91 sentra 1.6 liter possible cause of stumble on acceleration?
robbie
something i hadn't thought of looking at before.
the specs say the readings should be .9 ohms and 13k ohms. My readings
which i took multiple times were 1.6 ohms and 13k ohms. so - any
experts out there willing to say that this could be a potential
culprit? according to the (Haynes) manual - replace the coil if it is
out of spec. So with a higher resistance I am thinking weaker spark? =
poor performance? - especially when a lot of fuel is being added to
the fire (@WOT) ?
If this is the solution I will kick myself for not finding it sooner-
i was wholly focused on a fuel delivery/vacuum leak theory and used my
shade tree knowledge of ignition and spark that says if a coil works
it works correctly all the time! Thanks to all posters who can help me
out.
Peter Hill
RE: Primary 0.9ohm. Are you completely sure your meter is accurate at
such a low resistance? Milliohm meters cost.
make a milliohm adaptor
http://www.freeinfosociety.com/electronics/schematics/sensor-based/milliohmadapter.pdf
Find a 1 or 2ohm, 1 or 0.1% resistor, or put 10 x 10ohms resistors in
parrallel and calibrate it. Then test test lead quality by testing
resistance direct to meter terminals and though leads. Then throw the
leads away and get some very good ones.
--
Peter Hill
Spamtrap reply domain as per NNTP-Posting-Host in header
Can of worms - what every fisherman wants.
Can of worms - what every PC owner gets!
robbie
wrote:
> On Thu, 25 Mar 2010 09:00:09 -0700 (PDT), robbie
>
> >I just decided on a whim to test the ignition coil because it was
> >something i hadn't thought of looking at before.
> >the specs say the readings should be .9 ohms and 13k ohms. My readings
> >which i took multiple times were 1.6 ohms and 13k ohms. so - any
> >experts out there willing to say that this could be a potential
> >culprit? according to the (Haynes) manual - replace the coil if it is
> >out of spec. So with a higher resistance I am thinking weaker spark? =
> >poor performance? - especially when a lot of fuel is being added to
> >the fire (@WOT) ?
> >If this is the solution I will kick myself for not finding it sooner-
> >i was wholly focused on a fuel delivery/vacuum leak theory and used my
> >shade tree knowledge of ignition and spark that says if a coil works
> >it works correctly all the time! Thanks to all posters who can help me
> >out.
>
> RE: Primary 0.9ohm. Are you completely sure your meter is accurate at
> such a low resistance? Milliohm meters cost.
>
>
> Find a 1 or 2ohm, 1 or 0.1% resistor, or put 10 x 10ohms resistors in
> parrallel and calibrate it. Then test test lead quality by testing
> resistance direct to meter terminals and though leads. Then throw the
> leads away and get some very good ones.
> --
> Peter Hill
> Spamtrap reply domain as per NNTP-Posting-Host in header
> Can of worms - what every fisherman wants.
> Can of worms - what every PC owner gets!
nope i'm not completely sure. its a cheap craftsman dmm with ohms
reading. it read the 13 KOhms side perfectly but as i've found from
research in just a few minutes the low reading's accuracy is
automatically in doubt, because of the cheap design of the meter. how
about this for a cheap way to accurately measure the low resistance:
http://diyaudioprojects.blogspot.com/2008/11/simple-low-resistance-measurement.html
its a way to send a small current through the coil to measure the
voltage, then use the classic v= ir formula (or in this case r=v/i) to
get an accurate reading of the true resistance.
but before i build a test kit like this- could it cause drivability
issues? thanks!
Peter Hill
The link I posted before won't work on high inductance.
Scroll down to High Inductance Resistance Measurement on this page.
http://www.valhallascientific.com/applications/applications-6.shtml
Here's a better one.
http://www.wentztech.com/radio/Projects/Projects_assets/AN106.pdf
Just don't run it too long and overheat the coil. Power = Volts x
Amps, 5 volts at 1 amp, coil is going to get hot like it has a 5w bulb
inside it. A typical coil will dissipate 20W in normal use.
NissTech
the engine going into fuel cut or rev limiter mode, this feature is built
into ALL Nissans. the quick and easy fix is not to go to WFO (wide fucking
open) throttle.
The throttle position switch/sensor have a WOT contact so when you mat the
thing the contact closes and the rev limiter is engaged
"robbie" <robbie....@gmail.com> wrote in message
news:282bd56b-1530-4722...@l25g2000yqd.googlegroups.com...
robbie
> after re reading your previous posts , I think what you are experiencing is
> the engine going into fuel cut or rev limiter mode, this feature is built
> into ALL Nissans. the quick and easy fix is not to go to WFO (wide fucking
> open) throttle.
>
> The throttle position switch/sensor have a WOT contact so when you mat the
> thing the contact closes and the rev limiter is engaged
>
>
> news:282bd56b-1530-4722...@l25g2000yqd.googlegroups.com...
>
> >I just decided on a whim to test the ignition coil because it was
> > something i hadn't thought of looking at before.
> > the specs say the readings should be .9 ohms and 13k ohms. My readings
> > which i took multiple times were 1.6 ohms and 13k ohms. so - any
> > experts out there willing to say that this could be a potential
> > culprit? according to the (Haynes) manual - replace the coil if it is
> > out of spec. So with a higher resistance I am thinking weaker spark? =
> > poor performance? - especially when a lot of fuel is being added to
> > the fire (@WOT) ?
> > If this is the solution I will kick myself for not finding it sooner-
> > i was wholly focused on a fuel delivery/vacuum leak theory and used my
> > shade tree knowledge of ignition and spark that says if a coil works
> > it works correctly all the time! Thanks to all posters who can help me
> > out.
so is the rev limiter built into the tps able to be bypassed? or can i
test the tps/adjust it? or is my only real test replace the tps and
see if that fixes it?
Thanks!
NissTech
throttle contact has closed the ECM will engage the rev limiter to protect
the engine.
"robbie" <robbie....@gmail.com> wrote in message
news:349e085f-c71c-43b9...@b33g2000yqc.googlegroups.com...
robbie
> The rev limiter is built into the ECM logic, once the ECM see's the WOT
> throttle contact has closed the ECM will engage the rev limiter to protect
> the engine.
>
Well, I replaced the TPS with a new unit and adjusted it accordingly,
but still having the same problem.
Also spent more than a few minutes driving around with the fuel
pressure gauge mounted so I could watch it as I experienced the
shuddering/lack of power symptoms,
and whenever the problem occurred, the pressure actually went up to
about 44-46psi, then went down again to about 36-38 when the problem
went away. This leads me to believe
that there is something causing the computer to cut fuel to the
injectors (otherwise wouldn't the pressure drop?) also the EGR valve
is bypassed currently and i can find no vacuum leaks.
even so the theory that the engine is getting unmetered air from
somewhere is kind of shot down with the way the fuel pressure is
acting in my opinion- wouldnt the pressure maintain a
consistent reading if the injectors were pumping the same amount of
fuel and the intake just took in more air?
also the check engine light flashes sometimes now, but no codes are
stored in the ecu. it always reads 55.
the worst shudder/power cut occurs at about 1/3 throttle and WOT is
also just as bad- the fuel starved symptoms I have mentioned before.
Thanks for any advice!
NissTech
***told ya nothing was wrong with the tps****
Also spent more than a few minutes driving around with the fuel
pressure gauge mounted so I could watch it as I experienced the
shuddering/lack of power symptoms,
and whenever the problem occurred, the pressure actually went up to
about 44-46psi, then went down again to about 36-38 when the problem
went away .
****** the above mentioned is a normal condition, when the fuel pressure
regulator sences a loss in vacuum it increases
the fuel pressure to compensate for the lower vacuum condition that happena
to ALL engines when the RPM's are increased****
*** and no you dont have a problem with the fuel pressure regulator***
This leads me to believe
that there is something causing the computer to cut fuel to the
injectors (otherwise wouldn't the pressure drop?
*****read the above statement***
also the EGR valve
is bypassed currently and i can find no vacuum leaks.
*** bypassing the EGR valve is not good, one of the benifits of EGR is it
helps lower combustion chamber temps to reduce pre-ignition (pinging)
and to aid in complete combustion of the fuel and air mixture****
even so the theory that the engine is getting unmetered air from
somewhere is kind of shot down with the way the fuel pressure is
acting in my opinion-
****fuel pressure is acting as designed***
wouldnt the pressure maintain a
consistent reading if the injectors were pumping the same amount of
fuel and the intake just took in more air?
also the check engine light flashes sometimes now, but no codes are
stored in the ecu. it always reads 55.
***55 means no faults found****
the worst shudder/power cut occurs at about 1/3 throttle and WOT is
also just as bad- the fuel starved symptoms I have mentioned before.
Thanks for any advice!
**my guess is you may have a problem with the distributor **
robbie
> Thanks for any advice!
>
> **my guess is you may have a problem with the distributor **
so - faulty distributor cap/rotor/wires? or a problem with the actual
electronics in the distributor?
thanks again nisstech for a thorough walk through-
Roger Brodrick
the car and drive around at night.See if the timing light misses a
flash when the engine misses a beat. Check the article at Pico about
sticky injectors. http://www.picoauto.com/tutorials/diy-expert.html I
have a 1996 sunny behaving like yours but cant get to it at the
moment. Could try disconnecting the o2 sensor and also reseting the
computer by taking battery lead off for 5 minutes
Peter Hill
Old 80's Nissan ECU's have a built in diagnostic mode - mode III gives
55 for clear. Mode III is very crude, it only detects 2 things. 1: Has
it shorted out to ground or 12V? 2: Is the part connected? It won't
detect out of spec parts / systems. Haul it out of it's hole so you
can see it when driving, select mode V real time test. Mine will flash
error codes for ignition, crank angle sensor and AFM. But I only have
experience with direct coil on plug systems (and only have flash codes
for CA18DET) and they may have reduced/changed the diagnostics for
distributor models.
New ones like your Sunny from early 90's on (defo fitted to '94 S14
with SR20DET) are quite difficult without a consult interface and a
laptop/PC. They give far more detailed diagnostics but there is always
a procedure for testing without the Consult interface.
Either new or old the Nissan service manual has the best
troubleshooting info you can get.
CA18DET - no EGR.
14 poor driveability - stumble (while accelerating)
1: ignition
2: coil
3: air leak
4: idle switch not set correctly and/or throttle unable to close fully
so it doesn't close switch at idle. An open throttle due to carbon or
miss setting of factory set stop screw at idle is an air leak, the
throttle plate should be completely shut. Idle is set by base idle
screw and ECU control of ACC.
5: faulty fuel pressure. Pump or FPR. If you have pressure, pump is
OK. If you can suck a vacuum on the FPR hose that will hold the tip of
your tongue it's OK.
6: Idle mixture - mode I or II ECU test if you have a lambda sensor.
Make the leds flash 9 times in 10 secs at 2000rpm. No lambda then you
need a CO meter or you twiddle the screw on the AFM to get max engine
speed (don't, just don't, not ever, they never ever need setting it's
always something else like an air leak).
7: Mode III and V tests.
8: Unplug lambda, drive. If improved change it. Else check idle
mixture (but really go back and look for air leaks).
have I said AIR LEAK?
Just for good measure AIR LEAK.
robbie
wrote:
Heres a question- i found a tiny solenoid that has vacuum connections
to the charcoal canister, to the throttle body, and the egr control -
is there a test procedure for that one? its really small and i dont
know what activates it- but it may be the source of the AIR LEAK- any
suggestions on troubleshooting?? thanks.
PS- i replaced ALL small vacuum lines and checked the brake booster
etc for leaks- found none.