m.mcmillen
Member
A CASE relearn wouldn't hurt. I've seen it help with some misfire issues.
Very Slight Miss at Idle
- Thread starter Mooseman
- Start date
I think you should just put a new sensor in and do a CASE relearn considering all the other things you've gone over and tried. That was the only thing that remedied all my issues.
I ordered one and it's on its way. Will try a CASE relearn anyway. Can't hurt and costs nothing.
Best of luck bud, hope this'll solve your idle gremlins.
CASE relearn did squat.
Maybe I'm looking at it the wrong way. While talking with my son, was musing about lowering the compression of the other cylinders to match. What if the other cylinders are higher than what they should be due to carbon? I'll search for what others get on theeir compression tests and what the manual says. I.might just treat the entire engine to TEC.
Maybe I'm looking at it the wrong way. While talking with my son, was musing about lowering the compression of the other cylinders to match. What if the other cylinders are higher than what they should be due to carbon? I'll search for what others get on theeir compression tests and what the manual says. I.might just treat the entire engine to TEC.
I_Shoot_Back
Member
maybe your engine needs a good "grandma tune". Taking grandma's car out on the highway and drive the living piss out of it for about 15 miles to blow all the carbon and slush build up out of her.
littleblazer
Member
- Jul 6, 2014
- 9,267
If it's within 10% that wouldn't do it... Plug the PCV (vent thingy under the air box?) and see if it goes away after idling for a minute... I am curious now.
That's just it, I always drive it like I stole it.
Isn't that usually for a lifter tick?
Additional info. LTFT is now in the 10 to 12% at idle but drops to 6~7% at higher RPM.
I'm just pulling my grey hair out now. Next I'll be throwing some premium into the tank just in case the ethanol junk is doing something.
That's the fix for loud lifters.
I can attest to premium making some-what of a difference, that's why I run it.
littleblazer
Member
- Jul 6, 2014
- 9,267
It'll help with ring control too... Free to try and is easy as shit to do, just saying.
Winter time is hard to do an Italian tuneup. I might even try a whole can of Seafoam through the brake hose. Might have to use the Tech 2 to hold the RPM for me.
Still have the crank sensor coming.
Still have the crank sensor coming.
littleblazer
Member
- Jul 6, 2014
- 9,267
Can you watch the crank sensor square wave with the tech 2 and see if its dropping out? I just find it strange that it's only number 4 still.
The #4 Position along the Exhaust Flange of the Head is the "Pivot Point" where the 'rocking up and down' action of the Exhaust System usually causes the EM Bolts on the #1 & #2 positions to work harden ...and snap off. If you examine the Aluminum Exhaust Flange surface around the two bolts holding the EM firmly to the head at the #4 Cylinder and can see a wider area of a "Rusty-Bronze" Halo looking patina under the MLS Gasket... it is the clue that likely, one of them has broken off flush with head and the remaining Head/Stud piece has rusted fast inside of the Cast Iron EM Bolt Hole... concealing the underlying break.
This suggestion is prompted by what @littleblazer mentioned earlier about the "Paper-Flutter" test for Worn/Warped Valves and would be one additional place to look for un-metered air to get sucked back into the Exhaust Port during Valve Overlap ...and mess with the F/A ratio. I found these "Rusty-Bronze" patina markings very evident on the EM head flange during the engine tear-down of my '04 LL8. The only labor necessary for this inspection is the removal of the Heat Shield and a "Calibrated Eye-Ball" focused over the area adjacent to the #4 Flange:
This suggestion is prompted by what @littleblazer mentioned earlier about the "Paper-Flutter" test for Worn/Warped Valves and would be one additional place to look for un-metered air to get sucked back into the Exhaust Port during Valve Overlap ...and mess with the F/A ratio. I found these "Rusty-Bronze" patina markings very evident on the EM head flange during the engine tear-down of my '04 LL8. The only labor necessary for this inspection is the removal of the Heat Shield and a "Calibrated Eye-Ball" focused over the area adjacent to the #4 Flange:
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That is certainly another avenue to pursue. And as luck would have it, if needed, I have a spare updated exhaust manifold from the '02, which is the same.
It does have a graph of sorts for misfires but haven't seen anything for sensors. All it is is a counter for misfires. I think I would have to log data and then export it to the laptop to put it in an actual graph. Haven't delved that far into yet.
It does have a graph of sorts for misfires but haven't seen anything for sensors. All it is is a counter for misfires. I think I would have to log data and then export it to the laptop to put it in an actual graph. Haven't delved that far into yet.
psa55
Member
Hey Mooseman, have you found a solution to the miss at idle?
I still get the random P0300 code once or twice a month for a day or so.... seems everytime I spend too long in a drive thru. #6 mostly, and #4 sometimes, misfire at idle still. When on the gas and when driving the 4.2 works great with no misses.
I spent a lot of my fall chasing similar issues that you describe on yours. My compression checks out okay. I had spoke with my dealer about an injector balance test and a leak down test, but haven't gotten the TB in to them. Shop foreman said drive it, he has seen similar issues that people have just driven with for years on the TB/Envoy. Here is the thread: https://gmtnation.com/forums/threads/p0300-where-to-start.19008/#post-567942
This spring, when it warms up, I'll be getting close to oil change time, and plan to do the AC Delco TEC procedures to see if it helps. I haven't done the CKP, but could give it a shot too.
253 000 kms now, but still working well, other than the misfires at idle. Was hoping you found a solution that might help me out?
Thanks!
I still get the random P0300 code once or twice a month for a day or so.... seems everytime I spend too long in a drive thru. #6 mostly, and #4 sometimes, misfire at idle still. When on the gas and when driving the 4.2 works great with no misses.
I spent a lot of my fall chasing similar issues that you describe on yours. My compression checks out okay. I had spoke with my dealer about an injector balance test and a leak down test, but haven't gotten the TB in to them. Shop foreman said drive it, he has seen similar issues that people have just driven with for years on the TB/Envoy. Here is the thread: https://gmtnation.com/forums/threads/p0300-where-to-start.19008/#post-567942
This spring, when it warms up, I'll be getting close to oil change time, and plan to do the AC Delco TEC procedures to see if it helps. I haven't done the CKP, but could give it a shot too.
253 000 kms now, but still working well, other than the misfires at idle. Was hoping you found a solution that might help me out?
Thanks!
Cold weather and lack of a garage has put this on hold for now. Yeah, same with me if I idle it too long. I'll be tackling the TEC, crank sensor, O2 sensor in the spring. Someone had a slight miss that was caused by a cracked brake booster vacuum hose.
Unfortunately a revival. 
Never really did solve this issue or it just never manifested itself again. The TB is starting to act up again. Some misfires and a very noticeable chugging when cruising at 80km/h (50mph) and trying to accelerate a little without disengaging the TCC. I did have a flashing CEL once but wasn't able to make it come on again. Had a P0300 code pending. So this is reminiscent to this old thread but I get random little misfires here and there in all the cylinders.
I know, wrong engine. Wish I had done it when I still had my old S&W
So last night, I ordered a set of ACDelco 41-103 plugs from RA because I don't trust the ones I put in there last time because they were from Amazon. And I also ordered a set of Amazon CCC coils but I haven't heard of anyone else having issues with them. I know it's a shotgun approach but I don't feel like continuing this 6 year old thread too much. The TB is now at about 190k km.
Funny thing, I was thinking of getting some used coils from the u-pull yard but they charge just as much as the CCC ones, plus the $5 entry fee.
Never really did solve this issue or it just never manifested itself again. The TB is starting to act up again. Some misfires and a very noticeable chugging when cruising at 80km/h (50mph) and trying to accelerate a little without disengaging the TCC. I did have a flashing CEL once but wasn't able to make it come on again. Had a P0300 code pending. So this is reminiscent to this old thread but I get random little misfires here and there in all the cylinders.
I know, wrong engine. Wish I had done it when I still had my old S&W
So last night, I ordered a set of ACDelco 41-103 plugs from RA because I don't trust the ones I put in there last time because they were from Amazon. And I also ordered a set of Amazon CCC coils but I haven't heard of anyone else having issues with them. I know it's a shotgun approach but I don't feel like continuing this 6 year old thread too much. The TB is now at about 190k km.
Funny thing, I was thinking of getting some used coils from the u-pull yard but they charge just as much as the CCC ones, plus the $5 entry fee.
I like the idea of "Using a Gun" here... But my choice of Armament would be to use either a Laser Thermometer ...or better yet... A FLIR Camera-Gun focused on taking readings from each of the Coil Over Plugs... Looking for the results of LEAN A/F conditions prompting the Plugs NOT to be able to Fire in the presence of a poorly conditioned Combustion Environment (Low Ionization of the Hydro-Carbon to Oxygen Atmosphere... under High Compression).
If this phenomena is actually what is happening ...the Secondary side of the Coil produces Excessively High KV Oscillations that will tend to force their way back into the Primary Side of the Coil(s)... and overheat their Epoxy & In-Dwelling Electronics enough to cause Transient Coil Misbehavior... Ending eventually in a Failed Coil.
When you Pull The Plugs... Look for any signs of Carbon Tracing along their Ceramic Insulators...and... along the Rubber Boots of the COPs, too as these are clear signs that the Primary Coil side is dissipating the KV Spark (Plasma) Energy on the --OUTSIDE-- instead of occurring within the Combustion Chambers of those Random Cylinders:
www.tomorrowstechnician.com
If this phenomena is actually what is happening ...the Secondary side of the Coil produces Excessively High KV Oscillations that will tend to force their way back into the Primary Side of the Coil(s)... and overheat their Epoxy & In-Dwelling Electronics enough to cause Transient Coil Misbehavior... Ending eventually in a Failed Coil.
When you Pull The Plugs... Look for any signs of Carbon Tracing along their Ceramic Insulators...and... along the Rubber Boots of the COPs, too as these are clear signs that the Primary Coil side is dissipating the KV Spark (Plasma) Energy on the --OUTSIDE-- instead of occurring within the Combustion Chambers of those Random Cylinders:
VIDEO: Diagnosing Carbon Tracking On Spark Plugs
Always make sure you inspect the old spark plugs and boots before you install the new plugs. This video is sponsored by Autolite.
www.tomorrowstechnician.com
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Right now, my weapon of choice is the shotgun
That's another thing I need to look at is the fuel trims. I know I fixed an air leak at the MAF and resonator to TB connection that helped fuel consumption. I'll probably look over everything under the hood when I do the plugs and coils.
That's another thing I need to look at is the fuel trims. I know I fixed an air leak at the MAF and resonator to TB connection that helped fuel consumption. I'll probably look over everything under the hood when I do the plugs and coils.
Got to my work garage to do some work on the TB. Started with the rear wiper motor and arm replacement to give a chance to the engine to cool first.
Well, I also come here to receive as many jibes as you guys can muster. I replaced my plugs and coils, and while I was there, cleaned out the throttle body. It was dirty but not horrible. However, I got a surprise when I pulled the plugs:
They were worn down to just nubs on the center electrodes. Installed less that 100k km ago. Surprised it ran at all. The ones I previously installed were the infamous fakes with the "Assembleda" on them. I can't believe I fell for these
. I still installed the new coils because I had them. Runs a whole lot smoother and no shakes.
Well, I also come here to receive as many jibes as you guys can muster. I replaced my plugs and coils, and while I was there, cleaned out the throttle body. It was dirty but not horrible. However, I got a surprise when I pulled the plugs:
They were worn down to just nubs on the center electrodes. Installed less that 100k km ago. Surprised it ran at all. The ones I previously installed were the infamous fakes with the "Assembleda" on them. I can't believe I fell for these
. I still installed the new coils because I had them. Runs a whole lot smoother and no shakes.
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The search function on the site sucks .
I just copied the post I previously did in the "What did you do to your GMT today" thread so have a look at the post previous to yours.
I haven't had a chance to check for misfires but I'm pretty sure they're gone. I know the coils I replaced needlessly but I'm the type that if I have to take a bunch of stuff apart to do something, I'll replace related parts while I'm there as I hate doing something twice. My time is more valuable.
.I just copied the post I previously did in the "What did you do to your GMT today" thread so have a look at the post previous to yours.
I haven't had a chance to check for misfires but I'm pretty sure they're gone. I know the coils I replaced needlessly but I'm the type that if I have to take a bunch of stuff apart to do something, I'll replace related parts while I'm there as I hate doing something twice. My time is more valuable.