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Discussion Starter #1
Dealer said the misfire is probably from a bad lifter. Not sure if this is even a dod lifter? Injector was okay. Master tech said the ticking is probably a lifter.

How long can I drive it like this and not do any more damage? Not sure when I can get this looked at. Trying to call a few shops to get a dod delete with a stock LS3 cam.

Any rough costs from a shop??
 

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The more you run it, the more the damage. Stop now, a cam and lifters (if it's the problem). Keep running, getting closer to pulling the engine once all the shavings are scattered around. Keg is half empty on this one.
 

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Hello everyone I am new to the group but I have owned two g8gt's. I had one tapping before and I put a new oil filter and filled it with transmission fluid and poured the rest in the engine oil. It stopped tapping after a few minutes. I drove it like that for 2 or 300 miles. I then drained it and filled it with Mobil one full synthetic and a quart of Lucas and every oil change after that. I just ordered my second Dod delete kit Texas Speed. The first one was for my 08 Tahoe and the second one is for my G8
 

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If the tick is a lifter, it's the wheel or it's starting to rotate in the bucket. No elixir will cure it.
 

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That is true and the only repair for that is to disassemble the engine and replace the parts. It could also be a dirty lifter and that elixir will clean it. Never know until you try it.
 

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Discussion Starter #6
I talked to a local shop and he says it quite possibly be a broken valve spring on the 8th cylinder. Easy enough to pull the valve cover and look. Sound reasonable?
 

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You have nothing to lose, its all money now.
If its a broken spring its a win, for now.
 

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Discussion Starter #8
So I had a GM mechanic come over and he said it's probably not a lifter. I swapped coils, swapped plugs and plug wire to another cylinder. The misfire stays on cylinder 8. My OBD11 scanner detected the P0308 and it has the ability to show misfire counts on each cylinder. After swapping, still misfires on the 8th cylinder and no misfires on the swapped cylinder.
I read the dealer report again. They said they checked the injectors and said OK. BUT the description says all 8 even drop to 35 psi from 55 psi. So it seems they only did an injector pressure check? Doesn't look like they actually checked if the injector was actually firing? The 8th plug was dry but not sure if that means anything as the plug and coil are probably okay.

So by the above, I'm not sure the 8th injector is firing or not.

Does anyone know if OBD Link MXII has an check for injector pulse? I don't see it.

The only other thing I could see is if the wires to the 8th cylinder is bad.

It's odd though. When the mechanic started the car, his TechII showed no misfire when the car was cold. But as soon as the car was slightly warm, the misfires began again. And after I let the car cool down to swap the plug/coil/wire, it was still misfiring.

I guess I can unplug/plug in the injector plug. I haven't tried that yet.

Suggestions?
 

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AFM LIFTERS are cyl 1 4 6 and 7. You wrote: there was a drop when injector 8 was commanded for balance...55-35 psi- same as all other cylinders-so that fuel pressure was released when the injector 8 fired -where?- into cylinder. heck swap injectors if you have doubts- not hard at all on l76.
I havent seen many failed "regular non AFM" lifters but have seen ground cam lobes; some broken springs, and broken trunions. If you really need confirmation of any, collapsed lifter or even ground cam lobe.... pull the valve cover off . Inspect spring, then crank the engine- watch for cyl 8 rockers A rocking----- you will likely see one not MOVING if fully collapsed. Cam Lobe ground off diag needs the installation of a micrometer on the rocker. It only takes about .5 to remove coils and valvecover to check. about 1 hour with micrometer measurement of lift.
Basically if injector fires and there is spark, compression is decent and rockers rock some- no broken spring -->the head needs to come off and the lifter pulled- at that point you will likely visually see a pitted roller and worn cam lobe. honestly havent ever seen burnt or damaged valves on these motors- but that is also visually noticeable once head is off.
Estimate about 4hrs for right head pull. (maybe a little less- double that to replace lifter if its really collapsed and reinstall)
Cam ground- thats a much bigger job and then go DOD delete
 

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I have the same problem on my number 5 cylinder. change plugs, wires, fuel injector and intake manifold. Guy said the compression test was good. my lifters aren't making a Loud tapping sound. I'm think computer. I heard something about a bad cat caused a misfire. if I find something new I'll update.
p.s. dealer wants to wait because I just got the car and dont want the warranty company to deny claim.
 

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Discussion Starter #11
Update. I swapped injectors. Thanks for this site for how to undo the injector connectors. After putting all back together, I fired the engine up expecting the misfire to move from the 8th to the 4th. But all of a sudden no more misfires. My OBDLInk MX+ does seem to register some 8th cylinder misfires but it's well below the threshold. I reset the codes and have been driving the car to work for the last 2 days and no error codes and I believe the readiness is good to go. ie.. enough drive cycles performed. Not sure if that matters anyway the code should still show if there's still a problem
 

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Discussion Starter #13
I dunno. I swapped plugs, wire, coil pack (you should try this to see if the misfire moves) before. I could have been something as simple as unplugging the injector connector and plugging it back in. But who knows, it could come back. I won't really feel better until a few more days go by. It idles a little rough imho still But again I do have the good obdII reader.
Trying to see if the Torque OBDII reader app can see some additional information that the OBDLink app does not.
 

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Other than a less than solid condition of that # 8 injector connector (that may have been solved just by the reversal), I sure seem to remember somebody saying that "water" had somehow found a way to get trapped in the aft end of the fuel rail manifold. An that the rail has a small aft down slope design to it. If that's true, that would put cylinders 7 an 8 at the low points. If any water had accumulated around that # 8 position, maybe breaking into the fuel rail to reverse the injectors allowed any water to escape. I sure seem to remember that he also had a miss fire condition because of that.
 

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Discussion Starter #15
Oh nice theory. Could be as I physically lifted the rail up to swap the two injectors.
 

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I dunno. I swapped plugs, wire, coil pack (you should try this to see if the misfire moves) before. I could have been something as simple as unplugging the injector connector and plugging it back in. But who knows, it could come back. I won't really feel better until a few more days go by. It idles a little rough imho still But again I do have the good obdII reader.
Trying to see if the Torque OBDII reader app can see some additional information that the OBDLink app does not.
you have the OBD Link MXII or Mx? and I did swap injectors. what I notice was that I hear the misfire at idle skipping a beat or so. I unplugged the Injector to number 5 and heard the misfire every beat.
 

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Discussion Starter #18
Well on way home, I hear the motor start chirping. Mechanic says it's probably a lifter. And he wasn't that impressed with the health of the motor when he came by. So after discussing, we think an LS3 swap would be the best solution. I want this to be somewhat on a budget. Can anyone recommend a source for a good low miler LS3? And what years I should look for so it's as close to the L76 as possible? ie.. what year camaro or vette would work? Once we get the motor, we would want to see if we want to swap cams while it's out with another mild one
 

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Discussion Starter #19
LS3s are extremely expensive for a low mile version. Many of them are with the transmissions. I've even tried looking for the automatic versions with the L99 (still with DOD and cam phasers). Still expensive and would have to have the mechanic at least take out the cam phaser and consider removing it's DOD hardware. I suppose I could leave the dod in and just remove the cam phaser? The L99 is rated at 400 / 400.
Yet another choice is to find a L77 (Caprice 6.0 motor) which are available with low miles. Many with the auto trans hooked up. Would still run into the same consideration of DOD delete and cam install.

My question is this. Since some of these low mile engines come with the 6sp auto, I assume the auto drops in. BUT would the TCM have to be swapped to my original one in order for it to run? I assume it's on the valve body somewhere?
 

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Well on way home, I hear the motor start chirping. Mechanic says it's probably a lifter. And he wasn't that impressed with the health of the motor when he came by. So after discussing, we think an LS3 swap would be the best solution. I want this to be somewhat on a budget. Can anyone recommend a source for a good low miler LS3? And what years I should look for so it's as close to the L76 as possible? ie.. what year camaro or vette would work?...
That impressed with the health of the motor due to the suspected lifter issue or additional problems as well? Current mileage? Probably want to start a different thread regarding the LS3 engine questions.
 
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