misfire headache

[00 white lightn]

installed new plugs,new plug boots and springs. new fuel filter, did fuel injection service. scanned for injector faults, found none. Egr tube has a small leak (fabricated tube from header install) i will repair this today. I am not 100 percent sure if the header is leaking or not I will find out after i repair the egr tube. But i have been driving it for about 3 days with a Low rpm missfire 1500-2300 or so. after 2300 it doesnt misfire anymore. It is only under light acceleration also. if you give it more throttle it doesnt do it anymore. Anyone have any ideas. the truck made good power on the dyno. it is running rich, so i know it shouldnt be a fuel issue. The 02's are all switching. only thing i can think of is a coil pack, but i have no misfire codes. Possibly the exaust leak could be causing the misfire. Here is my theory behind the exaust leak misfire. If you have an exaust leak. You will read lean on that side. So the ecu dumps more fuel to compensate. Then you are flooding the engine and it cannot burn all the fuel at low rpms. So maybe at higher rpms it is burning it all, hence no missfire. I would appreciate anyones input. I also checked for leaks around the intake, and cold air intake and throttle body, also checked for leaks around the injectors. Maybe I have not driven the truck enough to throw a code? :shrug:

 

[PhLoBuS]

does it feel like the truck is slightly bumping?

 

[00 white lightn]

misfire

yes it is bumping, jerking only around 1500-2300 rpm, doesnt do it at idle or more than about 1/4 throttle, i think its my egr tube. I still havent fixed the egr tube leak

 

[00 white lightn]

?

i fixed the egr tube leak. the driver side header is leaking slightly i believe, but i was told this would nto affect the way it runs. i put plugs, coil pack boots and springs on it, checked all vacumes, checked all intake gaskets, tb gasket. no injector faults found with the scan tool. no codes found. i replaced the fuel filter, did an injection service to clean the injectors. It will not stop the low rpm misfire, i pressure tested the coolant system and i lost no pressure so i am assuming it has no bad head gasket, i tested it hot and cold. even running. it only misfires under light load at low rpms. which is annoying at low speeds cruising with the truck shaking and bucking. could my dpfe be bad? wouldnt this throw a code. could my egr valve be bad. would that throw a code also? and with all this misfiring. Why isnt it throwing a misfire code.

 

[PhLoBuS]

yeah I am having that SAME problem where the truck is like shaking/bumping around 1-2k rpms... so annoying. something is not right, i am sure someone knows the solution

 

[00 white lightn]

latest update, i replaced the egr sensor, dpfe sensor, and egr vacume solenoid, same problem, low rpm misfire, i was reading 1.2 volts from the dpfe at idle on the scan tool. i was told it should be .2 volts, but i just replaced the dpfe. and i have 4-6 volts at the connector which is the correct voltage. i also have 1.6 inch of vacume at idle on the egr valve which is correct, i have 22 in of intake vacume which is also normal. any ideas? if i unplug the egr it runs perfect. i could do an egr delete, but i would like to keep it if i can.

 

[bgstew6]

bad egr valve? might be sticking open on ya?

 

[00 white lightn]

misfire

i replaced the egr, i have the same problem. fuel trim looks good, is it going through a computer relearn? i read 1.0-1.2 volts on the dpfe. i can tell you any information the pcm is seing if you think you might know something to check chime in and let me know

 

[00 white lightn]

misfire

i compared pcm data readings with the egr plugged up and unplugged since the problem only occurs with the egr working. my timing is about 16 degrees at idle, cruising around 50-55 mph its about 30 degrees timing, this is with the egr off, well when i plug it up. my timing jumps up to about 40-45 degrees at low rpms. when i floor it it drops, 45 degrees of timing sounds like it is firing before the piston is near the top of the stroke, it is firing too soon. anyone have any input? it runs good at 30 degrees of timing adv. i am on the factory tune why would the factory tune be advancing the timing so much