Royaltrophy

I had an engine light come on about a week ago, I bought a tester to try to diagnose..
I found a P0301 and P1399 code a week ago

I then swapped number one coil to number 3 just to see if I could figure out the issue being either the coil or injector.

Then Reset the CEL.

Now, Today I went for a short drive, the CEL came back finaly
P300, P301, P302, P303, P304 and p1399 (6 in total) The P0301 code came up twice in the stored CEL list.

Now I'm a bit stumped.

Anyone have an idea what I should do?
Where to begin now?
Does this mean the P0301 code is my injector because I swapped out the coil to number 3 last week and the code didn't follow or... ?

Ive already changed out the spark plugs to new. so I can rule this out atleast.

On code p0301 there is freeze frame data below
Fuel sys 1 : CL
Fuel Sys 2 : NA
Calc Load (%) 55.3
ECT (degree C) 88
SHIFT B1 % : 3.1
Lift B1 (%) -5.5
MAP (KPA) 56
ENG RPM 3040
VEH Speed KPH - 92
IAT(Deg C) 34
TPS (%) 16.9

ssokolich

I have a 2004 s2000 with 115,679 miles. Yesterday i was driving home, accelerated into VTEC and suddenly it started misfiring. I was only a mile from home. I took it easy and limped it home on what felt like 3 cylinders. I put an obd2 scanner on it. Got a p0302 (#2 cylinder misfire) and p1399. (Misfire). It turned out the electrical wiring harness connector to the coil pack on #2 cylinder was loose. #1 connector was also not fully seated. These connectors are plastic. And after 100,000+ miles the engine heat renders them rather brittle. Especially the plastic clips that secure the connector to the coil pack. Three of mine had missing broken clips. So #2 cylinder coil pack connector had vibrated loose under hard acceleration, i.e. High vibration. I don't want to spend the money on a new engine wiring harness at the present time. Honda should have made these connectors out of better material. Or at least make them replacable without having to remove the entire wiring harness. I needed something i could use to wedge between each coil pack. Thus putting pressure on each connector preventing movement. I ended up using 1 inch pieces of fuel tubing. See the pics. Notice the clip on #4 coil pack connector is present. But the connector housing itself is also broken. These cips should be on each connector. But you'll notice they're gone on cylinder #1,2, and 3.

HarryD

Here's a DIY and some aftermarket clips you can use if you want something more stable than your wedge trick
https://www.s2ki.com/forums/s2000-un...ement-1123869/

ssokolich

Thanks for the link!

Royaltrophy

although great advice and I did double check my connectors to the coils but mine seemed to be ok. I did move the number one coil to number three and reset the CEL

this past week while driving the light came back on , re checked with the obd2 tester and the codes were p0301 and p1399 again.

I have already changed out the plugs a few weeks back and have gone ahead an ordered a set of injectors to substitute with number one injector

also to note, I'm getting quite a strong smell of fuel at start up at the back of the car although no leaks I'm starting to wonder what could be wrong there and if the two are linked somehow.

random misfires can be felt in traffic and low rpm but seem to be not as evident at higher rpm or on the highway..

waiting on new fuel cap and injectors to report back.

thanks all for advice.

wtfeezey

Have you checked the valves yet? When I was getting misfires it was due to a poorly seated valve. I hope thats not the case for you because it costs a pretty penny to get fixed but it sounds like you're having similar issues. The bad valve was in cylinder 1 but would cause all the other cylinders to misfire so when I pulled codes 2,3 and 4 would show up randomly but the code for cylinder 1 was consistent. You might have a bent or dirty valve if the injectors, spark plugs and coilpacks dont fix the issue.

623baller

make sure you do a valve adjustment too if you have not already. i had similar issue before but mine was because of bad plugs and tight valves which caused random misfiring. after spark plugs and valve adjustment , it runs strong now. havent seen the code pop back since knock on wood

92gli

Wish I knew the ratio of people who have a cat/are catless that have this issue. This started for me right after I hollowed out the aftermarket cat that was on my car because it was rattling. Thinking about picking up a used oem cat to see if it stops the misfires and also cause I'm getting tired of breathing uncatalyzed exhaust at traffic lights.

I'm going to check my coil connectors this weekend and brace them with some high density foam pieces. I know my plugs are good. Billman just adjusted my valves a few thousand miles ago. Injectors have been switched around. Still get the same 3 codes.

mirabileboy

If you have an Ap1, I'd replace the fuel filler neck. My 2002 threw a random misfire code and a misfire on cylinder 2 I believe. I also had a strong fuel smell after I turned the car off or if I can to a stop. Come to find out the fuel filler neck was faulty, which I guess is a problem for older ap1s. I ended up buying a used ap2 (2004-2005) fuel filler neck with the gas cap and swapped it out. Cleared the code and it never came back, and no more fuel smell. When you tighten your gas cap make sure it seats completely. I good sign that it's not is that it clicks too soon. I believe the fuel filler neck thread pitch is the culprit and doesn't allow for the gas cap to fully seat and make a compete seal.

Royaltrophy

I figure it my due diligence to reply as I was reading a thread the other night that I was right interested in and the length of the thread was over 25 pages long, when I got to the end it was left unfinished which really kind of sucks - this and dead links blow so I'm going to reply my finding in hopes that if someone else is reading this while trying to narrow down their own diagnoses of p0301 issues they can use the info to solve the problem.




I ended up replacing my fuel filler cap and I tighten it using the outside not the center handle as the difference in tension is drastic difference so I'm going to lean towards this being part if not 1/2 of the issue that I was having. Which might have been some of the reason the ECU was throwing codes over all injectors or cylinders.




Now I say this was 1/2 the issue because when I got the filler cap changed reset the codes and drove the car I was still getting the codes for misfires on cylinder one. So I ended up moving the coil as previously explained hoping that possibly the code would jump to the cylinder I changed the coil to from number 1 but it didn't and this might have been due to the fact that the gas cap was helping hide / hinder the readings. So I changed the plugs reset the ECU and still found this same codes. I felt it was time to replace the injector and so I did this with some used injectors from ebay which were quite inexpensive in hopes to find the solution




I also changed out the fuel rail as there was a killer deal on ebay for a used AEM fuel rail with fuel pressure gauge tapped into the rail and AEM FPR. I felt this was self explanatory as to why all cars would benefit from having this so I pony up and bought the rail as I didn't have a pressure tester and the manual explained the primary cause of misfires and p0301 codes was due to either compression or fuel pressure or at least this was the first place to being searching after doing the regular moving of coils and possibly plugs, the reasoning behind the fuel pressure being my suspect was because engines normally have the vacuum at the pressure regulator at idle and then at higher RPM they do not have this vacuum. So I was leaning towards vac leaks and FPR possibly being culprit with all these things looming I removed the vac line off the FPR and there seemed to be some change but not much. Anyways with all this an no fuel pressure gauge to know for sure of the correct pressure I just changed out rail with this tapped fitting for a gauge.




after installing the rail which came with adjustable FPR and gauge, the new injector and a new vac line to the FPR I adjusted the fuel pressure to the 47-54psi with the line off and then re connected to watch fuel pressure fall back into the correct range of 38psi to 46psi with the vac line connected and boom, she runs like a top again. No misfires over the last 3000kms and all seems to be going well knock on wood. I will say this tho one who wants to tap a fitting into their existing rail can do so and by no means do I think it was needed to go out and buy this stuff but I got a good buy and couldn't really pass up. In closing the AEM rail is pretty nice but it doesn't have a place to tie the wire ties to the rail as the stock rail does and if your planning on tapping yours I think its 1/8" NPT but I might be wrong on this so be careful of the chip getting into your rail and use the correct tap. Opening the hood and looking at the fuel pressure at idle always without having to attach a gauge is a super nice to have. Happy searching.