misfire issue - not a contour

[striker2]

for the past couple weeks my buddies 96 Accord EX has been misfiring on cylinder 2 only. it only does it at part throttle while cruising (low load). If you move the throttle to accelerate it cleans up and stops missing. it doesnt miss on decel either. its a 2.2L I4 MTX. we have already replaced plugs, wires, cap, rotor, and injectors. we have not done a compression test yet cause it runs great at half throttle or more or 0 throttle. im sort of leaning toward a dead spot in the TPS but that doesnt explain why ONLY cylinder 2 misses and not the other 3 as well.

Any other ideas?

 

[98SVTC]

Well, nobody knows anything about anything except Contiques on this site! Anyway, how do you know that you are getting a misfire on one particular cylinder? What manner of testing are you using? Are you using a laptop readout while driving the car? I'm asking this because any number of other things can cause the car to seem like it's misfiring (or missing) but it may have nothing to do with the ignition or fuel system.
Karl

 

[AliasJerk]

Lets see... you have eliminated all of the big possibilities... A TPS is possible, although I cant say its extremely high up on the possibility list, as the code that is being thrown is a misfire code, and TPS' rarely have anything to do with misfireing.

I would suggest checking his cylinder number 2 injector. If not that it could also be a faulty O2 sensor, BUT it should throw a code for the sensor as well, so that makes it low on the possibility list also.

Worst and rarest case scenario, you might have a burned exhaust valve. But what are the chances of that in an Accord? The fact that the car only does it at low load leads me to believe that it would be an injector, my crazy reasoning seems to think that the injector is having a hard time regulating fuel flow so at crusing speed it wont shoot enough fuel into the cylinder but once you go balls to the wall and it has to "drink" gas it can open wide up no problem. But thats my crazy reasoning.


Do you have the exact code you could post? is it just the generic "P0302"?

 

[Big Jim]

Think about the very basics that can cause a miss.

Ignition problems. Sounds like you have explored pretty well.

Fuel problems, particularly lean. Also sounds like you have explored pretty well. You should check the fuel filter and pump pressure.

Compression problems. Not usually intermittent. Still sounds like you have explored.

Vacuum leaks. Usually only at idle or slightly above.

Valve problems. If the valve lash is adjusted too tight it can cause a miss that can very with engine load. Many Honda's have adjustable valves. This is worth checking out.

Cam problems. A flat cam, or one that is worn and on its way to becoming flat can cause a miss that varies according to engie load.

EGR. Something that upsets the EGR flow, especially if it comes on sooner or heavier than it should.

Restricted exhaust. A plugged cat, plugged muffler, or collapsed pipe can cause a miss although it is usually manifested with a considerable loss in power under load.

Restricted intake. A plugged air filter or collapsed intake tube can show up as a miss but is more likely to show up as a power loss.

Good luck finding it.

With what little I know about Hondas I would be looking at the valve adjustment and possible flat cam.

 

[striker2]

Alias - already replaced the injectors so thats not it. it is just the generic P0302 misfire cylinder 2 code. i had the same thoughts as you about the injector.

Jim - vacuum leaks, EGR, restricted intake/exhaust, why would that effect only one cylinder those should effect all cylinders and it only has problems with the one. the valve lash could be out of adjustment or a flat cam lobe. im leaning towards the valve lash more simply cause it runs perfect at WOT and has no powerloss. it pulls just as hard as it ever has.

The low load thing is what has me confused. :shrug:

 

[Big Jim]

The vacuum leak and EGR possibilities could involve only one cylinder, usually the one closest to the vacuum leak or EGR introduction point.

I agree that restricted intake or exhaust is less likely to only involve one cylinder, but you would be amazed at what I have found over the years.

The main thing I was trying to get across was to list as many possibilities as I could for you to think through.

 

[striker2]

yes and i thank you for the ideas. however i can rule the vacuum leak out as it would not have a stable idle. and the EGR i believe connects at the plenum but i will have to check on that one. i guess the exhaust manifold could have a restriction in the number 2 runner but its not likely.

 

[mikeswartz]

how many miles is on the honda, honda had an emission extended coverage that lasted 15 years or 150,000 miles, so basically anything that can cause a misfire would be covered under that. its called the 98-081 warranty extention. good luck and hope that helps.

 

[striker2]

i thought i had posted in my OP how many miles it had on it but i guess not. sadly this one is at 162K miles so it does not qualify

 

[mikeswartz]

those cars were known for cylinder head issues and the valves burn easily, especially if there are any mods to the engine. if its missing on #2 go through and do the compression test next wet & dry. good chance you won't like the results though.

 

[striker2]

well the fact that it runs great at no load and high load is leading me to believe its not a compression issue but i will check it just to make sure. the only mods are air intake and a flowmaster muffler (not even a full exhaust).