Miss Firing

[Cashman11185]

I have a 98 Golf with the 2.slow. Now whenever i get it up to about 4000 RPMs the engine seems to miss fire. It could be doing it before but i'm not noticing it. Now the check engine lights on and i took it down to my local autozone and had them plug it in. They told me it was miss firing which i knew and also that the front bank O2 sensor needed to be replaced. I just ordered the O2 sensor but i wanted to know if that could be related to the miss firing, or if anyone else had any idea's why it may be miss firing.

I did a tune up on it last week. I did replace the plugs and wires. Filter and everything. So it doesn't need a tune up.

Also one other thing. whenever i let go of the gas it makes alittle nocking noise. Now it doesn't seem seriouse but i would like to know what someelse thinks.

[Cashman11185]

I was also wondering if anyone thinks it could be the Mass air flow sensor?

[boschmann]

What were the code numbers? The most common cause of misfiring for that year is a bad ignition coil, usually it will do it more in wet weather. When the coil goes bad it usually misfires wet, engine cold or under load, you can try spraying it with water to see of that triggers it to cut out.

[Cashman11185]

I actually did go through a car was the other day and when i came out of it the engine did sputter alittle. So your probably right, where could i find that ingnitor coil? I'm not really sure where it is. or what it is. Its raining out pretty bad and does seem to do it alittle more. So thanks a lot and i'll look into that.

[boschmann]

The ignition coil generates the spark for the spark plugs. Follow the spark plug wires to the distributor cap, the center wire goes from the cap to the coil, located on the firewall betwen the engine compartment & passenger area. It is supposed to be weatherproof, but the plastic coil case will crack near where the coil wire exits & when wet it will arc to ground. If you notice a difference in how the car runs when you spray it with water it has cracked & must be replaced.

[Cashman11185]

tried that today. It didn't do anything. I even went and bought a new one to be sure. its still miss firing at about 4500 RMP's. I'm just out of ideas, I guess my only choice from here is to bring it to the local VW dealer and pay the 100 bucks and have them plug the stupid thing in and see what they have to say is wrong. Just curious could either of the O2 sensors cause this miss fire?

Any other idea's would be appreciated.

P.s: i did go return that ignition coil after i bought it. The damn thing cost 150 so.

[Dave1979]

try checking your fuel pressure.....

[boschmann]

The O2 sensor probably would not cause the misfiring. You can easily pull #1 & #4 plugs to assess their condition. Have you looked at the distributor cap & rotor. Look for carbon tracking & cracking. Pull each plug & coil wire end to examine their contacts as they are common to deteriorate. You can also spray the rest of the ignition system (distributor/wires) with water, try it at night & rev it up until it starts sputtering & look for arcing. How many miles are on it & has the fuel filter ever been changed?

[Cashman11185]

the car has 85k on it. and i don't believe the filter has been replaced. although i just took it on a trip and came back. and now its getting worse. Like it starts miss firing at 3000 rpms and i can only get the thing up to like 65-70mph because of it. I'll take the filter out and replace it. I just need to find where it is. I heard they can either be on the tank or at the engine.

[Cashman11185]

Also how can i check the fuel pressure?

[Cashman11185]

i replaced the wires and i also checked the inside the distributer cap. It all seems clean. I haven't tried spraying them with water yet or at least the distibuter cap. Umm what would the arcing mean and i'm assuming that would be the wires.

[boschmann]

There is a test port on the fuel rail at the injectors, it only requires a simple gauge setup. Arcing means that a spark will jump to ground somewhere rather than at the plug. It will make a popping sound like static electricity. It can be easier to see in the dark.

[Cashman11185]

Alright i'll try seeing if i see sparks. Although my only problem with that is it does it just about the same when its dry out. It did rain today and seemed to do it alittle but still it does do it when its dry out.

[Cashman11185]

Alright i tried that and didn't see any sparks. i'm all out of idea's so i think i'll just bring it to the mechanic. Thanks for all your ideas..

[Cashman11185]

Could it just be the fuel filter???