Need new o2's?

T

Trav4011

Active member
I'm slowly getting the tune ironed out on my truck, but, I still have a lean low RPM/partial throttle condition.. Once the engine hits around 2800-3K rpm, or if I go more than about 25% throttle, it jumps into open loop, and A/F is good. But, partial throttle boost situations and low engine speed, I'm lean as hell (14.5-15:1). Should I toss a new pair of o2 sensors in, and see if that helps?

Travis
 
14.5-15.1 is completely normal as the O2's switch back and forth. Your wideband will bounce cruising and idling. If it bounces too crazy, then your MAF curve and/or you injector low slopes need to be modified.

Some other tweaks that help driveability are timing below your idle speed (ramped up, then as low as 5 deg at idle speed).

Do you go very lean (>16:1) at tip in? There's some acceleration enrichment parameters that JLP can adjust, along with the air manifold volume, etc. Things that you won't have the ability to modify with the handheld.

JL should be able to help, just be sure that you've got -0- exhaust leaks pre-O2's, because that will throw off any closed loop drivability.

BTW - datalog your LTFT/STFT's, and let us know what they show.
 
What he said. O2 sensors are not like they were 20 years ago when they needed to be replaced every few years. For the most part they will last for a very long time without replacement and then it's usually because the heater is burned out and causing a check engine light. It sounds like yours are working exactly as they should.
 
Right.. I know that in closed loop, while cruising, the A/F will fluctuate.. and that part is perfect.. but, what about lean misfire during partial throttle boost situations? At what point does the truck go into open loop?

Travis
 
Trav4011 said:
what about lean misfire during partial throttle boost situations? At what point does the truck go into open loop?

Travis
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Two different situations.

First question: Lean misfire can be due to many things - poor low injector slope setup, accelerator enrichment, load for failed maf table, not enough fuel pressure at that instant, possibly too much idle air, etc. You need to datalog a drive - start the logging at idle, then put into gear. Let the truck idle in gear and start moving. Do a few small stabs of the throttle. Close the log and send it to JL. You'll want to log as much as you can - IAC, IAT1/2, load, rpm, MAF V, LTFT, STFT - ask JL what he wants you to log.

Second question: Open loop occurs at a specified throttle position/rpm based on a function. .. or you can force it open loop all the time with some changes. Factory tune for OL occurs at 2.44 under 2400RPM, 1.96 @2600rpm, .98 @ 3500...etc.

Also, there's no way to tell if you're "perfect" at low loads/crusing unless you log you short term and long term fuel trims (STFT/LTFT).
 
Thanks.. :)

Here's my main problems..

Cruising along in closed loop.. 50-55mph.. and roll on the throttle to accelerate. The A/F goes to 15:1, as boost pressure climbs to 5psi or so, and the truck stumbles/hesitates (lean miss). If I go past 1/4 throttle or so, it snaps out of it, and A/F drops to 12.3:1 or so. I assume this is open loop..

Taking off from a stop, just partial throttle, low boost.. the engine runs lean (15:1) and I have some hesitation.

Cold start is pretty decent.. as is warm restart.

I set my base pressure at 43psi, with the vacuum line off. And, I have TONS of fuel (Fore setup with 2 walbro's, wired up to run full voltage), and a -10an feed split into twin -8an into each rail.


I'm just waiting on my new laptop to show up, so I can datalog.. My old one took a dump on me.

Give me a standalone, and I can tune anything.. But, I know jack squat about Ford ECM tuning! ;)

Travis
 
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I would call JL and let him know. He can adjust your MAF transfer table up a bit in the lower loads and see if that gives you less hesitation/more fuel. The problem with that is it will not necessarily remedy the situation, since closed loop relies on the O2 sensors, and they're commanding the fuel. If you can't datalog trims (some hand-helds can w/o a laptop), you're really flying blind. A leaky injector may add more fuel into the exhaust stream which could in-turn cause your O2 sensors to think you're running too rich and pull fuel. A vacuum or intake leak after the MAF will also do that.

Shoot, there's so many variables, it's the fun I went though over the last two years tuning my truck.

You 100% positive you dont have a leaky intake gasket or vacuum leak somewhere??? :? A smoke test might help find one.
 
Heh.. funny you should mention it..

I looked again, and found the bypass hose had blown off of the bypass valve on my 2.6. I hooked it back up, and now, I'm down to 11.8-11.9:1 up until about 5K or so, and it leans back out to 12.4 or so up to the limiter.

Driveability is better, but, I still have a nasty lean spike on tip in, and a some hesitation while cruising at low speed (under 50-55mph).

It's better, though.. Just gotta keep tracking down the bug and get it nailed down.

Travis
 
I've read here that part throttle stumble could be due to a cracked Y fitting in the fuel tank between the fuel pumps BUT it would straighten out when the fuel system goes to full voltage. An I see you have your pumps pypassed to full voltage all the time. Strange.
jeff
 
I have the Fore Precision Works fuel hat, so that's not going to be a problem.. Thanks for the input, though..

Travis
 
im no where near as powered as you but i am having a similar problem and i believe its my o2s. i have the stainless y so its not that. my truck will idle fine and WOT is fine. but when i give it some gas it shutters and goes very lean (17.0- ---) and than kicks back in and pulls like hell. I also have the dual walbros working at full voltage all the time. I am going to try replacing the o2s because i think they are shot (100k on them). even in park and i give the truck a good rev it shows (---) on thw dieband than goes to 11.0-11.5. i got the truck dialed in and it was fine, but on the 200 mile drive home it started acting up like this. i pout the old o2s back in with the LTs i just did so i am just going to replace them. When your that serious into the truck, why not just spend the 8- and by two new bosch sensors. cant hurt.
 
I cant remember which site it was on but there was a member selling 2 front 02 sensors for 50 shipped to the your door. One of the best deals i have gotten in a long time!

Wayne
 
Yeah.. I don't have the SCT racer software, so I can't tune it.. I'm working with Johnny to try and get it dialed in.

I am going to put a new set of o2's in tomorrow, and see if that helps. It sure can't hurt anything..

Travis
 
SVTLight2000 said:
im no where near as powered as you but i am having a similar problem and i believe its my o2s. i have the stainless y so its not that. my truck will idle fine and WOT is fine. but when i give it some gas it shutters and goes very lean (17.0- ---) and than kicks back in and pulls like hell. I also have the dual walbros working at full voltage all the time. I am going to try replacing the o2s because i think they are shot (100k on them). even in park and i give the truck a good rev it shows (---) on thw dieband than goes to 11.0-11.5. i got the truck dialed in and it was fine, but on the 200 mile drive home it started acting up like this. i pout the old o2s back in with the LTs i just did so i am just going to replace them. When your that serious into the truck, why not just spend the 8- and by two new bosch sensors. cant hurt.
Click to expand...

How old is your fuel filter? That's pretty much exactly what will happen when they start plugging up. I don't think that's the OP's problem, but it could be yours.
 
On a unrelated note.. I REALLY need to get my oil seperator installed.. lol.. I had a nice blue puff of smoke when I nailed it earlier.. ;) I live about an hour from L&S.. so, I'll probably go pick one up.

Travis
 
Took the truck out this evening.. it was cooler out after a nice shower had passed.. It was about 75 degrees, versus 95-100 degrees.

A/F was 11.5:1 or so at WOT.. So, I made a nice long pull on the highway..

At about 120mph or so, right as I was about to let off.. the truck felt like it lost about 100hp.. I let out, and slowed down. Everything seems normal.. I checked all of my vacuum lines.. no leaks.. no smoke.. nothing.. So, I drove it the rest of the night.. and got on it a few times around town. I didn't notice any more loss of power. So, that was pretty odd.

Other than that.. she's running great!

Travis
 
Trav4011 said:
Took the truck out this evening.. it was cooler out after a nice shower had passed.. It was about 75 degrees, versus 95-100 degrees.

A/F was 11.5:1 or so at WOT.. So, I made a nice long pull on the highway..

At about 120mph or so, right as I was about to let off.. the truck felt like it lost about 100hp.. I let out, and slowed down. Everything seems normal.. I checked all of my vacuum lines.. no leaks.. no smoke.. nothing.. So, I drove it the rest of the night.. and got on it a few times around town. I didn't notice any more loss of power. So, that was pretty odd.

Other than that.. she's running great!

Travis
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Did notice or log IAT2's by any chance? I wonder if they spiked towards the top of your pull and the ECM pulled timing.
 
Nah.. I wasn't logging at the time..

It feels fine, still.. so, that must be what it was.. But, not sure why it would do that all of a sudden? I just put a new intercooler pump in.. fresh fluid..

Travis
 
Trav4011 said:
Nah.. I wasn't logging at the time..

It feels fine, still.. so, that must be what it was.. But, not sure why it would do that all of a sudden? I just put a new intercooler pump in.. fresh fluid..

Travis
Click to expand...

How did you clean your I/C? The first time I cleaned mine I used a case of brake cleaner. Then somebody told me to try K&N air filter clener, so I tried a super stregnth degresser and couldn't believe how much more crap came out. It was like I hadn't even started yet! The other thing is with no oil seperator, you might be coating your I/C with oil, killing the efficiency. But a log of your iat2's will tell you for sure! These 2.6's get fricken hot! A KC system has really takin care of my problems here.
Jason
 
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