Running lean/lopsided fuel trims w/new engine

[Flapjack]

I drove the Mustang for about 40 miles yesterday. As long as I'm even partially on the throttle, it (barely) stays at stoich. If i put it in neutral, it almost immediately goes lean. I'm also getting lopsided fuel trims most of the time.

I parked it last night and don't plan on driving it until I get it running less lean. I plan on doing a compression test tonight, as well as double-checking for intake/exhaust leaks.

The attached log has two analog PIDs for my two widebands. I'd love for someone to say "it just needs tuning", but my gut is that something is off mechanically.

Link to log:
https://www.box.com/shared/3370a6075af0c87e59e7

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[stkjock]

I can't address a lot of the issues you mention. However, going lean when you take the load off by putting it in neutral is normal.

 

[dysan]

A few people have had issues where the o2 sensor plugs were swapped between driver's side and passenger side.

 

[Hawgman]

check your PMs. I have some questions and a story...

 

[Flapjack]

I can't address a lot of the issues you mention. However, going lean when you take the load off by putting it in neutral is normal.

I understand that... I'm used to it. However, this is different. Open loop (WOT) is fine. It is anytime fuel trims are involved (closed loop) that I see the lean condition (ie: idle, cruise, etc...). When cruising with a little more throttle than needed, the PCM is able to correct enough to bring it to stoich, but the fuel trims are way bigger than they should be. That is a straight-up tune issue. It is mostly the disparity between the two banks that worries me.

A few people have had issues where the o2 sensor plugs were swapped between driver's side and passenger side.

I will double-check the wiring again, but I don't believe they're backwards, as I actually labeled them last time I was worried they might've swapped (they weren't).

check your PMs. I have some questions and a story...

Replied back. Hope it helps.

 

[Tiddies]

A few people have had issues where the o2 sensor plugs were swapped between driver's side and passenger side.

i thought O2 sensors were universal between left and right but not front and back

 

[JeremyH]

The sensors are, the plugs themselves which Dysan is talking about are not and will swap banks.

 

[pmcferron]

I had a afr variance between banks and it was my camshafts. What cams are you using? I've heard of 2 different sets locally being incorrectly ground by comp. I'm not speaking of just the BBR spec'd grinds like mine either.

 

[Tiddies]

The sensors are, the plugs themselves which Dysan is talking about are not and will swap banks.

ah got it. thanks

 

[05stroker]

I had a afr variance between banks and it was my camshafts. What cams are you using? I've heard of 2 different sets locally being incorrectly ground by comp. I'm not speaking of just the BBR spec'd grinds like mine either.

Seems to be new trend of Comps...

 

[Flapjack]

I had a afr variance between banks and it was my camshafts. What cams are you using? I've heard of 2 different sets locally being incorrectly ground by comp. I'm not speaking of just the BBR spec'd grinds like mine either.

They're custom-grind Comp Cams.

Seems to be new trend of Comps...

I really hope not....

I just got done doing a compression test. 95psi on all 8 cylinders. Keep in mind, I'm at a very high altitude (6400ft), but that still seems a bit low. Used to seeing about 120psi on a stock engine. This engine is setup a little loose for higher boost, with 2618 pistons, 9.5:1 CR, .026/.024 gap, and Total
Seal rings at 1.5mm, 1.5mm and 3.0mm.

I did the compression test dry, with all 8 plugs removed (which looked great, btw). Still, does that sound a bit low?

 

[BruceH]

I'll preface this with I only have experience with my car and I'm just a hobbiest.

You have 37% load at idle. To me that's really high. I'm at around 22% at idle. Load is based on maf xfer and motor displacement, basically calculated airflow via the maf voltage vs displacement. Does your tuner know you have a 5.4?

 

[Flapjack]

I'll preface this with I only have experience with my car and I'm just a hobbiest.

You have 37% load at idle. To me that's really high. I'm at around 22% at idle. Load is based on maf xfer and motor displacement, basically calculated airflow via the maf voltage vs displacement. Does your tuner know you have a 5.4?

Yes, load is a bit high. I'm used to 20-25% myself.

I ran the car today and it does sound like I have an exhaust leak....

 

[pmcferron]

They're custom-grind Comp Cams.


I really hope not....

I just got done doing a compression test. 95psi on all 8 cylinders. Keep in mind, I'm at a very high altitude (6400ft), but that still seems a bit low. Used to seeing about 120psi on a stock engine. This engine is setup a little loose for higher boost, with 2618 pistons, 9.5:1 CR, .026/.024 gap, and Total
Seal rings at 1.5mm, 1.5mm and 3.0mm.

I did the compression test dry, with all 8 plugs removed (which looked great, btw). Still, does that sound a bit low?

i would honestly take a degree wheel and check the cams if you dont find out anything else. my RH bank the intake valves were opening 4 degrees sooner and closing 10 degrees later than the LH bank. when you laid the cams out side by side it was visable with the eye that they were not the same. even when i got my second set the intake centerline was off a couple degrees and we used trick flow adjustable crank sprockets to fix that. not even a week later my tuner said he had a 4V car come in with the same problems and it had comp cams as well

 

[Flapjack]

For what it's worth, I just looked up the numbers from right before I pulled the stock engine. I got around 135-140 per cylinder. Seems like a huge drop, even with heads and cams.

LSA is 116 on the cams, which is pretty much all I can publish spec-wise.

 

[retfr8flyr]

It sounds like the cams may be off and you have a valve opening when it shouldn't, to give that low a reading. Have you tried doing a leak down test yet?


Earl

 

[Flapjack]

It sounds like the cams may be off and you have a valve opening when it shouldn't, to give that low a reading. Have you tried doing a leak down test yet?


Earl

Haven't done one yet. Don't have the tester. A friend of mine does, though.

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[one eyed willy]

Haven't done one yet. Don't have the tester. A friend of mine does, though.

Sent from my DROID BIONIC using Tapatalk 2

make sure to grab a adaptor for the spark plug hole....normal kit wont have a adaptor for our heads....

 

[retfr8flyr]

I would definitely do a leak down test. That will show if your loosing pressure through the valves or rings. I just don't see how it could be tune, or fuel, related with that low of a compression.


Earl

 

[pmcferron]

I'm with earl, that compression seems too low for things to be just right. Hope you get it figured out though man, I've been there before.