Learn Me: Direct Injection maintenance

After six thousand miles without fault, while driving in traffic recently the dash on my Jag XK suddenly lit up with fault lights, the engine lost all power and huge clouds of smoke started blowing out the tail pipe.  I parked it in the first safe spot, then could never get it to restart.  I have to admit feeling some dread in the pit of the stomach.

It turns out that one of injectors stuck open, flooding a cylinder and blowing the smoke.  The open injector meant reduced fuel pressure to the other three injectors on that rail, causing the loss of power and fault codes.  Long story short, this turned out to be an easy fix.

The Jag forums say that dirty injectors aren't uncommon on these direct injection engines: "You cant drive a directed injected car without cleaning the injectors."  Someone else mentioned intake sludge and timing chain wear due to "micro dust."  Another mentioned "walnut blasting" intakes.

The 5.0L direct injection V8 in my Jag is the first GDI engine I've ever had to service.  Routine injector cleaning?  Sludge?  Micro dust?  Walnut blasting?  Is this all legit?  What other types of issues should I look out for?  Is there a checklist of preventive maintenance tasks and intervals for GDI engines?  Our Kia has one too, and I'd rather not risk my wife getting stranded like I did.

Well, DI engines do tend to accumulate filth on the back of the intake valves due to the lack of being constantly blasted with solvent by a port fuel injector. The filth comes mostly from evap flow, and egr if it has one. Walnut blasting is one method of removing it. In conjunction with a shop vac, that is. 

How much of the engine do you need to disassemble to do the walnut blasting? How much does that cost?

Vigo said:

Well, DI engines do tend to accumulate filth on the back of the intake valves due to the lack of being constantly blasted with solvent by a port fuel injector. The filth comes mostly from evap flow, and egr if it has one. Walnut blasting is one method of removing it. In conjunction with a shop vac, that is. 

Some do, some don't.  Pretty much the same ones that had (or didn't) have intake depositing with PFI.  

nderwater

To me, asking "is it normal...."- for pretty much all of your questions is no, it's not normal.  Does it happen, yes, it does- and like the powertrains that have (or not) intake issues, the sources of injection issues is pretty much on a handful of the suppliers.  Given who Jag has been getting parts from for my entire career, it does not surprise me that they have issues.  But that is speculation that they got their injection hardware from Denso and not Bosch.  

The only maintenance a GDI car might need that a traditional EFI car doesn't is walnut blasting to the back of the valves. But the problem you had has nothing do do with that. A fuel injector somewhere in the intake tract could stick open too...so I'd say you did nothing wrong and have nothing to worry about.

I plan to do a half a can of seafoam in the Koup every 30k (getting close to number 2). Then again, with no EGR and a relatively decent pcv system, the Koreans arent AS bad as some of the other brands (*cough GM *cough). 

On the ND they don't seem to be terrible. I did a seafoam type treatment at 15k and will do it every 15k after that.

I want to run a little E85, I've read some interesting theories about how it could help even though it's not sprayed at the valve, well you know and more power.

GTwannaB said:

How much of the engine do you need to disassemble to do the walnut blasting? How much does that cost?

Depends on the engine. 

For the I6 turbo in my 135i, local shop charges $350 or so (IIRC) to walnut blast the intake valves. Basically remove intake manifold, insert a special part that has a vacuum hose attached, place blaster tip in and work around. Obviously you rotate the engine so the valves on the cylinder you are working on are closed. 

There are lots of videos on YouTube of how to do it.

GTwannaB said:

How much of the engine do you need to disassemble to do the walnut blasting? How much does that cost?

Corksport makes a universal-ish tool for using a blaster and a shop vac if you don't want to pay a shop to do it. For BMW's there's places online that will rent you the official tool.

There's cheaper ways to DIY it but they're more labor intensive or don't seal as well.

Bob is probably more on this than I am but watch for oil dilution with fuel.

In reply to The0retical :

Fuel dilution is only a problem if A.) its thinning the viscosity or 2.) increasing wear (likely because its thinning the film strength). The ASTM methods that actually measure fd for gas stops at 5%, and most DI engines it's pretty normal to be well above that. As always, there's no one answer just monitor your stuffs. 

My wife's car had GDI.  I just make sure to give it an 'Italian tune-up' every time I drive it.  Rumor has it that this may help with the intake valve buildup...At least that's my story, and I'm sticking to it.

BG Products makes a really good fuel induction service that our dealership uses to a lot of success on GDI motors with misfires and other issues. Their generic induction service does the trick 90% of the time, but they also offer a GDI-specific version with even more stuff, although its a bit more pricey

In reply to Driven5 :

Unfortunately no. It worked great for PFI cars that had EGR and/or E36 M3ty PCV systems. The extra fuel flowing over those valves really helped. That doesn't happen with the DI cars. 

In reply to NickD :

I do miss having access to the Wynn's upper engine cleaner spray thingy. That stuff worked really well. 

GameboyRMH said:

The only maintenance a GDI car might need that a traditional EFI car doesn't is walnut blasting to the back of the valves. But the problem you had has nothing do do with that. A fuel injector somewhere in the intake tract could stick open too...so I'd say you did nothing wrong and have nothing to worry about.

Actually, PFI cars do have the intake system deposit problem- BMW had to develop the walnut blasting tool to clean some of their engines in the 80's.  Back then, I had an internship at Chevron, where we were developing new fuel additives to take care of that.  BWM was one of the worst for intake system deposits.  

And, as Bob has alluded to, not all DI engines suffer that problem.  So while it may be amplified by the fact that fuel isn't sprayed someplace, it's not a direct cause/fix etc that can be pinned to just direct injection.

I have a DI engine in my F150 (3.5L Turbo) with 150K on it. No problems.

What I have read is you need to change the oil regularly and to use "good" oil when you do.

Doing this reduces the build up "gunk" on the backs of the intake valves because it's the oil that has broken down that causes the most buildup.

I'm on the F150 Forum and it seems to be common to change the oil at no more then 5K intervals.

Those that push it longer seem to have issues with their engines while those that change more often have less.

This is just my opinion based on reading various posts there but what I said in the second line is something

I've read in a auto trade publication.

bobzilla said:

In reply to Driven5 :

Unfortunately no. It worked great for PFI cars that had EGR and/or E36 M3ty PCV systems. The extra fuel flowing over those valves really helped. That doesn't happen with the DI cars. 

There are some anecdotal claims that GDI cars run gently are still having greater rates of intake valve deposits than the same engines run harder, and there are a few plausible sounding hypotheses as to why this might still apply.  I don't really care that much one way of the other, it's just a cheap technical excuse to give it the beans and make (me and) my girls giggle...As if I really needed any other excuse.

Add oil vapour separator.

And, as Bob has alluded to, not all DI engines suffer that problem.  So while it may be amplified by the fact that fuel isn't sprayed someplace, it's not a direct cause/fix etc that can be pinned to just direct injection.

 

Fair point. There are also some DI engines that are also port injected, so that's a thing. The port injected cars tend to have all their filth upstream of the injector, which in some cases might be even harder to clean, but at least it rarely gets to the point of affecting airflow so much that you have a misfire/power balance problem. My view as a tech/mechanic, in the end I don't really care either way. It's just different sets of issues and i dont see the cost/benefit being decisively one way or the other.  

There are some anecdotal claims that GDI cars run gently are still having greater rates of intake valve deposits than the same engines run harder, and there are a few plausible sounding hypotheses as to why this might still apply. 

Makes me wonder what the difference is in G-force at the face of the intake valve  when it's slapping onto the seat at 2000rpm vs 6000 rpm. 

Driven5 said:

bobzilla said:

In reply to Driven5 :

Unfortunately no. It worked great for PFI cars that had EGR and/or E36 M3ty PCV systems. The extra fuel flowing over those valves really helped. That doesn't happen with the DI cars. 

There are some anecdotal claims that GDI cars run gently are still having greater rates of intake valve deposits than the same engines run harder, and there are a few plausible sounding hypotheses as to why this might still apply.  I don't really care that much one way of the other, it's just a cheap technical excuse to give it the beans and make (me and) my girls giggle...As if I really needed any other excuse.

Again, as one looks as anecdotal evidence, one also needs to look at patterns of WHO is having the issue.  Some OEM's have it, some don't.  And based on what I see, it correlates perfectly with OEM's who had deposit problems with PFI.

In reply to Vigo :

FWIW, PF-DI cars are going to become a LOT more common.  There are a lot of good reasons for it.  

In reply to alfadriver :

I'm surprised this hasn't happened sooner to be honest. There are a lot of really good things about DI. Better fuel control, more power from smaller packags due to better fuel distribution and higher compression etc. But like everything there are downsides. More fuel dilution requiring better oils, pre-det issues, caking the valves etc. I imagine the complexity of having two fuel systems working in tandem has what has kept it an either/or as long as it has. 

Before I bought my honda I asked all the guys in both the parts and service depts about this. As a fellow dealer group employee I know most of them fairly well and trust them to give me an honest answer. Every one of them told me it hasn't been an issue on any of their models. Time will tell but the issues I have heard of all seem to follow manufacturers and not technologies...

In reply to barefootskater :

Honda's haven't really ever had PCV/caking problems on their engines that I can remember. A little varnishy (technical term) from over extended oil drains and stretched chains but no sludgy/caky issues. Old fords (pushrod motors), GM 4's and 6's.... I don't know that I've ever seen the lifter valley of a 351W. 

bobzilla said:

In reply to alfadriver :

I'm surprised this hasn't happened sooner to be honest. There are a lot of really good things about DI. Better fuel control, more power from smaller packags due to better fuel distribution and higher compression etc. But like everything there are downsides. More fuel dilution requiring better oils, pre-det issues, caking the valves etc. I imagine the complexity of having two fuel systems working in tandem has what has kept it an either/or as long as it has. 

Toyota has had the system for nearly a decade.