Running Lean

[flint54]

From my other saga, you know I've just pulled the cylinder head.

 

Valve tops (and spark plugs) are tan-white rather than dark, which

I've always associated with running too lean. Machinist said the

same thing as soon as he saw it. I have good fuel pressure (30+psi)

and good fuel delivery (> 1 lpm). I have new injectors that I saw

flow tested. Truck runs smoothly (at least until I pulled the head)

and does not run hot. I don't (yet) have an A/F meter so I cannot

offer data. So, my puzzle is, how concerned should I be, and how

can I dial in a bit more fuel? I have a 63mm TB and I'm wondering

if this a contributor, and whether it's time for an adjustable FPR ($$),

or whether there's some simpler trick.

[flint54]

Forgot this info: current injectors are 20lb/hr (210cc/min @ 43.5 psi test).

[HOrnbrod]

W/o an A/F meter installed, there's really no way to accurately measure the ratio. Install one, then if you are in fact running lean, you can richen it up either by an adjustable FP regulator, or build an adjustable MAP, or both. As for myself, I use just the Hesco adj. regulator because the adj. MAP mostly affects the mixture only at near and up to WOT. The regulator affects the mixture over the entire power band.

[flint54]

Let's see what Santa brings.....

 

Somehow I had the naive idea that the O2 sensor was supposed

to detect a lean condition and tell the ECU to do something about

it, but perhaps the ECU is out of options with the current fuel

delivery components.

 

Meanwhile, Hesco is sending me a set of head bolts and I asked

him to toss in an AFPR for good measure.

 

Does anyone know what the dealer wants for head bolts ?!?!?!? :fs1:

Two bolts at the dealer pays for all fourteen from Hesco.

[flint54]

As a followup, I installed the Hesco AFPR and adjusted the setting to 34psi (vac on)/42psi (vac off).

Drove 800 miles and pulled plugs. They're much darker now, nearly sooty. No more too lean. Once

I modify the downpipe to receive a 2nd O2 sensor I'll put in the A/F meter and have real data. Now then,

the new development is unsteady idle. When driving, sudden release of pedal and motor will nearly stall.

Sometimes it will really stall. When sitting still, the idle is smooth, but an occasional downward (~200 rpm)

momentary drop. This new development is only after reworking the head (valve job and shave).

 

Double checked manifold bolt torque - all good (gasket is new)

Checked compression - 165-170 psi on all cylinders and full on 3 strokes

Looked for intake leak using propane - none found

Vacuum is steady at 18, and responds correctly when throttle is blipped

IAC is new and OEM

IAC and TPS connectors verified clean

 

:hmm: :hmm: :hmm: ?? Any ideas?

[carnuck]

I think you fixed the vacuum leak and over compensated with the fpr.

[HOrnbrod]

I think you fixed the vacuum leak and over compensated with the fpr.

 

Agree. 42psi (vac off) is too much for a stocker. Again, you're just shooting blanks until you can see real time A/F metered results .

[flint54]

Yeah, the A/F meter is in the near pipeline, I need the data.

 

My thinking was that the AFPR adjustment, set at only 2-3 psi

over original, was compensating for all the other things I've done

to improve airflow. (no cat, better intake, FIPK, porting, 63mm TB, etc)

 

I don't think I've ever had a vacuum leak, at least not one that shows

up on the gauge. I'll swap back the old IAC to see if that makes

any change also.

 

On the plus side, as long as the RPM is above 2500, this motor

now moves this truck like a scalded dog, especially in the dirt. :rotfl2:

[Jeep Driver]

Yeah, the A/F meter is in the near pipeline, I need the data.

 

My thinking was that the AFPR adjustment, set at only 2-3 psi

over original, was compensating for all the other things I've done

to improve airflow. (no cat, better intake, FIPK, porting, 63mm TB, etc)

 

I don't think I've ever had a vacuum leak, at least not one that shows

up on the gauge. I'll swap back the old IAC to see if that makes

any change also.

 

On the plus side, as long as the RPM is above 2500, this motor

now moves this truck like a scalded dog, especially in the dirt. :rotfl2:

 

 

Interesting. I lose all pull above 2500rpm. Optimum for me is 2000rpm. My bottom end is real strong but 2500-3500 just seems to be nothing there.........I assume air flow which is my next project. Any ideas?

 

Also can you expound on the A/F meter?