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Discussion Starter · #1 ·
So a bit of a background:
The car:
  • 2002 CR-V (not sure if it is LX or EX)
  • 4WD 2.4L I4
  • 221k miles

Started having misfires around last summer I want to say so I replaced all the coils and plugs (the coils were hard as a rock and the plugs were all fouled so I figured do it all at once and not run in circles).

Ran fine for a bit with no misfiring and then another code came on a week later for VTEC, basically oil was low, filled the oil and code went away.

Then the infamous P0420 which was odd cause the catalytic converter and O2 sensors were replaced less than a year prior so we got it replaced under warranty and the code went away.

Now recently the car is misfiring again, first it started off on cylinder 4 (P0304) and then moved on to be all misfires and random misfiring (P0300-P0304).

What I've done and tried so far:
- Made sure the plugs where all still good (none were fouled except for cylinder 4 so I replaced that one).

- Ensure that all 4 spark plugs generated spark with the ignition coil by testing outside the engine with the connectors (this worked).

- Did a valve adjustment (a lot of the exhaust valves were either too loose or too tight with one intake valve being too tight on cylinder 4)

- Did a compression test on each cylinder (between 110-120 on all cylinders)

- replaced all 4 fuel injectors and tested the connectors to make sure they were pulsing which they were.

If I leave all 4 injectors plugged in, the RPMs jump a lot which ends up causing the other 3 cylinders to misfire. However if I unplug the injector for cylinder 4, the engine stabilizes, and no random misfiring (except for cylinder 4 obviously). I'm at a loss as to why this happening.

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Discussion Starter · #3 · (Edited)
Compression looks low. On the k24a* series, minimum is 135psi. I'm not sure what engine series is in your vehicle.

Did you replace the spark plug wires, distributor cap and rotor?
The 02 CRV does not use a distributor cap and rotor, it uses coil on plugs and I replaced them and tested them as said in the original post.

As for the compression, I know it's lower than spec but it's not awfully low to the point the car can't function for now so overlooking that for the time being.

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Discussion Starter · #5 ·
You have a scanner?
Injector 4 shorted causing others to malfunction
Yes I have a scanner.

I tested the connecter and don't see any short. I still have to test the ECM side of the connectors. The connector on the injector itself works fine, tested it by connecting a led to it and watch it pulse.

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The injector itself. Check resistance measurements. Pulling more current than it should will cause issues. Have a scope too ? You could see current pulled by injector.
Move injector to another location , misfire follow it ?
 

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Discussion Starter · #8 ·
The injector itself. Check resistance measurements. Pulling more current than it should will cause issues. Have a scope too ? You could see current pulled by injector.
Move injector to another location , misfire follow it ?
The resistance is within spec (11.2 ohms). I do not have an oscilloscope. This is a new injector mind you. This issue existed before and after the injector was replaced. And the issue occurs no matter the ambient temperature.

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My 03 2.4l crv when it had 285k. miles had similar misfire issues that started in cylinder 2, and then moved to all cylinders, but predominantly in cyl 2. I did the same thing, checked out Coils, plugs, injectors, valve adjustment, cleaned IAC....

Compression was 145-155 in all cylinders.

Mine was a cold startup misfire ... I think TheMan5 above has alluded to ...

leakdown test, though ... I had a head gasket leak between cyl 2 and the coolant. It was small, not massive bubbles, but it pushed coolant out of the radiator filler neck.
 

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Discussion Starter · #10 ·
My 03 2.4l crv when it had 285k. miles had similar misfire issues that started in cylinder 2, and then moved to all cylinders. I did the same thing, checked out Coils, plugs, injectors, valve adjustment, cleaned IAC....

Compression was 145-155 in all cylinders.

Mine was a cold startup misfire ... I think TheMan5 above has alluded to ...

leakdown test, though ... I had a head gasket leak between cyl 2 and the coolant. It was small, not massive bubbles, but it pushed coolant out of the radiator filler neck.
I'll give it a shot. The misfire happens regardless of temperature as I stated in my response to theman above.

As I said, I know the compression is low, just trying to get the car running at the least. However if there is a similar leak with the head gasket, may it be better to just replace the engine?

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I'll give it a shot. The misfire happens regardless of temperature as I stated in my response to theman above.

As I said, I know the compression is low, just trying to get the car running at the least. However if there is a similar leak with the head gasket, may it be better to just replace the engine?

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well, the compression / leakdown teast was something I delayed doing until I did everything else, because I didn’t want to know the answer.

yeah, after confirming that I had a cyl 2 to coolant leak, I needed to make a decision. A head gasket repair vs. engine replacement. Both were out of my DIY home garage capabilities. I was looking at somewhere between 1100-1800 to get a head gasket and machining done right, and perhaps 7-10 days of downtime. Or around 2000 for a used engine swap, over 3 days. I went for the engine swap.

of course, I hope your leakdown test is normal. That would be good for your pocketbook.

regarding the “cold start misfire”. It was explained to me that small head gasket leaks often sealed up as it expands when the engine warmed. I’m not sure how you prove that, but it seemed true in my case.
 

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If I leave all 4 injectors plugged in, the RPMs jump a lot which ends up causing the other 3 cylinders to misfire. However if I unplug the injector for cylinder 4, the engine stabilizes, and no random misfiring (except for cylinder 4 obviously). I'm at a loss as to why this happening.
i just reread this portion of the original post. Thats totally weird to me, why would rpm jump? I would have suspected disabling a contributing cylinder to make the idle more unstable, and disabling a non contributing cylinder to have no change.
 

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Discussion Starter · #13 ·
i just reread this portion of the original post. Thats totally weird to me, why would rpm jump? I would have suspected disabling a contributing cylinder to make the idle more unstable, and disabling a non contributing cylinder to have no change.
I could not have explained it correctly so that could be my bad.

Cylinder 4 is our bad one in this instance.

With all 4 injectors plugged in, it can be observed that the RPMs (no matter if it is warm or cold) will fluctuate constantly and never stabilize. Say when the engine is warmed up, it will constantly fluctuate between ~700 to ~1000.

If I unplug the injector for cylinder 4 (again this is the bad cylinder) the engine stabilizes at 700RPM with no fluctuation on just the 3 cylinders with no other problems or codes.

I hope that makes more sense?

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Discussion Starter · #17 ·
Sounds like there's a wiring and/or fuel delivery problem with #4.
Tested the wiring, everything checks out. And when I was replacing the fuel injectors the fuel rail wasn't clogged at all.

However I do need to check the fuel pressure although I would believe that if the fuel pressure is low I would notice a problem on all the cylinders, not just the 4th cylinder.

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This is why taking to a proper mechanic would have been smarter. All the money in parts and such, only to have gained nothing.

If leaving injector 4 unplugged allows engine to run steady and plugging it in causes a ton of issues then it's the injector, wiring or the ECM. Check the wiring diagram, swap cyl 4 injector with say cylinder 2, see if the miss moves. Can do the same with coils and plugs.

Thing is, engine will not have serious changes beyond dropping or running the cylinder unless there is an electronic issue causing the ECM to freak out.

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Tested the wiring, everything checks out. And when I was replacing the fuel injectors the fuel rail wasn't clogged at all.

However I do need to check the fuel pressure although I would believe that if the fuel pressure is low I would notice a problem on all the cylinders, not just the 4th cylinder.

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Unplugging 4 wouldn't make any difference from unplugging another injector if you are thinking low fuel pressure and runs better with three. You could have bad injector even if new.
 

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Discussion Starter · #20 ·
Unplugging 4 wouldn't make any difference from unplugging another injector if you are thinking low fuel pressure and runs better with three. You could have bad injector even if new.
Fair, just didn't like the idea of taking the fuel rail off again to do an injector swap.

I'll do it for sanity sake once I have a moment.

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