granadablanca

Hi all,

New member here. Picked up a 2000 Integra LS about a week ago, wanted something simple, normal and fun to knock around in.

The car is stock and feels solid, the only significant issue I noticed is an exhaust leak. Perhaps a manifold gasket; it sounds like it's right up front. Valves seem a bit noisy, but nothing extreme. I put a bottle of Techron in about two tanks ago, and the oil is perfect as well.

However, last night the CEL went on, about 30 minutes into my commute home. Codes are random misfire (P0300), as well as three individual cylinders (I forget which ones right now).

I checked plugs, wires, cap and rotors - everything looks brand new. I cleared the codes, hoping it was a random fluke. About 30 minutes into my morning commute, the light came back on.

Can anyone shed any light as to what to check next? A step-by-step checklist of stuff to try? The previous owner mentioned something about tight valves, which I found to be an odd comment at the time, but maybe that's related?

Thanks.

FF for Life

You said the valves sound noisy? Might want to do a valve adjustment. Misfires can be caused by multiple things. If you checked the ignition system (cap and rotor look new with no corrosion on the rotor or cap) and plug wires are in good condition (clamps on the plug side inside the wire are still attached and clean) as well as your plugs in good condtion (proper gap and no carbon build up or unusual coloring), valve lash should be your next step. You could check the fuel delivery but if the previous owner mentioned tight valves that could be bad. Honda had a service bullitin for 97-01 CRV's (I know they have B20's) for tight valve lash that could cause burn valves (holes or nicks in the valve matting surface). I have personally replace a few valves at the Dealership for this issue. Being that B20's and LS engines are both non vtec and virtually the same except for displacement, you might want to do a compression test and valve adjustment first. Post your findings.

fcm

Ditto the above^^^, adjust valves, [replace timing belt if needed/due] and do a compression test.

Multiple/random misfires are most commonly caused by a fuel issue, low fuel pressure, injector pulse problems, old fuel filter, [clogged].

If it has not been done a general tune up including valve adjustment and timing belt, [if needed] and then a compression test is where I would start, if for no other reason then to eliminate them as the possible problem. 94

el crapitan

It's possible the misfires are being caused by your exhaust leak.
If a leak is bad enough, and upstream of the primary o2 sensor (which yours is), it can actually create a venturi effect and pull outside air in which fools the o2 into thinking the engine is running lean. The PCM sees the readings and Mistakenly over fuels. This would definitely cause random misfires.
It does happen. Fix that leak, clear the codes, and see if that doesn't solve your problem

granadablanca

Thanks for the replies, guys. Here's the latest.

Timing is spot-on. Valves are now perfectly adjusted (there were a few tight ones, but nothing insane). Compression is good, not perfect but within acceptable spec. Everything else looks well-maintained, clean and good. Cap & rotor are not OE, and plugs are iridium, which I'm not crazy about. Let me know if you guys think I should address those.

I should also point out that it passed smog with flying colors just a week ago, the day I bought it. Drove it like crazy for a week before the first CEL as well. So I'm thinking I can rule out internal/mechanical.

I can make it throw the codes immediately by holding at 3000 when dead cold (otherwise it takes about 30-40 minutes of driving, after a cold start). When cold like this, I can definitely hear the misses coming from the exhaust tip, and it runs a little crummy.

After clearing the codes, they won't come back at all, now that it's warmed up. Once warm, it runs smoothly. Whatever the issue, it's minor, since the engine feels and acts pretty much fine, aside from the light.

I bought a new gasket for the exhaust manifold, took the manifold off the engine but the existing gasket looked perfect. After poking around some more, I found the leak was actually at the bottom gasket (at the end of the manifold), so I have to get that one now. It's definitely a bad leak (sounds like a school bus), but wouldn't it throw an O2 code if it was causing the misfires?

Also, yesterday, I was only getting P0300, P0301 and P0302. This morning, I only got P0302 - not even a P0300 this time. (not counting the 1399s of course)

What do you guys think is next? Fix the damn leak?

Gage™

I'm having a similar problem. Although I know for a fact that my O2 sensors are bad and the only codes I'm receiving are bank 1, sensor 1 and bank 1, sensor 2 for my primary O2 sensor.

But it's doing a terrible knocking/misfiring/surging/etc.

I've replaced spark plugs, plug wires, distributor cap, rotor button, coil, fuel filter, oil, oil filter, fuel pump and so now I'm lost.

el crapitan

It won't throw an o2 code. As far as the PCM knows, the o2 is fine but you're running lean. So it thinks. Fix the leak. It may or may not be the cause of your problem. But it needs to be done anyways

eclipsedsundown

Yes fix the leak but a faulty Knock sensor will trip a miss fire code. Yes get rid of those iridium plugs and see if that works first because iridium is a higher burn temp. and more temp doesn't mean more power! There is a specific code for a knock sensor but many things can cause the same result. After my friend replaced his motor in his prelude he had the same problem with multiple miss fires and other codes but he changed his knock sensor and cleared it right up!

granadablanca

Thanks guys, I'm still waiting on the proper gasket to fix that leak. Of course it needs to be fixed regardless, and it if fixes these misfires too, I'll be a happy camper.

Picked up some proper plugs in the meantime, going to swap out those iridiums tonight (anyone in socal want them? they look brand new).

The light seems like it's going on less frequently the past two days. Almost makes me wonder if I had a bad tank of gas, but I'm never that lucky. Plus I've nearly gone through a whole second tank since this started.

As for the knock sensor idea - would that actually cause misses? Or just misfire codes? Because the car is definitely missing, it's not just a glitch.

el crapitan

It's a possibility. As the PCM retards timing if it detects a knock
But then, there are many, many possibilities

maxthemechanic

My wife has a 1998 CR-V
Stock B20B, 8.8:1 compression motor, so no knock sensor.
Started doing this about 2 weeks ago.
When warm it is sometimes hard to start.
New Cap & Rotor = no change
New Wires = better for 2 days then back to same.
New plugs (The guy at the store talked me into the iridium) = no change.
I went back to the stock NGK plugs (brand new) gapped at .44 = better but still throwing codes.
Any help is appreciated.

el crapitan

Which codes? And what happens when the problem occurs?
Ie, crank but no start, or no crank?

eclipsedsundown

your B20B is a low compression low rpm motor no need for a knock sensor on it. B18C have a higher compression and higher rev so it monitors knock. But this is for a LS B18B so yes sorry no knock sensor. But with VTEC a knock sensor can trigger a miss fire code. Your O2 sensor can cause this too, it can be faulty and reading a lean code for miss fires. Most likely your front O2 sensor. An NTK sensor is your best way to go.

granadablanca

Ok, here's the latest.

Put OE plugs (NGK/Honda) in, and fixed the exhaust leak (so much quieter!).

The codes came right back within half an hour or so.

So, summary:

Bought a car, ran fine for a week, passed smog perfectly, then starting getting CELs for: P1399, P0300, P0301, P0302, P0304 (and every possible combination of those - sometimes even just 1399/0302).

Plugs, wires, cap and rotor are all new. Valves are adjusted properly. Timing is correct. Compression is OK. I'm on my 3rd tank of gas since this started, so I don't think it could be bad gas. Definitely misfiring, so not an electrical glitch.

What's next? I'm running out of ideas. The light comes on every day, sometimes cold, sometimes after warming up for 20-30 min, sometimes not for hours of driving. It's totally random.

The only other existing issue I knew of (now that the leak is fixed) is the rear engine mount. It's trashed, making the car buck like a bronco when getting on/off the throttle. I can't imagine this causing misfires in any way. I already have the new mount, just haven't had enough time. That rear one is a total PITA.

granadablanca

Bump! Any ideas what to try next?

The codes I get are always one of these combinations:
P1399, P0302
P1399, P0300, P0301, P0302
P1399, P0300, P0301, P0302, P0304

I don't believe I've ever seen a P0303, so perhaps it's not truly "random," and is in fact a cylinder problem of some sort?

teg-SIR

hey buddy, ive beed reading this forum for tips for a long time, and had to register.

i JUST had this problem. random misfire across P1399, P0300, P0301, P0302, P0304

I changed:
Plugs
Wires
rotor and distribuitor
injectors
fuel rail
ecu
fuel filter..
took the head off and checked valve clearances (which were all fine)


sprayed brake cleaner along all the vac hoses to inspect for leaks..
pulled off the IAC (idle air control) and cleaned the **** out of it.

none of that fixed the problem.

after almost giving up, i tried to find a vac leak one more time with brake cleaner.
along the right side of the engine the intake manifold gasket had cracked and was leaking.
the actual problem was a cylinder 1 misfire because of air leak.

replaced the gasket and she ran like a champ again.

after reading this post, it sounded exactly like my problem.
check it out and post back.. im almost SURE that was the problem

(btw my same problem was caused by a loose rear engine mount too.... so get it fixed!)

granadablanca

wow, that's eerily identical to my story. i'll definitely check that gasket. that could also explain why i never got a cyl 3 code, since it's all the way on the other side.

out of curiosity, though, how the hell could the rear mount cause this? just from all the shaking around loosening the manifold?

anyway, fingers crossed! will report back after i check. thanks for chiming in.

TIMOTHY JONES

Hey guys my names Tim I have a 2000 Honda Civic DX I have a cylinder two misfire I pretty much did everything you could think up to fix the problem but I'm still getting the misfire it's only on start ups it will misfire for about five seconds then level out I replace wires spark plugs distributor all sensors head gasket compression test motor mounts but I will not stop getting the misfire I fix the crack in the exhaust manifold can you please help me i'm pretty much out of options thanks

fcm

I suspect an ECU problem, intermittent injector pulse to that, [misfiring] cylinder,
Do you know what cylinder is misfiring or is it all of them? 94