Dooney

Hey guys, I'm new to the forum. I've seen it a lot before but just got around to joining. With that being said. I need some help with this issue. I've seen threads about it before but none have helped with my issue. I've got an 01 GT throwing these codes. I've checked for vacuum leaks and everything checks out good. I've got good fuel pressure averaging around 39-40 psi. I have a brand new MAF. No leaks before the upstream o2's. no leaks after the MAF to the throttle body, and I just changed out my upstream o2's about 3 months ago. Now here are the two things that are throwing me off. I was looking at my live data with my Diablo and the long term fuel trims are reading -25% (rich) but when I look at the voltage on my o2's they are reading 0.89 v's (I believe from what I've read this means they are reading lean) I am getting the same reading on all o2's except bank 1 sensor 1 which is reading at 0.07 Can someone please help me out at figuring out what is going on? The car has a rough idle, is stumbling under acceleration. The only time it seems to run right is at WOT. I've also noticed that the car is going to closed loop at around 110 degrees. Is this normal? Any suggestions will help.

cliffyk

To begin, here is what the shop manual says about P1130, including possible causes and diagnostic tips. This all relates to the bank 1 (passenger side) front O² sensor; P1150 is the same, just for the bank 2 front sensor.

Here is some info about narrowband PZ O² sensors, you will see there that a high voltage (> 0.45 V) output from a PZ sensor indicates a rich mix. A low voltage (< 0.45 V) indicates a lean mix. Therefore the 0.89 V you observed is indicative of a rich AFR, the 0.7 V value indicates lean.

Real fuel trims, the short term fuel trims (STFTs) are much more important for diagnosing your problem than are the long term trims (LTFTs). The short term trims are based upon realtime feedback from the O² sensors and calculated by the PCM for closed-loop engine control. The LTFTs are accumulated into a table relating load and engine rpm, to averaged STFTs, (it is actually a more complex algorithm) and used for open-loop operation.

With regard to your -25% LTFT observation, this means that the PCM believes ("believes") the mix is rich and is pulling fuel in an attempt to lean it out. This is in keeping with the 0.89 V output, but not with the 0.7 V reading.

At this point I would disconnect the battery for 5-7 minutes to clear the KAM, this will make the PCM relearn the LTFTs, idle air trims, and other adaptive learning parameters--I.e. clear the slate.

Then check fuse #8, 30A, in the central junction box. It powers the heaters for all O² sensors and the EVAP and EGR solenoids and valves; if blown it can create all sorts of issues. If it is good then work the possible cause list from top to bottom, in particular check the O² sensor connectors and wiring, and ensure there are no exhaust leaks before or near the O² sensors.

Monitor the short term fuel trims if you can and see what they look like; see how they relate to the O² sensor output voltage, however looks for similar trends not exact mapping as the fuel trims lag the O² sensor output.

Let us know what you find...

Oh, the PCM will enter closed loop operation as soon as the O² sensors heat up, this should be within 45 to 60 seconds after startup, leading me to ask what O² sensors you used when you replaced them? The sensors on our cars have 3.3 Ω elements, older sensors generally had 6.0 Ω heaters--using the 6.0 Ω units on our cars will create problems.

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Also if you could use paragraphs next time it will make it easier for my 67 year-old diabetic eyes to read:

"Hey guys, I'm new to the forum. I've seen it a lot before but just got around to joining.

With that being said. I need some help with this issue. I've seen threads about it before but none have helped with my issue. I've got an 01 GT throwing these codes. I've checked for vacuum leaks and everything checks out good. I've got good fuel pressure averaging around 39-40 psi. I have a brand new MAF. No leaks before the upstream o2's. no leaks after the MAF to the throttle body, and I just changed out my upstream o2's about 3 months ago.

Now here are the two things that are throwing me off. I was looking at my live data with my Diablo and the long term fuel trims are reading -25% (rich) but when I look at the voltage on my o2's they are reading 0.89 v's (I believe from what I've read this means they are reading lean) I am getting the same reading on all o2's except bank 1 sensor 1 which is reading at 0.07

Can someone please help me out at figuring out what is going on? The car has a rough idle, is stumbling under acceleration. The only time it seems to run right is at WOT. I've also noticed that the car is going to closed loop at around 110 degrees.

Is this normal? Any suggestions will help."

Dooney

Thanks for the help, I have cleared the KAM with my tuner and it all returns to where it was within about 5 min. I have tried it with a cold start and at full temp to see if there was differences but it ran the same.

As for the o2's I used motorcrafts direct fit replacements from O'rilleys.

I already checked for exhaust leak before or around the o2's. I have long tubes on the car.

I will check the fuse after I get off work today and start working my way through the list and let you know what I find

cliffyk

You cannot clear the KAM with a tuner, all that can be done through the OBD2 ports is to reset the trouble codes--to clear the KAM you have to disconnect the battery for 5-7 minutes.

Ah long tubes--here is a table in the tune, the O² Transport Delay, that defines the amount of time (in seconds) the PCM will expect the O² sensors to report change in the AFR, after it makes a fueling adjustment. As the sensors are relocated further back with LT headers this value needs to be increased by 10% to 15%--sometimes more.

Here is the table for my '03; the highlighted numbers are the new values, the plain are the stock numbers:



Correcting this table will often clear up closed-loop operation AFR problems...

Dooney

Thanks for the table, so first steps are going to be to clear the KAM then adjust for the longtubes. I always thought I would need to adjust the fuel after I put them on but I was running them for about 8 months before I had the issue so I didn't figure it had anything to do with them.

cliffyk

There is some tweaking of fueling to be done after installing long tubes, however mostly they just let the engine breath better and as the MAF monitors all incoming air the tune will pretty much adjust itself as needed.

It is odd that 8 months have passed without issue--though how many of what sort of miles does that represent?

Do check that fuse also; and the wiring, t'would not be the first time LTs have burned something up...

Dooney

I would say there was at least a good 2-3k miles. I put a new clutch and flywheel in a few months after and wanted to get the break in period done as soon as possible. So it might be possible that I caught one of the o2 extensions when I was taking the transmission out and putting it back in.

cliffyk

That is not many miles then, if it were 10k I'd be wondering "why now?"

Do check the wiring and the fuse...

sn95_331_GT_ yellow

I was just about to ask pretty much the same question, cliff youre the man!!

Not to hijack, but would these codes also cause my car to pop ip P1000 (OBD systems readiness test not complete)?

Ive put about 250 miles on the car after I cleared the KAM and still no luck...

Thanks in advance again cliff!!

cliffyk

Any problem that can affect emissions control will prevent the I/M monitors from completing successfully, that is what triggers P1000. Do you have any active or pending DTCs now?

Here's a link to the 1996 OBD2 system operation manual, it describes each system in detail including the monitoring requirements and tests...