Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[iwasthestig]

I've got a 3.0 V6 that has had a misfire since I bought it, thought it would be a nice easy fix, started by changing the coil pack and leads which didn't help, have checked for air leaks/vac leaks and tried a crank sensor just on the off chance, my diag brought up a fault code relating to the maf sensor which I swapped with no joy. The misfire is without doubt on cylinder 6 and the engine sounds like it's tapping as well... Any ideas?

Cheers Chris

[terry paget]

Did you change the plugs? That's where I always start with a misfire. You my find one is broken, blackened, or you may find oil or water in the plug holes.

[iwasthestig]

I tried those along with the leads and plugs, all were nice and clean apart from cylinder 6 which was black.

[zirk]

I tried those along with the leads and plugs, all were nice and clean apart from cylinder 6 which was black.

Dry Black or Wet Black?

[iwasthestig]

Wet black,

[zirk]

Wet black,

Oil or Unburnt fuel?

[iwasthestig]

Unburnt fuel, only thing I could think of with these symptoms is lack of compression

[Nick W]

Is the coil actually firing that cylinder? At least with a coil and leads you can check easily. If there isn't a spark then you have an ignition fault, probably on the coil. But you do need to check why the plug is black. If there was a lot of unburnt fuel in the cylinder you could have contaminated the new plug before it had a chance to do any real work. It is also worth ensuring that you connected the leads to the coil correctly; the V6 will run OK(ish!) with a pair the wrong way.



But, your reported tapping suggests a further problem. That could be a stuck cam lifter, or even a stuck open injector. Both of those are much harder to diagnose, and in the case of the lifter much harder to fix.


A lack of compression is easily tested, but doesn't really match your wet plug.

[zirk]

Unburnt fuel, only thing I could think of with these symptoms is lack of compression

worth doing if you have access to a tester.

Where the replacement Dis Pack and leads known good ones.

[iwasthestig]

I have got a compression tester so worth doing, dis pack and leads were brand new, can't imagine the new ones having same fault as originals

[05omegav6]

I have got a compression tester so worth doing, dis pack and leads were brand new, can't imagine the new ones having same fault as originals

It can happen, especially with cheaper electrical components...

[sjc]

Easiest way to test if that cylinder is getting a spark is to plug a longer lead into the coil pack, put a spare spark plug in the end of it and (holding it by the rubber boot of course) touch it against the block while the engine is running or being turned over on the starter.

I had a coil pack fail on ports 1 & 5 recently and oddly enough in the middle of doing the head gaskets - guess it didn't like being disturbed 

In case it helps... the lead order should be

Type with oval wiring plug and all connections facing upwards:
-----------------------
|  |:|   5  x  3  x  1  |
|  |:|   2  x  6  x  4  |
-----------------------

Type with rectangular wiring plug (facing upwards) and plug lead connections facing the back of the car
------------------
|  1  x  3  x  5  |
|  4  x  6  x  2  |
------------------
\      - - - -        \
  ------------------