Redwingvksm
Well-Known LVC Member
1997 GMC Safari
4.3 CPI (Yes, the spider injection, VIN=W)
4x2
All temps in working are have been @ ~60 Degrees F with LOW relative humidity
I currently have a 1997 GMC Safari (Same as Astro - just GMC Style) that is missing. It won't miss when free-revving it (In Park or neutral) but as soon as you put it in drive i'll stumble for a sec and than from there any time you go more than 1/4 throttle, it'll miss like a SOB. WILL NOT DO THIS IN REVERSE - just in Drive, 3, 2, 1. It originally came in for dieing and found that the Ignition Control Module was bad (It was giving a code P1351 - IC Circuit High/Open) - that's when it started doint this missing. I have tried to put back the OLD module - but it won't even run with the old module anymore.(I'll sit and crank, crank, and crank) It will 'work itself out' if you hold the throttle there for 3-4 minutes (the miss) but as soon as you give it more gas it'll start missing agian. It does NOT matter if it's hot or cold.
I have the MODIS scanner and have gotten some values while missing...
O2 Sensors -
B1-S1=156 mV (for the duration of the missing, than jump back to normal) (Cyl 1, 3, 5)
B2-S1=100-900 (Normal readings) (Cyl 2, 4, 6)
B1-S3=300-500 (Before cat)
BOTH SETS of injectors are opening at 13.4+ms
Codes:
P0300 - Multiple cylinder missfire
P1351 - IC Circuit High/Open (Take care of with the changing of the Ign. Control Module)
This problem was dropped off from ANOTHER shop (They where like fawk it) and because I'm the lead drivability tech at my shop - I get the gift of figuring this out. I seriously need some help here, I'M LOOSING MY ASS. I have gone through the steps-by-steps from Mitchell for the following sensors:
CAM Sensor
CRANK Sensor
IGN Module (tested the new one too)
KNOCK Sensor
(I'm sure there's more but I'm tired as hell right now)
I have sprayed carb clean in the throttle body while running to determine if it's fuel related - and NO CHANGE, so I'm inclined to say it does have something to do with the spark - just what?! Why does it seem like the O2 sensor for Bank 1 just go down to 100mV?! I have NOT O-Scoped the firing wave patterns yet (that's tomorrow) but this has really bit me in the ass, but I have NEVER let a vehicle go with out finding out the root cause of the problem and fixing it, and I'm not gonna start now.
4.3 CPI (Yes, the spider injection, VIN=W)
4x2
All temps in working are have been @ ~60 Degrees F with LOW relative humidity
I currently have a 1997 GMC Safari (Same as Astro - just GMC Style) that is missing. It won't miss when free-revving it (In Park or neutral) but as soon as you put it in drive i'll stumble for a sec and than from there any time you go more than 1/4 throttle, it'll miss like a SOB. WILL NOT DO THIS IN REVERSE - just in Drive, 3, 2, 1. It originally came in for dieing and found that the Ignition Control Module was bad (It was giving a code P1351 - IC Circuit High/Open) - that's when it started doint this missing. I have tried to put back the OLD module - but it won't even run with the old module anymore.(I'll sit and crank, crank, and crank) It will 'work itself out' if you hold the throttle there for 3-4 minutes (the miss) but as soon as you give it more gas it'll start missing agian. It does NOT matter if it's hot or cold.
I have the MODIS scanner and have gotten some values while missing...
O2 Sensors -
B1-S1=156 mV (for the duration of the missing, than jump back to normal) (Cyl 1, 3, 5)
B2-S1=100-900 (Normal readings) (Cyl 2, 4, 6)
B1-S3=300-500 (Before cat)
BOTH SETS of injectors are opening at 13.4+ms
Codes:
P0300 - Multiple cylinder missfire
P1351 - IC Circuit High/Open (Take care of with the changing of the Ign. Control Module)
This problem was dropped off from ANOTHER shop (They where like fawk it) and because I'm the lead drivability tech at my shop - I get the gift of figuring this out. I seriously need some help here, I'M LOOSING MY ASS. I have gone through the steps-by-steps from Mitchell for the following sensors:
CAM Sensor
CRANK Sensor
IGN Module (tested the new one too)
KNOCK Sensor
(I'm sure there's more but I'm tired as hell right now)
I have sprayed carb clean in the throttle body while running to determine if it's fuel related - and NO CHANGE, so I'm inclined to say it does have something to do with the spark - just what?! Why does it seem like the O2 sensor for Bank 1 just go down to 100mV?! I have NOT O-Scoped the firing wave patterns yet (that's tomorrow) but this has really bit me in the ass, but I have NEVER let a vehicle go with out finding out the root cause of the problem and fixing it, and I'm not gonna start now.
