91 Nissan Sentra 1.6 4speed manual question about timing-
robbie
laptop to get the following numbers:
at idle, the timing is 11-12 degrees and when you increase idle up to
about 2500 and back the reading goes up to 40-44 degrees the returns
to 11-12. i'm really thinking this isn't normal and since I have
already replaced the distributor I'm thinking i have a worn timing
chain which allows such a great fluctuation. does anyone else agree
before I start tearing into the valve cover to see what the top end
looks like? the engine has 224k miles, so it is something to think
about. Would this be able to cause drivability issues that i have been
battling? hesitation/bucking on acceleration, lack of power at low
end? Thanks to all who have time to reply. This is my first foray
into diagnostic equipment, and those readings looked weird to me! If i
am way off then someone school me quickly- i am trying to learn!
-robbie
nucleus
timing should be 10 degrees BTDC (US) for manual transmission
with idle set at 650 rpm.
it is normal for spark timing to advance as engine speed increases,
i do not have info as to amount of advance at specific rpms.
robbie
Well at least one user thinks that this is the case and there's not
much play in my timing chain. It seems to have decent power when the
speed and rpms are up but its the acceleration during daily stop and
go driving where the stumbling occurs. it really feels fuel starved,
but that end has been checked. I am wondering if the coil could be
weak since i don't have an accurate multimeter to test it's ohms
reading while hot versus cold... i have never really been stuck on
reapiring these minor problems before but this stumbling has me
STUMPED. Anyone care to chime in again? I really have tested for a lot
of different issues and have ruled out things like: temp sensor/o2
sensor/EGR valve/vacuum leaks/etc but have made no progress. I have 2
different distributors that also have been checked out and unless they
both have bad sensor/control units in them then that item is ruled out
as well.
Me
of MAF sensor in a '91, but by mid '90s (GA15/16 "DE") they are a "hot
wire" type mounted just above the throttle body, and they frequently
fail. OEM replacement is not cheap, but you might find someone offering
reconditioned units at about 1/2 OEM price.
nucleus
condition of your spark plugs and plug wires during sudden
acceleration?
if not, have you tried NEW spark plugs? theory is that increased
combustion chamber pressures during sudden opening of the
butterfly, can cause marginal plugs to misfire.
have the plug wires ever been replaced in all those miles (heat
soak cycles)?
> as well.- Hide quoted text -
>
> - Show quoted text -
robbie
new plugs and wires have been done with no improvement. i am
suspicious of the coil but there's no good way to test it.
i have wondered about the maf sensor but it is supposed to set of the
CEL- which never went off and used to occasionally flash when it was
running poorly but the codes always checked 55
(all clear)
robbie wilson
Me
Not sure if a fouled / malfunctioning MAF sensor would always set a CEL.
If there's no reading from it at all, then probably yes, but if the
voltage is fluctuating and incorrect as described in the link below,
perhaps not.
link:
http://easyautodiagnostics.com/nissan_sentra_maf/sentra_maf_one_1.php
Which refers to a later model, but still a GA 16 DE engine, which when I
look at posts above is what you seem to have (my mistake - I thought the
GA 16 "DE" was introduced later than '90/91).
Are either of the distributors you have dirty inside from oil leaking
from the internal seal on the shaft? (not from the main O-ring seal
between the distributor and rocker cover) That's also a common problem
once they've got up there in mileage, and contrary to what Nissan told
me, relatively easy and cheap to fix yourself.
nucleus
it acceptable to insert a (straight) pin into each wire near the
connector,
to allow access for voltage measurement. if the wires are NOT totally
sealed, you may find it acceptable to "back probe" the connector pins
with (straight) pins for voltage measurement. respondent "Me" is
correct
about faulty MAF sensors, the MAF allows the ECM to calculate the
injector pulse width. if you ever have the need to see if the ECM is
sending a pulse to each injector, you can insert a "noid" light into
the
specific injector circuit (i once used an analog voltmeter to see the
pulse,
when diagnosing an engine that would not start).
does your 91 have the TPS (throttle position sensor)? if it does,
you
can check he TPS using the (straight) pin method, however, i would be
surprised if this is your problem.
can you give more details about the "stumbling" problem? does it
occur when you suddenly open the butterfly when NOT driving?
or does it occur only when you are accelerating (under load) while
going through the gears?
this thread assumes you have checked for constant fuel pressure to
the injectors (and that the fuel pump is NOT an issue).
would be interested in more details about your Consult device.
robbie
The car finally died and the coil completely died- after replacement
the car is 100% again. So if someone says "the coil either works or it
doesn't" DONT BELIEVE IT
About the Consult:
The Consult device for my car I got from an ebay buyer- it has the
ConZult free version of software shipped with it. It is a serial
device so I had to get a USB to serial adapter to use a laptop in the
car. I am currently trying to get some other more extensive software
to work with it, but so far haven't found a complete package that will
recognize this particular consult device. Link to ebay item I
purchased:
Without full-featured software it is not that useful, but I was
looking into buying a software package if I was sure it was
compatible.