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Car Forum / GMC Cars / August 2006

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96 Buick #4 misfire

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tpetaja@gmail.com - 08 Aug 2006 05:44 GMT
Just found this problem, engine light on showed a misfire.  Had shop
double check all of the injectors and fuel pressure, all good.  Install

a new fuel filter.  Then did a new plugs.  Thought it might be a spark
plug wire, installed a know good one, no fix.  Then swapped with the
one next to it, still no fix.  Replace coil, no fix. Replaced the ICM,
no fix.
Thought this could be related to the plenum problem noted here, not the
issue, the engine is not using any anti-freeze.
Tonight, I listened to all of the fuel injectors, all sound good.

Can a timing chain cause this kind of issue?  It has never been
replaced on this car and it has 165k miles on it.  However, why just #4
misfire.  Overall, the engine runs great at highter speeds, only
misfires at idle.
Shep - 08 Aug 2006 21:16 GMT
Not the chain, do a compression test first, check for vacuum leaks, switch
injectors see if the miss moves.
> Just found this problem, engine light on showed a misfire.  Had shop
> double check all of the injectors and fuel pressure, all good.  Install
[quoted text clipped - 11 lines]
> misfire.  Overall, the engine runs great at highter speeds, only
> misfires at idle.
tpetaja@gmail.com - 09 Aug 2006 02:45 GMT
Should the timing chain be replaced maybe the better question.  I did
not thing it could  case this problem, but I was wondering about the
life.
> Not the chain, do a compression test first, check for vacuum leaks, switch
> injectors see if the miss moves.
[quoted text clipped - 17 lines]
> http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
> ----= East and West-Coast Server Farms - Total Privacy via Encryption =----
JJ - 09 Aug 2006 04:59 GMT
tpetaja@gmail.com wrote in news:1155012288.758719.296030
@n13g2000cwa.googlegroups.com:

> Just found this problem, engine light on showed a misfire.  Had shop
> double check all of the injectors and fuel pressure, all good.  Install
[quoted text clipped - 11 lines]
> misfire.  Overall, the engine runs great at highter speeds, only
> misfires at idle.

The Mass Airflow Sensor(MAF) is dirty or needs to be replaced. If it's the
3,8, it screws in above the PCV valve. Check & replace that too.
Shep - 09 Aug 2006 18:27 GMT
The map sensor is above the pcv!!, the maf is in the air intake duct, be
careful with your advice.
> tpetaja@gmail.com wrote in news:1155012288.758719.296030
> @n13g2000cwa.googlegroups.com:
[quoted text clipped - 17 lines]
> The Mass Airflow Sensor(MAF) is dirty or needs to be replaced. If it's the
> 3,8, it screws in above the PCV valve. Check & replace that too.
steve_f - 10 Aug 2006 04:12 GMT
> Just found this problem, engine light on showed a misfire.  Had shop
> double check all of the injectors and fuel pressure, all good.  Install
[quoted text clipped - 11 lines]
> misfire.  Overall, the engine runs great at highter speeds, only
> misfires at idle.
steve_f - 10 Aug 2006 04:59 GMT
> > Just found this problem, engine light on showed a misfire.  Had shop
> > double check all of the injectors and fuel pressure, all good.  Install
[quoted text clipped - 11 lines]
> > misfire.  Overall, the engine runs great at highter speeds, only
> > misfires at idle.

is this the 3100 eng
tpetaja@gmail.com - 11 Aug 2006 14:42 GMT
No, it is a 3.8
> > > Just found this problem, engine light on showed a misfire.  Had shop
> > > double check all of the injectors and fuel pressure, all good.  Install
[quoted text clipped - 13 lines]
>
> is this the 3100 eng
steve_f - 10 Aug 2006 04:54 GMT
> Just found this problem, engine light on showed a misfire.  Had shop
> double check all of the injectors and fuel pressure, all good.  Install
[quoted text clipped - 11 lines]
> misfire.  Overall, the engine runs great at highter speeds, only
> misfires at idle.

if the exhaust stinks like sulfur then you are getting fuel but no
spark and the catalytic converter is trying to burn all the excess fuel
in the exhaust stream ......if this goes on for too long you will burn
up the converter and possibly cause a restricted exhaust making the car
sluggish or if the exhaust smell gassy like a beat up old pick up truck
the converter is already burned up ...if the exhaust smell normal, then
you are not getting any or enough fuel to that cylinder.  try
this...... your car has three coils one coil for each pair of mated
cylinders...2 and 5....6 and 3....1 and 4.     try removing the wires
from 2and 5 only at the coil.DON'T MIX UP THE WIRE LOCATION...have
someone try to start the car while  you watch the coil .  you should
see a sharp blue spark jump from one tower to the next. if you do,  put
the wires back on hte 2 and 5 coil  and move on to the  6 and 3 coil
... do the same thing remove the wires from the 6 and  3  coil and have
someone try to start the car ...you should seee the same sharp blue
spark.  if you do ,  put the wires back on the 6 and 3 coil  and move
on to the 1 coil  and 4 do the same thing and look for a sharp blue
spark ...if you dont; see a sharp blue spark at the coil tower then you
have a bad coil or ignition module .....as long as you dont; mix up the
wires you can move a coil you think might be bad to another location on
the ignition module .....like if you think the     2 and 5 coil is bad
you can move it to the 6 and 3 location as a double check ..if don;t
see a spark with the coil in a new location the coil is bad . if you do
see a spark at the new location you have a bad ignition module ...
.....as long as the wires stay in the same order as they did when you
started ...... the coil locations are interchangable  they are numbered
only from the factory for convenience however the sparkplug wire
locations cannot be moved . try that first ..if all check good you may
have a bad injector and if you have not replaced one before take it to
a shop .....i know a guy who set his car on fire because he nicked an
injector o-ring .  let me know ..
Todd A. Delk - 10 Aug 2006 20:46 GMT
sounds like timing to me.What do you think group.

Signature

Todd A. Delk

> Just found this problem, engine light on showed a misfire.  Had shop
> double check all of the injectors and fuel pressure, all good.  Install
[quoted text clipped - 11 lines]
> misfire.  Overall, the engine runs great at highter speeds, only
> misfires at idle.
tpetaja@gmail.com - 11 Aug 2006 14:50 GMT
Thanks for all the feedback.  On the electrical part, I have already
been done the path of moving coils around, put in a new coil, seeing if
the misfire followed the coil (if it is bad).  It proved not to be bad.
I bought a new ICM, and no fix, so I swapped back in the old one and
go credit for the new part.
I am almost sure it is not a injector problem now.  After listening to
it, doing presure check at a shop, it seems to be o.k.  The exhaust on
the car smells normal to me.  I have two Buick's, one old and new, so I
compared the two.
I am going to check the PVC value and the intake components this
weekend.  Also, will check the EGR value.  I did find small crack on a
vacuum line that hooks up to the high pressure sensor, but it was
pretty minor.  The crack was right at the connector.  I will replace
that line also.
I appreciate all you support here.  I will keep you posted.
Tom
Alpha One - 12 Aug 2006 03:48 GMT
I have a 94 LeSabre with 230,000 miles that I went through all the things
you did about 30,000 ago. I was pretty sure the injector were OK, they
sprayed fine, I though, but not well enough because I finally decided to get
a set for $165.00 from eBay and the car hasn't misfired since. I can't say
yours has the same problem, it may be something else, but just keep my case
in mind as you search for the solution.

> Thanks for all the feedback.  On the electrical part, I have already
> been done the path of moving coils around, put in a new coil, seeing if
[quoted text clipped - 12 lines]
> I appreciate all you support here.  I will keep you posted.
> Tom
tpetaja@gmail.com - 16 Aug 2006 02:34 GMT
I decided to bite the cost and install a new injector.  No fix.  Still
have the problem.  At this time, we have replace or at least swapped
with a know good, all the parts assoicated with misfire to #4.  The
problem stays there.  Guess we will live with it or until the problem
tells us more.
Alpha One - 24 Aug 2006 00:20 GMT
I did swap injectors all over the place and the misfire continued usualy on
two cylinder, forgot the numbers. The misfire did not go with the injectors.
It's wird. I think that's because several injectors , if not all, were not
working properly, but they were good enoug to keep the engine going. The
computer must be trying to compensate but couldn't, so it messed up or
thought the cylinders were misfiring. The sapark never failed but the
computer said it did. I checked these things using a timing light and a scan
tool. What I know is that once I replaced all 6 injector the problem ended.

>I decided to bite the cost and install a new injector.  No fix.  Still
> have the problem.  At this time, we have replace or at least swapped
> with a know good, all the parts assoicated with misfire to #4.  The
> problem stays there.  Guess we will live with it or until the problem
> tells us more.
Johnoz19 - 27 Aug 2006 15:49 GMT
If you have a miss in two cylinders, it could be a coil. Each of the three
coils fire two cylinders at the same time.
Remove all the wires from the coil pack and check Ohm resistance across the
two posts of each coil.
They should all be similar. Then look for carbon tracks down the sides of
the coil posts. If you don't find any problems, check
the resistance of each wire. All the wires should show an Ohm reading.
(longer wires will have more resistance)
 
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