ajerman

Hello all, I'm new here and to the car. I'm more of a fast car type guy, but after a bit of unemployment and some rethinking of things in my life, plus a 50 mile round trip to work, I've decided to pick up something a little practical (THEN I can build a monster on the side later, hehe).

So anyway, I've gotten a 98 Accord DX, 5 speed, but it looks like it needs a bit of work. I've got 10 days to drive until I need it inspected, so I need to get some things fixed to clear a CEL.

I had it scanned this morning, and it came back with several codes. P0420 of course, the front O2 was changed, not the back, that may need to be done still and could fix that. I also got P0302 for cylinder 2 misfire, P0401 for insufficient EGR flow, P1456 for the EVAP system, and P1399 for misfire again.

Symptoms: The only notable one is that the car runs rough when it's warm and I start it. RPMs run low, under 500, but it hasn't died when it did it. I give it a little gas and it seems to clear itself up. It also looks to be leaking a little coolant, but other than that, it definitely doesn't feel like it's misfiring and drives great.

So my question is, in anyone's experience, do all of those codes add up to anything specific that you've seen? The guy at Autozone said they all sound vacuum related and could be a leak. I went ahead and replaced the gas cap while I was there to rule that out. I think the cylinder misfires could be when it starts rough, because I really don't feel any problems once it's going. I'm wondering if it could be something like a clogged EGR system and it's causing it to start rough sometimes, and that's causing misfires and more codes.

Like I said, I'm new, this is a whole new engine for me, so I'm not sure what common places to start. I think I'll look into cleaning the EGR system, I saw a good thread on that. The gas cap is replaced in case that was causing anything, and it very likely could have a bad O2 sensor, but that could be caused by something else too I suppose. I'd appreciate any information anyone can provide to help me know where to start. I've got 10 days to drive before I require inspection to get tags, so I'll be working on it this weekend and next.

Thanks!

ajerman

Okay, well here's what I know so far. Please let me know if I'm on the right track or if you have any other ideas.

I see that the P1456 code points to the fuel tank area, and that the gas cap replacement was a good first step. If that doesn't solve the issue, I should be looking for physical damage to the tank (which would probably smell like fuel, something I haven't been looking for, but hadn't noticed), the fuel pump/gasket, the two way valve or bypass solenoid. This sounds like it's probably an isolated issue and not related to any of the other codes.

The misfire, I still think is being thrown during the rough starts that I get when it's warm. I definitely don't feel even the slightest misfire while driving, and read that a flashing CEL while driving means a misfire, so perhaps that's not happening normally. I think I will save this for last and hope that the other problems fix this.

Which leaves the EGR code and O2 sensor code. I think my best bet is to plan on cleaning the whole EGR system as noted in this thread: https://honda-tech.com/forums/honda-accord-1990-2002-2/diy-fix-all-had-p0401-code-2674082/. Hopefully this will clear the EGR code, and, correct me if I'm wrong, but could and issue with the EGR system not cause the P0420 code as well very easily? If it's clogged the mixture could be off and the downstream O2 sensor could be seeing that. If not, I'll replace the sensor, not too big a deal.

I'm fairly competent when it comes to working on cars (son of an aircraft mechanic), and have a garage full of tools at my disposal, so I'm definitely trying to do this work myself, but I do have a contact at Honda if I really need to get it professionally diagnosed. My biggest issue is just that I don't know this engine yet, but I'm trying to learn as fast as possible. Does anyone have any other ideas or corrections to my above plan for troubleshooting?

jdmcertified909

what you need to do is check for fuel pressure. before you cold start it disconnect the vacuum line to the fuel pressure regulator. does sound like a vacuum leak. what i do to find vacuum leak i fill a spray bottle with water and soap and shake it lightly and spray it all around everywhere intake vacuum lines. throttle body spray every crease. and look for bubbles. or change in idle. you can also try disconnecting the egr before cold start and see if it eliminates the shaking symptom. pull out your spark plugs and check the tips. what color are they? another thing the shaking kinda sounds like a stuck iacv idle air control valve or fitv. fitv can be open full making it choke cold start.

https://honda-tech.com/forums/honda-accord-1990-2002-2/cleaning-iacv-fitv-tb-1844067/

ajerman

Okay, I'll check all that as well. The plugs I ASSUME are new, because the distributor and wires are new, but that's probably not a good assumption, so I'll check on them. I need to pick up a Haynes on the way home tonight so I can get a location of all the vacuum lines to check them all out. Thanks for the link, I'll check the IAC valve as well.

Bad_dude

It looks like all of the other codes are causing you to have the P0420 code. Fix the other codes before your cat is toast.

joec44

What is a fast car type of guy? P0420=bad cat fix the missfire first then replace the cat and see what happens But you must fix missfire first so you do not take out a new cat (that sounded bad)

MAD_MIKE

Agreed.
Insufficient EGR flow(P0401) would cause a lean misfire at cruise speeds. But if the plugs are old/worn this could also cause a misfire condition. This could also set off the P0420 catalyst threshold efficiency code.

ajerman

Okay, thanks for all the input. I had a busy weekend working on the house and never got to work on the car, so I'll be doing that this week. I kinda of figured the EGR errors could be causing some of the others, so cleaning that will still be first priority, then I'll reset codes and get a fresh scan with that done and the new gas cap and see where I am.

ajerman

Okay, well Friday I pulled the intake plenum and cleaned out it and the EGR passage, throttle body, and RACV, and replaced the gaskets for the intake plenum and throttle body, as well as my water outlet connection that was leaking. The EGR passage was definitely blocked up, and the car drives noticeably better now. Low RPMs when shifting don't seem to bog it down quite as much and taking off from a stop in first is much smoother. Plus it didn't seem to have as much trouble with warm starts like it did before.

I drove 95 miles to see my friend and got no CEL the whole time. Saturday when I was heading home, I started the car with the A/C on, and it made it bog down again for the first time, and shortly after my CEL came on. When I got home I got the code pulled again (after about 170 miles), and my only codes were cylinder 2 misfire, and random cylinder misfire. Since I had looked at the spark plugs and they looked alright, but not new, I went ahead and replaced them. Drove another 75 or so miles over the rest of the weekend with no code, then on my way home about an hour ago, the light came on again.

I would assume that the light is, again, the misfire, so I guess after the spark plugs are changed, I should look at the injectors. Regardless, I went ahead and reset the computer again to clear the CEL and drove a little over 50 miles with no CEL. Hopefully this will be enough to pass inspection in the morning, because my 10 day pass expired tonight. Though that brings up an interesting issue. I HAVE to drive 50-100 miles to get OBD2 ready for inspection, but I have no plate and now not even a temporary registration. I guess if I don't pass I'll have to talk to the DMV about that.

So anyway, I've gone from 6 codes down to just the 2 misfire codes, so cleaning the EGR passage definitely fixed that and the P0420 code. Hopefully 50-60 miles is enough to pass in the morning and have time to diagnose the misfire. Otherwise I'll be sneaking miles with no plate each time I try a fix, haha. I did just find a link to speeding up OBD II testing by following a certain drive cycle, so maybe that will help.

Oh, as just a little side note. When I got the codes pulled after getting back to town with 170 miles or so, I had the two failures, everything else passed, but the evap system was still registering incomplete. I'm surprised that many miles weren't enough to complete that test, though it might be more related to number of drive cycles also rather than just miles.

Edit: Just read another thread that made a good point to use higher octane fuel if you're having misfire issues. Certainly isn't guaranteed to help, but it's not a bad idea I suppose to possibly help try and get an inspection in.

Lost Again

Have you checked the cap, rotor and inspected the wires? You say they are "new" but you never really know.

ajerman

Yeah, I've been under the hood extensively while working on this car. There's definitely a difference in new vs polished up and treated, and the distributor and wires are definitely new. My only concern is that I didn't see a name brand on the wires, so I don't know what their quality is. I've gone about 150 miles since my last CEL Sunday night, and haven't had any more codes thrown. If the issue starts up again, I'll probably hook a timing light up to each wire and make sure they are all firing properly. Plus I should probably check the timing on it anyway.

Either way, I'm a happy owner now. I've owned a Mustang GT, a Cobra, and a 335i, but this is definitely my smartest purchase for a car yet (especially after that 335i, hahahah). The car drives wonderfully and I'm already loving the gas mileage with my 50 mile daily round trip for work.

Now onto tint, finishing the sound system, and maybe some small suspension mods!