quote:

Originally posted by rizzle:
Drop in fuel pressure when misfire, time to go after #6 injector, as mentioned, excessive carbon clean if visible on disassembly.

Well, after studying on it some more, I don't think I want to tackle that job. Probably time to Call the Man. It would probably take my mechanic 2-3 hours to do the job, or me 8-12 (with massive amounts of frustration and a high risk of error)... I can spend less hours doing overtime at my day job to pay The Man to do it for me.

quote:

Originally posted by kgc4160:
if im not mistaken.. you can access the injector harness for both side.. 2 differant ones and if you can get a wiring diagram you can ohm test the injectors and compare readings

Would a intermittent failing injector be revealed by an impedance variation? Interesting.

quote:

Originally posted by rizzle:
Does it misfire if you power brake it?

Gave this another try last night. No misfire while power braking despite my best efforts. What does that signify?

quote:

Originally posted by thumperfbc:

quote:

Originally posted by rizzle:
Does it misfire if you power brake it?

Gave this another try last night. No misfire while power braking despite my best efforts. What does that signify?

Good test for ignition, if it did, most likely a coil or plug.

There are a series of tests that would narrow down a problem.

You need to determine if it's engine mechanical, ignition, or fuel/control first. Then go from there, instead of bouncing around checking all three at the same time.

quote:

Originally posted by rizzle:

Good test for ignition, if it did, most likely a coil or plug.

There are a series of tests that would narrow down a problem.

You need to determine if it's engine mechanical, ignition, or fuel/control first. Then go from there, instead of bouncing around checking all three at the same time.

I'm open to conducting any test I can with the tools at my disposal that you would think might help.

quote:

Originally posted by thumperfbc:...
So, this begs the question... how hard of a job is this? I've never done injectors of any sort. If I can manage, I'd like to do it myself, both to save money but also to learn and try to be more self-sufficient. Changing plugs/coils are easy.... how much past that is this job? Does it require special tools? Wish I could find a video, I'll have to do more looking.

Is it worth taking it to an actual mechanic with a better grade scan tool? Can they confirm bad/failing injector with a better grade of scanner? Is there a chance this is related to the water pump job? I had that work done by a pro, but he isn't the pro I would typically go to for diagnostics. But if it is potentially related, perhaps the situation properly calls for a return visit to him.

You have to remove the intake to get to the rails and injectors. Typically, an injector puller (slide hammer) is used to pull them. I know people have done it without, but it risks damage.

Inspecting and swapping the injectors (and inspecting them and the harness for damage you suspect) will be relatively easy, it's getting to them and putting everything back in place and the intake back on that is time consuming.

Unless you have the proper equipment, you cannot effectively "bench test" the injector of DI like you can with some lower pressure injection systems. Either remove the injector(s) and get it (them all) tested, or take it in.

The cleaning is also a job that should be done by a shop that has the experience and the tools/system to do it effectively.

This is one of those "if something goes wrong, better it happen in the operating room, than trying to get from the scene and dealt with in the Emergency Room.

You know your limitations, so I leave it up to you to decide if it is something you want to tackle.

Me? Hell, my life has been nothing but learning how to get out of the mess I got myself into, and I have all the experience to prove it.

That and $5 might buy me a cup of coffee at todays prices...

Unless I was pulling heads to clean them, I would take it in and pay to get it done.

Doing all the things you can do, helps make the cost of those things you really don't want to be doing, less of a sting.

quote:

Originally posted by sigmonkey:
You have to remove the intake to get to the rails and injectors. Typically, an injector puller (slide hammer) is used to pull them. I know people have done it without, but it risks damage.

Inspecting and swapping the injectors (and inspecting them and the harness for damage you suspect) will be relatively easy, it's getting to them and putting everything back in place and the intake back on that is time consuming.

Unless you have the proper equipment, you cannot effectively "bench test" the injector of DI like you can with some lower pressure injection systems. Either remove the injector(s) and get it (them all) tested, or take it in.

The cleaning is also a job that should be done by a shop that has the experience and the tools/system to do it effectively.

This is one of those "if something goes wrong, better it happen in the operating room, than trying to get from the scene and dealt with in the Emergency Room.

You know your limitations, so I leave it up to you to decide if it is something you want to tackle.

Me? Hell, my life has been nothing but learning how to get out of the mess I got myself into, and I have all the experience to prove it.

That and $5 might buy me a cup of coffee at todays prices...

Unless I was pulling heads to clean them, I would take it in and pay to get it done.

Doing all the things you can do, helps make the cost of those things you really don't want to be doing, less of a sting.

Thanks for the thoughts, Monkey. It confirms the way I was leaning, to Call the Man. I'm confident I could eventually get the intake off (and back together), but after watching some videos of the fuel rails and injectors coming out and going back, it's not something I want to risk. Best case scenario is it would take me far too long, and I don't have that sort of time to dick around with my primary means of transportation.

I admit I am curious to see wha the back of the valves look like.

This will give you an idea of no issue to OMG...

Looky here.

If the EB is anything like the Duratec in the N/A Flex, the intake is a pita to remove.
It's been a while, but I recall having to remove it once, i think for doing the rear plugs.

quote:

Originally posted by sigmonkey:
This will give you an idea of no issue to OMG...

Looky here.

Perhaps this is an utterly silly idea, and if so I accept my reprimands... but is there a possibility one could disconnect the throttle body and then send the scope into the intake that way to try and get a view into the ports and the back of the valves?

quote:

Originally posted by P250UA5:
If the EB is anything like the Duratec in the N/A Flex, the intake is a pita to remove.
It's been a while, but I recall having to remove it once, i think for doing the rear plugs.

The plugs in the boosted version are quite easy to access without removing anything, except maybe one quick-remove vac line. Changing out all 6 took me less than 20 minutes, I recall.

Remove the map sensor, faster than pulling the throttle body. (rear of engine, passenger side)
Just make sure the parts of the scope you send in there cannot be dislodged and live there rent free.

Your long term fuel trim of 9% to 12% is quite s shift from original calibration.

I think with both banks having high LTFT you are either have fouled injectors all around or are running high ethanol content fuel.

The injector cleaners as supplements in the tank are high concentrations of detergents and / or amines. An injector hole is quite small, and the pattern of holes is not symmetric by design (particularly for GDI). Chemistry does help remove deposits.

At the lab, the borescope was quite helpful in showing both intake valve deposits and combustion chamber condition. It also can show externally fouled direct injectors. Your engine does not have dual injection, so there could be heavy intake valve deposits. It is not possible to measure the internal fouling of the injectors, visually, and even taking apart the GDI injectors seeing the deposit visually is nearly impossible.

To me, the high LTFT suggests that all injectors are fouled. If we ever measured a shift in LTFT and got 10%, it would be viewed as quite dirty.

Injector 6 is on bank 2 which has higher LTFT. But, for 4% more LTFT than bank 1 it would have to be very very fouled! A positive LTFT means that the duration of the pulse to the fuel injector solenoid has been increased from nominal to longer duration. A ballpark figure for GDI injector duration is about 0.19 millisecond. A 10% shift positive would increase that duration, to allow more high pressure fuel into the cylinder. It is not trying to put more than necessary fuel, but trying to reach stoichiometric air:fuel ratio. Positive shift means the engine is running leaner than desired, with the original calibration fuel trims.

Have you typically purchased fuel from convenience stores? These fuels typically do not have (a) sufficient levels of detergents and (b) the correct chemistry detergent for GDI injectors. Believe it or not, different detergent chemistry is required. These detergents are found in Top Tier fuels, and in global fuel retailer formulations.

quote:

Originally posted by sigmonkey:
Remove the map sensor, faster than pulling the throttle body. (rear of engine, passenger side)
Just make sure the parts of the scope you send in there cannot be dislodged and live there rent free.

I actually spied that earlier and pulled it out and gave it a quick try. It'll work, at least for #5 for sure... maybe enough to get a sense of how bad it is, in general. But the batteries died in my scope so I'll have to try it some more tomorrow.

quote:

Originally posted by 4MUL8R:
Your long term fuel trim of 9% to 12% is quite s shift from original calibration.

I think with both banks having high LTFT you are either have fouled injectors all around or are running high ethanol content fuel.

The injector cleaners as supplements in the tank are high concentrations of detergents and / or amines. An injector hole is quite small, and the pattern of holes is not symmetric by design (particularly for GDI). Chemistry does help remove deposits.

At the lab, the borescope was quite helpful in showing both intake valve deposits and combustion chamber condition. It also can show externally fouled direct injectors. Your engine does not have dual injection, so there could be heavy intake valve deposits. It is not possible to measure the internal fouling of the injectors, visually, and even taking apart the GDI injectors seeing the deposit visually is nearly impossible.

To me, the high LTFT suggests that all injectors are fouled. If we ever measured a shift in LTFT and got 10%, it would be viewed as quite dirty.

Injector 6 is on bank 2 which has higher LTFT. But, for 4% more LTFT than bank 1 it would have to be very very fouled! A positive LTFT means that the duration of the pulse to the fuel injector solenoid has been increased from nominal to longer duration. A ballpark figure for GDI injector duration is about 0.19 millisecond. A 10% shift positive would increase that duration, to allow more high pressure fuel into the cylinder. It is not trying to put more than necessary fuel, but trying to reach stoichiometric air:fuel ratio. Positive shift means the engine is running leaner than desired, with the original calibration fuel trims.

Have you typically purchased fuel from convenience stores? These fuels typically do not have (a) sufficient levels of detergents and (b) the correct chemistry detergent for GDI injectors. Believe it or not, different detergent chemistry is required. These detergents are found in Top Tier fuels, and in global fuel retailer formulations.

I believe gasoline here in CA is 10% ethanol. I have not been able to locate an ethanol-free source locally when I looked for my chainsaw and blower. You seem to know quite a bit about this, do you think the Redline SI-1 fuel system treatment will be effective, to some extent?

I typically purchase my fuel at a variety of stations, often just going by the most convenient to me when needed. Sometimes it is a brand with Top Tier such as Costco or Arco, but sometimes from a place like Speedway or some local stop-n-rob stores. I can stick to Arco and Costco if it is substantially better for my car.

My comments are based on years of engineering and formulating at a major additive manufacturer. These fuel additives are purchased and distributed by well-known retailers of fuels. The global retailers do have cradle-to-grave control of the fuel, while others simply purchase quantities of fuel and treat that base fuel with some amount of additive.

So, if you purchase fuel based on location or price, and enjoy the convenience store features like gut-busting chili dogs, most often the fuel is not formulated to offer performance. Yes, it meets legal minimum additive quantity. Yes, it passes the minimum test requirements. But, those more expensive fuels do offer far more performance.

Of note, the amount of additive in a premium octane fuel is far greater than in a regular octane fuel. You may not need premium octane, but you do enjoy cleaner fuel system components if you do pay the man.

Regarding the suggested fuel system cleaner, I have no direct experience with that product. If the detergent within is as the internet suggests, a polyether amine, or PEA, this detergent does work. It is also found in the Techron product. It is also found in a global fuel retailer at their pumps. It's been around for years. Does it work? Yes. Does a higher concentration of it help clean systems? Possibly.

We often think of cleaning fuel systems as we do cleaning firearms. I can take the pistol apart, see the dirt and grime, use some chemistry, use a brush, use a patch, and get after it. Cleaning injectors is not like this. Deposits are not easily removed. Think about it...it is a "related rates" problem. You had those in high school, if you are as young as me.

Billy's mom yells at him to take a bath. Billy goes upstairs and grumpily raises the bathtub drain lever to fill the tub. He fails to raise it all the way, in his anger. He turns the water on, and waits for the tub to fill. 20 minutes later his mom comes to see why he hasn't finished. But mom, the tub never filled! Of course the reason is that the drain is letting water out while the faucet is putting water in, and the rate of outflow is only slightly lower than the rate of inflow.

It is the same way with deposits. The engine combustion process makes deposits. Sorry, that's just life. When you create deposits, they tend to stay there until something acts to remove them. Deposit creation rate can be higher or lower than the deposit removal rate. Poor quality fuel -- deposits remain. High quality gas -- deposits are slowly removed. You need to effectively remove the naturally-occurring deposits, with detergents, over time.

If you have to clean deposits that have been around for a while, you can use those deposit-removing bottles. But, I would never expect a one-tank deposit removal solution! The optimum solution is to always use quality fuel.

I appreciate you sharing your expertise, thank you.

While I am not declaring victory, I am adding this context: I just finished the tank of gas that had the Redline SI-1 added to it. After a couple of attempts I have not been able to recreate the misfire under the same conditions that I could reliably induce it before hand...

It has been drier here lately, more typical than the wet weather we had been having while this misfire issue was going on actively. Perhaps that points to a documented issue with condensation in the intercooler.

For whatever the reason, I can not get it to misfire at this point. I'll get the Forscan back up and monitoring again in the next couple days and see what the long term fuel trims look like. Maybe the Redline improved those some.

4MUL8R thanks for sharing your knowledge…

Cleaning all the fuel injectors with the PEA tank chemistry may have opened up those tiny direct fuel injector holes and cleaned up the interior bore and pintle of the injectors. You would not believe the design nor the precision of the holes.

Modern injector holes are not round. And, the holes are not regularly spaced like lugs on a wheel. The injectors are on the side of the combustion chamber, the intake air swirls around the chamber, and the finely atomized fuel is emitted with great care. I would characterize the GM injectors as having an irregular ellipsoid shape. You cannot use your barrel brush and Hoppe's 9 to get in these tiny holes.

A way to clean them is to send them off to a professional service. These technical experts have ways to measure the flow as received, to clean the injectors using ultrasonic vibration and solvents, and then to measure the flow after cleaning. The best systems energize the injectors during the ultrasonic cleaning process.

I think a set of six injectors would cost $300 or so. And, you do want to engrave the injector with the cylinder number before sending them.

If you have indeed successfully cleaned the injectors with in-tank chemistry, your engine computer will over time adjust the LTFT. In laboratory engine tests, creating a dirty injector might take 60 hours at 2500 rpm and 100 N-m engine torque. Putting a fuel with detergents present can restore the injector cleanliness in about 40 hours. The test condition of 2500 rpm corresponds to you driving your car at about 80 mph, and of course no one drives 80 mph for 60 hours straight. But, you get the idea. The chemical nonsense that occurs with poor quality fuel, prone to creating deposits, can materially change the interior (!) and exterior holes of the injector in about 60 hours.

What is amazing are the before and after high magnification images, showing the injector face. I don't know if you've ever seen a skin mole that is large, bumpy, and has a multitude of fissures running to and fro. That's what I think when I see these face deposits. And, after the fuel cleans the deposits, you can see bright shiny metal. Not everywhere, of course, because the fuel spray is being emitted from the holes, so the far reaches of the injector face might still show deposits. But, the LTFT is back to normal!

Happy to hear of the potentially successful fix! Don't forget that this is NOT a one and done. You have to use quality fuels to keep injectors clean.

Just wanted to say this was a cool thread to read along to. I know just enough about modern car engines to be dangerous (to myself) so from diagnosis to 4MUL8R's info on fuel detergents, I was kinda fascinated. Well done as always, Sigforum.

My only direct experience with fuel injectors were with my Porsche GT3 race car. Believe it or not that car had over 100k miles on it and most were on the track.

In an effort to maximize the performance of that flat six my mechanic suggested having the injectors pulled and sent to a professional cleaning service which I did. They ran a before and after cleaning flow test (along with confirming the spray pattern was correct) and found that the flow rate was something like 97-98% across all six injectors. So not much improvement with the cleaning but that car always got Shell premium gas and a bottle of Chevron fuel treatment at least every 6 months.

quote:

Originally posted by 4MUL8R:
Cleaning all the fuel injectors with the PEA tank chemistry may have opened up those tiny direct fuel injector holes and cleaned up the interior bore and pintle of the injectors. You would not believe the design nor the precision of the holes.

Modern injector holes are not round. And, the holes are not regularly spaced like lugs on a wheel. The injectors are on the side of the combustion chamber, the intake air swirls around the chamber, and the finely atomized fuel is emitted with great care. I would characterize the GM injectors as having an irregular ellipsoid shape. You cannot use your barrel brush and Hoppe's 9 to get in these tiny holes.

A way to clean them is to send them off to a professional service. These technical experts have ways to measure the flow as received, to clean the injectors using ultrasonic vibration and solvents, and then to measure the flow after cleaning. The best systems energize the injectors during the ultrasonic cleaning process.

I think a set of six injectors would cost $300 or so. And, you do want to engrave the injector with the cylinder number before sending them.

If you have indeed successfully cleaned the injectors with in-tank chemistry, your engine computer will over time adjust the LTFT. In laboratory engine tests, creating a dirty injector might take 60 hours at 2500 rpm and 100 N-m engine torque. Putting a fuel with detergents present can restore the injector cleanliness in about 40 hours. The test condition of 2500 rpm corresponds to you driving your car at about 80 mph, and of course no one drives 80 mph for 60 hours straight. But, you get the idea. The chemical nonsense that occurs with poor quality fuel, prone to creating deposits, can materially change the interior (!) and exterior holes of the injector in about 60 hours.

What is amazing are the before and after high magnification images, showing the injector face. I don't know if you've ever seen a skin mole that is large, bumpy, and has a multitude of fissures running to and fro. That's what I think when I see these face deposits. And, after the fuel cleans the deposits, you can see bright shiny metal. Not everywhere, of course, because the fuel spray is being emitted from the holes, so the far reaches of the injector face might still show deposits. But, the LTFT is back to normal!

Happy to hear of the potentially successful fix! Don't forget that this is NOT a one and done. You have to use quality fuels to keep injectors clean.

How long, with "typical" driving, might it take for the LTFT numbers to drift back towards normal, assuming the cleaning did in-fact work? Are we measuring in months or weeks? On work days, half the week, it does not get back about 7 miles driving each way... in the morning that is only 20 minutes or so of in-town driving with a very short stint on the freeway, on the way home it is 30 minutes of mostly in-town, less regular driving.

I'll stick with Top Tier fuel... Costco or Arco, as those are both pretty convenient to me. Would you also recommend an occasional dose of a PEA-containing cleaner such as Techron or the Redline? Maybe with every oil change (for me that is about 10 months if I follow the oil life calculator in the car)

When you said you'll stay with Top Tier fuel, is that still using regular unleaded E-10 fuel? Running a cleaner though the system was probably all it needed. I use a product called ISO-HEET (red bottle) throughout the year. After each fill up during the winter months, and once or twice a month the rest of the year. It helps remove water in the fuel, but also has fuel injector cleaner. See if this will help.