Cold Start Issue - Possible Injector Replacement

[midwestdenaliguy]

I think I might have an injector issue. I'll first give the symptoms and what I've done to diagnose it, but the one thing I cannot find on here or the interwebs is how to replace the fuel injectors on my L86 engine. I understand it's a GDI engine and not as simple as a port fuel injection engine, but I figured there'd be something out there...no go. I'm pretty sure I've read every thread on here about cold start/injector issues, but pardon me if I state something that's already been said. Not looking to rehash any other threads, just get thoughts on my situation and others experience with replacing these GDI injectors.

 

My truck is a 2016 GMC Sierra Denali, 6.2L, 8 speed, 75k miles. Only run 93 octane fuel and all routine maintenance is completed on-time or early by me. Only use top end recommended products in all maintenance.

 

Symptoms/Diagnosis

• My issue is only a cold start issue and it's intermittent, but now happening more frequently. It drives fine with full-power and has no other issues. The cold start issue first came up around 70k miles when I did an auto-start in my driveway. I could hear the truck struggling to keep rpm's, it sounded like it was barely chugging along. I opened the door and looked at the rpm's and they were bouncing like crazy. Truck stalled out and threw a code for cylinder 3 misfire (P0303). I cleared it and it started up perfectly. I chalked it up to it needing spark plugs/wires replaced (had original OEM still in). I did so the next weekend with the OEM ACDELCO iridium plugs and Taylor 10MM racing wires (much better than stock). She cold started flawlessly for the next 5k miles and the issue was long gone in my mind.
• Fast forward about 3 weeks ago when it did it again after sitting in my work parking lot all day. The code this time was P0106 (MAP Pressure Sensor reading issue). I installed a CAI system (aFe Power Momentum GT) around 72k miles, so I figured maybe I accidentally messed up the MAF sensor in the install (even though it was fine for 3k miles). So I replaced the MAF sensor.
• Was fine until a week ago, when it had another rough cold start but didn't throw a code. I assumed it was the P0106 code again so I replaced the MAP sensor this time.
• Good for another week and now it's had 2 rough starts this week and stalled once right after starting, so getting progressively worse. This time it threw the P0303 code again.

 

I happen to be borrowing a tech tool and did a diagnostics check on the cylinders and it showed cylinder 3 has had 699 misfires, the next highest was 19 (both cylinders 6 and 8). I also checked the code history on the ECM and it showed P0106 (map sensor pressure fault), P0300 (multiple misfires), and P050D (cold start rough idle). I read the cold start rough idle can also mean coolant is leaking into the oil and/or through the head. I have not noticed my coolant running low, regardless I change my oil and just did it as recently as last weekend, but it's never looked milky or smelled like coolant. I also checked all the head bolts and around the head gaskets - didn't see any coolant.

 

Ruling everything out to this point, all I'm left with is bad seals on injector 3 that's allowing leak back during initial engine start - causing the misfires on cylinder 3. What's strange is that about 20 seconds after start-up the idle evens out and drives smoothly the entire time. It's only a rough cold start intermittently (getting more frequent), but no other issues. Am I missing anything?

 

How-to on replacing GDI fuel injectors?

I've read how costly it is for a shop to change out these GDI fuel injectors so I was hoping to do this on my own. I do 90% of my repairs/maintenance - with exceptions to major work. This is the first GDI engine I've owned so I don't want to jump into something and cause more damage - but I feel confident I can learn and do it right.

• Are there any instructions/how-to's on doing this job?
• From what I understand, with a GDI engine the pressure is much greater in the fuel lines so it's important to properly relieve the pressure. Also, I've read that I may need to replace the fuel injector rails/lines when I replace any injectors due to the stainless steel being so soft that it will leak in no time after replacing only the injectors.
• I don't mind spending money on the right tools if it'll save me money in the long run. Thoughts on doing the job myself? PS - I've searched YouTube and Google for ANY instructions (even for other GDI engines) and have found nothing on how to bleed the fuel pressure, just videos about putting on new injector gaskets.

[tbarn]

By you're description, it is very likely a #3 injector. Not an extremely hard job. Depends on your talent level I guess. You will need 1 injector, Injector seal kit, intake seals, and all high pressure lines that you remove. 2 if I remember correctly. You will not need rails. Assuming #3 injector only is replaced all lower seals on the other injectors (1,5,7 ) need to be replaced. There is a special tool kit to install and  "size" the new seals.Here is an aftermarket kit. http://www.freedomracing.com/en-51105-kit-bosch-sidi-injector-seal-installer-sizer-set.html

or a genuine GM kit. https://www.ebay.com/itm/Kent-Moore-EN-49245-Injector-Seals-Installer-Sizer-Tool-Set/372497151708?epid=657266770&hash=item56ba8f76dc:g:FwUAAOSwQuZb5fdu

[midwestdenaliguy]

56 minutes ago, tbarn said:

By you're description, it is very likely a #3 injector. Not an extremely hard job. Depends on your talent level I guess. You will need 1 injector, Injector seal kit, intake seals, and all high pressure lines that you remove. 2 if I remember correctly. You will not need rails. Assuming #3 injector only is replaced all lower seals on the other injectors (1,5,7 ) need to be replaced. There is a special tool kit to install and  "size" the new seals.Here is an aftermarket kit. http://www.freedomracing.com/en-51105-kit-bosch-sidi-injector-seal-installer-sizer-set.html

or a genuine GM kit. https://www.ebay.com/itm/Kent-Moore-EN-49245-Injector-Seals-Installer-Sizer-Tool-Set/372497151708?epid=657266770&hash=item56ba8f76dc:g:FwUAAOSwQuZb5fdu

Thanks for the reply. Couple of questions:

 

1. How do I safely relieve the fuel pressure? In port fuel injector jobs all I had to do was pull the fuel pump relay while the engine was running and it would quit once the engine ran out of fuel. That's when I shut off the ignition and would replace the injectors with no fuel pressure. I'm assuming a GDI engine is not that simple, but I could be wrong.

 

2. You mention needing to replace all high pressure lines that I remove, do you know where I can find out all the lines I'll need to remove? I'll obviously have to order them before I pull everything apart, I have no clue where to even start.

 

3. I'm the type where if I have everything apart I might as well replace them all while I'm in there. It doesn't make sense to me to do all this work for one injector. I found a deal for 8 brand new ACDELCO injectors for $250, but is that overkill when all I really need are just gaskets/seals?

 

Thanks again.

[tbarn]

1.

1. Disable the fuel pump by removing the B+ fuel pump control module fuse. Fuse 21 (30a) should do the trick. In the underhood electrical center.
2. Start the vehicle and allow the engine to idle until the engine stops. The engine will stop in approximately 5-20 seconds.
3. Attempt to restart the vehicle to ensure pressure has dropped to a minimal level.
4. Turn the ignition OFF.

2. From a dealer is all I know. There may be aftermarket line but I don't know. 2 lines, 1 from the high speed pump to the intermediate pipe. And the intermediate pipe itself.

 

3. That would be your call. But if OE injectors are problematic one wonders about cheaper ones.

 

 

3240317.bmp

 

 

[tbarn]

One more thing. on the 6.2, for OE at least, there are different injector p/n's used. The only way to tell which is to check the number on your injectors. Not sure about aftermarket. At least that was the last I knew when I retired 6mo. ago.

[midwestdenaliguy]

39 minutes ago, tbarn said:

1.

1. Disable the fuel pump by removing the B+ fuel pump control module fuse. Fuse 21 (30a) should do the trick. In the underhood electrical center.
2. Start the vehicle and allow the engine to idle until the engine stops. The engine will stop in approximately 5-20 seconds.
3. Attempt to restart the vehicle to ensure pressure has dropped to a minimal level.
4. Turn the ignition OFF.

2. From a dealer is all I know. There may be aftermarket line but I don't know. 2 lines, 1 from the high speed pump to the intermediate pipe. And the intermediate pipe itself.

 

3. That would be your call. But if OE injectors are problematic one wonders about cheaper ones.

 

 

3240317.bmp

 

 

 

Yeah I had the same thought about going with OE again if the originals only lasted me 75k miles. Plenty of people have had them go sooner too. I've also had bad luck with other aftermarket parts though. I'll do more research around aftermarket injectors.

 

You have been a huge help, truly appreciate your guidance here. My best to you. I'm sure I'll be back with more questions so don't go too far though...

[midwestdenaliguy]

I'm getting the BG GDI fuel air induction service done in the morning hoping that'll be the solution. I figure worst case I still replace an injector (or 8), but my valves/injectors/cylinders will now have little to no build up on them (I'm sure they're pretty bad). Best case, the induction cleaning is all I need :-)

[midwestdenaliguy]

Got the BG GDI fuel air induction service this morning and there was an immediate, noticeable difference. I thought my truck was running great with a custom tune and various mods, but it's surprisingly more responsive now on the throttle. I put about 100 miles on it and they say it takes a full tank of gas to finish the last stage of the service (they put BG 44K in the tank after doing a 2 stage cleaning of the intake/valves with some of their other products). Cost me $180 to have it done at a dealer and it was well worth it for my 75k mile engine. Time will tell if I have another cold start issue/misfire, but I'm feeling optimistic.

 

On another note, I'll be doing the BG EPR oil flush next weekend and adding BG MOA to treat the new oil. The induction service is a great cleaning for the top end and the EPR will finish out my cleaning with the bottom end. I've been doing a ton of research and am becoming a big fan of BG products. FYI - I'm in no way affiliated with BG, just super impressed with my experience with them so far.

[tbarn]

Per GM

General Motors Corporation does not endorse or recommend engine crankcase flushing for any of its gasoline engines. Analysis of some of the aftermarket materials used for crankcase flushing indicate incompatibility with GM engine components and the potential for damage to some engine seals and bearings. Damage to engine components resulting from crankcase flushing IS NOT COVERED under the terms of the New Vehicle Warranty.

[midwestdenaliguy]

43 minutes ago, tbarn said:

Per GM

General Motors Corporation does not endorse or recommend engine crankcase flushing for any of its gasoline engines. Analysis of some of the aftermarket materials used for crankcase flushing indicate incompatibility with GM engine components and the potential for damage to some engine seals and bearings. Damage to engine components resulting from crankcase flushing IS NOT COVERED under the terms of the New Vehicle Warranty.

Appreciate you looking out for me, but I'm out of warranty so I'm not worried about that. Additionally, the GM dealership that did my BG induction service this morning offered to do the BG EPR crankcase flush service as well. I spoke to a couple techs there about the flush and they all spoke highly of it, even having done it on their personal vehicles. I checked a couple other GM dealers who offered the crankcase flush as well to compare prices. So why would multiple GM dealerships offer it if GM "does not endorse or recommend crankcase flushing"? Also, do you know anyone who's done a crankcase flush and caused damage? I did it on my last 2 GM vehicles (not with BG products though) and only saw better performance after.

 

I'm not looking to argue and am genuinely open to having my mind changed if you can support not doing it with evidence (ex, your own bad experience or others). I did some searching tonight and only found positive reviews of the BG crankcase flush. Can't find a single testimony stating it ruined their engine.

[tbarn]

If you have changed your oil regularly, I can't imagine what a flush could possibly get you. I just don't see the  upside. Dealers sell it to make money (highly profitable ). They don't care about your engines long term issues. If it ruined every engine, they wouldn't be able to sell it. Just not worth the potential issues, unless the is a history of a lack of oil changes and I doubt that is an issue here.

[midwestdenaliguy]

Yeah, no doubt it's a money maker for them (like all of them). I always have the same suspicions whenever I get a pitch about a service, but what sold me on the BG route was review after review of positive results. I didn't happen to go into a dealer for something else and get sold on it while there. I had been looking into my cold start rough idle issue and this kept coming up as a potential solution. I know the tech at the dealership, and he knows I do majority of my maintenance/repairs myself, so he even told me to buy the BG stuff on ebay or amazon if I don't want to have the dealer do it (the EPR flush that is, the induction service requires a tool you can't by unless you're a dealer).

 

You're right, my truck has received regular oil changes with Mobil 1 full-synthetic 0W-20. It's also closely cared for in all other aspects, but yet here I am with a cold start issue that has happened a handful of times. Clearly, there's build up that needs to be addressed. Maybe I got suckered into an induction service, but I can absolutely feel an improvement in performance. I would gladly admit if I didn't feel anything different. As far as the crankcase flush, I'll give it another week of research to try to find actual negative cases. I might change my mind by next weekend :-)

 

Again, thanks for looking out. 

[tbarn]

I'm not saying the induction service is bad. Just possibly the crankcase flush. I'm no chemist so I have no idea whats in the BG products or if they will harm an engine. Nor does GM mention any specific chemicals or brand. So I guess it's up to the individual to do what they feel is right for their vehicle.

[Nitrousbird]

I've done the DI injectors on my BMW (different motor but still a direct injection setup).  On that motor, it isn't a hard job.  The fuel pressure is high. For that motor, simply make sure the low pressure fuel pump won't kick on (either pull the fuse or keep the key away and don't open the door).  When disconnecting the line to the fuel rail, simply start to loosen and place a rag around it - that simple.  It sprays into the rag and all is good in the world.  Injectors were easy to swap in that motor and only speciality thing was needed to code the DME for the new injector values.

[midwestdenaliguy]

1 hour ago, Nitrousbird said:

I've done the DI injectors on my BMW (different motor but still a direct injection setup).  On that motor, it isn't a hard job.  The fuel pressure is high. For that motor, simply make sure the low pressure fuel pump won't kick on (either pull the fuse or keep the key away and don't open the door).  When disconnecting the line to the fuel rail, simply start to loosen and place a rag around it - that simple.  It sprays into the rag and all is good in the world.  Injectors were easy to swap in that motor and only speciality thing was needed to code the DME for the new injector values.

Thanks for sharing. Did you have the programmer or did you take it in for coding? I'd have to take mine in and have it done, so wondering if that drive to the dealer without them programmed would hurt anything.