BoostedSUV
Active member
Ok Guys, it has been requested of me to start a new thread (based of my "One Last Shot" thread) to try and compile and condense everything I have tried to attempt to solve my truck's breaking up through the exhaust issues. I know the other thread got long (46 pages/700 posts) and it was getting hard to follow and jump on board. Please bear with me, there's a lot of info and I'm sure I've forgotten a lot.....
Dating back to 2006 I've had a very RPM specific "misfire" through the exhaust at cruising speeds when the trucks warms up. The RPM spots were 1100, 1900, and 2500 consistantly (with the 50# injectors). I've since changed to 65's and the miss moved up the scale about 300 RPM's and is now at 2200, and 2800. The lower RPM "misses" are more like a slight quick hesitation, but the 2500 (which is now 2800) is very drastic and more pronounced. At the time of the miss the O2 counts drop below 100 (indicating lean) and the WBO2 climbs to 17+ also indicating lean. The S-term counts jump to +42 if I hold the throttle position at the specific RPM and it will continue to "miss", but the truck will not clear up until I continue to increase throttle position to get passed it. During hard acceleration, at WOT, anything in boost, or anywhere passed 3000rpm's the truck runs perfect. It only seems to act up when I slowly increase spead or throttle to the "trouble spots" I can hear the popping out of the exaust and not the intake...
How it all started: I did not noticed this issue until I had a full rebuild done on the motor (.030 over, eagle rods, srp pistons, 412 cam, stock heads etc) after blowing up the original motor. With the new motor I added an ultimate chip, 50#er's, an A2A IC, AFPR, and relocated battery. That's all... Since that time the motor has been out 4 times (don't ask) and each time I put the motor in the problem still existed. Even after I swapped over to Vortec heads, different lower intake, custom Nolan tune (after the last removal). That's the gist of the "issue" and the point it started..the truck ONLY does it when it warms up to operating temps, it runs and idles perefect cold. Also the truck (once warm) idles steady at 850 but the O2 and WBO2 bounce all over the place. The problem has come and gone at times, and gets less noticable when it's "gone" but right now it's not even really drivable. The truck will fall on it's face when it hits those RPMS and miss and bucks until it get beyond them. I haven't driven the truck since June, and I have been determined to solve this once and for all since then...
now for what I tried.
new ECM
new Distributor (went from MSD to a stock tester)
changed coil pickup and ign module in MSD prior to changing
2 different O2 sesnors
new map sensor
replaced engine wire harness
replaced injector harness
swapped coils
new plugs/wires/cap/rotor
moved plug gap from .025 to .022
chased grounds and added grounds
ran truck with out alternator (looking for elec feedback)
new fuel pump
checked AFPR
new injectors
switched from Ultimate chip to Moates adapter and Nolan tune
ran truck on stock memcal
leak down tested the motor
changed throttle bodies
new TPS and IAC (verified both work)
new upper intake and TB gaskets
New vac line kit (vac tested each line)
verified all sensors operate properly
scoped the dizzy and checked for spark 'drop out'
verified timing at specific RPM's (stays solid)
Fuel Pressure is perfect and rises and falls as it's suposed to
ran with Cat and no Cat
ran truck with O2 connected and disconnected (to test open vs closed loop operation)
changed FP (gets worse when raise pressure/gets better when lower pressure)
Tested grounds with VM
tested voltage to injectors (13.8 at all times)
ran ECM voltage fix (13.8v)
Vacuum reads 18ish at Idle and doesn't do anything crazy with increased RPM
Checked PCV system (best way to my knowledge)
Verified TDC mark on balancer
ran truck with and without MSD 6A connected
I'm sure I forgot some things... I'm in the process of reading through 46 pages and pulling out the important stuff. I'm sure stuff will get added on by others!
Dating back to 2006 I've had a very RPM specific "misfire" through the exhaust at cruising speeds when the trucks warms up. The RPM spots were 1100, 1900, and 2500 consistantly (with the 50# injectors). I've since changed to 65's and the miss moved up the scale about 300 RPM's and is now at 2200, and 2800. The lower RPM "misses" are more like a slight quick hesitation, but the 2500 (which is now 2800) is very drastic and more pronounced. At the time of the miss the O2 counts drop below 100 (indicating lean) and the WBO2 climbs to 17+ also indicating lean. The S-term counts jump to +42 if I hold the throttle position at the specific RPM and it will continue to "miss", but the truck will not clear up until I continue to increase throttle position to get passed it. During hard acceleration, at WOT, anything in boost, or anywhere passed 3000rpm's the truck runs perfect. It only seems to act up when I slowly increase spead or throttle to the "trouble spots" I can hear the popping out of the exaust and not the intake...
How it all started: I did not noticed this issue until I had a full rebuild done on the motor (.030 over, eagle rods, srp pistons, 412 cam, stock heads etc) after blowing up the original motor. With the new motor I added an ultimate chip, 50#er's, an A2A IC, AFPR, and relocated battery. That's all... Since that time the motor has been out 4 times (don't ask) and each time I put the motor in the problem still existed. Even after I swapped over to Vortec heads, different lower intake, custom Nolan tune (after the last removal). That's the gist of the "issue" and the point it started..the truck ONLY does it when it warms up to operating temps, it runs and idles perefect cold. Also the truck (once warm) idles steady at 850 but the O2 and WBO2 bounce all over the place. The problem has come and gone at times, and gets less noticable when it's "gone" but right now it's not even really drivable. The truck will fall on it's face when it hits those RPMS and miss and bucks until it get beyond them. I haven't driven the truck since June, and I have been determined to solve this once and for all since then...
now for what I tried.
new ECM
new Distributor (went from MSD to a stock tester)
changed coil pickup and ign module in MSD prior to changing
2 different O2 sesnors
new map sensor
replaced engine wire harness
replaced injector harness
swapped coils
new plugs/wires/cap/rotor
moved plug gap from .025 to .022
chased grounds and added grounds
ran truck with out alternator (looking for elec feedback)
new fuel pump
checked AFPR
new injectors
switched from Ultimate chip to Moates adapter and Nolan tune
ran truck on stock memcal
leak down tested the motor
changed throttle bodies
new TPS and IAC (verified both work)
new upper intake and TB gaskets
New vac line kit (vac tested each line)
verified all sensors operate properly
scoped the dizzy and checked for spark 'drop out'
verified timing at specific RPM's (stays solid)
Fuel Pressure is perfect and rises and falls as it's suposed to
ran with Cat and no Cat
ran truck with O2 connected and disconnected (to test open vs closed loop operation)
changed FP (gets worse when raise pressure/gets better when lower pressure)
Tested grounds with VM
tested voltage to injectors (13.8 at all times)
ran ECM voltage fix (13.8v)
Vacuum reads 18ish at Idle and doesn't do anything crazy with increased RPM
Checked PCV system (best way to my knowledge)
Verified TDC mark on balancer
ran truck with and without MSD 6A connected
I'm sure I forgot some things... I'm in the process of reading through 46 pages and pulling out the important stuff. I'm sure stuff will get added on by others!
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