engine is misfiring?

Recheck the plug and injector for that cylinder. These guides should help us fix it.

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

and

https://www.2carpros.com/articles/how-to-tune-up-a-car-engine

Please run down these guides and report back.

I was told seal was leaking oil into that cylinder, which was fouling plug, yet no smoke.

If its not smoking what make them think its a valve seal/stem/guide-Are you using OEM part on the plugs-if its fouling use a hotter plug and see what happens

If it is the plug tube seals that is leaking, there would be no smoke as oil is not getting into the cylinders. Instead the oil is causing bad conductivity and could have damaged the coil wire.

is the plug tube seal you mention, the same as the valve guide seals. The original was missing on ALL cylinders, later determined to be loose wires on contact pin of ignition module. Before that the car ran great, no problems. Afterwards, one cylinder doesn't fire, and leaking inside head was given as reason, with repair of $1200 as solution.

No, the plug seals are those under the valve cover. There are O'rings under the cam carriers as well.

How can the valve guide seals be missing? They are not easily removed unless someone forgot to reinstall them when cylinder head was worked on.

What are the compression on all cylinders?
Were the valve clearances checked and adjusted?
Do you have oil in the plug tubes?

the engine was missing all cylinders because of loose ignition module wires. The problem is now pretty much solved. Your advice to check the fuel injector was good, as the cylinder wasn't getting fuel, so thanks. Another, better mechanic found there was a pulse through the injector and agreed with you that was no oil leak in the missing cylinder. The problem turned out to be a faulty wire connection in that part of the wiring harness just behind the valve cover. When he moved the harness slightly, all cylinders fired again, including the bad one. He explained that the loose wire was the one activating the fuel injector for that cylinder, so it wasn't getting fuel, even though it was getting spark. It's running fine, although I may have to eventually take apart the protective shield on the wiring harness and check the connection for the affected wire. Thanks for all your help; you definitely pointed me in the right direction.

Ensure the connectors are good. Quite often the locking tabs breaks off as they becomes brittel due to age. This would result in the connectors not being locked securely into position and can cause a break in the circuit.

will do. The original problem of loose wires on the ignition module caused the engine to run very rough, which probably jiggled the connection inside the harness loose and caused the 2nd problem. Thanks again, for pointing me in the right direction.

Hello,

I hope someone can help me. Recently, I noticed my car jerking between automatic shifting between 3rd and 4th gear. During this period of jerking, the car can not accelerate. It maintains its current speed despite me pressing on the accelerator. It is only after I let up on the accelerator and try to accelerate again does the car accelerate smoothly as it transitions between 3rd and 4th gear. Sometimes, it takes 3-4 tries and during each of these attempts, the car jerks forward and backward (enough to move the passengers bodies a little), and does not accelerate beyond about 60mph.

On a side note, recently my car failed inspection for emissions. I purchased "Guaranteed to Pass" emissions cleaning fluid from Pep Boys and ran it through my fuel system. This problem started about 4-5 fillups following the use of this fluid. Not sure if the problem is related to the use of the fluid.

ANY HELP WOULD BE GREATLY APPRECIATED!!!

Thank you in advance,
Sam

Your check engine light should be on right now if you failed you state emission test. The shop that performed the test should have given you paperwork as to what codes that popped out. Please post the code numbers so we can begin the diagnostic follow this guide

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Please run down this guide and report back.

Hello Zackman,

The code was 0420. According to AutoZone diagnosticsc, it was specific for Catalytic efficiency. The probably causes were a defective catalytic converter, engine misfire or running condition, large vacuum leak, or engine oil leakage into exhaust-valve guide seals or piston rings.

I will say that my check engine light has been on for 3-4 years with my Maintenance required light being on intermittently during this time also. I DO get regular mainenance, engine flushes, transmission fluid changes, and routine tune-ups. My mechanic told me the check engine light was on because it was a faulty oxygen sensor but that was 3-4 years ago when it first came on.

Not sure what to make of these issues. Hope you can help.

Thanks,
sam

This is from Honda Technical Service Bulletin

This is from Mitchell1

Your Maintenance light comes on due to the check engine light problem. P0420 is serious enough cause for the computer to flash the Maintenance light on since the check engine light has been "ignored". All your problem is around a bad catalytic converter. Replacing the cat converter is the only remedu for you to pass the emission test. According to Honda, there are two different converters being used for that particular year, and you have to make sure that you get the right one. Description is on the TSB.

Zackman,

Thank you so much for your response. I truly appreciate it. However, are you saying that the jerking between gear shifts 3 to 4 (~65mph and 2800rpm) is directly related to the catalytic converter problem? I mean my check engine light has been on for ~4 years. Will the jerky movements and stoppage in acceleration cease once the catalytic converter is replaced? I noticed today that I hav to let go of the gas and accelerate very slowly in order to avoid the jerky movements i described above.

Hope you can help,
Thanks,
Sam

You may have had the CEL for years, but now the cat actually is plugged up. At that speed and rpm, there is a bunch of exhaust trying to escape and and the plugged cat is preventing the gas to leave. Once the computer "sees" that you have too much pressure in the exhaust system, it retards the fuel and air intake into the combustion chamber. That means less power, and the computer also cuts other attempts to create power, you meshing the the gas pedal to increase speed.

While there is in no way for sure that this is your only problem, but I am leaning towards that as being the main contributor. You may have a fault in the transmission shifting solenoid, but the cat has increased the effect of the problem. I have seen this happened to a Nissan in the past.

I have a 1999 Honda Accord 4cyl. coupe.

I recently started having problems with my car in which the vehicle was shaking violently. I got the oil and air filter changed and asked for a reading. The mechanic said that the machine read cylinders 3 and 4 misfiring as well as a random misfire.

I took his advice and changed the spark plugs (wich I changed only two months ago), the distributor cap, the distributor button and the spark plug wires.

I made a mistake with my spark plug wires and now I don't know if they are on correctly.

I read that the firing on the distributor is 1-3-4-2 starting from the top rear (closest to the firewall). The problem is, I don't know if the right cords are in the right place. I also read that the cylinders are in a linear position going from 1-2-3-4, starting at the right of the engine when facing the car.

There is a short one, a medium sized one and 2 long ones of the same length.

I have the shortest wire matched to cylinder 4 on the engine and the distributor. The medium sized wire is matched to cylinder 3 and the 2 longest ones are matched to 2 and 1.

Are these wires placed appropriately? Is there a spark plug wire diagram I could find for a 1999 Honda Accord 4cyl? I've searched all over google and can't find a thing.

Also, what could be causing the car to misfire like this, excluding the things I've just troubleshooted.

this is the firing order
#1 cylinder is where the belt

This is helpful thankyou. However it did not completely answer the question.

Does it matter which wire is used for any given cylinder? For instance, is there a certain wire of the 4 that hould be used or does it not matter so long sas all wires reach and are in the appropriate place?

Wire should not matter as long as its connected in the correct order

usually longest is # 1 and shortest # 4

hope this answer your question if not let me know

I believe you have given me the wrong firing order for my 1999 Honda Accord. I followed the diagram you provided and the car failed to start.

What kind of damage can be caused by attempting to start the car in the incorrect firing order?

Have a 1998 accord ex vtec 4cyl. Im getting misfire codes for a couple cylinders(cant remember which) but im also getting the random cylinder misfire code. It idles and runs fine when the engine is still cold up until it reaches normal operating tempature. Once its hot and still on idle, it misfires and shakes, the whole exhaust system shakes. Its not constant but happens every 4 to 6 seconds. Twice as bad w/ AC on, almost feels like its going to turn off. Accelaration feels slugish. I can feel and see the sudden drops in rpms every now and then during accelaration and when cruising at steady speed but AC can be turned on without any noticeable increase in misfires though I have to turn off the AC at every light until I start moving again.
It was so bad that I couldnt drive it safely but since then ive fixed a huge intake leak, cleaned the injectors, replaced the rotor, spark plugs and wires are good and replaced the knock sensor.
All these things did make an improvement one by one and now my mechanic is saying I might need to replace the distributor cap or the whole distributor. What would your advice be?

distributor is possible but since it runs ok cold it could be o2 sensors, etc sensor or injectors.

Have the valve clearances checked as well. If they are too tight, erratic idling can occur.