Dealer not honoring warranty work..2018 5.3 Yukon issues

[smokey_mountain]

I decided to postpone running cat idle measurements as I still have that BG Platinum in the fuel. I know it is snake oil indeed but I am desperate to try about anything as my wife is about to send me to the couch for buying this masterpiece truck for that much money.

Another question when someone sprays CRC it is supposed to be into the open Throttle Body and PCV line with batwing part of the air intake removed and PCV ventilation disconnected, is it supposed to set codes when I disconnect air intake connections, PCV valves and run engine like that?

 

[wjburken]

I decided to postpone running cat idle measurements as I still have that BG Platinum in the fuel. I know it is snake oil indeed but I am desperate to try about anything as my wife is about to send me to the couch for buying this masterpiece truck for that much money.

Another question when someone sprays CRC it is supposed to be into the open Throttle Body and PCV line with batwing part of the air intake removed and PCV ventilation disconnected, is it supposed to set codes when I disconnect air intake connections, PCV valves and run engine like that?

If you have the air intake removed, you will get a code because it’s looking for air flow across your MAF sensor.

Disconnecting your PCV hose will likely cause a code as well as your vacuum levels will be off.

 

[smokey_mountain]

Asking for more advice if possible. I spent 8 days just driving and trying to document how to re-create the problem. If anyone has any additional thoughts based on the steps described below, please let me know.
GM finally called back saying that they will take another look at my case (it only happened because I have opened BBB Autoline claim, they must respond by their contract with BBB doing mediation.

Here are the steps to re-create the problem + new issue, I am hearing. Just a reminder (this is a very long thread now), 2018 Yukon SLE with 5.3L 4x4 6-speed, 9,200 miles.

1) Truck needs to be driven for 15+ minutes at 40+ MPH to achieve the max. engine working temps

2) After intense driving when come to a full stop while still in Drive, let the engine idle for 15-30 secs and only then it would start to miss.

3) It is not a reqular miss, it is irregular, but happens every 2-5 secs.

4) Observe the Tach needle, it fluctuates, RPMs dip to 480-490 when engine misses.

5) Here is another found problem. When driving uphill in low 1100-1400 RPM 30-40 MPH and accelerate a bit on the driver's side I hear what could be either cyl #7 lifter chatter or exhaust leak sounds, sometimes like metal clunking in the engine.

 

[swathdiver]

Asking for more advice if possible.

1) Truck needs to be driven for 15+ minutes at 40+ MPH to achieve the max. engine working temps

4) Observe the Tach needle, it fluctuates, RPMs dip to 480-490 when engine misses.

5) Here is another found problem. When driving uphill in low 1100-1400 RPM 30-40 MPH and accelerate a bit on the driver's side I hear what could be either cyl #7 lifter chatter or exhaust leak sounds, sometimes like metal clunking in the engine.

1) It takes that long to heat up? How about a remote start, is the engine to temp at the end of ten minutes of idling?

4) Dips to 480-490 from what?

5) AFM is probably active and if at 35 or below you're in 5th gear. This is probably at the point where AFM turns on and off regularly, try to stay out of this.

Get the tune to raise the idle, GM will never know. If you test drive another I reckon its idle will be higher than yours.

 

[smokey_mountain]

Thank you, @swathdiver
1) It takes that long to heat up? How about a remote start, is the engine to temp at the end of ten minutes of idling? [ Good point, I know it is not correlated probably but somehow I am noticing that misses are more obvious after real driving, e.g. especially after highway. I thought for a while if my issue has transmission in the mix, something about transmission warm up... Probably not. I do not have remote on mine but I will start and let it warm up.]

4) Dips to 480-490 from what? [It stays around 500-505. When it misses it dips to 480.]

5) AFM is probably active and if at 35 or below you're in 5th gear. This is probably at the point where AFM turns on and off regularly, try to stay out of this. [This is noise is actually at 40+ MPH clunking is quite obvious when driving uphill without pushing accelerator, kind of lugging the engine maybe in some way].

Get the tune to raise the idle, GM will never know. If you test drive another I reckon its idle will be higher than yours. [ Given my fragile situation with this warranty truck, anything that I do to the truck will be used against me. Blackbear guys said they do a lot to make sure that ECM does not get re-flash mark that GM can see, but they cannot confirm it 100%. Local tuner told me that there is no way to avoid an ECM re-flash mark, no matter what people say. Not sure who is right and who is wrong. ]

1)
1) It takes that long to heat up? How about a remote start, is the engine to temp at the end of ten minutes of idling?

4) Dips to 480-490 from what?

5) AFM is probably active and if at 35 or below you're in 5th gear. This is probably at the point where AFM turns on and off regularly, try to stay out of this.

Get the tune to raise the idle, GM will never know. If you test drive another I reckon its idle will be higher than yours.

 

[swathdiver]

Thank you, @swathdiver
1) It takes that long to heat up? How about a remote start, is the engine to temp at the end of ten minutes of idling? [ Good point, I know it is not correlated probably but somehow I am noticing that misses are more obvious after real driving, e.g. especially after highway. I thought for a while if my issue has transmission in the mix, something about transmission warm up... Probably not. I do not have remote on mine but I will start and let it warm up.]

4) Dips to 480-490 from what? [It stays around 500-505. When it misses it dips to 480.]

5) AFM is probably active and if at 35 or below you're in 5th gear. This is probably at the point where AFM turns on and off regularly, try to stay out of this. [This is noise is actually at 40+ MPH clunking is quite obvious when driving uphill without pushing accelerator, kind of lugging the engine maybe in some way].

Get the tune to raise the idle, GM will never know. If you test drive another I reckon its idle will be higher than yours. [ Given my fragile situation with this warranty truck, anything that I do to the truck will be used against me. Blackbear guys said they do a lot to make sure that ECM does not get re-flash mark that GM can see, but they cannot confirm it 100%. Local tuner told me that there is no way to avoid an ECM re-flash mark, no matter what people say. Not sure who is right and who is wrong. ]

If BlackBear's tune was ever detected by GM and it became a problem, we've NEVER heard about it on this and many other forums. I would think that if GM detected their tune, we'd sure know about by now. To each his own though, I get it.

Hmm, maybe you have a torque converter issue, maybe the transmission needs new fluid? This is a common complaint with the 8-speeds and less so with the 6-speeds in the K2s.

Mine varies that much at idle and don't consider it an issue.

 

[91RS]

Still sounds like an engine mount issue.

 

[smokey_mountain]

It could be, however according to the Hendrick GMC dealer they were told not to do engine mount replacements anymore as it is an expensive temporary fix. @Bob2C had rough idle come back after engine mount replacement but I think finally his issue resolved itself somehow (which is a terrific news!) but engine mount swap did reduce the problem, but not completely eliminated it for a few weeks if I am not mistaken. He did something right and now the root cause of rough idle is gone and his truck is smooth.

Still sounds like an engine mount issue.

 

[smokey_mountain]

Finally found a very honest dealer - Medlin GMC in Wilson, NC, highly recommend them. I know they have tried everything that GM told them to try, it was in the shop for 2 days now, they have tried re-programming the truck, did couple more technical notices on the truck. GM now wants me to drive my truck for a few days and see if it made any difference. I am driving to pick it up tonight, wish me luck!

 

[smokey_mountain]

Dealer did check everything according to the work order:

• Engine mounts with picoscope
• Misfires cold and hot they said they see zero misfires on their equipment
• Injectors via afit test are all within 15% of each other
• Lugging/engine noise on the acceleration, not heard

Conclusion was - cannot reproduce any of my complaints. Truck is within GM specs. Advisor genuinely felt there is nothing that can do. Service manager was very accommodating and friendly but there is nothing that they can do.

I drove it for several hours since the pickup, absolutely no change, still misses as before, $06 monitor still shows misfires on cyl 7, cyl 6, cyl 4, cyl 3, cyl 1. Engine still makes noise on the acceleration up the hill in higher gear.

I think dealer did everything that they could without spending their own money. I respect them for that. I will take it on the longer drive this weekend and then if all the same - Nissan Armada is no longer as ugly as it was 3 months ago when I was buying this Yukon I will be crying at the pump but and when cruising at 70 mph. Yukon is just that super-plush.