Here is a video for fellow GM 3400 & 3100 liter engine owners. Have a misfire? This video explains the causes for what could be causing the problem. Mine sho…
Here is a video for fellow GM 3400 & 3100 liter engine owners. Have a misfire? This video explains the causes for what could be causing the problem. Mine sho…
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11.24.13. I’m doing a L.I.M. Gasket installation on a 99 Chevy Lumina,
3.1L. I’m using the Fel-Pro Perma Dry gaskets,& I noticed that the metal
indexing tab is a tight fit,in the hole in the head! If it pops out and you
do not notice it, when you go to torque down the L.I.M. You will crack the
upper middle intake port on the L.I.M. You must make sure the metal
indexing tab fits in that hole in the head! Thanks,Vactiontime247 for the
follow up, this gives insight to the cause.
well we decided to tear that 98 monte carlo 3100 engine down with just over
134000 miles and we found out by the previous owner that a shop had already
replaced the intake gaskets right before 54,000 miles. well they used the
plastic gaskets again and they were about blown. plastic was brittle and
cracked in one place. problem was the head gasket was blown on cylinder #1
which my scanner kept saying cylinder #1 missfire. all fixed now and
running like new
Wrong brand spark plugs installed will cause a missfire in these
engines.Last one was a 2004 Impala with the 3400,someone else installed E3
spark plugs and this caused the missfire.Replaced the spark plugs with the
AC Delcos,missfire was gone.Do not install E3 and Bosch spark plugs in
these engines and use the AC Delco spark plugs only.
Besides the intake manifold gasket, guess what else goes bad in the 3100 /
3400’s. The head gaskets. They get brittle and fall apart. Could be the
cylinder has to much air entering the chamber such as a lean misfire. Or
coolant entering in the cylinder. Also, check for a vacuum leak by spraying
water. Then listen for rpm change and a suctioning noise. VT247 VT247
I been working or cars and even building engines for over 20 years. here
recently my brother and i have been trying to figure out a missfire on a
monte carlo with the 3100 engine. keeps showing a cylinder#1 missfire. have
tried a coil, control mod, spark plug wire, spark plug and fuel injector
and its still there. they were all perfect working used parts also. car has
around 130,000. im suspecting a bad intake gasket. whats your thoughts,
thanks for the vid
In the Fel-Pro Tec sheet for the L.I.M. Gasket, there are two cautions that
may have resulted in the cracked castings. The first one being: Vin J & Vin
E engines have the locating pins offset over the port. Vin M engines have
locating pin centered over the port. Also you must make sure that the
original gaskets plastic locating pin is not broken off in the locating
hole in the head!!!
If you’ve never replaced the intake manifold gasket or the head gaskets,
they are highly suspect. Both go bad over time. Pretty much every 3400 I’ve
had has needed both replaced at some time. Usually to find a bad gasket
it’s a process of elimination. Spark, Fuel and compression. In that order.
Spark is ok, I’ll assume the fuel is ok, next check your vacuum reading.
Vacuum can help diagnose many problems also. Check compression and possibly
a leak down test. VT247
With any luck, it just bent the pushrod. But without pulling the head, it’s
hard to determine if the valve was bent unless it’s running rough on that
cylinder. If it runs rough, the valve may be bent. Hopefully it isn’t. VT247
The misfire was most notable at idle. But I’m sure it was doing it all the
time, just less noticeable while driving. Could be the gaskets too, the
head and intake gaskets are known to go bad. Especially if stock. Sorry for
the late response. VT247
Couple ques: My push rods got tipped over and mixed up. U guessed it i put
the exhaust in the intake, bent it pretty good my ran it w/o driving it. Do
u think I bent a valve??
did it only msfire at a idle but drove fine i have a 01 montana cylinder 4
random misfire i changed plugs wires coils coil base every time i tried
somthing new it ran good for couple minutes then the misfire came right
back
I ran it a total of 30 seconds without driving or revving. Have u done
this? This is to clear up the last post
1. Tighten the vertical lower intake manifold bolts (1) to 7N·m (62 lb in).
2. Tighten the diagonal lower intake manifold bolts (2) to 7N·m(62 lb in).
3. Tighten the vertical lower intake manifold bolts (1) to 13N·m(115 lb
in). 4. Tighten the diagonal lower intake manifold bolts (2) to 25N·m(18 lb
ft). But I just tightened them up by hand being careful not to over torque
them again. VT247
Hey bud.do you know the proper torque for the manifolds? I’m sure you do lol
A classic case of: a little bit more torque being too much! Thanks for the
follow up. This will help people.
Thanks! Couldn’t for the life of me figure out why it was missing out after
having fixed it. Guess I got a little over zealous when I torqued down the
intake bolts : / VT247
Good Video
Seems I’m not the only person that’s done this either. There are a few
others that have experienced this issue as well. People would post their
odd misfire about this engine online but never with a follow up on how to
fix the problem. So in case someone else out there has done this, now they
know how to correct it! : ) VT247