One bank lean

whipped · Post by **whipped** » Sat Oct 29, 2005 8:57 pm

:scratch:

I moved the wideband from the rear to the front bank, and low and behold, it confirmed the narrowband's findings... The front really is running 10% leaner.

Only thing I can guess is vacuum leak on the front, or exhaust leak on the front. I'm 90% sure it's neither. So what else would cause this?

:cussing:

Fast88Fiero · Post by **Fast88Fiero** » Sat Oct 29, 2005 9:50 pm

Weak injectors/dirty fuel rail?

whipped · Post by **whipped** » Sat Oct 29, 2005 10:07 pm

injectors are new.

dirty fuel rail? mmmkay, :scratch:

Fast88Fiero · Post by **Fast88Fiero** » Sat Oct 29, 2005 10:36 pm

I've seen crap inside of fuel rails before at work. Will plug injectors and restrict flow through the fuel rail.

whipped · Post by **whipped** » Sat Oct 29, 2005 10:48 pm

huh... well the rail is less than a year old, so I doubt that's the problem...

whipped · Post by **whipped** » Sun Oct 30, 2005 12:23 pm

One suggestion was one of my (new) injectors may be out of spec. So I switched the injectors around, and now we'll see if the rich bank switches sides...

I also tried spraying for vacuum leaks, but again couldn't find any.

whipped · Post by **whipped** » Sun Oct 30, 2005 7:59 pm

swapped the injectors with little difference noted.

Kohburn · Post by **Kohburn** » Sun Oct 30, 2005 8:45 pm

whipped wrote:swapped the injectors with little difference noted.

compression check for difference between cylinders

The Dark Side of Will · Sun Oct 30, 2005 9:21 pm

If you wired it the way you "should" have, then the banks are fed from different fuses. The ECM switches ground. Check the supply voltage for each bank.

whipped · Post by **whipped** » Sun Oct 30, 2005 9:24 pm

compression check would be a large PITA.

I actually wired the injectors through one fuse, so they should be the same. Keep 'em comin!

whipped · Post by **whipped** » Sun Oct 30, 2005 9:52 pm

Here's an idea,

http://web.camaross.com/forums/archive/ ... 23102.html

Could it possibly be the IAC or PCV? It would be wierd to see one bank effected more than the other, but I don't know. How are the throttle body passages set up?

Post by **admin** » Sun Oct 30, 2005 10:24 pm

Usually if there is a vacuum leak it affects all cylinders however I am unsure how the Nstar vacuum lines are setup.

I highly doubt its a vacuum leak.

Perhaps it is the fact that you have both banks wired into the same fuse that is causing the problems. I am just throwing things out there though. You have a 7730 trying to control this stuff and modified programming so I have no idea where to start with this.

whipped · Post by **whipped** » Mon Oct 31, 2005 12:46 pm

So I'm pulling plugs to see if there's any obvious differences between the two banks... I haven't seen any yet, they're both the pretty standard light greyish color.

Although I don't really know how to read plugs, I can tell a melted one from a normal one. I also am not really sure if 10% is enough to make a difference in the plugs.

But considering they're both looking about the same, I'm starting to wonder if it might just be an exhaust leak. I mean, unless one of the cats plugged up or something.

whipped · Post by **whipped** » Mon Oct 31, 2005 8:16 pm

well I had an idea... force the timing to 10 degrees, disconnect the ISC after it's warmed up, start a datalog, and start unplugging the injectors one at a time.

This powerbalance check should at least isolate any problems to one or more cylinders. Right now it could be one cylinder getting excess fuel, or one cylinder not getting enough (or misfiring). It will be interesting to see if the rpm drops across the cylinders are close or not.

The Dark Side of Will · Mon Oct 31, 2005 9:25 pm

Hadn't really thought of it, but I guess the power balance check also works on the $a1 code...

whipped · Post by **whipped** » Mon Oct 31, 2005 10:23 pm

as long as I remove the IAC connector, disable idle spark (remove the wire), and run open loop... I think it should give a good place to start looking...

whipped · Post by **whipped** » Tue Nov 01, 2005 12:04 pm

ok, here's the results:
The idle ended up to be about 1000 (completely by mistake

), so these are the actual measured rpms with that cylinder's fuel injector disabled:

Cyl rpm
1 976.4
3 970.9
5 965.5
7 965.5
2 975.5
4 983.3
6 997.5
8 984.3

4,6,and 8 are quite out of line. But #6 appears almost dead. It's possible I didn't wait long enough or something, so I'm going to do a retest of 4,6,8 with 7 as a control. I hope it's nothing sucky like an early headgasket leak... <knock on wood>

whipped · Post by **whipped** » Tue Nov 01, 2005 3:39 pm

I pulled the plugs on that side (more work than I really wanted to do), and compared them. Everyone looks the same except #6.

It has more heat coloration on the body, it has this pearlescent blue at the very base of the ground tang (signs of over heating?), and has a lighter porcelain than the rest. All have a very white ground tang...

I think all these point to it running lean, but want to get other opinions. I'm sure you can tell which is which in that pic. :blah5:

Since it didn't move when I swapped the injectors, wouldn't that HAVE to mean an intake leak????????????

The Dark Side of Will · Tue Nov 01, 2005 7:21 pm

How's your wiring on that bank? Have you checked injector voltage at the injector during operation?

whipped · Post by **whipped** » Tue Nov 01, 2005 7:34 pm

wiring's good, if it weren't, I'm sure more than one would be suffering from a problem. When you say "during operation", what do you mean? It's a pulsed coil, so I don't know how I'd get a meaningful reading.