Randomly goes +16 ltft 10.1AFR stalls P1133

[94GrandPrixSE]

I have been working on this one since I installed the Headers and IC a year ago. When the car is warm sometimes at low rpms (idle, reverse, stop lights) it starts pulling 10 AFR +16 ltft and my o2 stops switching stays at about 1035 and stalls unless I hold my foot on the gas. The tune is overkill and the rear o2 has been deleted along with the cat testing.
My o2 is in the SD headers by the firewall. I tried it in the u bend with no luck as well. This is like the 3rd o2 Im on all ac delco oem. More details about the car in my signature. Any thoughts or ideas is very appreciated. Going nuts over this.

[Turbocharged400sbc]

the ECM ground and rad fans ground are to the same points, if the grounds are bad then when the fans are turned on voltage drop will cause all sorts of funky problems.

temporarily delte the evap/purge, dirty maf element, cracked vac line/rubber at map sensor are all possibilities

hows it do with the o2 unplugged? did you use a canned tune? its possible the tune is bad on the lower maf table/fatfingered

[94GrandPrixSE]

Is that one of the grounds that's connected with a bolt to the trans? Tried 2 mafs, has all new vac lines. The overkill tune was fine before header and ic install and half of the time it idles good just when that o2 stops switching.

[Turbocharged400sbc]

also clean the ones on top of the unibody rails

any leaks on the headers? is the afr readuing off a separate wideband? whats the pcm read for commanded afr?

you could even have a leaking injector/fpr

[94GrandPrixSE]

Possibly a small leak at flex but that's after the o2. The AFR reading 10 is my wide band the car is commanding 14. The fpr is new. Injector leaking where?

[Turbocharged400sbc]

wb/oem sensor locations currently?

the PCM has the maf, tps, map, and O2 as trusted sensors. check the tan/black wires at the block/bellhousing stud, often its damaged, headers often interfear with the starter wires

if the pcm is reading air properly, then it should calc correct fuel for the nb to be near 450mv (switching as r-l transitions)........
you have uncalculated fuel ingress, or overestimation of air

if one injector is stuck open/fpr leak into then its .....

any leak within 12" of the sensor can EASILY suck air in at idle with the larger interval of reversion at low speed exhaust events

[94GrandPrixSE]

Oem o2 is in the original bung by the firewall. WB is in the u bend. Which stops switching when the cars o2 stops now that I think about it.

[94GrandPrixSE]

the ECM ground and rad fans ground are to the same points, if the grounds are bad then when the fans are turned on voltage drop will cause all sorts of funky problems.

temporarily delte the evap/purge, dirty maf element, cracked vac line/rubber at map sensor are all possibilities

hows it do with the o2 unplugged? did you use a canned tune? its possible the tune is bad on the lower maf table/fatfingered

Tried unplugging egr and evap no luck. When I disconnect my o2 it runs fine a bit rich at 13 AFR at idle but runs well. What does this mean?

[94GrandPrixSE]

Also checked for leak no leak by the headers

[SgtMarshal]

just unplugging the egr and evap won't have the desired affect, you also need to disable the codes from reporting. and I think an exhaust leak would make the car go lean.

last year my car went from running fine to pig rich like yours, it ended up just needing a mass air flow sensor adjustment. it happened basically in between the winter and spring weather changes, and I also moved so the elevation that I lived at dropped about 1200 feet. I'm not sure if that is your problem, just sharing my experience.

[94GrandPrixSE]

It has all the symptoms of the catalytic converter testing problem. I'm thinking maybe Will at overkill missed it.

Does anyone know if HP tuners now has the option to disable it? Tiny tuner? Haven't really found a forum that solves it other than tiny tuner but that's not even a sure fix.

Thanks

[Scottydoggs]

TT will kill the cat test. its the only way i know of.

unless will uses TT then hpt to flash his pcm's,. wills not a dope, im sure hes got the cat turned off.

check the o2 fuse, and its wires to it.

[94GrandPrixSE]

Fuse and wires check out. The codes are set to not report. Unless I need the rear o2 plugged in still for some reason?

[Scottydoggs]

should not need the rear o2 at all if the cat test is truly turned off.

you got the stock pcm still? if so pop it in and see if it does the same thing. you'll get a rear o2 code asap cause its not plugged in, but the fuel trims will might turn normal.

if you have the rear o2 still, put it back in for the test.

[94GrandPrixSE]

I put the old PCM in does the same thing right off the back even tried learning it with no luck. It runs fine if I unplug the o2 and run it off the maf if that helps at all.

[Scottydoggs]

if its the same with both pcm's you got another issue then.

[94GrandPrixSE]

any more ideas? willing to try anything at this point.

[Scottydoggs]

got a o2 harness extension? make sure its ok. if all this started after the pcm and header install, and the o2 acts up like this id think the harness is bad if you bought one.

[94GrandPrixSE]

After ic, headers and fuel pump. Tested harness with voltmeter it was ok.

Another note, when the o2 does decide to switch it's not as fast as it should be.