[09V8G8]

Car had ARH 1 7/8 headers with catted x-pipe installed at the shop with rotofab cai and a dyno tune coulple weeks ago. First I was running muffler delete but got too loud so this past saturday I through some hooker max flo mufflers on it.

The problem......

Once I made the car quiet I noticed four slip fit joints on the arh kit are leaking but didnt have time to fix it, I may take it back to the shop that installed it for them to fix it.

Next problem. ....

I wanted to check fuel trims and misfire on my Snapon solus ultra scanner to see how things looked and was curious about the "missfire" feel.

Sure enough if I held the throttle at about 1400-1500 rpm every cylinder is missing, 0 misfire readings at idle, didnt check anywhere else on the rpm range.

Fuel trims....

STFT 1&2 adding between 2%-5% at idle
LTFT 1&2 pulling -3%

What are some thoughts? Could the leak before the cats cause it to go that lean to add fuel? Also, the misfires? Can the tune cause this?

After the mods the car put down 350 rwhp where others with same mods do about 370rwhp. Could these issues be stealing 20hp? Car does not rip like it should butt-dyno I dont feel it pull harder than before. I see videos where cars are barking between gears and mine is kind of mellow.

I have sent an email out to the installer/tuner waiting for reply. He is a great guy so im assuming he will take care of whatever is wrong.

I want to sort all these things out before I install my dod delete very soon.

Thanks for any input guys.

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[jpG8GT]

Might want to check your plug wires and plugs. Could have cracked a plug or have a plug wire loose. Fuel trims are ok from what you say. Want them as close to 0 as much as possible. Fix your exhaust leaks and have your tuner make sure everything is right. Don't always get mad about the dyno numbers. Keep us updated.

 

[Dulvalius]

345-360 hp is about the norm for those mods, youd be lucky to get 370 out of those mods or haveing more supporting mods (ported intake/ tb etc) could get you there. Yeah and remeber...its tough mentally but dont always rely on dyno numbers..i went through the same thing with my cam.

 

[09V8G8]

Might want to check your plug wires and plugs. Could have cracked a plug or have a plug wire loose. Fuel trims are ok from what you say. Want them as close to 0 as much as possible. Fix your exhaust leaks and have your tuner make sure everything is right. Don't always get mad about the dyno numbers. Keep us updated.

Once I hear back from them Ill see what is the next step. When they put the headers on they also installed some new plugs, im guessing they are still good.

345-360 hp is about the norm for those mods, youd be lucky to get 370 out of those mods or haveing more supporting mods (ported intake/ tb etc) could get you there. Yeah and remeber...its tough mentally but dont always rely on dyno numbers..i went through the same thing with my cam.

You got that right, I was like "thats it" when I saw the results. My tuner definitely knows his stuff, im sure he will sort it out. Its just frustrating you know. Have a little ocd about perfection

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[todds87ss]

The type of dyno also affect the numbers, but based on your "feel", I'd say there is power on the table somewhere- likely in the trans tune or as jp mentioned, you likely have a plug/wire issue. I have similiar leaks at all of my slip fit connections that I cannot correct. I managed 401hp on a dynojet, and since have put down 451hp with cam and still have leaks.
When you say every cylinder is missing, are the misfires throwing codes? How can you tell that every cylinder is missing? If both sides are missing, there may be a fuel pressure issue. It is unlikely that both sides are seeing the exact same lean issue from identical/symetrical leaks.
sorry I cannot be of more help.

 

[09V8G8]

The type of dyno also affect the numbers, but based on your "feel", I'd say there is power on the table somewhere- likely in the trans tune or as jp mentioned, you likely have a plug/wire issue. I have similiar leaks at all of my slip fit connections that I cannot correct. I managed 401hp on a dynojet, and since have put down 451hp with cam and still have leaks.
When you say every cylinder is missing, are the misfires throwing codes? How can you tell that every cylinder is missing? If both sides are missing, there may be a fuel pressure issue. It is unlikely that both sides are seeing the exact same lean issue from identical/symetrical leaks.
sorry I cannot be of more help.

I checked that its misfiring on all cylinders with my snapon scanner. It has a misfire monitor and shows you live which cylinder and how many times its missing. Equal across all 8 cylinders.

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[jpG8GT]

Even though your scan tool is showing random miss on all cylinders you could really only have a couple true misses. Remember, misses are a computer calculated counter. A miss on one cylinder can cause a companion cylinder to show a miss when its really not missing. Get your tune looked at and verify you have no plug or wire issues. A MAF not tuned right can cause all kinds of issues. Or low fuel pressure.

 

[09V8G8]

Even though your scan tool is showing random miss on all cylinders you could really only have a couple true misses. Remember, misses are a computer calculated counter. A miss on one cylinder can cause a companion cylinder to show a miss when its really not missing. Get your tune looked at and verify you have no plug or wire issues. A MAF not tuned right can cause all kinds of issues. Or low fuel pressure.

Its definitely missing, I can feel the engine shaking and the pop pop pop from the tailpipe. Misfire should usually make the car show rich readings but mine is lean, strange

 

[zepcom]

I'd take it back to the people who were last messing with it and have them fix it; if it wasn't misfiring before the mods, then something changed.

Those fuel trims otherwise look good so it doesn't seem related to your tune.

All 8 misfiring "equally" might point to CASE RELEARN, but that's just a hunch. Like the old days when the distributor was off "a notch". If the engine and ECM are not sympatico with where TOP DEAD CENTER is, then you could have misfires like this.

 

[09V8G8]

I'd take it back to the people who were last messing with it and have them fix it; if it wasn't misfiring before the mods, then something changed.

Those fuel trims otherwise look good so it doesn't seem related to your tune.

All 8 misfiring "equally" might point to CASE RELEARN, but that's just a hunch. Like the old days when the distributor was off "a notch". If the engine and ECM are not sympatico with where TOP DEAD CENTER is, then you could have misfires like this.

Just got a reply saying my lifters are in their way out and I need to do the cam thats why its doing this

 

[jpG8GT]

Do you have any valvetrain noise? Any low oil pressure codes? I can't see the lifters causing this from the header install and tune. I think you have a plug or wire issue still...


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[09V8G8]

Do you have any valvetrain noise? Any low oil pressure codes? I can't see the lifters causing this from the header install and tune. I think you have a plug or wire issue still...


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Only noise I get is when I first start it up, I hear lifters ticking for about 10 seconds. I think I will check plugs and wires today. I just dont want to install a cam kit before this is sorted out.

 

[Agose25]

Is the car stumbling and lurching when driving? Are you throwing any TRACTION CONTROL light ups in the center cluster?

During my header install I cracked a couple plugs and threw all kinds of misfires codes. You'd be surprised how easy it is to crack a plug.

 

[09V8G8]

Is the car stumbling and lurching when driving? Are you throwing any TRACTION CONTROL light ups in the center cluster?

During my header install I cracked a couple plugs and threw all kinds of misfires codes. You'd be surprised how easy it is to crack a plug.

No codes no lurching. At idle I feel it. If I rev to about 1500 in park I can definitely feel it.

 

[Agose25]

Reading back through your original post I noticed you never indicated that your ECM threw a misfire CEL i.e P0300, 301, 302, ... You just felt the car misfiring and then scanned it?

It'd be highly unusual for the ECM not to throw a CEL immediately if you were multi-misfiring.

 

[09V8G8]

Reading back through your original post I noticed you never indicated that your ECM threw a misfire CEL i.e P0300, 301, 302, ... You just felt the car misfiring and then scanned it?

It'd be highly unusual for the ECM not to throw a CEL immediately if you were multi-misfiring.

Thats what confused me too unless the light is around the corner. Misfire monitor showing all 8 misfiring at light throttle in park around 1500 rpm.

Also if I look at history codes there is a crap load of them, maybe from when it was tuned?

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[todds87ss]

Just got a reply saying my lifters are in their way out and I need to do the cam thats why its doing this

Who is that reply from? Lifters don't cause "misfiring". They make noise. When they are done making noise, they tear up the cam. Then there may be "misfiring". You would hear it long before that.
Someone likely wants your money. Could be the tuner who "knows his stuff"

The other info in this post that seems "off" is misfire without codes. Very odd. See if you can find another "scanner" to compare it to. Anyone with Powercal (or whatever the VMS scanner interface is called) should be able to look at this for you.

 

[09V8G8]

Who is that reply from? Lifters don't cause "misfiring". They make noise. When they are done making noise, they tear up the cam. Then there may be "misfiring". You would hear it long before that.
Someone likely wants your money. Could be the tuner who "knows his stuff"

The other info in this post that seems "off" is misfire without codes. Very odd. See if you can find another "scanner" to compare it to. Anyone with Powercal (or whatever the VMS scanner interface is called) should be able to look at this for you.

I am hoping the misfires are just from a bad tank of gas and it goes away or sets the light. The tuner does know his stuff, should see the cars that go in and out of there. He said its the lifters because of a prior convo we had about the ticking. He hasnt seen the car yet.

 

[gr8lover]

Who is that reply from? . Could be the tuner who "knows his stuff"

Gosh I sure hope this isnt the person I am thinking it is...... someone out there told me my old stroker was messed up and also said my trans was messed up..... and I ended up spending a ****load on a new engine and trans he "happen" to have at his shop.... then found out trans was perfectly fine from someone else and then engine was also in perfect condition!!!!! but in the end.... I spent a ton of money and someone was surely happy.... but not sure it was me... ...

hopefully this is not the same person "trying" to talk you into redoing your engine!!!!! cause if it was.... then this could be a "trend"...... or tatic whatever you want to call it....

 

[jpG8GT]

My advice. Find a local G8 member close to you that knows a thing or two and have them help you. DO NOT take it back to your tuner installer guy. Sounds like he is gonna get you for all your worth. A second and 3rd opinion is needed in your case. As said before a failed lifter is not gonna cause a miss without a hell of a noise. Your car probably would not still be running.


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