1987 GN.
when (engine) cold, wont stay running without giving it gas.
once warmed up, its fine (can shut off & restart no problems).
when trying to do a brake torque, from 1-2000 rpm, stutter/stumbles/bogs & rpms drop, feels like it wants to die, O2 drops to almost zero.
(before, car use to blow away the tires at 2-3k rpm)
now it just feels like its lacking power.
its running lean (according to O2 & blm), but I can't figure out why!?
here's SM readings, in idle, in park, engine hot (loop blinking):
O2 576-590 (but see below)
af 5
l8 35
batt 13.3 (it does go up when revving)
int 128
blm 116
clt 167
ats 79
r 850-900 (always idled this high previously & ran great)
tps 44
iac 22
cc (initially ran up all the way & started counting again, but see below)
pu 1.8
sp 27.8-28.2
mal 0
map 37
bst -19
those were the readings after it was fully warmed up. left car running.
then I removed air filter (to check dirtiness, etc.) & kept it off:
O2 = 650-660
then tried brake torque to see if it made a difference (nope, still stumbles):
O2 now 790-820 when idling, cross counts very slow movement (even when revving), but when revving (brake torque) O2 drops to near zero.
WHY is thing going lean? Whats making it stumble? and why are my O2 readings all over the place?
What I've done / checked:
all grounds good (with many extra & redundants in place as well).
all power wires (at battery, alt & starter) ok & fuses good.
all vacuum lines (& pcv) checked & good.
all I/C couplers/hoses checked & good.
No egr, seal is good.
did the carb cleaner spray around hoses (etc) test, no change.
new O2 sensor (denso).
new fuel pump (racetronix 340 w/ hangar) [fuel pump ground wire + stock harness wire + hot wire relay (basically) tied together & grounded to frame & also gastank strap bolt].
new (bigger, full length #6 braided) return line.
new AFPR, 43 line off, 38 line on.
new FP hotwire kit.
new factory FP relay.
new Fuel injector harness, with hotwire, good.
(unplugging each inj, idle drops a tiny bit, but doesn't make that much a difference running, I can tell when plugging back in runs better though. Injectors are 72# low imp.)
new gas in tank.
new spark plugs (autolite 103 @ 28). {old plugs were very black}
cam sensor checked (took cap off, no wiggle on ring) & reset.
crank sensor, tight & clears, looks ok.
IAC cleaned & reset. (from 0 ref point procedure)
TPS checked & reset.
coolant sensor/wires look ok & seems ok based on SM reading (& fans come on at 160ish).
computer chips/plugs checked ok, not loose/no corrosion.
TT 5.6 chip, (with whatever settings are default) {I do have a 6.0 chip I could try, havent yet)
swapped out coil pack & ignition module, no difference.
(& extra ground added on IM base to firewall).
plug wires all ohm out within each other. good.
checked coil/IM plug, snug & good.
drivers side rockers (for cam lobe check) checked ok. (suppose to be roller cam, but never verified)
MAFTPRO, so NO MAF, connections ok, settings I believe are correct.
battery, alternator (& electrical connections) all checked good.
cruise control/brake switches (vac line) good.
-----
unplugged O2 sensor, reset comp., engine runs worse in general:
I READ THIS FROM ANOTHER THREAD, & CHECKED, {MY ANSWERS} IN CAPS:
so, you unplugged the O2 sensor, and reset the ECM, and it runs ok? {NO}
(The BLMs should all be stuck at 128 now). {THEY ARE}
the O2 volts should be stuck at .399 to .440 v (no cross counts) {MY O2= 176-184, NO C/C}
else to check:
check your ECM connector for corrosion? {DID THAT, ITS OK}
loose grounds on the back of the cylinder head? {OK}
replace the O2 sensor regardless. {ALREADY DID THAT}
(post from turbobob)
{MY VDO TACH READS STEADY 800RPM BUT SM SAYS 650-900 & ENGINE RUNS REAL LUMPY}
SO WHY ARE MY O2 READINGS SO LOW WITH THIS TEST?
DO I HAVE A LAZY/BAD O2?
-----
the below tests all done within 10 minutes, 1 right after the other:
1 hour later (from above), after warming engine up:
O2 560-580 int 120-129 bl 119
then unplugged cam sensor:
rpm doesnt change, then revving it up (1-2k rpm, in park) engine seems a bit stronger/quicker (sort of).
at idle in park:
O2 627-630 int 112 bl 115 cc slow moving
pu 1.2 mal 41 (unplugged C/S)
still having the stutter when brake torquing & O2 drops again.
shut off car (key off), plug cam sensor back in, reset computer, start back up:
O2 starts at 230 goes up to 600 then runs sporadic 100-600 (never more than 600)
int back to 128 bl 128
------
Maybe its the computer? Any way to check? It gets warm, but not hot.
With the crazy SM readings, thought maybe that was bad, but its relatively new too.
I do have a PL if that'll help (its hooked up), and can run tests, what do you want me to do / what do you want to see?
Also have a WBO2, not installed yet, (but will if that'll help narrow down this problem!)
Any help/suggestions appreciated! I'm lost at this point...
when (engine) cold, wont stay running without giving it gas.
once warmed up, its fine (can shut off & restart no problems).
when trying to do a brake torque, from 1-2000 rpm, stutter/stumbles/bogs & rpms drop, feels like it wants to die, O2 drops to almost zero.
(before, car use to blow away the tires at 2-3k rpm)
now it just feels like its lacking power.
its running lean (according to O2 & blm), but I can't figure out why!?
here's SM readings, in idle, in park, engine hot (loop blinking):
O2 576-590 (but see below)
af 5
l8 35
batt 13.3 (it does go up when revving)
int 128
blm 116
clt 167
ats 79
r 850-900 (always idled this high previously & ran great)
tps 44
iac 22
cc (initially ran up all the way & started counting again, but see below)
pu 1.8
sp 27.8-28.2
mal 0
map 37
bst -19
those were the readings after it was fully warmed up. left car running.
then I removed air filter (to check dirtiness, etc.) & kept it off:
O2 = 650-660
then tried brake torque to see if it made a difference (nope, still stumbles):
O2 now 790-820 when idling, cross counts very slow movement (even when revving), but when revving (brake torque) O2 drops to near zero.
WHY is thing going lean? Whats making it stumble? and why are my O2 readings all over the place?
What I've done / checked:
all grounds good (with many extra & redundants in place as well).
all power wires (at battery, alt & starter) ok & fuses good.
all vacuum lines (& pcv) checked & good.
all I/C couplers/hoses checked & good.
No egr, seal is good.
did the carb cleaner spray around hoses (etc) test, no change.
new O2 sensor (denso).
new fuel pump (racetronix 340 w/ hangar) [fuel pump ground wire + stock harness wire + hot wire relay (basically) tied together & grounded to frame & also gastank strap bolt].
new (bigger, full length #6 braided) return line.
new AFPR, 43 line off, 38 line on.
new FP hotwire kit.
new factory FP relay.
new Fuel injector harness, with hotwire, good.
(unplugging each inj, idle drops a tiny bit, but doesn't make that much a difference running, I can tell when plugging back in runs better though. Injectors are 72# low imp.)
new gas in tank.
new spark plugs (autolite 103 @ 28). {old plugs were very black}
cam sensor checked (took cap off, no wiggle on ring) & reset.
crank sensor, tight & clears, looks ok.
IAC cleaned & reset. (from 0 ref point procedure)
TPS checked & reset.
coolant sensor/wires look ok & seems ok based on SM reading (& fans come on at 160ish).
computer chips/plugs checked ok, not loose/no corrosion.
TT 5.6 chip, (with whatever settings are default) {I do have a 6.0 chip I could try, havent yet)
swapped out coil pack & ignition module, no difference.
(& extra ground added on IM base to firewall).
plug wires all ohm out within each other. good.
checked coil/IM plug, snug & good.
drivers side rockers (for cam lobe check) checked ok. (suppose to be roller cam, but never verified)
MAFTPRO, so NO MAF, connections ok, settings I believe are correct.
battery, alternator (& electrical connections) all checked good.
cruise control/brake switches (vac line) good.
-----
unplugged O2 sensor, reset comp., engine runs worse in general:
I READ THIS FROM ANOTHER THREAD, & CHECKED, {MY ANSWERS} IN CAPS:
so, you unplugged the O2 sensor, and reset the ECM, and it runs ok? {NO}
(The BLMs should all be stuck at 128 now). {THEY ARE}
the O2 volts should be stuck at .399 to .440 v (no cross counts) {MY O2= 176-184, NO C/C}
else to check:
check your ECM connector for corrosion? {DID THAT, ITS OK}
loose grounds on the back of the cylinder head? {OK}
replace the O2 sensor regardless. {ALREADY DID THAT}
(post from turbobob)
{MY VDO TACH READS STEADY 800RPM BUT SM SAYS 650-900 & ENGINE RUNS REAL LUMPY}
SO WHY ARE MY O2 READINGS SO LOW WITH THIS TEST?
DO I HAVE A LAZY/BAD O2?
-----
the below tests all done within 10 minutes, 1 right after the other:
1 hour later (from above), after warming engine up:
O2 560-580 int 120-129 bl 119
then unplugged cam sensor:
rpm doesnt change, then revving it up (1-2k rpm, in park) engine seems a bit stronger/quicker (sort of).
at idle in park:
O2 627-630 int 112 bl 115 cc slow moving
pu 1.2 mal 41 (unplugged C/S)
still having the stutter when brake torquing & O2 drops again.
shut off car (key off), plug cam sensor back in, reset computer, start back up:
O2 starts at 230 goes up to 600 then runs sporadic 100-600 (never more than 600)
int back to 128 bl 128
------
Maybe its the computer? Any way to check? It gets warm, but not hot.
With the crazy SM readings, thought maybe that was bad, but its relatively new too.
I do have a PL if that'll help (its hooked up), and can run tests, what do you want me to do / what do you want to see?
Also have a WBO2, not installed yet, (but will if that'll help narrow down this problem!)
Any help/suggestions appreciated! I'm lost at this point...