G8 with an issue on while shifting

[pitstop190]

New to the Forum and I've got a 2009 G8 with an issue it has just started recently. It was built and tuned about 4 years ago, always done very well. Recently the customer said it was surging bad at idle in drive and would run very poorly until warmed up. Worse on cold days. We replaced his injectors at his request and replaced the spark plugs. Seems to run a lot better almost all of the time, but when shifting it feels like the shift is long and sometimes flares, and stumbles real bad with exhaust popping real bad. I've included the tune file and the data log of a run that starts out shifting well but at the end of the file the last event is terrible. Any insight on this will be greatly appreciated. Tuning is super cool and we look forward to learning the tricks of the trade.

run with bad fall off and popping after 1st gear.hpl
T Roy G8 tune.hpt

[Alvin]

add o2's to the log and we might be able to find a miss

[pitstop190]

I will get that this evening. Thanks

[pitstop190]

So it is raining here and a hard pull is pretty slick, but what I did capture is cruising and then down shift, when it down shifts it definitely feels like misfires, so I'm curious to see what you see in these that would support that or take it in another direction.

Thank you for your insight!1.hpl2.hpl3.hpl

[abc]

It's deff. going lean in places it should not. This may be better served in the GEN 4 section. I don't know how much the VVE table is used, but it sure is a disaster right now, massive holes in it.
Probably should start with verifying fuel psi under a load, seeing how you stated it used to run acceptable with the current tune.

[edcmat-l1]

Fuel trims are off pretty bad. VVE is a mess. Needs tooned.

[Alvin]

The tune is off. Lean, not going into PE when it should.. etc.

There might be other issues too but right now it looks like tuning is main issue.

[pitstop190]

The problem has gotten deeper. This car has misfires and a noise. The misfire is evident from start up, but at times will rev smooth like is has no issue, next rev it shudders on initial snap of the throttle,

Because of the cam, the misfire counter is off, so we are using temp readings on the header to try to understand what cylinders are contributing and which are not.

Things we have done to try to find or resolve the miss..
1 changed both coil pack complete assemblies
2 changed all plugs
3 changed all wires
4 changed all injectors with new Bosch injectors
5 Compression tests show 175 to 200 so compression is good
6 removed the left valve cover because the temp readings and o2 readings indicate that the miss is on the left side, and looked for broken springs, check for lifters getting tight, verify movement of the rockers look the same.

If the ecm is set to open loop and no fuel trims happening, there are spikes down on the left side showing misfires. Removing the new plugs reveals that #1 is still clean with fuel on it, #3 is black with soot, #5 is black, and #7 is clean with fuel on it. That was the first look and with 1 and 7 showing lower temps than 3 and 5. This morning only 7 showed low temp but the miss sounds the same.

The noise we hear in in the left valve cover but it does not make the noise on initial startup. This morning the exhaust temps were up to 400, except for #7 which was 275, before the noise started. It's a loud tapping noise in time with a rocker arm, not exactly sure which one. It the engine is shut off and restarted immediately, the noise does not start for about 10 seconds. That can be repeated over and over with the same results. The noise is alarming but when it's not there all is just normal valve train sounds. With the valve cover off, it is extremely easy to verify when its making it and when it is not.

I have tried the testing with the tune that the car came in with and with an initial tune supplied by another tuner and the reactions are the same so I don't think it is a tune issue making the misfire.
I consider mechanical because of the noise, although the noise does not make the misfire worse or better, but compression is good and even for a 235k engine.
I consider the ECM because of the abnormal temps and misfire with no other real reasons for the coming from mechanical.

The car is an 09 G8 GT with L76 and Auto Trans, Long tube headers, Cold intake, we believe a stage 2 cam. DOD was deleted and heads have BTR Springs seals and retainers. Car ran incredibly for 4 years and now has this issue.

Any input is welcome and Thanks in advance!!

[Alvin]

You've got to figure out where the sound is coming from asap. It could be a bad lifter or something.

My favorite method for finding misses is a cheap toy squirt gun. It's very obvious which cylinders are missing. The temp guns are a waste of time. it says right on them that the reflectivity of the object you are shooting will skew results. One darker primary and the results are out the window.

[horsepowerguru427]

My favorite method for finding misses is a cheap toy squirt gun. It's very obvious which cylinders are missing. The temp guns are a waste of time. it says right on them that the reflectivity of the object you are shooting will skew results. One darker primary and the results are out the window.

Interesting, I never thought of something as simple as that to use

[edcmat-l1]

You've got to figure out where the sound is coming from asap. It could be a bad lifter or something.

My favorite method for finding misses is a cheap toy squirt gun. It's very obvious which cylinders are missing. The temp guns are a waste of time. it says right on them that the reflectivity of the object you are shooting will skew results. One darker primary and the results are out the window.

We used to use a spray bottle back in the day. I'm talking decades ago LOL.

I use either a temp gun or thermal imager now. Temp guns work fine is you know how to use them and where to shoot the tubes. The tool is only as good as the operator.

[RDF1]

We used to use a spray bottle back in the day. I'm talking decades ago LOL.

I use either a temp gun or thermal imager now. Temp guns work fine is you know how to use them and where to shoot the tubes. The tool is only as good as the operator.

Yep. A spray bottle is the most useful tool.

[blindsquirrel]

Yep. A spray bottle is the most useful tool.

OK, teach me how to use the spray bottle to find the one single hot relay in a fuse box, or the one wire in a bundle that's slightly warmer than the others!

[RDF1]

OK, teach me how to use the spray bottle to find the one single hot relay in a fuse box, or the one wire in a bundle that's slightly warmer than the others!

SIlly... Didnt say it was the only tool. But if the relay is hot enough it will steam when hitting it with water....

[blindsquirrel]

Can't find the source of a key-off draw with a water bottle, was my point. Can't find out which of those two heater hoses is the inlet and which is the outlet. Can't let you see with your eyeballs and then save a snapshot to show the customer who never ever believes you that 60% of the tubes in that A/C condenser are plugged up from all the previous morons who worked on the car and added 2oz of oil every single time the system was opened "just in case"... thermal imager can do all those otherwise-impossible things plus show which exhaust runner is cooler than the others.

[Alvin]

yeah but I thought we were diagnosing a miss.. not a wiring issue?

[gametech]

We used to use a spray bottle back in the day. I'm talking decades ago LOL.

I use either a temp gun or thermal imager now. Temp guns work fine is you know how to use them and where to shoot the tubes. The tool is only as good as the operator.

I barely get out the point and shoot temp gun since I started using thermal imaging. Started using a Seek thermal that plugged into my cellphone a few years ago, and finally bought a dedicated thermal when the Seek quit working recently. Found a usable handheld on amazon for $139. Being able to view a full header all at once is very useful.

[pitstop190]

Today we will run running compression tests to see if a lifter is keeping a valve open once the oil pressure comes up. Was told to loosen the rockers while running to see if the miss went away, but the rocker arm starts to rotate off of the valve, don't want to chance wrecking something else. The noise really seems like an oil pressure related thing. When the noise is present, you can shut the engine off, restart right back and the noise won't come back in for about 6 seconds.

Definitely getting thermal image. Every test mentioned in this thread would be awesome with thermal...

[Alvin]

A lot of wiped cam lobes show up as a miss first.. then a noise.

There is usually no metal in the filter either.

[pitstop190]

Started the car today and it ran fine, we did the running compression tests on the bad cylinder and a known good, looks exactly the same on both, they hit 130 psi steady. So after not seeing anything that shows issues, we put it back together and let another tech listen to it and it sounded fine. So I drive it down the street and it is absolutely normal. In fact I will data log it tomorrow and send it in for tuning. I do not understand. And yes I know it will be back, but at the moment it is running like it has in the past.

Till I update again....