have an 01 with 90k on the clock. i bought it used with 80k. about 2 months ago i drove about 30 min to a different town. sat around for a couple hours... then went to start my car back up. my check engine light came on and my car sounded like a subaru. i drove it home the next day. every gear lagged and i was missfiring/backfiring realllllly bad. i had a scanner at my place and scanned it.. the codes it threw were p0300 p0301-p0304 and p0499. random missfire in all cylenders and bad egr. (i assumed the egr was the secondary air valve because we do not have an egr) first things first. changed plugs/ coil packs. put stock airbox back on.(left after market exhaust on) checked oil. ordered a new secondary air valve. i also replaced my cat thinking it might be carbon buildup. after all of this the CEL went off and the car drove decent up until about 2 days ago. during the time it ran okay it would missfire a little bit. but never enough to mess anything up. 3 days ago it started missfiring alot. 2 days ago the CEL came back on. and now its sounding like a subaru again. i dont want to drive it cause i dont want to mess anything up. i took my car into a shop the first time and they said they didnt know what was wrong. (real helpful, right?) im pretty sure im going to take it in again tomorrow becasue the CEL is still on. basically if anyone has any other idea id LOVE to get any imput. my ideas were fuel filter/pump. or fuel injectors. i always use premium. i always change my oil every 3000 miles with full synthetic. i just am at a loss here and cant figure out what it can be. again... any imput will help. thankkk you all!

-nick

 

could it be a bad coil pack or 2 or maybe the ECU is taking a break?

 

i replaced the coil packs. i was also thinking that i could get a reflash on the ecu?? maybe i needs to be rebooted.

 

i'd be willing to bet you ECU is fine. Have a valve adjustment, i went through hell for 3 weeks with that on my car. Tried a buddies coils, i knew it wasnt ecu, and the wires all had the proper current. After having a guy take a snake light/camera in my cylinder he said the cylinder was fine as well, and no det marks on the pistons. He decided maybe an off valve could cause it, and i agreed, so i got the valve adjustment, and boom, all my problems went away! try a valve adjust, look for a recessed piston also.

-> ap1's have a few quirks, once you swap out keepers/retainers/etc the risk of valve float and recession go away, and it seems to stay adjusted much better also.

 

Did you check your spark plugs when you replaced the coil packs?

I was at 98K and got a random misfire code/shuddering and my plugs were shot.

 

yup. replaced the plugs as well. how much did that valve adjustment cost you?? just so i know what im lookin at.

 

i got the valve adjustment... it did not fix anything.

 

both my mechanic and honda said the engine looks in great shape. valves were a tinnnnnnnnnny bit off he said but it shouldnt have cause the problem it did. pistons/valves were all okay.

 

I just solved this for my car but my fix probably won't fix yours. My car previously had an AEM in it as well as various gauges I presume. The ECU harness was hacked into, and a blue wire disconnected itself (I mounted it loosely and the soldered wire broke apart).

But during the process of troubleshooting, I ran various other things that may help.
-MAP sensor (unscrew it and clean the sensor as well as the plug/socket with quick drying electronics cleaner from the parts store)
-TPS sensor's plug/socket to make sure it's making a clean connection.
-spark plugs (since you swapped fresh plugs in you should be ok)
-coil packs (since you replaced them and you're getting all 4, you should be okay)
-fuel components such as injectors, fuel pump, fuel filter. Wadzii on here suggested to me that if you pinch the fuel return line while it's misfiring, it will bump up fuel pressure a couple points which may resolve the issue. If it does, then you have narrowed down the cause of the issue to fuel.
-what fuel are you running?

Though it's not likely, I wouldn't completely rule out the ECU either. If you have someone local who can lend you their AP1 ECU with matching key you can troubleshoot further.

If all mechanical components are in order, then it's time to move on and approach it from other areas. the TPS/MAP sensors may have gone bad, so testing them or swapping them for known-good ones would be the only way to determine.

 

well. i already cleaned my MAP. i was thinking fuel filter and or fuel pump.. but odds of those going bad are not very likely. my fuel injectors are all good. reading the right ohms and functioning perfect. i took my baby into honda yesterday and just told them to fix it. im sick of trying to figure this out. a mutual friend of mine works there, so im having him do the work. i wont get my car back till tomorrow AT LEAST. so i will let you know the outcome as soon as i find out. in the meantime im going to sulk at home while this beautiful weather eats me alive because i cant take her out for a cruise.