Focus St170 Annoying Problem With P1131 Dct

[kez9213]

Hi Guys,
I have a 2002 ford focus st170. It's throwing up code p1131 Lack of Upstream Heated Oxygen Sensor Indicates Lean - Bank No 1. I am getting loss of power, rough idling and poor fuel economy. After some research I cleaned the maf, plugs and checked for air leaks, but couldn't find any. The car is running slightly better but the cel came back on again with p1131. The lamda that it refers to was replaced last year then the car was stood for 11 months as i was away, so I can't see it being a bad sensor. Any ideas anyone?

Andy

[AdeMk1]

Pull the HO2S out and check if its fouled up with carbon, maybe being stood for 11 months hasn't helped & its a bit gunked up.

A little trick I do is pull the sensor out, pour a bit of lighter fluid on the end, light it & let it burn off. Trust me it works.

Also check for breaks in the wiring harness or water ingress in the plug connector.

What sensor did you buy, OEM, Bosch or other generic one?

[kez9213]

*Update*

Thanks for the advice AdeMk1. I did as you suggested but no different so today I changed the O2 sensor which has also made no difference whatsoever. I am still getting p1131 code, rough idling and hesitiation which is worse when hot. I have managed to get some live data info which I hope someone can shed some light on. At idle when cold the MAF reading is around 5.5 g/s and drops to around 3.5 - 4 when warm. short term fuel trim fluctuates between 0 and +35. however long term trim stays at 0! the pre cat sensor fluctuates between 0 and 0.2 and post cat goes upto 0.8.

Is it possible for bad plugs, leads or coil pack to cause these symptoms?

[FOCA]

If you have duff plugs/leads/ coil pacs then one or more of the cylinders may not be firing/ be firing intermittently

without a spark the fuel does not ignite and no power is produced in that cylinder (so its running on 3 cylinders instead of 4) - the fuei is still squirted in, but it is not burnt, this can cause problems

when the car is ticking over, take each of the plug caps/ leads off in turn (each cylinder at a time) if its ok, the note should change or the engine should stall - if nothing happens when you disconnect the "spark" that may be beacause its a duff plug/lead/coil etc

Examining each plug in turn and evaluating the condition/ colour can give you an idea about the mixture/ etc and potential problems (wot no codes/ computers )

The plugs should be regularily changed (probably more often than the rediculusly long recomended intervals from Ford)- they are a "service" item - the HT (high tension) system is like lightning - it finds the easiest/ shortest path, if the plugs get fouled/ worn, the easiest path may be the HT leads or inside the coil packs - so good/new/fresh plugs help protect the rest of the HT system (leads/ coil packs etc) - if the plg gap is too wide it puts mure strain on the leads/ coil packs, the plug gaps gets wider with age - gapping it down a little helps (shortest path etc )

[kez9213]

If you have duff plugs/leads/ coil pacs then one or more of the cylinders may not be firing/ be firing intermittently

without a spark the fuel does not ignite and no power is produced in that cylinder (so its running on 3 cylinders instead of 4) - the fuei is still squirted in, but it is not burnt, this can cause problems

when the car is ticking over, take each of the plug caps/ leads off in turn (each cylinder at a time) if its ok, the note should change or the engine should stall - if nothing happens when you disconnect the "spark" that may be beacause its a duff plug/lead/coil etc

Examining each plug in turn and evaluating the condition/ colour can give you an idea about the mixture/ etc and potential problems (wot no codes/ computers )

The plugs should be regularily changed (probably more often than the rediculusly long recomended intervals from Ford)- they are a "service" item - the HT (high tension) system is like lightning - it finds the easiest/ shortest path, if the plugs get fouled/ worn, the easiest path may be the HT leads or inside the coil packs - so good/new/fresh plugs help protect the rest of the HT system (leads/ coil packs etc) - if the plg gap is too wide it puts mure strain on the leads/ coil packs, the plug gaps gets wider with age - gapping it down a little helps (shortest path etc )

Thanks for the quick response.

Would the above also cause a lean condition then?

[FOCA]

Thanks for the quick response.

Would the above also cause a lean condition then?

No, it would be over-fueld if the cylinder(s) does not fire, with unburnt fuel going through the engine - lean obviously means lack of fuel/ too much air

Sometimes you need to check the basics/ go through everything a step at a time - the fault may be simpler than you think (eg - if you hear hooves - its most likely a horse, a zebra is less likely, and a unicorn is rare - if you see what i mean)

[kez9213]

Ok guys, I'm still having the p1131 problem. However for the past few days I have been reading up and learning how to properly use diagnostic equiptment to read live data, and have been able to rule various things out, but I am still pretty stumped as to what the problem could be, so let me run a few things by you all.

The symptoms I am having are all intermittent and include, bogging down in all gears at all rpm's hesitation, severe lack of power and high fuel consumption. Along with code p1131. I am able to clear the code and it might be a few days before it comes back or it might come back in a few hours.

With the diagnostic equiptment I have logged the following live data at idle:

Fuel status closed loop

STFT1 +36%

LTFT1 +0.8%

O2 b1 0.63v (fluctuates between 0.1 - 0.9v)

MAF 4.3g/s (Does drop to 2.8 after a while at idle and stays there)

RPM 843

Absolute throttle 18.4%

The thing is the above values happen as soon as the car goes into closed loop. The stft shoots up very fast to over +30%. If I rev the car up the stft dosen't drop at all but stays still at over 30%, which I believe rules out air leaks? Now if I set off driving after about 30 seconds the stft will drop and fluctuate between -2 to +2 as does the ltft, which I believe is normal and pretty good. The o2 voltage also fluctuates betwen 0.01 - 0.09 which I believe is also normal. If I pull over and idle again everything is fine and the trims and o2 voltage stay well within normal and the car idles smoothly. If I now turn the car off for about a minute and start again the car will be in open loop and as soon as it goes into closed loop the stft shoots up over +30 again!!! Then will drop again after a little driving!! I also noticed on the scanner that I was idling in closed loop and the car went back into open loop and the trims shot back up, so I gave a little tap on the accelerator and it went back into closed loop and the trims dropped again.

I have recently changed the cts, and thermostat, had the timing belt done and replaced the rocker gasket and put in new motorcraft plugs.

So there you have it! It certainly has me stumped! Any ideas from you guys?

[Sacha]

On 10/26/2014 at 8:28 PM, kez9213 said:

Ok guys, I'm still having the p1131 problem. However for the past few days I have been reading up and learning how to properly use diagnostic equiptment to read live data, and have been able to rule various things out, but I am still pretty stumped as to what the problem could be, so let me run a few things by you all.

 

 

 

 

The symptoms I am having are all intermittent and include, bogging down in all gears at all rpm's hesitation, severe lack of power and high fuel consumption. Along with code p1131. I am able to clear the code and it might be a few days before it comes back or it might come back in a few hours.

 

 

With the diagnostic equiptment I have logged the following live data at idle:

 

 

 

 

 

Fuel status closed loop

 

 

STFT1 +36%

 

 

LTFT1 +0.8%

 

 

O2 b1 0.63v (fluctuates between 0.1 - 0.9v)

 

 

MAF 4.3g/s (Does drop to 2.8 after a while at idle and stays there)

 

 

RPM 843

 

 

Absolute throttle 18.4%

 

 

 

 

 

The thing is the above values happen as soon as the car goes into closed loop. The stft shoots up very fast to over +30%. If I rev the car up the stft dosen't drop at all but stays still at over 30%, which I believe rules out air leaks? Now if I set off driving after about 30 seconds the stft will drop and fluctuate between -2 to +2 as does the ltft, which I believe is normal and pretty good. The o2 voltage also fluctuates betwen 0.01 - 0.09 which I believe is also normal. If I pull over and idle again everything is fine and the trims and o2 voltage stay well within normal and the car idles smoothly. If I now turn the car off for about a minute and start again the car will be in open loop and as soon as it goes into closed loop the stft shoots up over +30 again!!! Then will drop again after a little driving!! I also noticed on the scanner that I was idling in closed loop and the car went back into open loop and the trims shot back up, so I gave a little tap on the accelerator and it went back into closed loop and the trims dropped again.

 

 

 

 

 

I have recently changed the cts, and thermostat, had the timing belt done and replaced the rocker gasket and put in new motorcraft plugs.

 

 

 

 

 

So there you have it! It certainly has me stumped! Any ideas from you guys?

 

Hi Kez,

I am currently facing the same issue on my 2002 Focus (2.0l Zetec engine). The symptoms are exactly the same as yours, and I also have the P1131 code showing up on my diag tool. After checking on a lot of different potential causes, and replacing several parts/sensors the problem is still there... which really annoys me.

I just found this discussion and I was wondering if you had figured out what was the root cause at the end. That would help me a lot !

Thanks. Sacha