JOHAN; Toon is throwing codes

[Mike_Levy]

Johan, I'm still running the base toon you wrote for my truck. Its been fine for over a year. Last weekend I put the stock cat-back back on my truck and now the truck is throwing the two lean codes (P0171, P0174).

My first thought was that the O2 sensors went south. Monitored them, and all 4 are bouncing all over the place. All 4 went bad at the same time? Maybe, but unlikely.

Then I started thinking that perhaps one or two injectors weren't firing right. Any way to test them?

I have a message into AJ to see if we can get her on the dyno this week for proper tuning, but I have no idea if he still in the Middle East or if he came back.

Whats my next step? I assume adding fuel with the Trinity won't do anything since the problem is also at part throttle. Should I reinstall the CMR tune? Will that do anything? Or maybe put back the aftermarket noisy exhaust?

I gotta do something. Can't leave it alone and possibly burn a piston..... though that would be a decent excuse for a stroker.

Engine mods are:
Modified aFe Cold Air Intake,
180° Thermostat,
Billet Tech Catch Can,
90mm Arrington Billet Throttle Body,
Inertia Ported Intake Manifold,
BWoody Thermalnator Intake Gaskets/Spacers,
Superior/GSM Ported and Polished Heads,
Comp XFI 268H-13 Cam,
SRT4 Stage 1 (55#) Fuel Injectors
Stainless Works 1 3/4" headers w/ Random Tech cats

I DO NOT have a wideband.

Any thoughts?

[Quick]

Jees-o-petes Mike, get a wideband already. And wasn't that tune just to get you from the garage to the tuners?

P0174 Fuel Trim System Lean Bank 2

No P0171? did you dump all the codes?

Doesn't that mean the adaptives are pegged lean?

Should I reinstall the CMR tune?

You put the regular performance tune back on there? With those injectors?
Let's see, bigger injectors, same injector pulse width ==> lots more fuel...
PCM is trying for 14.7, you're dumping all that fuel in there and it's got the adaptives pegged lean and still isn't getting to 14.7.

Short term can go 25%, long term can go 25% for a max adjustment of 50% (with throwing codes I assume) over the base injector pulse width. Just what percent larger are those injectors?

That's my guess. And yes, you should put the tune you had on there last back on it (assuming you took it out). Changing the cat back isn't going to make much difference, and especially not in closed loop.

[Mike_Levy]

I haven't had good luck getting with AJ. Everytime I'm supposed to meet with him, something happens. First the motor wasn't ready, then the truck got hit.

It is running the P0171 and P0174. Both banks are lean.

I'm still running the CMR tune. Just wondering if perhaps it got corrupted and I should reinstall it.

[Quick]

First find out if I'm reading that code right.
Does that mean the adaptives (fuel trim) are pegged/maxed lean -- narrow bands are reading RICH and the PCM is trying to bring it back to 14.7 and it isn't getting there?
What does the log show for the narrowbands? (voltage)

I'd just wait. If it's actually running lean enough to throw a code I wouldn't drive it.

[Mike_Levy]

I'll log it tomorrow. I need to drive it, since its my only vehicle. I have to get to work. I'm just babying it.

It just comes up as "System Too Lean (Bank 1)" and "System Too Lean (Bank 2)". Not sure exactly what it means. I would think too much air, or too little fuel. I tried resetting and they came right back, so I don't think they're false codes.

Strange thing is, no Check Engine light. If I hadn't been screwing around with the DashHawk, I'd have never known.

[Quick]

I think you're right. Too lean.
How long has it been since you changed the exhaust? I assume you took the cats loose at the headers to get it on there?
Air leaks?
That could be a stored code? that has to persist for a while before throwing a CEL?

Jees-o-petes, Mike, get a wideband already . You were just under there replacing the exhaust. what better time to install a bung?

[Mike_Levy]

We swapped the exhaust last weekend. The cats haven't been moved since they were installed. The Jeeps exhaust bolts to flanges that are clamped to the cats.

I'm not sure if there are any sort of leaks. I have noticed that the flow isn't balanced properly. One pipe smokes alot more then the other. I thought that was due to the OE muffler design though.

No codes are in History. Just the two current ones.

I'll order a wideband when I sell my MagnaFlow exhaust. I need to find a shop to install the bung. My normal shop isn't allowed to weld. Its against NY State regulations to weld in a place that also sells gas.

[mikel]

Could very well be an exhaust issue causing a 'false lean condition'....

If there is a small leak in the exhaust, near the O2 sensors, outside air is drawn in during low engine speeds, which contaminates the O2 sensors with fresh outside air, leading them to believe the truck is running lean, and thus pegging the trims and adding fuel till it throws a code.

My guess is a WB would show a crazy rich condition as the PCM is adding 33% more fuel for a problem that does not really exist....

[Mike_Levy]

I'll have the system checked for a leak tomorrow. I hope the problem is that simple.

I have a log that I did tonight. Its pretty sorry. Its snowing, so I never hit WOT I don't think. Not sure it matters since at WOT its in Open loop.

[Quick]

hmmm, I don't know how to read "adaptives"... I was kind of hoping for the O2 sensor voltage. You got a pid for that?
(yea, yea, I know, we don't have those kind of narrowbands but I believe the PCM converts the results and reports "voltage"?).

Anyway, the short term adaptiives are fluctuating and those "track" the narrowband readings. It did seem like the +peaks were way more than the -peaks. I would expect them to be kind of symmetric. I wouldn't expect an air leak to be real even and the +peaks did seem to be sort of sporadic.

[Mike_Levy]

I thought I measured 02 Voltage, but I guess I chose the wrong PIDs. Any idea what they would be under?

[Quick]

Ummm, no. I use a different device for all my monitoring.
But it probably isn't necessary. The short term adaptives should be tracking (or leading) the narrowband output.

Short Term
The first fuel correction program that begins functioning is the short term fuel correction. This system corrects fuel delivery in direct proportion to the readings from the Upstream O2 Sensor. The PCM monitors the air/fuel ratio by using the input voltage from the O2 Sensor. When the voltage reaches its preset high or low limit, the PCM begins to add or remove fuel until the sensor reaches its switch point. The short term corrections then begin. The PCM makes a series of quick changes in the injector pulse-width until the O2 Sensor reaches its opposite preset limit or switch point. The process then repeats itself in the opposite direction. Short term fuel correction will keep increasing or decreasing injector pulse-width based upon the upstream O2 Sensor input. The maximum range of authority for short term memory is 25% (+/-) of base pulse-width. Short term is violated and is lost when ignition is turned OFF.

The preset limits or switch points are the range of the narrowbands. That's something like 13.8 to 15.5 or there abouts. On the narrowbands that everybody thinks about that corresponds to an output voltage of 0v to 1v? So the PCM switches direction somewhere around .3v and .8v or there abouts. So if you logged a wideband it would look like a sine wave cycling between those afr values. The short term adaptives are constantly being adjusted up then down. It samples the reading periodically and feeds the long term adaptives. So the end result is that your afr/fuel is determined by base injector pulse width + long term adaptive adjustment + short term adaptive adjustment (during closed loop). You start with a base value and then adjust the long term adaptives until the short term is bouncing up and down with 14.7 in the middle. If the car is running lean then the short terms are spending more time going up than down ... sort of.

I think it throws a lean condition code when the long term (and maybe the short term too) are adding fuel over some threshold.

[Mike_Levy]

I normally use my DashHawk for monitoring. But I figured that since this is DS's board I should log it with the Trinity. :p

The DH does show O2 figures in mV.

[mikel]

just monitor those, thats fine....they are inthe trinity too somewhere, just buried in one of those menus.

[Mike_Levy]

Well, trucks at the service station. They're fairly confident that its probably just an exhaust or vacuum leak. I hope so.