One bank lean

[whipped]

mmmmmkay, new intake installed with new gaskets, and torqued to specs. Exactly the same results according to the BLMs.

So, short summary:

One bank lean
Searched for intake leaks, found none
Switched injectors between banks, found no difference.
Did power balance test, found 3 cylinders not giving their all, centered around cyl #6, which seemed to be just short of dead.

Found cylinder 6 spark plug to be a lot lighter than the rest. Probable indication of lean condition.

Replaced intake manifold and gaskets in case of cracks or leaks.

Back to square 1.

Oh! Maybe my spark plug wire for that cylinder is shot. I'll swap it between the banks, and while I'm at it, I'll switch around the injector harness in case that one connector is screwy or something.

Any other ideas while I'm at it?

[Kohburn]

if the plug wire was shot i'd expect the plug to be darker not lighter

try swapping injectors between cyls and seeing if the lean condition travels with the injector

[The Dark Side of Will]

get your injectors cleaned?

play with plug wires.

the power balance test showed telling results. Now act on them.

[whipped]

try swapping injectors between cyls and seeing if the lean condition travels with the injector

Switched injectors between banks, found no difference.

Just tried swapping the injector harness between banks as well, no difference.

Unfortunately, none of the rear plug wires are long enough to reach the other side.

I was also thinking that spark plug could have a hairline crack or something, causing a random misfire, causing a lean condition to be read...

so... I don't know what to do. I can afford a new spark plug, no problem there...

The problem is I don't have enough money to replace the wires, and since I can't swap them between banks...

I guess I could wait until night and try spraying them with water?

[eHoward]

If you've got a timing light, you can try hooking it up to each wire as the engine is idling and it should flash. IF one doesn't flash, you've got a problem.

[whipped]

I tried the misting trick, and couldn't find any arcing. So I drove it back home, and then was opening the garage door (had to get out) and I heard it missing pretty good. So I sprayed the wires again, and couldn't get it to do that again, so I don't know if it was a coincidence or what...

The plug wires are only like a year old though.

Now from what I've read, the timing light trick doesn't really mean much for DIS? Something about even if one plug is dead, it will still fire the light? I can give it a shot though.

after I do, I'll get that spark plug swapped out just in case, and I think i have a spare coil to swap in to check.

[The Dark Side of Will]

The timing light trick worked on my 3.1 w/ DIS.

[whipped]

tried timing light, ok there.

Changed the #6 plug, same BLMs as before (actually slightly better, 139 instead of 141... probably statistically insignificant)

hmmm
:lamer:

Here's my general thoughts..

all of the cylinders seemed to have some noticeable drop in RPM and a change in idle quality. The odd bank most definately is the "strong" bank, as all of them really hit hard when their fuel injectors were unplugged. Cylinder #2 seemed as strong as the odd bank. The others, I'm not so sure about.

It *may* be safe to assume #4,6,8 are equal in terms of power loss. If that's the case, I wonder what would cause that... Lets assume it's the whole bank is lean, and for whatever reason, one cylinder is "okay" with that.

Anyways, what would cause that? There are only 3 things that I can think of that might cause that... Maybe one side of the exhaust is more restrictive than the other side? The other, which i guess is common on northstars, is the fuel pressure regulator is leaking into the odd bank.. causing it to appear rich, and the other side to appear lean. The one I hope its' not, is a burnt valve(s) or head gasket.

Now I pulled the FPR vacuum line and didn't notice any gas... the others remain to be tested.

Oh, and I guess it could still be an exhaust leak in the lean side. I don't know how I would test for that..

none of the above really explains why I would see one spark plug a lot lighter than the rest though... well except the evil one. that = teh suck.

[whipped]

going to do a compression check on #6 and #7 to compare, and go from there.

[whipped]

done. exactly the same, 130. 150 if I hold the TB open... not that that means anything, but I don't have an air compressor for a leak down test.

[Shaun41178(2)]

Cylinders and gaskets are fine then.

Is 10% or less that significant? I mean its just a stock engine right? Why worry about the BLm's being off a smidge?

I say drive it and enjoy it.

Unless that 10% causes some real driveability problems I wouldn't worry about it. I mean how does it run and drive? If it feels good then I wouldn't worry about it. I am sure my 02's aren't the same for every cylinder or to even go as far as each bank. I am not concerned about it in the least.

:dontknow:

[whipped]

Is 10% or less that significant? I mean its just a stock engine right? Why worry about the BLm's being off a smidge?

I say drive it and enjoy it.

Unless that 10% causes some real driveability problems I wouldn't worry about it. I mean how does it run and drive? If it feels good then I wouldn't worry about it. I am sure my 02's aren't the same for every cylinder or to even go as far as each bank. I am not concerned about it in the least.

:dontknow:

I don't know... but it means if I tune for 12.6:1 at WOT, I'll be running 13.9 in the other bank... I think that could possibly burn holes in things. If I tune on the rich side, it won't make all the power it could.

Like I said before, it's possible the lightly colored spark plug (#6) was just a fluke or something, and the "lean" bank was just an exhaust leak or whatever. Either way I want to find out wtf is up. It pisses me off now, and i bet it's somethig rediculously stupid, like a knicked plug wire. All it takes is one cylinder to misfire occasionally, and it will fuck everything up.

How does it run and drive? "okay". I REALLY want to start tuning, but I'd be pissed if I burned a piston or something because of a stupid plug wire or bad coil or clogged cat or whatever.

I'll check the coils tomorrow.

I am a slave to my car. :whip: