2002 Honda s2000 with 141xxx miles

Over the last year or so, I've been trying to figure out my misfiring problem - at first I thought my injectors were gummed up because the misfiring took place randomly, and it didn't seem to matter when I switched around my coil packs. I would throw in some fuel injector, clear the code, and be on my merry way for another few thousand miles. Whenever the misfire CEL popped back on again, I'd just toss in some more injector cleaner, clear it, and it wouldn't come back for awhile. I figured my injectors were just gummed up and I was putting off getting them cleaned.

Up until yesterday... here's what happened. I'm guessing this will help some of you out eventually too in how failing coils... go BAD? Chime in and let me know what you think.

Yesterday I was driving around downtown, minding my own business, when my car started lugging terribly. The CEL came on flashing within about 5 seconds, so I turned the key off and coasted into a street parking spot (and got a $15 ticket later for not feeding the meter, but I'll let that one slide). When I turned the ignition to ON, the CEL was gone - so I fired up the engine again and within a few seconds (again, lugging badly) the CEL started flashing and I shut it down. This time however, the CEL stayed lit in the ON position.

Anyways, I was pretty low on gas (not out) so I figured maybe I sucked up some bad fuel at the bottom of my tank or that my lying fuel gauge wasn't indicating that I was completely empty. I walked a solid mile to the Chevron station, bought a gas tank, gallon of supreme and some injector cleaner and walked back.

Filled up the car, fired it up, let it run for a little bit at idle with the CEL flashing, and the gas made no difference.

I tucked my tail between my legs, and called up a tow truck - making SURE they would be either towing it by the rear, or putting me on a flat bed. Don't ever let anyone tow you with your rear wheels freely spinning! I learned my lesson in advance from other people destroying their differentials on here.

ANYWAYS - DAY 2

Pulled the CEL codes - one yellow warning code with a general "misfire detected" diagnosis, and one RED code with a "Cyl 1 misfire detected"

Decided #1 priority would be a compression test to rule out some initial horrible things that *could* be the cause of it.
Cyl 1 - 240 Cyl 2 - 245 Cyl 3 - 240 Cyl 4 - 243

Whew! That made me feel better. Now I figured, let's swap some coils around.

I swapped Cyl 1 and Cyl 2's coil packs.

Cleared the CEL and started it up.

Within a few seconds, flashing CEL started up again. Shut it down, and when I turned the key back to ON, the CEL was off again. Hmm... same as what happened when I first needed towing.

Pulled the code - came back as "general misfire detected"

I guess the way the car works is it throws an initial warning code before it determines what cylinder is misfiring? This was new-found knowledge to me, and something to keep in mind. Warning codes will not leave the light illuminated.

Alright, I started up the engine again. Within a few seconds, CEL started flashing. Shut it down, and this time when I turned the key back to ON, the CEL was finally "set" on.

Pulled the codes - came back as warning yellow code "general misfire detected" and RED code "Cyl #2 misfire"

This was making me feel a bit better, since I figured maybe just one of my coils was going out. I had heard people on here say numerous times that once one coil is dead, the rest start to follow suit. Now KEEP IN MIND - I have had these issues on/off the last 12 months... this is where the good diagnosing comes in.

I decided as final insurance, that I would swap #2 and #3 (basically now Cyl #1 was on Cyl #3 and Cyl #3 was now on Cyl #2 and Cyl #2 was on still Cyl #1 - hopefully not too confusing) just to make sure it was just the one bad coil...

Cleared the CEL, and fired up the engine.

Same thing - CEL flashing, engine running rough, shut it down, and only got the yellow warning code again.

Started it up again, flashing CEL, shut it down, CEL stayed lit, but THIS time I pulled three codes:

Yellow warning "multiple misfires detected"
RED Cyl #3 misfire
RED Cyl #1 misfire

Whoa! I didn't touch #1 this time, and #1 had #2's coil pack on it - there was nothing wrong with #2's coil pack in the initial diagnosis. Maybe they're all on their way out??

Also during all of these tests, I could smell gas in the engine bay, indicating that either the gas can in my trunk was really starting to permeate into past my cabin, or that there was unburnt fuel being shot into the engine and out the exhaust. Also between each time that I swapped around the coils, the engine ran rough in a different way. You could feel that it was missing, but it ran rough slightly differently between each coil swap. Again, further evidence of bad coils.


MY DIAGNOSIS:

I put off replacing my coils because of suspecting gummed up injectors. My coils began to fail about a year ago, and by resetting the engine light over and over again, I just allowed the coils to get worse and worse. Finally, one of them completely failed. Then while diagnosing the completely failed one, I determined one of the others starting to go out too. You can read my misfire thread previously HERE

Another other thing that I could think of is being unfortunate enough to have my injectors gummed up, along with my coil packs intermittently failing out? You can see in my other thread that I was pulling misfire codes from nearly every cylinder, but the engine was running just fine with the code set (it was NOT flashing in that case). I guess it could have missed a few times on all of my coil packs failing and not stayed flashing because they hadn't completely conked out yet? <-- I'm leaning towards that since the engine never ran rough in that case.

LASTLY - I had the Honda Dealership do a valve adjustment around 100000 miles and they said my valves were all within specs and that they didn't have to do anything other than adjust two exhaust clearances. When I did my retainers/cotters swap for AP2s about two months after that, I had to do my own valve adjustment. I took my time and the engine fired right up with no CEL, so I figured I did it right. If my valves were way off, wouldn't my compression also be bad? I assumed that because my compression test came back good, that my valves were within the correct clearances. Correct me if I'm wrong.

Anyone want to chime in here? I figured this may help someone down the line with the whole random misfiring issues.

I am also very open to being told that I'm completely wrong and that I'm an idiot.

Thanks guys/gals!

PS - New OEM spark plugs pre-gapped were installed at the correct 105000 interval, so they shouldn't be suspect.

 

Did changing the coils fix your issue?

 

Haven't changed them yet, just diagnosed today. Would like a confirmation before shelling out the dough for new ones.

 

I wouldn't be surprised if they were coils, but I'd check the valve clearances since it's just the time you'll spend.


I've seen a few general misfires from bad in tank pump units that house non serviceable filters.

Misfires come from dirty/faulty injectors too. It might be worth the peace of mind just to have em cleaned for the $100.

My last misfire ended up being faulty ignition coil connectors that weren't making a good connection every so often. As s200 get older, the wiring and plastic get brittle, especially since it sits right on top of the engine.

If you grab a general scan tool, view live data and check your short term fuel trims(stft). Is it + or - when it's running bad? That will tell you is its adding fuel or taking it away to correct whatever problem you have.

You might get lucky and see a drastic change when wiggling things around.

 

If you can find someone, get them to swap coils with you and then injectors. That's probably the best fix

 

This is a general question I have not seen answered yet - if my valves are off, wouldn't my compression be low too? I always thought those two were directly correlated.

I have OBDII tool thst shows live data. How do I go about using that to check fuel trims?

Thanks

Also UPDATE: I switched Cyl #3 with Cyl #4, did the same procedure, and am now receiving a misfire on Cyl #4. There's something DEFINITELY wrong with that coil, right? It throws a failure no matter what cylinder I put it on.

The only thing that throws me off is that it threw a #3 and #1 misfire when it was on Cylinder #3. I retested it again after clearing the ECU and the second time it only threw a #3 misfire. Not sure what is happening or if it's either a fluke that #1 threw a misfire code, or if that coil pack is potentially on its way out too.

Also the smell of gas coming out the exhaust is quite bad. There is DEFINITELY gas coming out the exhaust.

I followed my plastic coil harness all the way around and while it looks a bit worn, the heat shields are still intact and I didn't see any exposed wiring or notice of extreme wear.

One other thing - in the last three - four fill-ups or so, I have lost (on average) 3-4 MPG. I blamed it on new front tires, but may be it's related to this?

 

If your valves are very loose you won't lose any compression, you'd lose compression only if they're too tight.

The smell of gas is because a cylinder is not igniting, the fact that it moves with the ignition coils leads me to believe you have bad coil(s) or bad wiring to the coils.

You can check your injectors with a voltmeter, putting the negative probe to ground and the positive probe to ground on the injector connector, you should see voltage drop smoothly as you increase the throttle while the car is running. The ECM grounds the injectors, and will ground them more as rpms increase. If the voltage drop isn't linear you may have a sticking injector. Alternately you can check the on time in m/s. Unfortunately unless you have a fancy scanner with a scope you won't be able to see the injector waveform.

 

If your valves are very loose you won't lose any compression, you'd lose compression only if they're too tight.

The smell of gas is because a cylinder is not igniting, the fact that it moves with the ignition coils leads me to believe you have bad coil(s) or bad wiring to the coils.

You can check your injectors with a voltmeter, putting the negative probe to ground and the positive probe to ground on the injector connector, you should see voltage drop smoothly as you increase the throttle while the car is running. The ECM grounds the injectors, and will ground them more as rpms increase. If the voltage drop isn't linear you have a sticking injector.
[/quote]

I definitely have a voltmeter and know how to use it. However, is it safe to be checking this / revving the engine a bit if I'm having a flashing CEL / misfire? I don't want to cause any more damage. Figured it was worth asking.

Thanks

 

Oh true indeed, well no you probably don't want run the car then.

 

I bought a set of 4 coil packs and I'll post back up once I've got em' installed.