Misfire on cyl. 2
Doug Yoder
yoderw at msoe.edu
Wed Jun 29 22:02:55 EDT 2005
Car is a 1991 100 FWD, NF engine.
I've had a misfire that has been gradually getting worse. Decided to
try to do something about it today.
Bought new spark plugs, distributer cap, and rotor. Changed them and
the oil & oil filter. Start it up and the misfire is worse than ever.
Take it for a short drive to the village recycling center (drop off the
used oil) to see if it clears up with some driving. No - runs terribly,
sounds terrible, and shakes the car - also the exhaust smells gassy,
like it is running way rich. Get home and check the cap and rotor - all
5 contacts look like they're firing. Pull the plugs, one by one, to see
what they look like (the old ones looked uniformly normal) - #2 is very
sooty and dark, the other 4 are still almost white (the drive was about
1.5 miles).
So I start swapping things around to see where the problem is. Put an
old plug in cylinder 2, same behavior. Swap the plug wires for #1 and
#2 (at both the plug and cap end), same behavior. Leave #2 unplugged,
same behavior. Swap #1 and #2 wires and leave #1 unplugged, engine
barely runs (firing on 3 cylinders now). Put all the wires back where
they belong and swap the old cap and rotor back in, same behavior.
Finally, pull all the plugs and do a compression check: 185, 185, 190,
185, 180. Put all the new components back in and come inside and turn
the computer on.
Conclusions:
1. There is something wrong with cylinder #2 (not plug #2 or wire #2 or
cap/rotor).
2. #2 is running way rich (hence the sooty plug).
3. There is not a valve problem with #2 (because the compression checks
out OK).
4. This seems to indicate too much fuel to #2, as opposed to ignition.
Questions:
1. Do the above assumptions sound reasonable?
2. How can one cylinder get way more fuel than the others? (Or is it
getting way less air??)
3. What should I check next?
Thanks in advance,
-Doug
PS. Thanks to all (Tony, Nick, Kent, Kneale) who contacted me about my
antilock brake issue - it sounds like most likely a sensor, but I still
haven't had a chance to check them.
--
*------------------*--------------------*------------------------------*
| Doug Yoder | wdy at zordok.net | http://www.zordok.net/ |
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| Don't tell me the sky's the limit... |
| ...there's footprints on the moon. |
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