bucking and stalling

[douginhull]

Hello to all, New Guy Here,
 I have a 93 Geo tracker 8V 3 speed w/120,000 mi
some time ago my truck started to buck at cruising speed so i replaced the fuel pressure regulator. This did not make a difference so i got use to it. Then the truck started to stall for no apparent reason just going down the road???  This happens periodically, I put it in neutral  and coast to the shoulder. The truck would continue to idle around 600 rpm but if  accelerated, it stalls? After turning the ignition off and back on the truck starts up and runs great (except for the bucking) until a random amount of time when it will do it again. so where should I look next as i know that the next time it may not start again. 
Thanks for any help 
 Douginhull

[fixkick]

Hello to all, New Guy Here,
 I have a 93 Geo tracker 8V 3 speed w/120,000 mi
some time ago my truck started to buck at cruising speed so i replaced the fuel pressure regulator. This did not make a difference so i got use to it. Then the truck started to stall for no apparent reason just going down the road???  This happens periodically, I put it in neutral  and coast to the shoulder. The truck would continue to idle around 600 rpm but if  accelerated, it stalls? After turning the ignition off and back on the truck starts up and runs great (except for the bucking) until a random amount of time when it will do it again. so where should I look next as i know that the next time it may not start again. 
Thanks for any help 
 Douginhull

random bucking,
Does the check engine light glows?, key on  every time?, then goes out running and stays out running but if the engine stalls, CEL goes go back on, sure. back to key on only state.
so at the stall, right foot can not save the stall?
the engine ever get a full tune up the last 60,000 milles? spark parts all new? plugs/wires/cap/rotor?  (got excess miles on the cam belt 60k is spec)?
check the front large 17mm crank pulley bolt set to 94ft/lbs.  if not kiss of the crank front snout key damage there.

600 rpm most times means the EGR main valve is suck open  it must be clean or it sticks or replaced.
if fuel pressure is ok then the pump is ok.  but low fuel pressure cases bogging not bucking, bucking Implies gross spark loss, (spark loss is the most violent of events not fuel starvation)

to witness how fuel pressure acts, pull the fuse marked,  FI  ,  while parked and running,,this kills the fuel pump and see how the throttle acts , it bogs and slows and dies.

spark  can fail for lots of reasons on old cars, not just the above.
drive with the DTC   diagnostic jumper in place, when it bucks the the code 12 (normal good) changes to 41, or 42,  then BINGO you know why.

a bad ECU can also do this , the infamous bad caps  caused.  easy fix for $5 and soldering pencil
other causes the spark coil connections rusty and distributor side plug rusty (corroded) 
all the ground to the ECU , bad? rusty,  seen under hood fire wall, bolts distrib ground wire lug loose. seen here?  https://fixkick.com/Good_Bad_Ugly/common-failures.html


when the engine bucks or stalls do you lose power 12vdc to the cluster in any way?  gauges drop dead, or the like? (radio does, head lamps dim, all things electric act up?)

[douginhull]

Hello to all, New Guy Here,
 I have a 93 Geo tracker 8V 3 speed w/120,000 mi
some time ago my truck started to buck at cruising speed so i replaced the fuel pressure regulator. This did not make a difference so i got use to it. Then the truck started to stall for no apparent reason just going down the road???  This happens periodically, I put it in neutral  and coast to the shoulder. The truck would continue to idle around 600 rpm but if  accelerated, it stalls? After turning the ignition off and back on the truck starts up and runs great (except for the bucking) until a random amount of time when it will do it again. so where should I look next as i know that the next time it may not start again. 
Thanks for any help 
 Douginhull

random bucking,
Does the check engine light glows?, key on  every time?, then goes out running and stays out running but if the engine stalls, CEL goes go back on, sure. back to key on only state.
so at the stall, right foot can not save the stall?
the engine ever get a full tune up the last 60,000 milles? spark parts all new? plugs/wires/cap/rotor?  (got excess miles on the cam belt 60k is spec)?
check the front large 17mm crank pulley bolt set to 94ft/lbs.  if not kiss of the crank front snout key damage there.

600 rpm most times means the EGR main valve is suck open  it must be clean or it sticks or replaced.
if fuel pressure is ok then the pump is ok.  but low fuel pressure cases bogging not bucking, bucking Implies gross spark loss, (spark loss is the most violent of events not fuel starvation)

to witness how fuel pressure acts, pull the fuse marked,  FI  ,  while parked and running,,this kills the fuel pump and see how the throttle acts , it bogs and slows and dies.

spark  can fail for lots of reasons on old cars, not just the above.
drive with the DTC   diagnostic jumper in place, when it bucks the the code 12 (normal good) changes to 41, or 42,  then BINGO you know why.

a bad ECU can also do this , the infamous bad caps  caused.  easy fix for $5 and soldering pencil
other causes the spark coil connections rusty and distributor side plug rusty (corroded) 
all the ground to the ECU , bad? rusty,  seen under hood fire wall, bolts distrib ground wire lug loose. seen here?  https://fixkick.com/Good_Bad_Ugly/common-failures.html


when the engine bucks or stalls do you lose power 12vdc to the cluster in any way?  gauges drop dead, or the like? (radio does, head lamps dim, all things electric act up?)

[douginhull]

OK lots of info!
the truck dose not stall as if it had a bad electrical connection or fuel pump quit working type of stall...... it suddenly louses power at no particular speed. When i put it in N to pull over it continues to idle very nicely (at 800 rpm not the 600 that i originaly reported) but will not allow me to accelerate or it stalls completely.
I turn the ignition on and off (sometimes several times) and it will take off again.
i have thought that the fuel pump relay may be the cause but why would the vehicle continue to idle???
If it was the fuel pump wouldent it just quit running all together? i can also hear the fuel pump running when i turn on the ignition.
thanks in advance for your good thoughts

[fixkick]

it is not the FP relay , if it idles.
seems it is intermittent.
so is not  the spark or key switch bad or other things that kill spark
its and injection limit.
my guess is what I call BOGGING is your buck or just total lack of engine power, but random.
and use the 2 wires to the pump and the pump can do all that.

the car is 2doors, the first thing to check is behind the leaf rear tail light.
this loves to have the pink or black pump wires there RUST>

ground G420 rusty and pink at . at c430 both wires at LARGE RED ARROR.





best is to see my page here, and all things there, see photos for sure. see where the PINK can fail, and loves to.


https://fixkick.com/INJECTORS/PUMP/dead-pump.html

[fixkick]

I assumed 2 door car, most are 8 valve, but if living in canada , they have more choices up there.
the harness are radially different 2 door to 4 door. so...

[douginhull]

that's the first thing any one has told me that makes any sense!
ill get right after it.... love the diagrams!
Thanks

[douginhull]

i didnt see any rust or decay at ground g402 location behind the left tail light but i took it apart and reattached it looked real good?????

[douginhull]

Checked and cleaned grounds and connections to no avail. After running smooth for several miles the engine lost power so i put it in N and coasted to the shoulder where it continued to idle but would not accelerate????? Again turned the key on and off again the engine would idle but not accelerate. after talking real dirty to her, for no apparent reason, while idling for a while, as if to flip me the bird she just took off again?!?!?!?! any guess would be appreciated.
Thanks