2010 4.6 - HELP! - Multiple Cyl Misfires & Other Issues - Dealer No Help

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Looking for help here. Have a dealer playing Parts Darts and lying to my face (or are ignorant).
2010 Genesis 4.6 with 92,000 miles. I've owned it since ~50k miles and it's been extremely reliable.
Only repairs being battery replacement (~70k miles), and Alternator replacement (~80k miles)

CLIFF NOTES: TLDR:
• Sudden onset (cold start on cold morning) of multiple cyl misfires, primarily on 4/6/8, but random misfire at 3 as well.
• Also got Fuel Injector Circuit Malfunction on 6
• Dealer changed Plugs - didn't fix
• Seems to smooth out a bit as it warms up. Worst at idle or under low RPM load. Smooths out a bit at 2-4k RPM.


MORE DETAILS:

Last TUES - Check Engine light comes on. I head to autozone and get a P0128 (Coolant Termostat) Error which is correctly triggered by low coolant. I fill it up and it hasn't run down since. The engine never got hot.

Last WED: Driving to work it's abnormally cold. Not far from my house the car gets ROUGH. CEL Blinking. I immediately pulll over, and get it towed to the dealer. They find multiple misfires and suggest Plugs and wires, on top of the coolant sensor replacement. I agree. No issues prior to this.

4 days pass... This MONDAY: I pick up the car after work. Plugs are replaced. Car is still misfiring. He tells me it's 6 misfiring only, now.... and to run it for a bit with seafoam to try to clean injectors. If that doesn't help, then they will look at changing injectors out.

TODAY: I realize since picking up it feels like one side of the engine is missing (rocking car a bit, steady "hit, miss, hit, miss" not "Hit hit hit miss hit hit hit..) I check codes and this is what I get:[/URL]



I've been doing some reading and these are my assumptions (please feel free to correct):
• This engine has been known an ECU issue causing similar issues (based on this forum) : may be solved with reflash
• I've heard about VVT Solenoid issue that will take out one bank (odd/even cyls).. but misfire on 3 plus injector code makes this unlikey? Or no?
• The Injector Circuit Malfunction on 6 is interesting and makes me think electrical not mechanical?
• This is not the "short cycle on/off" induced stumbling that some experience. This has persisted for about a week now and wasn't short restarted.

Symptoms:
• Engine is very rough at idle when in gear. A bit less so when not in gear (higher RPM?)
• Misses feel to be consistent (like every other cyl misses, vs one of 8).
• CEL tends to flash when idling and when cold, then stays on
• When engine warms up it smooths out a BIT and CEL blink at idle goes away.
• When running at higher RPM (2-4k range) it runs smoother, but can still feel when under load.
• When under load at lower RPM the misses are more evident.

I would LOVE any guidance on this. I'm dropping the car off Monday after work to have the coolant sensor dropped in, and hopefully taking the next step on this repair (leaning ECU reflash?). Even the Autozone Code readout suggests an ECU reflash. They will have a week with the car.

What is the expected cost of an ECU reflash? Are there other possible things/causs they should be looking at? Any diagnostic suggestions to look that may indicated other common causes for this?

PLEASE HELP!

 

[homeofstone]

Anyone check fuel pressure? Also, has the fuel tank air filter been replaced as per maint. schedule? Has the fuel filter been replaced as scheduled?

 

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They did not check fuel pressure to my knowledge. I have no replaced the fuel filter in the last 35k miles (my time with the car). That might be worth having them look at. Lack of fuel would certainly trigger misfires.

Would they be more evenly distributed across the engine, vs almost exclusively be located on one side (4/6/8)?
Would that trigger a Injector 6 Circuit Malfunction? Perhaps indirectly?

Seems a fuel pressure check would be a relatively easy way to check that angle.

Very much open to other ideas as well!

 

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Coolant Temp sensor replaced... no help

Claim they updated the ECM... no help.

Now claiming I should replace the ECM (expensive game of parts darts)....


Help!

Getting an OBD2 reader and running an app to track data to see if any clues surface...

 

[EdP]

Had a similar problem with a different brand of car. It was coils. I have no idea if it would apply in your case, but a bad coil will not fire a plug. I wonder if that would show up on the computer? I would think so.

 

[wallymn]

Have you tried moving injectors from 1 cyl to another see if the Misfire moves?

 

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Re: 2010 4.6 - HELP! - Multiple Cyl Misfires & Other Issues - Dealer No Help

Put a OBD scanner on it with Dash Commander and pulled some data:

Short Term Fuel Trim is swinging wildly with 02 sensor readings when under throttle/load. When foot is off the throttle while moving, the O2 and STFT drop to 0. Havent gotten LTFT numbers yet.

Most concerning are timing numbers are swinging, often hitting +20-45 degrees which seems really high.

HEre is a video of me looking at various settings, mostly at idle with some runs up to 2500rpm in park. Not entirely sure what I should be looking at, just looking for outliers.

Raw Excel data dump from all sensors on a 90 second ride around the block where I pushed it a bit on a straightaway.

Found a fairly knowledgeable guy and have it in his hands right now. He's testing coils and injectors this morning to see where that stands. MAF and O2 sensors should be next.

Will report back and would LOVE any input in the meantime.

- - - Updated - - -

Have you tried moving injectors from 1 cyl to another see if the Misfire moves?

Thanks for the reply... my buddy is testing coils and injectors today. Would be odd for several (4/6/8 and possibly 3) to go out all at once (MPI), but who knows!

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Had a similar problem with a different brand of car. It was coils. I have no idea if it would apply in your case, but a bad coil will not fire a plug. I wonder if that would show up on the computer? I would think so.

Thanks for the reply. I agree coils could be the issue. I'm unsure of how many coils there are on this engine and how they're arranged (2 or 4 plugs per coil?)

 

[Mark_888]

This is not the "short cycle on/off" induced stumbling that some experience. This has persisted for about a week now and wasn't short restarted.

I don't know how you can rule that out, even if you didn't short start it. There was fundamental problem with the early Tau V8's that relied on gravity to get valves and other internal engine parts in correct position for next start up. Some people reported problems just by parking on a steep incline, without short starting. Cold weather aggravates the ability of gravity to get internal engine parts in correct position for start up.

Once the problem occurs there is usually some permanent damage to the engine that throws the timing off.

 

[[icon]]

I don't know how you can rule that out, even if you didn't short start it. There was fundamental problem with the early Tau V8's that relied on gravity to get valves and other internal engine parts in correct position for next start up. Some people reported problems just by parking on a steep incline, without short starting. Cold weather aggravates the ability of gravity to get internal engine parts in correct position for start up.

Once the problem occurs there is usually some permanent damage to the engine that throws the timing off.

Interesting regarding permanent damage. I would love to read about that if you had any links? Everything I've read seems to indicate that the issue corrects itself pretty quickly. You make an interesting point if there is indeed evidence that timing is thrown off permanently somehow.

 

[Mark_888]

Interesting regarding permanent damage. I would love to read about that if you had any links? Everything I've read seems to indicate that the issue corrects itself pretty quickly. You make an interesting point if there is indeed evidence that timing is thrown off permanently somehow.

My comments are based on recollection of members posting on this forum who had those problems back starting in 2009 and continuing for several years for the Tau V8.

In most cases, even when violent shaking of the engine occurred at startup (due to misfires), when the engine was shut off and re-started, things appeared to be back to "normal." However, it became clear that some engine damage had occurred, and sometimes at a later date that led to premature engine failure.

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Re: 2010 4.6 - HELP! - Multiple Cyl Misfires & Other Issues - Dealer No Help

Coils, Plugs, Injectors passed testing. Compression / Leak down underway... valve cover may be next. ugh.

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ISSUE DIAGNOSED:
Broken Valve Spring.

Apparently pure dumb luck the valve never hit the piston.



Broken Spring

 

[Mark_888]

Re: 2010 4.6 - HELP! - Multiple Cyl Misfires & Other Issues - Dealer No Help

Broken Valve Spring. Apparently pure dumb luck the valve never hit the piston.

How difficult (and expensive) is that to fix?

 

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Re: 2010 4.6 - HELP! - Multiple Cyl Misfires & Other Issues - Dealer No Help

How difficult (and expensive) is that to fix?

THE GOOD NEWS: It's only a $20ish part

THE BAD NEWS: Very tight quarters and often involves pulling the head, which is a ~20hr job at a dealer. My guy was thankfully able to get it out without pulling the head. Others may not be so lucky.

My guess is I'm looking at 6-10 hours between diagnosis, pulling valve cover, retrieving old broken spring, getting new spring in place, and re-assembling. Better than 20+ hours from pulling the head, but still not cheap work. The rate of your local engine guy is what will determine the cost. Dealers tend to be higher end ($125-150/hr)... independent shops can be lower at times.

I'll be sure to update the thread when I get a refined number.

 

[Mark_888]

Re: 2010 4.6 - HELP! - Multiple Cyl Misfires & Other Issues - Dealer No Help

THE GOOD NEWS: It's only a $20ish part

THE BAD NEWS: Very tight quarters and often involves pulling the head, which is a ~20hr job at a dealer. My guy was thankfully able to get it out without pulling the head. Others may not be so lucky.

My guess is I'm looking at 6-10 hours between diagnosis, pulling valve cover, retrieving old broken spring, getting new spring in place, and re-assembling. Better than 20+ hours from pulling the head, but still not cheap work. The rate of your local engine guy is what will determine the cost. Dealers tend to be higher end ($125-150/hr)... independent shops can be lower at times.

I'll be sure to update the thread when I get a refined number.

I wonder if any dealers would even do it. When that sort of problem occurred under warranty, dealers almost always got new engines from HMA.

 

[Mandrake]

If my Tau V8 is affected by this (Manufactured in 2008) and it has 105,000 miles, am I better off just leaving it or should I proactively replace the valve springs? I have the dealer service history and it never mentions replacing a valve spring.

 

[Hero6]

In my opinion, I would be proactive with this an replace them now, before you have an issue. Not sure your experience level working on cars and what tools you have, but I would do this myself. You can pull the valve covers, and with a proper fitting and air compressor, fill the cylinder with air to hold the valve in place. Using a cheap valve spring compressor, remove and replace each spring one at a time. The compressed air keeps the valve from dropping into the cylinder, this way you do not have to remove the cylinder head. Any local shop should be able to do this, not really a Hyundai dealer specific job. Just my opinion...
Also, may as well replace the valve stem seals while you are in there. they will be completely exposed and easy to swap out.

 

[jimmy buoy]

So we all know that hindsight is 20/20, but wouldn't trying a simple compression test reveal an issue with that cylinder and simplify diagnosis?