iamdub
Full Access Member
Milk jug is way too thick. IIRC, a standard aluminum soda can is really close to the specified thickness. It'd be a PITA to cut that shape of ring, though.
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Dreaded Random Misfire at high speed or under load- next steps?
- Thread starter Tbruz
- Start date
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Milk jug is way too thick. IIRC, a standard aluminum soda can is really close to the specified thickness. It'd be a PITA to cut that shape of ring, though.
If his other shims are still good he can reuse.
You didn't mention having shims under CPS, I have only seen one truck that contacted CPS and required shims. Look for a stripe on end of sensor. Use old sensor to determine if you need a shim. No stripe = no shim required. CPS generally work better the closer they get.
Tbruz
Full Access Member
Latest update as of 2:00 10/24.
I installed brand new AcDelco distributor yesterday and retimed; No Change.
Took it out for a highway up hill pull and it stared misfiring at around 75MPH.
Back into the garage to replace the Crank position sensor(CPK); installed a new sensor and I could NOT get vehicle to start. Tried with shims x1 x2 x3 and with no shims. - same results crank - but no start. I suspect I received a bad AcDelco part. Put back my old Crank sensor and the truck fired right up. I've ordered a replacement AcDelco Crank sensor and it should be here today( Gotta love Amazon!)
Today I decided to dig into the timing chain itself. I have torn down the front to the engine and found an extremely sloppy chain; I'm in cleaning mode right now and there are a bunch of while you're in there items I'm doing simultaneously, oil change, replace high pressure oil lines, new hoses....so I wont have it all back together today to prove once and for all what the root cause of the misfire is............waiting on the cam gear to heat up right now so I can slip that back on......
Will update hopefully tomorrow with results.
Thanks for everyone's help
Tbruz
I installed brand new AcDelco distributor yesterday and retimed; No Change.
Took it out for a highway up hill pull and it stared misfiring at around 75MPH.
Back into the garage to replace the Crank position sensor(CPK); installed a new sensor and I could NOT get vehicle to start. Tried with shims x1 x2 x3 and with no shims. - same results crank - but no start. I suspect I received a bad AcDelco part. Put back my old Crank sensor and the truck fired right up. I've ordered a replacement AcDelco Crank sensor and it should be here today( Gotta love Amazon!)
Today I decided to dig into the timing chain itself. I have torn down the front to the engine and found an extremely sloppy chain; I'm in cleaning mode right now and there are a bunch of while you're in there items I'm doing simultaneously, oil change, replace high pressure oil lines, new hoses....so I wont have it all back together today to prove once and for all what the root cause of the misfire is............waiting on the cam gear to heat up right now so I can slip that back on......
Will update hopefully tomorrow with results.
Thanks for everyone's help
Tbruz
Tbruz
Full Access Member
Sunday 4 PM update:
Job completed; I struggled with the timing set but I overcame that issue and finished the job.
Took it out for a test run/uphill pull and yup........I still get a random misfire above 75 MPH.
To make matters worse I have a slight leak on the BRAND NEW AcDelco water pump from where the hard line meets the top of pump body...if this doesn't heal itself ill be replacing this new pump shortly with a non AcDelco one... Two bad AcDelco professional parts(crank sensor and water pump) in the past two days...I'm done with them!!
EDIT: Thankfully the water pump leak issue resolved itself; only one bad AcDelco part the crank sensor
Last week was new spider and fuel filter; this weekend new timing set and a new Crank sensor along with a brand new dizzy in the past two days and i'm still getting a random misfire above 75 MPH..............
Could the mote or just be plain worn out at 212K?
Next ideas appreciated.
Thanks
Tbruz
Job completed; I struggled with the timing set but I overcame that issue and finished the job.
Took it out for a test run/uphill pull and yup........I still get a random misfire above 75 MPH.
To make matters worse I have a slight leak on the BRAND NEW AcDelco water pump from where the hard line meets the top of pump body...if this doesn't heal itself ill be replacing this new pump shortly with a non AcDelco one... Two bad AcDelco professional parts(crank sensor and water pump) in the past two days...I'm done with them!!
EDIT: Thankfully the water pump leak issue resolved itself; only one bad AcDelco part the crank sensor
Last week was new spider and fuel filter; this weekend new timing set and a new Crank sensor along with a brand new dizzy in the past two days and i'm still getting a random misfire above 75 MPH..............
Could the mote or just be plain worn out at 212K?
Next ideas appreciated.
Thanks
Tbruz
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wjburken
Supporting Member
I try and avoid anything from AC Delco that is not OEM. Their Professional series, or Gold series now, is a step down from OEM.
Sorry to hear you’re still getting the mis-fire. Looks like you’ve done about everything that you can do.
Agreed, don’t buy AC Delco professional, get the OEM line.
I see two things to try. Wrap a small strip of paper towel underneath hose not touching water pump proper. Might just be a hose leak.
On the misfire, Try resetting the coil wire, or even replacing. Sometimes a 90 degree turn will dig in for better contact.
I still think you should go through your scanner and graph or log live data when you are misfireing. Could be as simple as a spark plug. Just need a direction to go.
Thanks for keeping us updated.
On the misfire, Try resetting the coil wire, or even replacing. Sometimes a 90 degree turn will dig in for better contact.
I still think you should go through your scanner and graph or log live data when you are misfireing. Could be as simple as a spark plug. Just need a direction to go.
Thanks for keeping us updated.
Tbruz
Full Access Member
Final update: 1 year later. After confirming a misfire via scanning live misfire data it was observed that one of the plug wires recently replaced(Ac Delco) was actually bad as well-right out of the box. Confirmed via spray test(water misted onto the wires while truck is running) and you could see the spark jumping from the boot end of the wire to the block. I'm so done with the crap quality of brand new parts these days. Truck runs smooth has silk now.
