More advice for Mitsu 2.6L in 87 Voyager? (& Mikuni carb)
Nathan Anderson
Last December, I posted a question to this group about my early-1987
Plymouth Voyager LE with Mitsubishi 2.6L 4-cyl engine and 3-spd automatic
tranny. I received a couple of nice replies, but unfortunately I still
don't have my problem solved, and in fact it seems to have gotten worse.
(Don't think for a minute that I didn't appreciate the suggestions I got
from you all, though.) I may even have several unrelated problems on my
hands. So, I come here yet again to pour my heart out to you all, hoping
against hope that *someone* out there has the answer(s). ;-) (Seriously,
I realize it isn't as simple as all that.)
Before reading on, you might wish to read my original post which did make
the Google Groups archive. The URL for that thread is:
<http://groups.google.com/groups?th=f2707f2613ee342f&ic=1>
Since posting that message, I have taken my van into 3 or 4 other garages
hoping to get other opinions. Unfortunately, none of them really were
able to hear the noise I was hearing, and said that as far as they were
concerned my engine sounded fine! It's a bit frustrating when you know
that the engine is noticeably louder than it was before, and yet no one
can find the problem! Aren't there any mechanics out there who know what
a healthy (if there is such a thing) Mitsu 2.6L should sound like? Have I
just been hitting all the wrong ones?
One thought he heard some valve/lifter noise and suggested a valve job,
and also said that there "might" be some noise coming from the timing
chain/silent shaft chain areas after I asked him about it (I think I will
refrain from making suggestions to mechanics from now on). Because
repairs would probably cost me more than the van was worth, the guy was
honest with me and told me that he couldn't guarantee that the work he
would do would cure the problem, and so he recommended that I just
continue to drive the thing until it finally breaks (and I've basically
been carrying out his advice, heh).
I had a local engine rebuilder have a listen, and at first he concluded
that the engine sounded great. Thus he reasoned that the noise I was
hearing must not be coming from the engine. After revving the engine
several times he then said that he thought he could hear something, but it
was faint. He said that if it was a bearing, it was probably only
beginning to fail. This gave me some hope that it was not a problem with
the engine.
Regarding this vibration noise (which I discussed in my first post), after
revving the engine myself repeatedly, it seems as if it may actually not
be engine noise. It's quite weird, actually...if you listen under the
hood, you can't really hear it, but if you are *in* the car, it is very
easy to hear. It's like the interior is vibrating. It also appears that
the noise is at its loudest only within a certain narrow RPM range...if
the engine is turning any slower or faster, then the noise isn't as bad
(but is still noticeable).
I began driving it again, and took it back with me to school in January
(the trip is about 300 miles). Before I left for school, I changed the
oil. Shortly after this (and I have no idea whether it is related to the
oil change or not), I noticed a knocking noise that I had not heard
before. It becomes noticeable when I accelerate, but unlike the vibration
noise that I described in my original post, it is *not* so noticeable
when the transmission is not in gear! The knocking noise is very
noticeable when the engine is cold, seems to get quieter after it has
warmed up, but then over the course of a long trip it gradually becomes
louder again. To the present day, the noise has not gotten any worse, and
I not only drove it approximately 300 miles back to school after the
noise started, but also drove the car back home for spring break and then
again back to school, so it's racked up close to 1000 miles since this new
knocking sound started. Could it still be a bearing? A mechanic friend
of a friend (heh) had a listen, and said that the noise *could* be my
lifters. So, there's yet another vote for the lifters.
However, two other shops have both given me similar opinions
independently of each other and without my having told the second
mechanic what the first one said. The first garage told me this before
the knocking noise became obvious, and I took it to the second mechanic
specifically to have this new knocking noise checked out. What they both
told me is that it could very well be a worn bearing, and that partly what
may be contributing to the bearing's failure is my *carburetor*. The
carburetor (the Mikuni "auto-choke via thermal wax element" thing that
comes with the Mitsu-equipped Chrysler cars) runs waaaay too rich when the
engine is cold (a problem that I knew about and that that it has had for a
long while, even before I acquired the vehicle; it spews out black sooty
exhaust for the first couple minutes and runs really roughly until it
is warmed up), and according to both mechanics this is causing gas to get
mixed in with the oil, whic is diluting it! The second mechanic changed
my oil and added some "Motor Honey" (what is this stuff, an oil
thickener?) to see if that would quiet the engine down, and it did seem to
help some for a while, but I don't see how this conclusively proves that
it is a worn bearing since I've been lead to believe that a weightier oil
could also help quiet lifter noise as well.
Another odd thing which happened shortly after I changed my oil was that,
along with this new knocking sound, my oil pressure gauge was showing that
every time I gave the engine gas, the oil pressure bottomed out! It acted
okay when the engine was cold, but the oil pressure became weaker and
weaker as it warmed up, and became even lower whenever I accelerated.
After the second mechanic changed my oil, this symptom disappeared and has
not occurred again. I've even since changed the oil myself again (just
using straight 10W-30) and the oil pressure gauge is still showing normal
pressure.
But as of two days ago, I have a new problem: all of a sudden while I was
driving, the engine started to vibrate even more. Now it idles much more
slowly and roughly, and this time there *was* a noticeable loss of power.
I thought maybe the head gasket had blown again, but the engine did not
overheat (at least according to the thermostat gauge). Oil pressure is
still normal as well.
AAAAUGH! Time to take it into the shop again, I guess, and blow more $$$
on this thing. I don't know how much more of this I can take!
Is this thing just a lost cause? I know from reading this newsgroup that
this engine isn't well liked, but good grief, it's only 97K miles old!
So, I beg you all for your advice. What do you think it is? What should
be done with it/how should I spend my money? Would it be cheaper in the
end for me to just have the engine rebuilt? I'm a college student with
limited funds, and I want to make each dollar count with the end result
being a functioning vehicle that I can rely on!
If you see an engine rebuild in my future, what would you say is a
reasonable price to pay? I was quoted around $3,500 from the rebuilder I
mentioned earlier. Do you think I could find someone who would be willing
to do it for less?
Also, one final question regarding the carburetor: I really want to
get this fixed, especially if what the two mechanics I talked to
said was true. I understand it's a rather expensive carburetor to
replace. But, before Google's acquisition of DejaNews, I found a post to
rec.autos.makers.chryster by an individual who said that the fix for the
Mikuni running too richly while the engine is cold is fairly easy to fix:
apparently one has to grind the rivets off of the tamper-proof cover to
get to the various adjustments, and then simply adjust what I think he
called the "choke adjustment valve." Unfortunately, I can no longer find
his post, and I regret that I did not print it out, so I'm not confident
that I remember his exact wording. I have all of the service manuals for
the '87 Chrysler minivans, and it does describe how to take the
tamper-proof cover off, but there is no mention of a "choke adjustment
valve." The closest I was able to come to was the fast idle adjustment.
I did adjust this, increasing the fast (cold?) idle speed, but if it
helped, it only helped very little, for the engine *still* runs roughly
when cold and black, sooty exhause is still spewing forth out of the tail
pipe. What exactly do I need to adjust, or do you not think it is likely
to be that simple?
Thanks a TON in advance for any insight you can provide! Also, if you
got this far, thank you for reading the entire message! I apologize for
its length, but I like to lay out the details and history of a problem as
clearly as I can. I hope that the detail helps. If you need more
information or if I've left something out, please let me know.
Regards,
--
-- Nathan Anderson
<mailto:nat...@anderson-net.com>
"Programming follows several 90% rules. One of those rules
is 'The first 90% of the project takes 90% of the time, and
the last 10% takes the other 90% of the time.'"
-- Blake Watson,
OS/2 Warp Programming for Dummies (IDG Press)
BG
"Nathan Anderson" <nat...@anderson-net.com> wrote in message
news:Pine.LNX.3.96.10104...@socrates.anderson-net.com...
Nathan Anderson
> Catalytic Converter rattle perhaps ??????
BG,
Thanks for the suggestion, but I've already had the exhaust system checked
out (I failed to mention this in my post; sorry).
Ed Gin & Shirleen Kajiwara
I have experienced most of your symptoms on my 86 2.6 liter Voyager.
The sudden vibration "loud noise" problem turned out to be the couterbalancing shafts going out of timing due to worn guides and a jumping timing chain. If your chain/guides are nearing their useful life, they can make a real racket.....
I actually readjusted the choke butterfly on my carb along time ago having experienced the "rich" running condition. What I did was bend the "flapper" slightly to have the carburator not close completely. I know.....some may say the car won't start due to too leaning....but here in Chicago with our brutal Winters....it has started fine and didn't spew out black smoke.
Good luck with your problem.
BTW, I junked the van at 238,000 miles when it sucked a valve and suffered terminal failure.
Ed Gin....now have a 99 Caravan with 55,000 trouble-free miles.....after
updating the head gasket at Daimler Chyslers cost.
Nathan Anderson
...just to let y'all know, I solved the Very Latest Problem (rough idle,
loss of power). It really didn't seem like a head gasket problem, because
it did not overheat, the exhaust wasn't white, and the oil didn't look
like there was any coolant in there. But I had grown to assume the worst
about this engine whenever problems cropped up, so nothing else occurred
to me...
Then, while I was under the hood, I noticed an unattached wire. An
unattached spark plug wire. It had worked its way off of the distributor.
Heh.
Actually, it's quite a relief, knowing that that was all that it was,
rather than a progression of whatever it is that is causing these noises
I'm hearing.
I'd still appreciate thoughts on the vibration noise and the knocking
noise!
Nathan Anderson
Thank you for all of the replies I've received so far, both on the
newsgroup and privately via e-mail.
I've now had a number of people suggest that it could be that the guides
for the timing chain are worn out. I know that this is a common problem
with this engine, and it is quite reasonable to assume (having not heard
my van's noise for yourself) that this could indeed be the problem.
However, I was thumbing through all the past service invoices (which the
previous owners kept) and discovered that the engine had already had the
timing chain, silent shaft chain, the related guides, and the oil pump all
replaced exactly two years ago (as of this coming Monday) when the
odometer read 80K miles. Now it reads 97K. How likely is it that the
chain or chain guides have already become worn again after only 17K miles?
I suppose it is still a possibility, but it doesn't seem likely to me...
Could the job have been done shoddily, causing them to wear out
prematurely?
Thanks again,