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Topic: lambda sensors (Read 1282 times) |
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panzer
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lambda sensors
« on: Aug 29th, 2005, 1:54pm » |
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iam a bit of a newbie,can anybody help! i want to change my sensors pre cat on my 1996 24v i had scan done with codes p1133 & p1154 i know what these codes mean, but am i ok to change sensors without clearing codes, i have no lead obd2 or code reader
i dont want the car to fault out and go into limp home mode,can i leave it until i vist garage.
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Eric_R
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Cosworth Owner 1998 - 2006 & site co-founder
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Re: lambda sensors
« Reply #1 on: Sep 4th, 2005, 11:14am » |
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Panzer,
Even if the HO2S sensors completely fail, the fuelling will stay in OPEN LOOP and will run quite happily, although it will fail an MOT for excess emissions and use a lot of petrol. These sensors don't cause Limited Operation Strategy.
The HO2S sensors can fail to switch for other reasons than failing themselves, so if the problem is elsewhere then even new sensors will fail to switch and you won't be any further forward.
P1133 usually means that a sensor is failing - but not always. If you do mean P1154 and not 1134 then the bank 2 fuelling is too high.
Before you commit yourself I would try and meet an owner equipped with an OBD lead and get him to do a scan, while the engine is hot at idle and a run round the block. Get him to select
RPM
MPH
HO2S11 and 12
HO2S21 and 22
LTFT1 and LTFT2
and zip the 3 data files together. You can put the files up on the Anyboard site. From this we will have a much better idea of where the fault lies. 
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panzer
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Re: lambda sensors
« Reply #2 on: Sep 5th, 2005, 9:26pm » |
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thanks eric,iam listing all the codes from scan i had done at garage,
p0131- bank 1 sensor 1 (low voltage)
p0174-lean bank 2
p0443- purge valve (have looked at this there is good vaccum at petrol cap)
p0505-idle valve (have fitted new one)
p0755- gearbox (but no problem with that)
p1133- bank 1 shifted lean
p1152-ho2s 12 not fluctuating to rich
p1154-ho2s21 shifted rich (have put new sensor in)
p1406- egr (have looked at pipes look ok)
dont know anybody with lead, scorpios are a bit rare around these parts, now the symptoms idle is not to good when engine is hot some times trys to stall, and problem 2 is engine is down on power when under light throttle at anything from 40 to 70 mph a sort of hesitation? misfire?, thanks panzer.
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Eric_R
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Re: lambda sensors
« Reply #3 on: Sep 6th, 2005, 1:36am » |
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Blimey, Penzer - that's the longest list I've ever seen. 
P0131 is a low volts showing a Characteristic Shift Down - the HO2s may be contaminated or the wires are crossed or shorting. Check the wiring to this and you may need to change this sensor as well.
This may be connected with P1131 where the same sensor is failing to switch indicating to lean.
P1152 is showing the reverse, that Bank 2 is too rich and the HO2S sensor is not switching back to lean and the Fuel Trims ar etoo rich for Bank 2 - P1154.
These together kind of rule out the MAF, although you ought to clean it as a matter of course. There is clearly a fuelling problem - one bank is too rich and the other too lean.
The EGR system can cause the engine to hesitate at part-throttle, but so can failing HO2S sensors.
It's a pity you can't read the DTCs yourself, because I would have suggested that you clear the codes and see what codes return in case there is a wiring loom problem - it worries me that you have so many problems, including a Shift Solenoid B error (P0755) and an EVAP DTC when there is vacuum at the fuel cap. But since we can't we're going to have to take it step by step.
Change the upstream driver's side HO2S11 and check the wiring to make sure it's not chafed.
Change the Fuel Rail Pressure Regulator to make sure that there is a not a fuel pressure problem - see http://www.fordscorpio.co.uk/fuelreg.htm
Both of these should then stabilise the fuelling and improve the running.
Block off the pipe running to the EGR valve at the back of the engine to make sure this can't operate wrongly and see if this makes a difference to the part-throttle running.
Do that first and see if there's a marked improvement. If there isn't then we might need to start looking at the wiring loom - but we can test this for continuity between the bulkhead plug C112 and the PCM multiplug, so don't panic yet.
Get back to us with the result.
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panzer
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Re: lambda sensors
« Reply #4 on: Sep 7th, 2005, 6:46pm » |
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Iam going to change ho2s11 at weekend as first step and clean maf again,will let u know of result, regards panzer.
ps, love my scorpio to bits.
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Eric_R
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Re: lambda sensors
« Reply #5 on: Sep 8th, 2005, 1:17am » |
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Good man.
Don't worry about cleaning the MAF again if you've already done it, it can't be to blame if one bank is rich and the other lean - it can only affect both.
Block off the top pipe on the EGR valve at the rear of the engine as well - this prevents the poppet valve from opening wrongly in part-throttle conditions, and see if that makes a difference. If it doesn't, put it back.
If the Fuel Rail Pressure Regulator is faulty it can be causing periods of over-lean and over rich fuelling. Because we can't data log your system we can't tell if this happens simultaneously or at separate times - but it would certainly fit.
BTW, get some injector cleaner and put it at double-strength into the fuel and take the car for a good blat. This should clear any injectors that might be gummed up.
When you instal the new HO2S disconnect the battery for a minute and reconnect it (you'll need the radio code - if you don't have it give us the serial number of the radio on top of the case begiining with M and we'll tell you what the security code is That will zero the fuel trims and force it to recognise the new sensor more quickly.
Let us know how you get on. 
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panzer
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Re: lambda sensors
« Reply #6 on: Sep 26th, 2005, 6:25pm » |
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hi eric, sorry about the long wait for results, i didnt get round to changing ho2s11,will do at later date,but followed your advise on
injector cleaner, this seems to have cured idle prob and hesitation,just had m.o.t
done and passed on emissions so i can only assume that changing
the ho2s21 and injector cleaner has done some good ,
regards, panzer.
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