Throwing codes

[Command Car]

Had to dynotune and burn a new chip for my trilogy MM with OBD2 sensors turned on to get thru emmissions. Getting PO172 and PO175 codes, been back once already to adjust, Anyone have a trick to solve this? I think the codes are being thrown when off throttle coasting down hill???

[blazen71]

The rear O2's can be turned off and still pass emissions. Mine has passed twice now. As long as the computer in communicating correctly with no CEL it should be OK.

[RacerX]

Sytem too rich on both banks. I know Trilogy Intl. adds fuel to make sure that you have a very safe tune. You should Call Jerry Barnes, I'm sure they've bumped into this before. Give him a call. 1 (313) 336 6135


The rear O2's can be turned off and still pass emissions. Mine has passed twice now. As long as the computer in communicating correctly with no CEL it should be OK.
It depends on the State. Some states won't pass you if you have things even turned off.

[SC Cheesehead]

Had to dynotune and burn a new chip for my trilogy MM with OBD2 sensors turned on to get thru emmissions. Getting PO172 and PO175 codes, been back once already to adjust, Anyone have a trick to solve this? I think the codes are being thrown when off throttle coasting down hill???

PO172 = Fuel Trim too Rich (Bank 1)
PO172 = Fuel Trim too Rich (Bank 2)

Could be an O2 sensor issue:

http://www.stealth316.com/misc/obdii_fuel_trim.pdf

[Command Car]

Replaced all 4 O2 sensors.

Need rear O2's turned on now in NJ

Been the Jerry route, too far from Lido's shop

[RacerX]

They're not going to rev to car up tyo WOT. Lower the fuel table for mid to low/idle rpms for the test. If you can reburn a chip, should be no prob.
OR... You could throw some MIL eliminators on those rear O2s. How soon do you need the inspection???

[Command Car]

already way overdue.

Would like to fix this with a tune, or something lik ethe boost sensitive vacuum or other easy mod.

Don't really know how to solve the problem. Trilogy solved it by turning a bunch of stuff off. My mm went thru inspection in '06, '08, but they needed all OBD2 gear turned on in '10.

Just need to fix the PO172, PO175 so I can get enough miles to reset all sensors.

[RacerX]

What rpm ranges is it happening in? If you're in closed loop, the pcm should be bringing you back to stoich and there shouldn't be an issue. Are they going WOT/OL??? Maybe set the TP to go OL a little later just to pass the test then change it back after?

[Command Car]

I've been driving very conservatively to try and reset the sensors as fast as possible. Plus the tuner believes the WOT settings are correct as he used his O2 sensor on the dyno. so we are talking about 1-2K rpm or so on the tack when the code gets tripped.

[RacerX]

It would seem that it's running rich enough in idle that the pcm can't correct enough to lean it out. MAF xfer accurate on the lower values??? Did you ever swap MAFs or have a MAFia installed, etc.?

[SC Cheesehead]

It would seem that it's running rich enough in idle that the pcm can't correct enough to lean it out. MAF xfer accurate on the lower values??? Did you ever swap MAFs or have a MAFia installed, etc.?


That's what I was thinking...

[Command Car]

It would seem that it's running rich enough in idle that the pcm can't correct enough to lean it out. MAF xfer accurate on the lower values??? Did you ever swap MAFs or have a MAFia installed, etc.?


Have not touched the MAF, what are my options?

I take that back, I hit it with some expensive electronic cleaner spray...

[RacerX]

Lean out the maf xfer by multiplying lowest above zero to 300 by 0.9 for a 10% decrease in lbs/minute telling the pcm to lower fuel going in at those points. Then raise it back up when the test is done.

I don't think the cleaner could have done anything unless it was dirty beforehand and someone tweaked you MAF xfer, then you cleaned it.

[Command Car]

Thanks

The cleaner had no effect.

[JoeBoomz]

Can you get by pulling the battery to lose the memory? Do the codes come up right away or after it's learned for awhile?

[Command Car]

I can clear the codes with a handheld, but can't seem to get the 30 or so miles with out throwing the code. I am fearful if I could get there that I would throw a code while in line at the inspection station.

[JoeBoomz]

I can clear the codes with a handheld, but can't seem to get the 30 or so miles with out throwing the code. I am fearful if I could get there that I would throw a code while in line at the inspection station.

My thought is, because it's a fuel trim code, that if it takes 30 miles to throw the code while relearning all of the AF tables, you could pull the battery right before the inspection and make it through before the codes pop up again (while it's re-learning).

Or do as RacerX suggests and adjust the tune for less fuel. Or hell, even disable those codes from coming up at all (also possible in the tune).

[RacerX]

Unfortunately, they look for that here. If the PCM hasn't received enough drive cycle time, the inspection stations computers show a Not Ready state and you have to come back after driving it for more power cycles. Turning off items in the PCM is now recognized by a lot of states inspection systems and will give a Fail. IT SUX!!!! :( Get it registered as a classic car and skip the emissions inspection! ;)

[JoeBoomz]

Bah, no kidding mucho sucko. Guess if adjusting the AF isn't an option trying some new O2 sensors might be the best route but is not a guaranteed fix.

[justbob]

My money is on a vacuum leak or a BAD MAF. Yes, they do go bad.

I would clean it again, or better yet (if possible) swap with a close by member. I would also check thoroughly for vacuum leaks with propane.

[Command Car]

Would you go with a factory MAF, or an upgrade? If an upgrade, which one?

Wouldn't a vacuum leak show up during the recent dyno tune?

[justbob]

What is your boost guage putting out for vacuum at idle? It only takes a tiny leak to run rich. Check all around the manifold, injector o-rings, MAF and zip tube, the three main vacuum lines on the back of the blower, PCV valve, along with all the other vacuum lines.

As for the MAF, yes motorcraft. I'm not sure of your power level or what your tuned with, but a MM one, or a 90MM Lighting one is fine. Ebay is where I get mine.

[Command Car]

just over 16 on the Auto Meter gauge at idle.

[justbob]

You should be at 19-21. Either the guage isn't accurate, or you do have a leak.

[SC Cheesehead]

You should be at 19-21. Either the guage isn't accurate, or you do have a leak.

Agreed, I'm pulling a consistent 20 at idle.

[RacerX]

You should be at 19-21. Either the guage isn't accurate, or you do have a leak.
I think it may be inaccurate. Does it fully zero when off? If it was getting that much air through a leak, your idle should be up higher and you would be running lean, not overly rich.

[Command Car]

Gauge is at +2 psi when engine is off. So that gets me to a little over 18+ psi vacuum if the gauge is otherwise correct.

I ran propane everywhere while watching a tach. Found nothing, but when I pulled a vacuum line and ran propane directly in, maybe moved up 20-30 rpm, but no real audible change.

Am I to take off an idle control plug or something before running the test?

[1stMerc]

Someone posted a cure for your issue in a previous thread, but i can't remember who. Might have been Fordnut, if he is the one maybe he will see this.

[justbob]

Was there ANY symptoms before your tune? Also has anything been touched after or during the tune? We need to focus on exactly when this all started.

[Meteorite]

What is your boost guage putting out for vacuum at idle? It only takes a tiny leak to run rich. Check all around the manifold, injector o-rings, MAF and zip tube, the three main vacuum lines on the back of the blower, PCV valve, along with all the other vacuum lines.


I am getting similar codes for running rich on one of my O2 sensors, on the rebuilt engine I just installed. I suspect a vacuum leak.

But ... can someone explain why letting extra air in makes you too rich? You'd think it would make things too lean.

Oh, wait, maybe I've got it: Extra air is coming in downstream of the MAF. Based on the O2 sensor saying things are lean, the injectors are commanded to stay open
longer to compensate. At some point, the limit of adaptation is reached (i.e., you can't command it any richer) and the "too rich" code is set off. Does that make sense?

[Command Car]

Was there ANY symptoms before your tune? Also has anything been touched after or during the tune? We need to focus on exactly when this all started.


I have an early Trilogy kit with the chip. The tuner ran the car with the Trilogy Chip on the Dyno to analyze the settings. Then burned a new chip with the OBD2 sensors turned on.

[Command Car]

It seems to behave (not show PO172/PO175) in hot weather. I just drove 35 miles or so, slightly aggressively, after a reset. The air temp was 95+ and the egt was 205 or so. No codes and I'm ready on all sensors except CAT, yes Evap is ready. I'm detecting this pattern after the last 250 miles or so.

When I run in 70-88 degree or so weather, I get a code in 1-10 miles.

Any clues from this info?

[WhatsUpDOHC]

Replaced all 4 O2 sensors.

Need rear O2's turned on now in NJ

Been the Jerry route, too far from Lido's shop



If you're in Joisey - You have to correct/adjust for BRUTAL humidity!

[Meteorite]

You should be at 19-21. Either the guage isn't accurate, or you do have a leak.


I am getting similar codes for running rich on one of my O2 sensors, on the rebuilt engine I just installed. I suspect a vacuum leak.

Now I guess I don't have a vacuum leak.

I'm pulling 22 inches of vacuum idling in Park and 19.5 idling in Drive.

So, I am now scratching my head to figure out why my idle is rough.

[Command Car]

So I'm getting the PO172 rich code when the air temp is below abt 88 degrees. Not sure yet if it is intercooler temp (which I monitor too) or IAT or something other that is critical.

When below 85 or so degrees, the code gets tripped under one of 2 conditions I've identified. So far. One is while crusing with more or less constant pedal pressure. When I crest a rise or go into a general slope and back off the pedal slightly, I get a short term rich spike (minus reading) and the code is thrown.

The other condition, also around 85 or less ambient temp, is when decellerating to enter an off ramp. There seems to be a delay in the shift to closed loop and the richness spikes for a moment tripping the code.

I eventually get it in bank 2, but the gremlin is much worse in bank 1. I can see that Bank 1 is slightly richer while driving with the scanner.

Any guesses? Anybody know what is wrong?

MM Trilogy.