03 ZO6 replaced fuel injectors, still misfiring/bogging down /hesitating/bucking
06-13-2018, 06:18 PM
#1
Instructor
Thread Starter
03 ZO6 replaced fuel injectors, still misfiring/bogging down /hesitating/bucking
Hey guys made a thread a few weeks ago trying to diagnose my car. Thought it was fuel injectors so I replaced all of them. Still having the same issue.
LS2 motor with less than 5k miles on it. Fresh head job, perfect compression.
Scanned it with my friends GM scanner, even with it plugged in while driving, giving live info during a misfire episode it wouldnt throw a code other than p0300
As of two weeks ago only after start up, while crusing at a steady pace around 1.5-2K rpm the car will start misfiring/bogging down /hesitating/bucking if I just keep my foot on the pedal giving it gas it will continue to misfire for 10-30 seconds then "kick back on" to normal power again.
When it has started doing this and I got caught at a red light I had to rev it up and give it gas or else it will flood itself and die. I say flood because when it does this I can smell a strong fuel odor burning in my exhaust.
Any ideas what to swap next? Coil packs, Plug wires, new spark plugs (again), 02 sensors, vaccum leaks?
Thanks....
LS2 motor with less than 5k miles on it. Fresh head job, perfect compression.
Scanned it with my friends GM scanner, even with it plugged in while driving, giving live info during a misfire episode it wouldnt throw a code other than p0300
As of two weeks ago only after start up, while crusing at a steady pace around 1.5-2K rpm the car will start misfiring/bogging down /hesitating/bucking if I just keep my foot on the pedal giving it gas it will continue to misfire for 10-30 seconds then "kick back on" to normal power again.
When it has started doing this and I got caught at a red light I had to rev it up and give it gas or else it will flood itself and die. I say flood because when it does this I can smell a strong fuel odor burning in my exhaust.
Any ideas what to swap next? Coil packs, Plug wires, new spark plugs (again), 02 sensors, vaccum leaks?
Thanks....
06-13-2018, 07:09 PM
#2
Instructor
What fuel injectors and size did you install? Was the LS2 tuned for the original or current injectors? When you say flood I think of bigger injectors on a stock tune.
Also so check your plugs and wires and the condition of where the coil packs and injectors connect to the harness.
Also so check your plugs and wires and the condition of where the coil packs and injectors connect to the harness.
Last edited by evolmotorsprt; 06-13-2018 at 07:10 PM.
06-13-2018, 08:03 PM
#3
Uneducated overachiever
I would suspect loss of spark/spark breakdown before fuel based on your description of the symptoms. Check per evolmotorsprt directions and see what you find.
06-13-2018, 08:43 PM
#4
Moderator, Tech Contributor
Member Since: Sep 2013
Location: Cape Coral, Florida
Posts: 9,525
Received 2,125 Likes
on
1,690 Posts
Hello Mr. Dom !!
What data PIDS were you looking at with your friends Tech 2 ??...I'd be looking at your your O2 sensors and long and short fuel trims...also MAF gm/sec at idle and under load...also Baro and ECT PIDS...were you able to do this ??...you said you were looking at live data driving...if you can post these here I probably give you some direction (numbers at idle and 3000 RPM)..now you said you changed injectors...did you check the injectors for feed and signal ??...if either were no good new injectors won't help ya !!...now as far as vacuum leaks the car will run better under load but crappy at idle...vacuum leak fuel trim numbers are high at idle and more normal at high RPM...you don't have a vacuum leak !!...you can check your fuel trims with that Tech 2...a bad MAF sensor or low fuel pressure will have good trim numbers at idle and high fuel trim numbers at high RPM. I don't know if you know how to read Mode 6 data but I'd look there (A2 -A9)...you most likely will find your cylinder that is misfiring there...maybe your friend that owns the Tech 2 is familiar with mode 6. You can probably do a cylinder balance test with that Tech 2...or just pull each plug wire and see if you notice a change in RPM...with 8 cylinders it's a little more difficult to tell...I don't know what else to tell you...if you want to just fire the "parts cannon" go for plug wires, coil packs, O2 sensors, MAF sensor, fuel pump...if you need direction on how to check some things let me know.
p.s. Fuel pressure KOEO is 55-62...with key off less than 5 psi drop in 1 minute !!...with engine running fuel pressure should NOT drop when you snap the throttle !!
What data PIDS were you looking at with your friends Tech 2 ??...I'd be looking at your your O2 sensors and long and short fuel trims...also MAF gm/sec at idle and under load...also Baro and ECT PIDS...were you able to do this ??...you said you were looking at live data driving...if you can post these here I probably give you some direction (numbers at idle and 3000 RPM)..now you said you changed injectors...did you check the injectors for feed and signal ??...if either were no good new injectors won't help ya !!...now as far as vacuum leaks the car will run better under load but crappy at idle...vacuum leak fuel trim numbers are high at idle and more normal at high RPM...you don't have a vacuum leak !!...you can check your fuel trims with that Tech 2...a bad MAF sensor or low fuel pressure will have good trim numbers at idle and high fuel trim numbers at high RPM. I don't know if you know how to read Mode 6 data but I'd look there (A2 -A9)...you most likely will find your cylinder that is misfiring there...maybe your friend that owns the Tech 2 is familiar with mode 6. You can probably do a cylinder balance test with that Tech 2...or just pull each plug wire and see if you notice a change in RPM...with 8 cylinders it's a little more difficult to tell...I don't know what else to tell you...if you want to just fire the "parts cannon" go for plug wires, coil packs, O2 sensors, MAF sensor, fuel pump...if you need direction on how to check some things let me know.
p.s. Fuel pressure KOEO is 55-62...with key off less than 5 psi drop in 1 minute !!...with engine running fuel pressure should NOT drop when you snap the throttle !!
Last edited by C5 Diag; 06-14-2018 at 12:33 PM.
06-14-2018, 02:19 PM
#5
Instructor
Thread Starter
What fuel injectors and size did you install? Was the LS2 tuned for the original or current injectors? When you say flood I think of bigger injectors on a stock tune.
Also so check your plugs and wires and the condition of where the coil packs and injectors connect to the harness.
Also so check your plugs and wires and the condition of where the coil packs and injectors connect to the harness.
Last edited by ZO6_Dom; 06-14-2018 at 02:21 PM.
06-17-2018, 09:15 PM
#7
Instructor
Thread Starter
Just replaced spark plug wires. Spark plugs. Header gaskets. Still did its usual cold start misfire before I even got down the street. 02 sensors and coil packs next? 
06-17-2018, 11:42 PM
#8
Drifting
Member Since: Jul 2011
Location: Boise, ID
Posts: 1,589
Received 377 Likes
on
187 Posts
2022 C5 of the Year Finalist - Modified
2021 C5 of the Year Finalist - Modified
C5 of Year Finalist (appearance mods) 2019
Before throwing anymore parts at the problem. I would bust out the multimeter and check voltage on the injector pigtails with the key in the on position and not running. I just successfully troubleshooted my p0300 in this thread. Check it out, maybe it will be of some use to you troubleshooting your issue.
https://www.corvetteforum.com/forums...ine-build.html
https://www.corvetteforum.com/forums...ine-build.html
06-18-2018, 03:11 PM
#10
Melting Slicks
When (whomever) was doing the major engine work, did they disconnect any of the wiring around the torque tube area?
I had a similar issue many years ago - source was the mechanic did not reconnect a cable retaining clip to the body - car ran fine for a while, vibration/bumps etc caused the cable to move, wore through the insulation, groundout.
Sputter, buck, no power. (we're talking 3rd gear at 55 or so, foot to the floor losing speed) additional vibration, etc, the wire shifted again, power restored.
Took the car back in - they found the disconnected retainer and the harness pinched between the torque tube housing and chassis.
This caused an intermittent groundout and the same symptoms you describe.
fixed the harness, reconnected the retainer - no more problem.
I had a similar issue many years ago - source was the mechanic did not reconnect a cable retaining clip to the body - car ran fine for a while, vibration/bumps etc caused the cable to move, wore through the insulation, groundout.
Sputter, buck, no power. (we're talking 3rd gear at 55 or so, foot to the floor losing speed) additional vibration, etc, the wire shifted again, power restored.
Took the car back in - they found the disconnected retainer and the harness pinched between the torque tube housing and chassis.
This caused an intermittent groundout and the same symptoms you describe.
fixed the harness, reconnected the retainer - no more problem.
Last edited by aj98; 06-18-2018 at 03:13 PM.
06-18-2018, 07:49 PM
#11
Instructor
Thread Starter
Car is now throwing tons of codes. Here's the list.....
PCM
P0135 C - Drivers side 02 sensor
P0155 H. C - Passenger side 02 sensor
P0522 H - Oil Pressure Sensor
P1637 H - Generator L terminal circuit PCM connections and grounds.
TCS
C1214 H C - EBCM bad relay
C1282 H - Yaw rate sensor bias circuit malfunction
C1287 H - Steering rate malfunction
C1288 H - Steering wheel position sensor
C1296 H - Master cylinder sensor circuit
SDM
U1016 H - Loss of connection with PCM
IPC
B0521 H Tachometer Signal Circuit malfunction - issues with the IPC reading rpm signals from the PCM
U1255 H Serial data line malfunction
HVAC
B0333 H C - outside air temp open
B0361 H C - left actuator short to GND
B0441 H - left actuator out of range
LDCM
B2284 H - battery #2 fault
B2262 H - horizontal position sensor fault
B2264 H - verticle position sensor fault
U1016 H - loss of communications with PCM
U1096 H - Loss of communications with IPC
RDCM
U1016 H - loss of communications with PCM
U1096 H - Loss of commutation with IPC
PCM
P0135 C - Drivers side 02 sensor
P0155 H. C - Passenger side 02 sensor
P0522 H - Oil Pressure Sensor
P1637 H - Generator L terminal circuit PCM connections and grounds.
TCS
C1214 H C - EBCM bad relay
C1282 H - Yaw rate sensor bias circuit malfunction
C1287 H - Steering rate malfunction
C1288 H - Steering wheel position sensor
C1296 H - Master cylinder sensor circuit
SDM
U1016 H - Loss of connection with PCM
IPC
B0521 H Tachometer Signal Circuit malfunction - issues with the IPC reading rpm signals from the PCM
U1255 H Serial data line malfunction
HVAC
B0333 H C - outside air temp open
B0361 H C - left actuator short to GND
B0441 H - left actuator out of range
LDCM
B2284 H - battery #2 fault
B2262 H - horizontal position sensor fault
B2264 H - verticle position sensor fault
U1016 H - loss of communications with PCM
U1096 H - Loss of communications with IPC
RDCM
U1016 H - loss of communications with PCM
U1096 H - Loss of commutation with IPC
06-18-2018, 07:49 PM
#12
Instructor
Thread Starter
When (whomever) was doing the major engine work, did they disconnect any of the wiring around the torque tube area?
I had a similar issue many years ago - source was the mechanic did not reconnect a cable retaining clip to the body - car ran fine for a while, vibration/bumps etc caused the cable to move, wore through the insulation, groundout.
Sputter, buck, no power. (we're talking 3rd gear at 55 or so, foot to the floor losing speed) additional vibration, etc, the wire shifted again, power restored.
Took the car back in - they found the disconnected retainer and the harness pinched between the torque tube housing and chassis.
This caused an intermittent groundout and the same symptoms you describe.
fixed the harness, reconnected the retainer - no more problem.
I had a similar issue many years ago - source was the mechanic did not reconnect a cable retaining clip to the body - car ran fine for a while, vibration/bumps etc caused the cable to move, wore through the insulation, groundout.
Sputter, buck, no power. (we're talking 3rd gear at 55 or so, foot to the floor losing speed) additional vibration, etc, the wire shifted again, power restored.
Took the car back in - they found the disconnected retainer and the harness pinched between the torque tube housing and chassis.
This caused an intermittent groundout and the same symptoms you describe.
fixed the harness, reconnected the retainer - no more problem.