hello
so hot suddenly goes good. odd that.
I still have my suspicions about the EGR valve maybe sometime being sticky. (get it cleaned, and closed then defeat if (temporary) by pulling hose to it and using golf Tee to plug hose)
now its out of the picture, (could ping, on a real hot day so, use gentle right foot)
The EGR loves to stick as you come to a stop sign. (its commanded closed then( and ported vacuum too) , and rpm will be as low (egr stuck open) as 400 rpm and engine shakes and ISC can not correct this.
Misfire (hot)
yes, each intake stroke pulls in clean fresh 20% air slug and some fuel , the if it fails to fire, (misfire) the oxygen rich air slug, goes to the exhaust, and 02 sensor (hot engine) sees that slug of air. (02 sensor reads lean and ECU closed loop matches that with rich fuel) or +25% (guessing %)
-25% (means low oxygen was detected) the -25 means ecu removed 25% fuel, due to low oxy readings.
keep in mind, 1 misfire, can send 20% oxy rich air, (and fuel) to the exhaust port.
The O2 RAILS to 0vdc, even with 1% oxy seen. so is 20x leaner in truth. and and ecu goes richer, to cure, that +40%. (1/2 time the wrong way,OBD1/2 sickness i call it.)
---------------------------------------------------------------------------------
now cold , that is different, totally , no 02.
open loop cold start works from tables.
phases...
(IAC+ISC +bleed screw = air supply) and then the ecu assumes these air paths all work , to crank start with this air supply, if not , bad deal. flooding.
The ECT is now the major player, here, if read wrong say too low, it goes rich and misfires. (the ECT allows colds starts even in Alaska)
The MAF comes on line as it starts. (and is not very accurate at idle. kinda crude there. at low idle speeds, very good at 1500 rpm)
what is your cold start RPM, 700, 1200 1500s? ,usually its around 1500, and winds down to 800 hot and then regulates (ISC servo action) at 800 solid.
ECT:
The ECT needs to read near 3000 ohms (50F) on cool day to start engine. or 6000 ohms, 32f freezing morning , then go to 300 ohm hot. this is a key sensor.
http://www.fixkick.com/ECU/temp-sensors.html
check out my Exel plots too.above.
the one thing we dont know (weakness in OBD2 designs) is are all 4 cylinder working same way, all misfiring, or all 4 lean? hot. or all 4 doing same thing cold..
this is the weakness. we all face, and the ECU's bad act of adding fuel on a rich engine, during gross misfire, takes the cake on dumb ECU (measuring oxy instead of fuel is reason...)
HOT running, issues. (common)
I'd run Bosch mag wires on this engine, it has weak spark, (by today's standards) so mag wire is best. or NGK mag (pricey)
make sure spark TIMING is dead on, with timing freeze jumper set.
compression over 150PSI on all 4 at sea-level. (mine did 180psi warm)
my 2: (bench marks)
"My 1996 Geo Tracker 1.6Liter 16valve. , pulls 183-185 PSI on all 4 cylinders. (warm not fully hot. )
My 97' pulls 185 PSI min. dead cold. (a new head) later and hot it does 195 PSI. Old 100k mile engine, now with new oil rings, new crank and new head."
altitude 500ft.above.s
Leaks, on 16v MPI are all bad, unless very tiny. (even injector base cushions can leak air, causing one cylinder to go super lean,)
no induction air leaks, as they can cause maf to read too low, and under-report air flows , engine goes rich and if 02 is working, goes -25% (possible)
that huge big pipe on top , no cracks allowed. no cracked, big pipe seals there. from TB to MAF. some have accordion flex pipes that love to crack there.
This leaks cause a physical lean, stated, that the ECU Closed loop servo will go +25 or more, not -25% so is not it.
COMMON fails:
No crack? at #4 header tube (cast iron) this causes oxy leak and 0xy sensor to rail lean (0v) and trim goes rich. +40% Fuel (so is not this)
I'm listing super common failures here. for this old car. and symptoms.
FPR is new. and most are failing now. So fuel pressure i bet is ok, 36to 43psi, (at idle) and rises 6psi(about) up to WOT. (not this i bet)
bad spark at anytime will cause the 02 (hot) to read lean. and ECU to go rich. (to a large + number) on pre 96s far worse rich, it can go.
what if only 1 cylinder misfired?, same results on last line above, but may then cause all cylinders to go rich and misfire. (like lemmings) +25% or more.
(not your cause this)
high fuel pressure (probably not. with new FPR) will cause your -25% or more.(goes super rich but ecu corrects it)
Induction leaks (large) will cause +25% or more LTFT
MAF reads low all the time. (causing physically lean AFR, then (un-metered air cause lean burn ) , but closed loop the ecu is correcting it to +25%)
unmetered air is same effect at air leaks. (but is not -25% , so is not it either.)
keep in mind a hot engine can stick a head valve.
check vacuum is about 20 "hg at idle and no bouncing vacuum allowed.
-25% (raw causes)************************************
means 02 reads too low oxy. "0v lean, 1v rich, rules."
means 02 reads high voltage, for too rich. (means low oxy)
means ECU closed loop servo, action sucks fuel out of mix by -25% (all injectors go lean by -25% , shorter pulses)
that is not misfire.
injector leaks., yes.,
HIgh fuel pressure,yes.
maf over reporting air flows. (reads too high volts for reality) (a very rare failure mode this) yes, with me skeptical.
its all things that can cause gross rich conditions.
usually 02 sensors never stick high (Bosch says, designed to not ever do that) (seen some cracked inside)
but if the heater inside fails and leaks to the +CELL side, it will in fact stick +voltage. (crying wolf for rich, fibbing link a mad dog.) how old is your 02./?
one more 02 oddity, told by Bosch, (great white papers there )
is the carbon blanket effect (short list) (lets say FPR jammed to 55psi.)
engine goes rich, then the ECU sees, what, sees, 02 lean? due to gross misfiring (air slugs)
so the ECU adds fuel to rich misfiring engine, (silly huh?)
then the 02 sensor is covered in a carbon blanket.
the 02 sensor is now dead (for a time) and reads 0v. lean now. stuck at 0vdc.
this causes ECU to cut fuel. (closed loop actions) and this carbon burns off... then,. goes rich again.
and the cycle repeats.
so hot suddenly goes good. odd that.
I still have my suspicions about the EGR valve maybe sometime being sticky. (get it cleaned, and closed then defeat if (temporary) by pulling hose to it and using golf Tee to plug hose)
now its out of the picture, (could ping, on a real hot day so, use gentle right foot)
The EGR loves to stick as you come to a stop sign. (its commanded closed then( and ported vacuum too) , and rpm will be as low (egr stuck open) as 400 rpm and engine shakes and ISC can not correct this.
Misfire (hot)
yes, each intake stroke pulls in clean fresh 20% air slug and some fuel , the if it fails to fire, (misfire) the oxygen rich air slug, goes to the exhaust, and 02 sensor (hot engine) sees that slug of air. (02 sensor reads lean and ECU closed loop matches that with rich fuel) or +25% (guessing %)
-25% (means low oxygen was detected) the -25 means ecu removed 25% fuel, due to low oxy readings.
keep in mind, 1 misfire, can send 20% oxy rich air, (and fuel) to the exhaust port.
The O2 RAILS to 0vdc, even with 1% oxy seen. so is 20x leaner in truth. and and ecu goes richer, to cure, that +40%. (1/2 time the wrong way,OBD1/2 sickness i call it.)
---------------------------------------------------------------------------------
now cold , that is different, totally , no 02.
open loop cold start works from tables.
phases...
(IAC+ISC +bleed screw = air supply) and then the ecu assumes these air paths all work , to crank start with this air supply, if not , bad deal. flooding.
The ECT is now the major player, here, if read wrong say too low, it goes rich and misfires. (the ECT allows colds starts even in Alaska)
The MAF comes on line as it starts. (and is not very accurate at idle. kinda crude there. at low idle speeds, very good at 1500 rpm)
what is your cold start RPM, 700, 1200 1500s? ,usually its around 1500, and winds down to 800 hot and then regulates (ISC servo action) at 800 solid.
ECT:
The ECT needs to read near 3000 ohms (50F) on cool day to start engine. or 6000 ohms, 32f freezing morning , then go to 300 ohm hot. this is a key sensor.
http://www.fixkick.com/ECU/temp-sensors.html
check out my Exel plots too.above.
the one thing we dont know (weakness in OBD2 designs) is are all 4 cylinder working same way, all misfiring, or all 4 lean? hot. or all 4 doing same thing cold..
this is the weakness. we all face, and the ECU's bad act of adding fuel on a rich engine, during gross misfire, takes the cake on dumb ECU (measuring oxy instead of fuel is reason...)
HOT running, issues. (common)
I'd run Bosch mag wires on this engine, it has weak spark, (by today's standards) so mag wire is best. or NGK mag (pricey)
make sure spark TIMING is dead on, with timing freeze jumper set.
compression over 150PSI on all 4 at sea-level. (mine did 180psi warm)
my 2: (bench marks)
"My 1996 Geo Tracker 1.6Liter 16valve. , pulls 183-185 PSI on all 4 cylinders. (warm not fully hot. )
My 97' pulls 185 PSI min. dead cold. (a new head) later and hot it does 195 PSI. Old 100k mile engine, now with new oil rings, new crank and new head."
altitude 500ft.above.s
Leaks, on 16v MPI are all bad, unless very tiny. (even injector base cushions can leak air, causing one cylinder to go super lean,)
no induction air leaks, as they can cause maf to read too low, and under-report air flows , engine goes rich and if 02 is working, goes -25% (possible)
that huge big pipe on top , no cracks allowed. no cracked, big pipe seals there. from TB to MAF. some have accordion flex pipes that love to crack there.
This leaks cause a physical lean, stated, that the ECU Closed loop servo will go +25 or more, not -25% so is not it.
COMMON fails:
No crack? at #4 header tube (cast iron) this causes oxy leak and 0xy sensor to rail lean (0v) and trim goes rich. +40% Fuel (so is not this)
I'm listing super common failures here. for this old car. and symptoms.
FPR is new. and most are failing now. So fuel pressure i bet is ok, 36to 43psi, (at idle) and rises 6psi(about) up to WOT. (not this i bet)
bad spark at anytime will cause the 02 (hot) to read lean. and ECU to go rich. (to a large + number) on pre 96s far worse rich, it can go.
what if only 1 cylinder misfired?, same results on last line above, but may then cause all cylinders to go rich and misfire. (like lemmings) +25% or more.
(not your cause this)
high fuel pressure (probably not. with new FPR) will cause your -25% or more.(goes super rich but ecu corrects it)
Induction leaks (large) will cause +25% or more LTFT
MAF reads low all the time. (causing physically lean AFR, then (un-metered air cause lean burn ) , but closed loop the ecu is correcting it to +25%)
unmetered air is same effect at air leaks. (but is not -25% , so is not it either.)
(03-02-2016, 01:16 PM)Mike8500 Wrote:(03-01-2016, 11:10 PM)fixkick Wrote: welcome bad from road trip..
-25% means the ECU is removing 25% fuel from a gross over rich mixture. (-5% is normal because MAF is 5% naturally rich on purpose)
The MAF is designed (or ECU tuned) to be always on rich side (safe side, because lean burns valves) so the closed loop corrects this, error.
then when you go wide open throttle and he 02 closed loop shuts down, it must not go lean, every, and this is the MAF air flows, that prevent lean, WOT or just accelerating.
if it misfires, at all at idle, this sends, excess oxygen air slugs to the exhaust ports, and 02 sees that as lean , oxy lean. and goes huge Plus percent to correct it. (so is not it)
same with exhaust leaks near 02. huge oxy (air 20%) land there and huge + percent LTFT. ( so is NOT IT)
so what on earth causes -25%
too high fuel pressure tops my list
leaking injectors. (1 or more)
MAF stuck high,(but under the DTC error stuck high point, nah) very rare for MAFs to stick high say 1volt more than REAL air flow) seen 1 china clone maf do that , magic.
not clogged injectors as LTFT goes +25% to compensate.
its nice having scan tool data, no?
see whats going on with fuel trim... is a very good thing.
so you have zero DTC errors.
Yes so another day driving home from work I monitored some PIDs.
Today it started running properly much more quickly than the previous trip. Idle still started out shaky but it started running fine almost as soon as it warmed up. No DTCs present. STFT and LTFT were both a lot more normal today (0-6%).
I didn't change anything from yesterday to today. When I parked it, it was running perfectly normal. Strange beast this is. I considered a leaking injector, but that wouldn't fix itself after 20min of driving. Brand new FPR although I haven't actually put a gauge on it. I'm going to continue driving it and see if the problem continues to clear up (wouldn't that be nice).
I'm trying to think of what would cause horrible idle when cold with hesitation, and wouldn't cause a problem when warm. Dark and rainy out tonight so I'm not pulling the plugs just yet, but I will do it sometime this week. I still have my suspicions about the EGR valve maybe sometime being sticky.
That should make it read lean, but maybe when it misfires, the raw fuel gets dumped and burned one the next ignition event (in the exhaust manifold). Possible?
EGR open at idle, makes it do gross misfire and 02 will read lean. (air slugs) +20% (my theory)
I really need to get a proper datalogging software so I can datalog when it's running weird.
keep in mind a hot engine can stick a head valve.
check vacuum is about 20 "hg at idle and no bouncing vacuum allowed.
-25% (raw causes)************************************
means 02 reads too low oxy. "0v lean, 1v rich, rules."
means 02 reads high voltage, for too rich. (means low oxy)
means ECU closed loop servo, action sucks fuel out of mix by -25% (all injectors go lean by -25% , shorter pulses)
that is not misfire.
injector leaks., yes.,
HIgh fuel pressure,yes.
maf over reporting air flows. (reads too high volts for reality) (a very rare failure mode this) yes, with me skeptical.
its all things that can cause gross rich conditions.
usually 02 sensors never stick high (Bosch says, designed to not ever do that) (seen some cracked inside)
but if the heater inside fails and leaks to the +CELL side, it will in fact stick +voltage. (crying wolf for rich, fibbing link a mad dog.) how old is your 02./?
one more 02 oddity, told by Bosch, (great white papers there )
is the carbon blanket effect (short list) (lets say FPR jammed to 55psi.)
engine goes rich, then the ECU sees, what, sees, 02 lean? due to gross misfiring (air slugs)
so the ECU adds fuel to rich misfiring engine, (silly huh?)
then the 02 sensor is covered in a carbon blanket.
the 02 sensor is now dead (for a time) and reads 0v. lean now. stuck at 0vdc.
this causes ECU to cut fuel. (closed loop actions) and this carbon burns off... then,. goes rich again.
and the cycle repeats.
http://www.fixkick.com