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Hi,

Recently completed a cylinder head change on my 2008 Mini cooper. Currently the car drives perfect as if like a new car however when its sat idling its very choppy and rough. It doesn't stall or get to the point where its about to stall it just shakes the whole car and clearly something isn't right. I occasionally get the error code P0036 but i cant recreate what causes it, its purely random as i'm driving and it doesn't effect how the car drives or anything like that. I know this code relates the the post cat sensor in the exhaust but does this mean that the sensor is faulty or is it potentially whats coming out of the exhaust that's causing bad readings? I assume this would throw a different code but i thought id check.

Also if this is the case and the sensor does in fact need changing could it also be the source of the rough idle? i don't know how much effect this sensor has on the intake of the engine if any at all.
Just as an addition i also got a code for a misfire in cylinder 2, it didn't cause a check engine light and i don't think its related to the rough idle as its only happened once and it was a good 200 miles after the rough idle started.

As always thanks in advance for any help!
 

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Hi,

Recently completed a cylinder head change on my 2008 Mini cooper. Currently the car drives perfect as if like a new car however when its sat idling its very choppy and rough. It doesn't stall or get to the point where its about to stall it just shakes the whole car and clearly something isn't right. I occasionally get the error code P0036 but i cant recreate what causes it, its purely random as i'm driving and it doesn't effect how the car drives or anything like that. I know this code relates the the post cat sensor in the exhaust but does this mean that the sensor is faulty or is it potentially whats coming out of the exhaust that's causing bad readings? I assume this would throw a different code but i thought id check.

Also if this is the case and the sensor does in fact need changing could it also be the source of the rough idle? i don't know how much effect this sensor has on the intake of the engine if any at all.
Just as an addition i also got a code for a misfire in cylinder 2, it didn't cause a check engine light and i don't think its related to the rough idle as its only happened once and it was a good 200 miles after the rough idle started.

As always thanks in advance for any help!
below is the generic meaning of that code and its effects and solutions,

This diagnostic trouble code (DTC) is a generic powertrain code, which means that it applies to OBD-II equipped vehicles, including but not limited to Toyota, VW, Ford, Dodge, Honda, Chevrolet, Hyundai, Audi, Acura, etc. Specific repair steps may vary depending on the model. Fuel injected vehicles use heated oxygen sensors in the exhaust system before and after the catalytic converters to determine oxygen content. This feedback is used to adjust the fuel system accordingly to maintain a proper air/fuel ratio of 14.7:1. The oxygen sensors used a heated circuit to warm up the sensor for faster feedback operation. The oxygen sensor may use three or four wires depending on the vehicle, two are usually used for the sensor feedback to the Powertrain Control Module (PCM) / Engine Control Module (ECM) and the other wires are for the heater to power the heated circuit. Three wire sensors are usually grounded through the exhaust system, and four wire sensors have a seperate ground wire. The P0036 code refers to the sensor after the catalytic converter on bank 1, which is on the side of the engine with the #1 cylinder. The heater circuit may be supplied power or ground by the PCM/ECM or another source that can be controlled by the PCM/ECM. Note: Be careful not to work around an exhaust system that has been ran recently as they can become very hot. This code is similar to P0030 and basically identical to P0056. Symptoms Symptoms of a P0036 DTC includes MIL (Malfunction indicator lamp) illumination. You will probably not notice anyother symptoms associated with the failure of the heated circuit since it only runs momentarily when the vehicle is first started. This sensor is also after the catalytic converter, so it will not affect the air/fuel ratio input to the PCM/ECM; it is primarily used to verify the catalytic converters efficiency. Causes Potential causes of a P0036 trouble code may include: Open circuit inside oxygen sensor or open power or ground wires to oxygen sensor Exhaust system ground strap may have become corroded or broken PCM/ECM or oxygen sensor heater circuit wiring has failed Possible Solutions Visually inspect the oxygen sensor wiring for damaged or loose wiring to the sensor. Unplug the oxygen sensor and using a digital volt ohm meter (DVOM) set to the ohms scale, test the resistance of the heater circuit using a wiring diagram for reference. The heater circuit inside the sensor should have some resistance present, excessive resistance or an over limit reading would indicate an open in the heated portion of the circuit and the oxygen sensor will need to be replaced. Back-probe the ground wire at the connector and check for resistance between a good known ground and the connector to the oxygen sensor. Back-probe the power supply wire at the connector with the DVOM set to DC volts with the positive lead on the power supply wire and the negative lead at a good known ground to check for power to supply at the oxygen sensor. If no power is present at the connector during initial car startup (cold start), there may be a problem with the power supply circuit to the oxygen sensor or the PCM itself.

i use autocom cdp plus diagnostics a lot to work on these kinds of faults its useful with live data and can read all codes dealer level,,
if you were getting this code right after doing a head and timing chain change i would say take it for a good 200 mile run get cat and 02 sensors hot let cool then repeat it as this will force car to adapt to the new in time timing over 2 to 6 cycles of heat and cool down redo it have seen a lot of them come back right again,,, i suspect with this code the upstream 02 sensor has got cooked by over heating by retarded ignition form chain being out and fuelling from over lap on valves being out, see many where a new ct and both 02 sensors have been needed after such issues, even worse if was burning oil or gasket failed and kept feeding cat with antifreeze steam etc, if you replace the 02 sensor you will need to run car like i said above a few times to get adaptations back to parameters that the eml light will stay off after link below for best diagnostic for money,


https://www.ebay.co.uk/itm/2018-R3-...m=263847475976&_trksid=p2045573.c100506.m3226
 

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Discussion Starter #3
below is the generic meaning of that code and its effects and solutions,

This diagnostic trouble code (DTC) is a generic powertrain code, which means that it applies to OBD-II equipped vehicles, including but not limited to Toyota, VW, Ford, Dodge, Honda, Chevrolet, Hyundai, Audi, Acura, etc. Specific repair steps may vary depending on the model. Fuel injected vehicles use heated oxygen sensors in the exhaust system before and after the catalytic converters to determine oxygen content. This feedback is used to adjust the fuel system accordingly to maintain a proper air/fuel ratio of 14.7:1. The oxygen sensors used a heated circuit to warm up the sensor for faster feedback operation. The oxygen sensor may use three or four wires depending on the vehicle, two are usually used for the sensor feedback to the Powertrain Control Module (PCM) / Engine Control Module (ECM) and the other wires are for the heater to power the heated circuit. Three wire sensors are usually grounded through the exhaust system, and four wire sensors have a seperate ground wire. The P0036 code refers to the sensor after the catalytic converter on bank 1, which is on the side of the engine with the #1 cylinder. The heater circuit may be supplied power or ground by the PCM/ECM or another source that can be controlled by the PCM/ECM. Note: Be careful not to work around an exhaust system that has been ran recently as they can become very hot. This code is similar to P0030 and basically identical to P0056. Symptoms Symptoms of a P0036 DTC includes MIL (Malfunction indicator lamp) illumination. You will probably not notice anyother symptoms associated with the failure of the heated circuit since it only runs momentarily when the vehicle is first started. This sensor is also after the catalytic converter, so it will not affect the air/fuel ratio input to the PCM/ECM; it is primarily used to verify the catalytic converters efficiency. Causes Potential causes of a P0036 trouble code may include: Open circuit inside oxygen sensor or open power or ground wires to oxygen sensor Exhaust system ground strap may have become corroded or broken PCM/ECM or oxygen sensor heater circuit wiring has failed Possible Solutions Visually inspect the oxygen sensor wiring for damaged or loose wiring to the sensor. Unplug the oxygen sensor and using a digital volt ohm meter (DVOM) set to the ohms scale, test the resistance of the heater circuit using a wiring diagram for reference. The heater circuit inside the sensor should have some resistance present, excessive resistance or an over limit reading would indicate an open in the heated portion of the circuit and the oxygen sensor will need to be replaced. Back-probe the ground wire at the connector and check for resistance between a good known ground and the connector to the oxygen sensor. Back-probe the power supply wire at the connector with the DVOM set to DC volts with the positive lead on the power supply wire and the negative lead at a good known ground to check for power to supply at the oxygen sensor. If no power is present at the connector during initial car startup (cold start), there may be a problem with the power supply circuit to the oxygen sensor or the PCM itself.

i use autocom cdp plus diagnostics a lot to work on these kinds of faults its useful with live data and can read all codes dealer level,,
if you were getting this code right after doing a head and timing chain change i would say take it for a good 200 mile run get cat and 02 sensors hot let cool then repeat it as this will force car to adapt to the new in time timing over 2 to 6 cycles of heat and cool down redo it have seen a lot of them come back right again,,, i suspect with this code the upstream 02 sensor has got cooked by over heating by retarded ignition form chain being out and fuelling from over lap on valves being out, see many where a new ct and both 02 sensors have been needed after such issues, even worse if was burning oil or gasket failed and kept feeding cat with antifreeze steam etc, if you replace the 02 sensor you will need to run car like i said above a few times to get adaptations back to parameters that the eml light will stay off after link below for best diagnostic for money,
I've decided to just bite the bullet and replace both sensors, the car has just ticked over 130K and chances are they've never been changed as i read somewhere you should change them around the 100K mark anyways and thats the mileage it had when i bought it. Problem being that the local parts store only stocks the sensors in two different brands, i cant imagine this matters but if i grab on sensor from FAE and one from HAAS will this matter? I feel i know the answer but thought id check before i waste the money.


Thanks Again
 

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they should be same spec prob find made in same factory in china and stamped differently that said i would try and fit two the same for piece of mind,
 

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Discussion Starter #5
they should be same spec prob find made in same factory in china and stamped differently that said i would try and fit two the same for piece of mind,

Well digging a little further this morning, i got a misfire on cylinder 2 so i thought id just swap the ignition coils and the spark plugs around and see if they're the reason or whether its related to the bad O2 sensor and alas cylinder 1 spark well i full of oil. Clearly a gasket issue so ive ordered a new one. I did a quick check and it seems that oil in the spark plug well can lead to a rough idle but it was a general search not just for mini. Does this sounds familiar, could it be the source of the rough idle and it just so happens the O2 sensor went at the same time. As you said it has no interaction with the engine anyways except from checking emissions.
 

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Well digging a little further this morning, i got a misfire on cylinder 2 so i thought id just swap the ignition coils and the spark plugs around and see if they're the reason or whether its related to the bad O2 sensor and alas cylinder 1 spark well i full of oil. Clearly a gasket issue so ive ordered a new one. I did a quick check and it seems that oil in the spark plug well can lead to a rough idle but it was a general search not just for mini. Does this sounds familiar, could it be the source of the rough idle and it just so happens the O2 sensor went at the same time. As you said it has no interaction with the engine anyways except from checking emissions.
02 sensors have everything to do with changing the fuelling over all 4 cylinders at same time via car ecu,
yes leaking oil ring gaskets on the under side of rocker cover and filling spark plug oil with oil would have a effect on that cylinder,, i always use wellseal gasket sealer on them very thin layer.
 

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Discussion Starter #7
02 sensors have everything to do with changing the fuelling over all 4 cylinders at same time via car ecu,
yes leaking oil ring gaskets on the under side of rocker cover and filling spark plug oil with oil would have a effect on that cylinder,, i always use wellseal gasket sealer on them very thin layer.
Sorry i thought you said earlier that the post cat sensor was only used for emissions, i know the pre cat sensor effects the air/fuel ratio but i didnt think the one im getting the error for had any effect.
 

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below link
good link,
First off id like to thank you for all your help thus far its very much appreciated and that link did clear everything up regarding the O2 sensors.

Today i pulled the valve cover off to see exactly where that first spark plug well was filling up from and it wasnt the best of sorts inside the head. Piston 4 had forced one of its rocked arms off causing the retaining spring to slowly grind into the cam shaft itself. Luckily the retaining spring hasnt been damaged in the process and it hasn't actually dug into the cam shaft enough to do damage or effect the way runs or anything that isnt aesthetic, its just a matter off putting the rocker arm back on the valve spring and pushing the retaining spring on top of that (hopefully). I also took a quick check of the timing and it looks to be out, not by alot i must admit but it is noticeable. Im assuming the bad timing is why the rocker arm was forced off and because i dont really need to buy anything to re time it bar a few bolts my plan is just do that. I hope that the piston hasnt damaged the valves i wont know that unless i pull the head off again which would be costly so hopefully just by running it again ill be able to tell. I may invest in a better timing tool but i dont think i can comfortably spend £199 on the draper version so if you know of any other reputable brands that would be great. Other than that i still plan of replacing the post cat O2 sensor so hopefully ill have a running car soon enough. If you have any thoughts on what i plan on doing please do share im very grateful for you input.



Thanks Again
 

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First off id like to thank you for all your help thus far its very much appreciated and that link did clear everything up regarding the O2 sensors.

Today i pulled the valve cover off to see exactly where that first spark plug well was filling up from and it wasnt the best of sorts inside the head. Piston 4 had forced one of its rocked arms off causing the retaining spring to slowly grind into the cam shaft itself. Luckily the retaining spring hasnt been damaged in the process and it hasn't actually dug into the cam shaft enough to do damage or effect the way runs or anything that isnt aesthetic, its just a matter off putting the rocker arm back on the valve spring and pushing the retaining spring on top of that (hopefully). I also took a quick check of the timing and it looks to be out, not by alot i must admit but it is noticeable. Im assuming the bad timing is why the rocker arm was forced off and because i dont really need to buy anything to re time it bar a few bolts my plan is just do that. I hope that the piston hasnt damaged the valves i wont know that unless i pull the head off again which would be costly so hopefully just by running it again ill be able to tell. I may invest in a better timing tool but i dont think i can comfortably spend £199 on the draper version so if you know of any other reputable brands that would be great. Other than that i still plan of replacing the post cat O2 sensor so hopefully ill have a running car soon enough. If you have any thoughts on what i plan on doing please do share im very grateful for you input.



Thanks Again
the big wire springs on each cam follower pivot arms are a proper pain in arse to put back on without the correct tool, and correct tool is not cheap and if anyone knows of a cheap on can point me in that direction,, as i'm still living in dark ages using a mate with two works hands and lever bar screw driver even a small hammer to tap them in past the last bit of tension... the followers that are off the valves for these tend to bend most of time,
to me your car like i think i may of said from first post timing chain issues or tensioner has broken in to two pieces i common as the travel gets to large then chain slaps the tensioner and top chain guide snaps off most common then it bends things, if your car was scanned and came back with misfire on all cylinders random then 02 sensor maybe, and chain stretched, see the chain stretches over time the car gets driven on and on until finally the driver notices a misfire, or if car driven hard high revs all the time would notice wont rev to red line very well feels all retarded..
this all said when i get a car in like yours, i will do this to rule out or rule in things,,
fit new timing chain kit but use the old bolts will explain, because your car may have valve damage it needs compression testing to do this the timing must be correct, so new chain old bolt tighten old bolts to 60nm just to hold the timing in place just to do a compression test,, if find have good compression then relock timing put new bolts in because they need cams 20nm plus 180 degrees stretched, bottom pulley bolt 40nm plus 120 degrees or as tight as 4ft breaker bar will go,,
its poss to do leak off test but needs compressor special gear etc and what that dont tell you is whether the valve stick or not when in use like a compression test off the starter will,, remember fully charge your battery before doing said tests all spark plugs out, you will need a special 16mm multipoint slim socket for spark plugs, will also need some what i use is brass rods off ebay to drop in plug holes to locate all pistons half way in bores to find the locking pin in crankshaft, some links below will help you.
brass rods,, never rotate engine with rods in when at bottom of the stroke will bend rod on up stroke,, i have done was a royal pain in arse, lucky brass is sort dont snap and bends
https://www.ebay.co.uk/itm/Brass-Ro...hash=item3f45b54466:m:m3vAXr-0NhVRRnLs-fUIMKw
timing tool i know i dont agree with chep ones but if any slack in the sqaure [part use a feeler gauge to remove it as such
https://www.ebay.co.uk/itm/BMW-Mini...692119&hash=item3b15f35f04:g:WK8AAOSwtN5bI~C4
timing chain kit used one the other day was ok
https://www.ebay.co.uk/itm/Engine-T...e:Mini&hash=item33cacdb66a:g:918AAOSwmVBbDszK
oil pump chain kit worth doing
https://www.ebay.co.uk/itm/SWAG-Oil...e:Mini&hash=item25ddb82b5b:g:xkAAAOSwxk9Zlwp3

how to videos
https://www.youtube.com/watch?v=HQyyGEg7uSQ

https://www.youtube.com/watch?v=qySLGAD7DRg

https://www.youtube.com/watch?v=19gFe8P12VU

you will need a 27mm spanner to hold the cam shafts when doing up the cam sprockets you can not do the job right with out either spanner of a method to hold cams ie no movement as will knock timing out,
its also pays to replace the bottom oil seal, and must replace all the cam shaft and bottom sprocket bolts, genuine ones are £3.80 for cam bolts and thing the pulley bolt £8 ish, when doing the plus 180 degrees i mark the socket with marker pen so can see how much rotation stretch the bolts get, can also buy a angle gauge link below
https://www.ebay.co.uk/itm/1-2-Driv...915138?hash=item2cc9020a42:g:ApkAAOSw1cNZ-YlZ

its so important to lock and check and recheck as you go when setting up the locking tools,, very important after doing first lock and 20nm on cam sprockets and 40nm on bottom pulley to rotate the engine a few times then relock it back to check it all locks without force,, those viseos are really good the best i ahve found but do miss out the importance to that stel lock and check i also recheck with the spring tensioner in place to be sure,
my first ones i ever done i ended up getting it slightly wrong as tightened the cams up with out a 27mm spanner and the cams moved on stretch part very common mistake the first time good luck
 
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