For the future, coils are easy to diagnose. Unplug them one by one. If a coil is bad, you’ll notice when you unplug it the idle doesn’t change at all. I’d check for vacuum leaks. Start it up and while it’s cold spray some starting fluid or carb cleaner on the vacuum hoses to see if you can find one

As a DIY person (not a real technician) my only suggestion is to invest in a quality scan tool to isolate the problem. Electrical vs. fuel delivery. But after following you for a while I suspect you already knew that.

Check your engine mounts. Common to fail on the Envoy/Tralblazer. They will give you false sense that you have a misfire and it’s the mounts. Also, check the throttle body, it tends to gunk up. Also the camshaft positioning sensor can make the vehicle vibrate.

My 2 cents.. check the Mass Airflow Sensor as it may need replacing. Second to that, the throttle-body may require some cleaning .. lastly.. check if the O2 sensor is after the Catalytic Convertor, as it may be throwing codes to confuse the engine fuel & air mix. Let me know if it helps. Cheers!

I have that same engine in my Buick and the ignition coils are one of the few things I've ever had replace. That they were nearly 20 years old and had fired millions of times might have been the real issue. But, even the scan tool they loan you at the parts store was able to point at the correct cylinder for the misfire. Other that that and a water pump it's been quite trouble-free and it runs smooth as silk. When it's idleing at temp, you can't hardly tell it's running because it's so well balanced. If it's just running rough, I'd suspect a vacuum leak because that will mess with the AFR. If you have a smoke generator it's not hard to see where a leak is. Otherwise I've had luck with spraying brake cleaner around places I suspect a leak and listening for a change in the idle. One other possible thing to look at that's cheap to do is to get a can of throttle body cleaner and get the extra carbon out of the throttle body. That engine doesn't have an IAC valve, so it does regulate the idle by just slightly keeping the throttle plate open. Just remember not to move the throttle by hand inside the throttle body. Put the key in the ignition, put it in accessory and use the accelerator pedal to open the throttle plate. Then afterward, google the throttle relearn for that car, I can't remember how it went but it's pretty simple. Though, if you leave the battery disconnected for more than a few minutes, the PCU will basically run a relearn for the entire engine and it will rev itself up and down for a few minutes before calming down. In fact, that may have been what you experienced after replacing your coils because you did have the battery disconnected for an extended time.

When you pulled the spark plugs out, I think you should remove the plug from the socket and inspect the ceramic for carbon tracking …a black streak running up and down the ceramic portion. Even a small portion would affect it.

Another grand slam of a video Jimmy! Always nice when the Mrs makes an appearance!

G'evening Jimmy 🤠 . I have a 98' S10 Blazer w/ 315k on it. It has the 4.3 V6 vortech in it. When I bought it it was throwing multiple random cylinder misfire codes, so I changed the oil and the plugs & started running 2 bottles of Berryman B12 chemtool to a full tank to clean the tank, the fuel lines, the pump and the injectors. After 1 full tank it stopped misfiring and runs great. Take my word for it, give Berryman's a try and I bet you'll be glad you did. I hope this helps 🤠 ..

Jimmy i had an 05 trailblazer had the same issue andndid oretty much all that you have done to it but my problem was throttle body . I cleaned it many times till i decided to change it problem fixed .hope it helps

Jimmy, thanks for another cool video! Do include your lovely lady Farris in more of your videos, she is a cool person! Glad to see your Envoy has an inline 6 engine instead of the dreaded 3.6L V6. You need to buy a good quality scanner tool such as an Autel unit, takes the guesswork out. If this engine is direct injected, it may have a lot of crud on the back side of the intake valves restricting airflow into the engine.

You have a good channel! It deserves a good scanner!

Auto zone loves you guys! Here comes the parts cannon!

All parts cannons aside, you did what you thought was best. If it's vibrating, it might be your engine mounts.

Check the fuel trim. I have a $30 Launch device that reads engine codes and it will also read fuel trim. The Launch professional scanners are not that expensive. For someone like you who has a youtube channel, you should get one.

I like your videos, I recommend everyone have a car to own a scan tool. It helps me a lot, I can diagnose the problem by research the code and finding out what happens to my car and fixed it myself. Rough idle can be many different things, leaks of the valve gasket, clogged injectors, O2 sensor issues, air fuel mixture, compression, dirty throttle, dirty airflow sensor…I will start with cleaning throttle, sensor, and clean injectors, then checking for leaks next before replacing parts

Thanks for sharing your troubleshooting on this. Just a thought, have you done any cleaning of the intake manifold and injectors? I was able to see some pretty heavy carbon on one of the piston heads too when you provided that top down plug out view. Let me know if my thought helps you beat this particular gremlin.

Also try replacing the injectors and make a video on that. Keep up the good work. I love your channel. I too have a hard time diagnosing my car problems. It’s part of learning.

You might try cleaning the throttle body. My 2006 had a similar issue and it went away after I cleaned it.

Hey Jimmy I love your videos. Will there be an actual diagnosis to this video soon to come?

How did it "road test"...curious since video not showing leaving garage

Have it scanned to see the misfire counts if there are any. Also have the injectors professionally cleaned. Also make sure you map sensor and throttle body are clean.

I bought an Xtool D8. I have cleared, diagnosed and fixed all my cars: best money spent. I am a Shade tree mechanic, with patients

I had an Evoy 2002 300520 km on it changed spar plugs 2 times and never had a problem with the coils did never leek or burn oil best motor i ever had in a car i have been driving cince 1958

Hi Jimmy of One Road. Love watching your show. In this video (time index 10:57), you mentioned manifold gasket and fuel injectors. I would smoke-test it for vacuum leaks. As with fuel injectors, when is the last time the fuel filter was replaced? Start with something cheap first.

My chevy suburban for the last three weeks or so has been misfiring after it gets hot and is driven slowly in a parking lot or anywhere slowly, but on the hiway is seems to run fine; I replaced my coils, wires, plugs, crankshaft position sensor, and the fuel pump, my truck has more miles on it, 350 000 km's, but it's well looked after, I finally broke down and took it to our local chevy dealer last week, they charged my almost $500 and said its your pre cat oxygen sensors... these hadn't been changed since 2015 so I ordered them, they wanted $900 to change the two, they'll be in tomorrow and hopefully it fixes our issue. Maybe that will help with yours?

Idle air control or clean the mass air flow sensor with some cleaner? Could always get a cheap fuel pressure tester and see if it's reading a couple less than it should be

Man, hope you get more miles out of those Delphi coil pack. I’m still running 4 of the 6 original packs on my 04 Envoy with over 335k miles👍

You could figure it out. Sometimes we have to get lucky to fix things. I subscribed. 👍

Thanks!

Just the way it runs I’ve been dealing with the same stuff with my mothers trailblazer for years!!

As a few other were commenting & even you said near the end of the video... Possibly a vacuum leak. Follow up with a video on that, especially spraying a non flammable chemical around the intake manifold area & see if the idle changes Also, AutoZone, Advanced Auto, O'Reilly's, or similar parts store in your area offer FREE OBD2 scanning. If it's a general P3000 code, then yeah... Check for that leak Let us know on an update video soon!

Have you tried the code reader

@1road how much do you want for the coil packs?

Can measure their impedance... may or may not show which one is bad... if any of them. I actually turned off misfire counter on my LQ9 build as its problematic. That online 6 engine is super cool though. I'd love to build one of those up.

Looks like the ignition coils are Wet soaking from what looks like a oil leak into the spark plug wells some spark plug wells were brown and wet and some were shiny and dry 4:09 @1Road

Jimmy, I been watching and waiting for that magic bullet moment. One of these times it will happen.

Holy parts cannon, Batman! Not a surprise that a coil set didn't fix it. Too bad there weren't any codes to set you in a particular direction.

Could try checking the throttle plate for any carbon build up or idle air control valve if it’s sticking

I'm not sure if it has a crankshaft position sensor but you might want to check that I know mom's high-end a had a problem with that and the vehicle ran really rough when the sensor was felling

Take it to a shop they have equipment/tool to check each coil and can tell which need replace and which don't. Dont have to wast money if the rest are in good shape

You could have variable valve timing sensor and the sensor next to it that's bad but if those two sensors were bad your cruise control would only works sporadically and it won't trip the check engine light and those are the sensors in the head right underneath the duct hosing for the intake from the air box.

Does it have Auto fuel management. Maybe one of the lifters is bad.

The vvt solenoid or bad timing chains.

Could be a few things.. Clogged fuel injectors from sitting, fuel filter, vacuum leak, dirty throttle body, idle air sensor, maf sensor.. But just throwing parts at it for something that mild is kinda silly. Get a scan tool or take it into a shop

check your air flow sensor?

Can also just do a major tune up. Clean MAF sensor, run seafoam through top end, check fuel pressure, etc.

Try running some fuel injector cleaner like royal purple or anything that contains PEA (nitrogen baised cleaner). Maybe the mass airflow sensor is dirty? Maybe it just needs an "Italian" tune up..... flooring it from stops and driving on the highway.

First order of business is to buy a quality scanner. You probably know that. After confirming no codes than you can skip checking sensors. Could be engine mounts worn or a vaccum leak. Spray brake clean around the intake tube & If you hit it the rpm’s will dip way down for a few seconds. Lastly, clean the throttle body.

Exhaust manifold gasket leak?

Engine mounts?

Try cleaning the mass air flow sensor. If that starts to get a little off it can affect these things without setting a code.

Fuel injector cleaner?

That's probably just how it runs, if there's no codes I wouldn't worry about it, newer GM's love throwing check engine lights for every little thing so if it didnt then just drive it. If you realy think its misfiring you could get a scanner that reads live data so you can see if theres a slight missfire that's not happening enough to set the check engine light

Sounds odd, I know, but have you checked your engine mounts? Your diagnostics aren't seeing a problem so it may be more of a physical issue, and bad motor mounts can cause what seems like a misfire type shake and any extra engine movement can produce all kinds of odd external sounds,

It sounds like intake gasket or one of the fuel injector my opinion of course.

Clean your mass airflow sensor and your throttle body paying close attention to the throttle body butterfly. My Honda CR-V was running rough, especially with the AC on, and I cleaned those components and it smoothed up. My Honda has 260.000 some odd miles and still going strong.

Timing Chains?

Stupid question, did you check the spark plug gaps?

Can you ohm out those coils?

Maybe it’s needs the old Italian tune up. 😅😅😅 When was the last time the pedal hit father floor? Cleaned the webs out of the exhaust 😂😂😂 Also today some scanners are not to much. Some connect to your phone via bluetooth and they are not that expensive. I bought the cheap one. The craftsman’s one

dude... you don't need a fancy expensive scanner. launch makes a scanner, x431 for gm. i bought one for my old car. it'll show you everything if you understand the numbers. it's reasonably cheap at 180. i got mine for fuel trim resets. it does all that stuff and i think it can even code computers and keys. idk, never tried it. if you want a good guy on here to learn about live data and diagnosing, schodinger's box is on another level of intelligence and he breaks it down pretty well in his videos. i went through this on my old gmc.. i would also point out that mechanical issue with a miss won't always kick a dtc. mine ended up being a combination of injectors and coils. sending a 0300 code, running ROUGH and crazy fuel trims. i've also seen an oil change solve so missing like behavior on vvt engines. had to change the oil before it was due on my old car once lol. gone now and driving a brand new canyon.

I have the exact same problem.

Get a scanner for the price of the new coils and the mechanic’s labor charge. It would tell you which cylinder is the problem. You could also have a vacuum leak.

Your wife seems so nice. Your a lucky man. You two look great together

Check the variable cam solenoid. Its on the passenger side behind the power steering pump. They get gummed up and can cause a ruff idle and poor economy. I would clean it and see if it makes a difference. If that helps they are cheap and easy to replace.

Check timing, engine and transmission mounts.

For the cost of those coils, could have bought a GM Tech2 or scanner from Launch.

Here's something else to check. My f150 had a rough idle. Turned out my alternator was not putting out enough voltage. I had it rebuilt and rough idle is gone.

Sounds like a PCV issue. Hope it works.

Check your Mass Air Flow Sensor

I recomend that you buy seafoam transtune put it inside with high octane fuel and take you vehicle for a long highway drive then change the oil.

I'm surprised you've never ordered a scan tool.. Without a scan tool my guess would be changing the mass airflow sensor. If that thing is bad it's not going to idle correctly. It regulates and lets the engine know how much air to flow into the engine. It also lets the engine know how much fuel to flow into the motor.

Happy late birthday day🎉

No pun tang tonight!!

Looks like a vacuum leak. It's pretty common on cars with plastic intakes.

Pocket full of solutions looking for a problem, imo. Fill up with a mid grade or better fuel on top of a double dose of Marvel Mystery oil. That will cleanup that bit of carbon a little and certainly shine up the injectors.

You might want to test the spark plugs with a volt / ohm meter

Do you have a code reader with live data? That might point you in proper direction.

A bad knock sensor could make gas engine sound like diesel engine but check engine light would comes on.

Clean the throttle , flow sensor & replace the fuel filter then add injectors cleaner, drive the car for long trip. Everything will be much smoother

appears #6 was a dirty plug. not firing. #5 plug appears firing was sporadic the rest looked fine. actually the #6 plug should be replaced or cleaned(?) [id replace it] & #5 as these might eventually work, but they are dirty & might never be as good as they should be. appears coil pak #6 wasnt firing #5 now n then [sporadic] hoping its the pacs & not something else. yes its odd the light didnt come on. a miss fire will often show up in code checking. mine has & i have a cheapie code reader from walmart also invest in some good mas sensor cleaner & use it. that will help most efi systems. the 02 sensors are another matter - those connect to the computer for adjustments needed in your air/fuel mix [gee I hate computer stuff in cars] ugh even with the scan tools it is still just a guess at what it "might" be on yours Id replace those back 2 plugs. that ought to smooth it up even more. (?) still a guess ;)

Check if the PCV is clear and clean.. Check for vacuum leak

This is why I hate/love GM cars. My 2003 Chevy Astro van with a Vortex 4.3L had similar issues. Changed spark plug, coil, distributor cap,etc. I had the ECM swapped for a rebuilt one. All to no avail. My 2008 Chevy HHR with the 2.2L same roughness as it aged. Later my 2014 Cadillac ATS 2.5L inline4 did not run smooth after 5years. (current car) My 2016 Cadillac CTS AWD 2.0L is good but once these cars hit 6 years or after60K miles..issues pop up. I like the advice others gave: engine mounts, MAP sensor, camshaft positioning sensor, oxygen sensor, throttle body and vacuum leaks. I go broke hunting these issues down ...even mechanics with scan tools cannot always find my cars issues but take it in and see what they charge to diagnose it. Just sucks overall. Love your videos...keep up the good work!

You may have a broken exhaust manifold bolt. It will create a rough sound at idle.. and seem normal driving.

Some of the spark plug housings are wet and others are dry that looks like issue with the Coil packs

You have to determine if it's a misfire, vacuum leak, engine shake, ruff idle.

Mine was dirty throttle body.

You could have a dirty injector..seafoam or berryman's

Dirty fuel filter can make it seem like there's a misfire as well.

Maybe a quality of the fule it is not good

I'm just surprised the fuel gauge works!

Made in Mexico that's why they are the best 👌 👍

You should buy a scanner in a multimeter just wanna help you

Probably should have changed the plugs. Bad plug can cause a misfire. Also, check the gap

Yeah... Fire the parts cannon again loaded with six new injectors. It's probably not them either, but what the heck. 😬

You need a quality scan tool and learn how to use it. This is what I tell guys that diagnose by guess, “guessing is expensive, how much can you afford “

Hey Boss, You don’t have that Tennessee accent. 🧐

Just take it out and spray, wait until a hour until dry

I know it's not true for all makes. But sometimes when you change ignition coils you have to have them reprogrammed🤷‍♂️ let us know👍👊🇺🇸🍺

Definitely not a pro myself but fuel injector cleaning might be a cheaper fix than replacement.