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I have a 2002 Honda CRV with 94,000 miles. Check engine light is on with codes P300-304. So far I have had the valves adjusted and spark plugs replaced after Honda ran a diagnosis. Check engine light stayed off for 200 miles then reappeared. I checked the new plugs and they have carbon build up on them. Any suggestions of where to look next? Vacuum leak? Clogged EGR? I’ve also heard that a weak battery would cause misfires? Please let me know where I should look next. Thanks!
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No paperwork yet. Car is throwing P300, 301, 302, 303, 304 and a rich condition code. Dealer did compression test and all is well there. Also did a cylinder leak test, not sure what that is (seems like compression to me but im no mechanic), and determined that cylinder 1 is leaking 35% so that is why they are focusing on that cylinder. They took off the valve cover and checked everything on the top half of the engine. All checked out. Spark plug on cylinder on also has major carbon build up even though it has less than 250 miles on it. Dealer thinks that the leak in cylinder 1 is causing it to run lean, so the car is compensating by making the fuel/air ratio too rich. They believe that that is why the other three cylinders are misfiring. By switching the injector to cylinder 4, they want to see if the rapid carbon build up switches to that plug. If so then the injector is malfunctioning. I’m thinking that they are out of ideas. Valves are good, no vacuum leaks, no clogged EGR or PCV, no cam damage from bad valve job that was done one this vehicle,
heres a video that Eric made on how to do a power balance test. this will help in your diagnostic. C8-)
http://www.youtube.com/watch?v=bAOmUjAj … plpp_video
Welcome to the forums!
A weak battery will not cause misfires.
Make sure you are using OEM Honda parts on that vehicle.
+1 with the cylinder balance test as a starting point.
If the power balance test does not show any good results, you will need to stress test the ignition system and i would also do a fuel pressure test.
Did you check for vacuum leaks?
Here is a video by Eric on checking for Vacuum leaks without a smoke machine –
http://www.youtube.com/watch?v=9CPqbaSg … h5ma49U%3D
I ended up taking to the dealer because I need this car to be safe to drive and I need it soon. So far they have no idea. No vacuum leaks, good compression, cam shafts look good, valves look good. Now they are leaning towards injectors. They are swapping them around to see if the problem moves with them. Hopefully they’ll find it fast.
Not sure what swapping them around will do because you were getting the codes on all 4 cylinders (P0300-0304). I would think they would be looking for something common to all cylinders like fuel pressure, coil, etc. not an individual injector. i guess all 4 could be bad, just really unlikely. I’ll be interesting to see what they come up with.
They think the one bad injector is causing a rich condition for the other three cylinders causing them to misfire. I don’t know. As long as it gets fixed I dont care what they do.
Quoted From johnzcarz:
Not sure what swapping them around will do because you were getting the codes on all 4 cylinders (P0300-0304). I would think they would be looking for something common to all cylinders like fuel pressure, coil, etc. not an individual injector. i guess all 4 could be bad, just really unlikely. I’ll be interesting to see what they come up with.
P0300 is a random misfire. I’m surprised you got that along with P0304, which is obviously the no. 4 misfire. Did both codes come back after the plugs were replaced? Or just one?
Beefy – I thought he meant P0300 through P0304. If it’s just the 2 codes that that changes things a bit.
Quoted From johnzcarz:
Beefy – I thought he meant P0300 through P0304. If it’s just the 2 codes that that changes things a bit.
Oh, my bad, you’re probably right. I misread it the other way obviously..
However, I would think if it was all 5 codes, they (the dealer) wouldn’t learn anything by swapping injectors around. So now I’m confused…
Quoted From Hondafreak2003:
They think the one bad injector is causing a rich condition for the other three cylinders causing them to misfire. I don’t know. As long as it gets fixed I dont care what they do.
This doesn’t make any sense… Can you provide more info on what the dealer’s diagnosis is? Do you have any paperwork by chance?
Yea I hate to say it but I don’t think they have a clue and it’s sad because they should be the best around for your vehicle especially for the money you’re paying them. You don’t just start ‘swapping’ injectors around, they have a scan tool that they can use as a lab scope to look at the injector firing event to see if the injector is having an issue or not they just don’t seem to be aware of this or know how to do the test. I also think their theory is crap, if you have low compression on one cylinder do a leak down and see where it’s going especially on Honda’s if the valves don’t get adjusted correctly it will burn up the exhaust valves and cause a compression loss. Have they even bothered to check the cam timing? Or even check for slack in the chain? This is a HUGE problem on the K series engine, when it runs low on oil it will starve the timing chain for oil and cause it to wear out prematurely as a result the cam timing will be off causing misfire codes. BTW misfire codes are not accurate at all so you have to take them with a grain of salt. Also Honda’s hardly ever have fuel delivery problems so I think chasing a bad injector is a waste of time, I think you’re looking at a mechanical issue and they are chasing their tails with their theories and backward tests at this point.
This type of ignorance is one of the main reasons I became ETCG, good luck and keep us posted.
I’m surprised if they do suspect an injector issue that they aren’t actually checking them by looking at their leakdown rate. All that means is they activate each injector individually for a short time (5 sec. or whatever the spec. is) and measure how many PSI the fuel pressure drops in the system. They compare the 4 results to the spec. (or to each other), and see if there is a problem or not. If one is leaking that would be pretty obvious. I would think the test is faster and more conclusive than swapping them around.
They have done a leakdown test, Cylinder 1 showed 35%. With swapping injectors, cylinder 1 is now normal and the cylinder they switched now has the issues. Car has been in the shop for two days and only just over $100 is labor so I’m not complaining. They seem to be pretty certain it is that injector. Valve lash was checked, timing chain checked, cam timing, everything you can without taking the whole engine apart. All checks out. They’ll know by tomorrow if the new injector solved the problem. I’ll ask them about the scan tool and see if they did any tests with it. This is the fourth time this car has been in for misfiring. I really hope this fixes the problem.
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