engine misfire

[vdubracr98]

Last july I bought a '98 VW GTI VR6 with 60k miles on it. It already had some aftermarket parts such as a catback exhaust and a cold air intake. Soon after I bought it it started backfiring but i thought nothing of it and it was only once in a while. Recently I was driving and it backfired so bad that it set off the check engine light. After that I noticed it was misfiring. So i had the codes read and it said the secondary air injection system was incorrect for the current engine operating conditions and that there was a misfire in cylinder 4. So I changed the plugs and wires thinking it needed a tune up and it worked. For about a week. Then I started getting multiple misfires and someone told me to separate the wires so i did that and it drove better but now it still misfires at low rpm, but it is only if i give it too much gas. could that be something with fuel delivery or something with air intake such as the mass air flow sensor? could my timing be off? Also I changed the battery before the misfiring began and at first I bought the wrong battery with the terminals on the wrong side and connected pos. to neg. and neg. to pos. and it sparked really bad. could I have fried something in the electrical system?

[LukeM]

Did you have that code checked out at the dealer? I have the same code so info on a fix would be appreciated. As for the misfire's id look at your coil pack as they are known to fail.

[veedubmechanic]

I would say a coil pack before a maf sensor (cheaper also by 300$). Let you engine idle and mist water on the coil pack, if it misfires or dies then its time to replace. Check the Secondary air injection fuse on the firewall behind coolant resivor-they burn out most common, also check the vacuum lines to the combi valve on exhaust they shound not be cracked, also check if the combi valve holds vacuum.

If your battery terminals arent melted then it looks line nothing is damageg, just check all your fuses in the engine bay and in the car.

[vdubracr98]

i just found that my timing chain is loose could that be causing the hesitation? or maybe my clutch is worn?

[veedubmechanic]

If your timing chain was loose you Would get misfires but you could also hear it ALOT.. a clacking sound on the trans side of the engine. Sometimes replacing the adjuster bolt can save the adjuster and save some time/money.

[vdubracr98]

i do hear it but it is not very loud, but it has gotten louder in the last couple months. I bet that is the cause then. I tried spraying water on the coil and it didnt do anything so I think the coil is fine. How long can I drive my car with a loose timing chain? Will it snap?

[veedubmechanic]

The timing chain wont really "snap" it will just loosen up and cause some valves to bend when they hit the pistons.

[vdubracr98]

so approximately how long can I drive it like this and about how much to fix it?

[veedubmechanic]

Call the dealer and ask. Dont have some "after market" shop do it.

[vdubracr98]

I called the dealer. They said that the timing chain doesnt normally go bad and if it was bad that it wouldnt jump and/or cause any misfiring. I dont know if I believe that. They think its the ignition coil. Also they said to replace the timing chain is like a fifteen hour job because they have to drop the trans and remove the heads. Thats insane there is no way I can afford a fix like that. Do you know if i were to just change the tensioners if it would be just as much work? The VW dealer wants $125 just to tell me whats wrong with my car and I dont know if I trust them