My car's throwing a P0300 code (multiple cylinder misfire). Now I don't have the supercharger belt hooked up yet, as I just rebuilt the top end. The heads were ported, had a valve job done, then reinstalled LIM & blower, etc. The guy that ported my heads took a little too much material off above one of the injector spots, so there is a small hole there, but I'm pretty sure the o-ring on the injector is well below the hole. I know that an injector problem could throw that code, but it's only one cylinder - so I'd get a different misfire code if it was in fact that injector.

There are no driveability symptoms whatsoever. The only thing that comes to mind would be the EGR. I do keep getting a code for a bad EGR, but I didn't throw the P0300 before the rebuild, and I'd had the EGR code for over three years. The only issue that I'm seeing - other than the obviously bad EGR - are my lean fuel trims. I'm not sure which fuel trims are out of whack, but it's only one of them. One is slightly lean - ~2.3 or so, but the other one is ~10.5 or so. I have no exhaust leaks FWIW. Any ideas other than the EGR constantly throwing exhaust gas into the LIM?

 

Remove the XPZ cam and it will go away... lol

Wait, what? So is there a hole from your intake runner venting to the atmosphere (I imagine so if the hole is above the lower oring)? If so, that's a real problem. I'd see if you could get it welded up or something. I hope that guy gave you the port job for free since it sounds like he practically ruined your head.

If that is a +10.5 for your long term trims, that probably means you have a problem somewhere- a vac leak or something, and if its a +10.5 long term, and keeps hitting a +2.3 short term- its going to eventually 0 that short term out and move it to the long side- making your long term trims almost +13. I could see fuel trims being out a bit, and needing a tune- but with how mild your mods are so far, and no SC belt yet- it having to add that much fuel could be an issue. (try and find out which is STFT and LTFT- and try driving until the STFT's settle to almost 0- eventually it will get all the common changes transferred over to the LT side)

That could be a possibility, and those fuel trims being wacky are odd too.


Unfortunately, I think the P0300 code is one of the harder ones to figure out, just because there is a lot of stuff that can cause a misfire. Do you have access to a scan tool where you can log some scans to post up? Maybe try logging misfires and see if its just a couple cylinders (maybe a shorting out coil pack)- or scattered all around.

I could've swore you could put something under the EGR to block it off (like a penny or something?)- obviously you'd get goofy readings while driving, but since EGR doesn't activate at idle- maybe you could try doing the blockoff temporarily and letting it idle to see if the misfires clear up?

 

[QUOTE=bumpin96monte;216650]

It must be venting to the atmosphere - I honestly didn't think much of it. Hell, I didn't even notice it until I was about to install the injectors. If you could, help me understand how the intake part of the head works. Air enters through the intake/lower intake, and from there it flows through the intake runners in the heads? How serious is this issue? From my perspective, it has extra air coming into the runner(from the hole), going into the combustion chamber, causing.... what exactly?

I do believe it's the LTFT's that are +10.5 or so, and the STFT's that are +2.3. Could the aforementioned problem be a vacuum leak? My vacuum at idle is ~21 inches, which is right on target for me.

Sadly enough, I have no scanner, other than the Aeroforce. I've been considering a Powrtuner recently, but I dropped ~$400 on tires for the Monte instead. I figured I kinda needed them more than a scan tool at the current time.

Oh, and I wish I had an XPZ cam. lol

 

Here are some cutaway pics:
LS3

LS7

L67 (you can see the fuel injector hole above the intake ports in the head)


The second pic shows a little better with the intake manifold hooked up- and is pretty much how the L36's are set up with the injector in the LIM- so if you have an actual hole that is between the intake runner- and above the oring on the fuel injector, you're sucking in air from outside (bypassing the MAF). With how bad iron can be to weld, and depending how bad the hole is- I'd bet that head is scrap.

Air comes out of the supercharger, into the big hole in the top of the LIM, then flows out through the 6 rectangular ports in the bottom sides of the LIM into the heads. In the heads it flows past the fuel injector, and then down to the valve then into the combustion chamber. So pretty much as you said.

Very, any vac leak is a problem that needs to be fixed. All air coming into the engine needs to come in through the intake system so it is filtered and measured by the MAF. However, your problem is worse because its after the supercharger- so once you get into boost (anything above ambient pressure)- its going to blow you pressurized air out of that hole (and the more boost you run, the more air will escape. This will do the exact opposite, because the air has already been measured, but is now lost- so now that one cylinder will go rich.

Neither is a good thing because A) your screwy fueling to that cylinder will effect the rest because there is only 1 O2 sensor and B) your leak is right by the fuel injector- so that one cylinder is going to have very unusual flow around the injector spray compared to the others.

What makes it worse is cast iron sucks to weld- its not like mild steel or stainless where you can just MIG away. There is some stuff that can patch it without welding- but it kinda depends how bad the hole is. Depending how bad the hole is, and how common L67 heads are- I'd almost think it would be worth it just to scrap them. If your porting guy really did poke through, he should reimburse all your money for the port job, and for the replacement heads- it is his/her fault they're ruined.

Lean when not in boost, Rich when in boost - just on that one cylinder; then the goofed up exhaust output from that cylinder is going to hit the O2 and skew the whole engine to try and compensate.

Yeah, as I said before- the STFT's will always bounce around a bit- but if they keep hitting the same number at the same rpm and load point- then they'll be 'learned' to the LTFT's (so it will add on to them). Even driving around with +10 LTFT's doesn't seem right, but if those ST's learn over to the LT's, then that's really out of whack- especially since you don't have many mods. Is this reading at idle, or while driving or what?


Oddly enough, that vacuum seems pretty good to me. Do you have a picture of the hole? I'd say regardless what else is wrong, that needs fixed first- then work on making sure the EGR is fixed and not leaking, then go from there.

 

Thanks for your expertise. I don't have a picture of the hole right now - but I have a short day of work tomorrow, so I'll pull the rail & injectors and get a picture. It's really not a huge chunk of material missing, but I'm going to do some research on ways to fix the head. I'm hoping there's some way to patch it without having to tear the motor down again. But, if that's what needs to be done, I'll do it. The vacuum is basically the same as it has been the entire time I've had the motor, which is weird, especially since this problem.

Those LTFT & STFT readings were at idle. Now, the STFT's have zeroed out and the LTFT's are at 14.0 at idle.

 

Another update. I drove the car ~5 miles today, and the LTFT's are down to 7.0.

 

How big of a hole are we talking? A pin hole or 1/4"? Only way I can think to repair it with the head on the car is some sort of metal epoxy. Just make sure you don't mess up the Oring seal area for the injector- or you'll just end up with a vac leak there instead.

Really though, there are only about 2 ways I know to do a permanent fix though- weld it (which may be tough if its super thin around that area) which is tough on cast iron- but doable, or they have a brazing rod that you can use with an oxy torch for repairing cast iron. You'd have to put something behind the hole, so you didn't get buildup inside- and so you wouldn't have to grind it down again.

If it were me, and the hole was much bigger than a pinhole- I'd just pick up some new stock heads and be done with it. Who did the port job anyways? Hopefully they gave your money back for the port job?

That is the part I don't get, and what makes me think that it can't be that big of a leak.

IMO something is seriously wrong with that. You're definitely way off of normal, and you're coming up on the limits of the system (+16.4 I think). Only thing that I can think that would cause that is your fuel system not keeping up (pump low on pressure- mine pegged +16.4 when the pump started going out)- or a vac leak- but your vac readings don't correspond to having any major leak.

At idle still? That's odd- could maybe be something going bad in your fuel system causing pressure to go up and down?

 

It's a fairly small hole. Here's a pic.



I'm considering a temporary fix for now, as I'm moving out of this house fairly soon - and I don't want the Monte to be torn apart when it comes time to go.

I understand where you're coming from, but the hole is very small, and I'd hate to toss a set of heads when only one of the heads is messed up, and that's a small hole. A guy from CGP did them. I tried to get up with him, but no avail thus far.

I moved the car into the driveway today, and the LTFT's were at 3.8 at idle, so at least the trims are going down to normal.

 

Can you circle the hole in mspaint or something? I want to see if what I think is the hole- actually is- so you've got the head, its got the chamfer, then the straight wall area, then another chamfer then the injector hole.

If I'm right- the hole is in the lower chamfer? If so, you should be ok- because from what I remember, the injector lower oring seals in the straight wall center section.

 

You're right. The hole is in the lowest section where the o-ring seals. I still sealed it today with JB Weld.

Back to the EGR though - what was it you said about putting a penny in there? Do you mean taking the nuts off and taking the top part of the EGR off, and putting a penny over top of the valve inside?