The dreaded intermittent misfire issue possible injectors ?

[GarringtonL]

Hi All, hope your enjoying your Jazzies 
Just had a nightmare getting my daughters Jazz MOT'd due to emissions, but they waited for it to run correctly then so passed the test. It has suddenly started this misfire at low speed before MOT but still returns 46 MPG. I've tried injector cleaner for the last 3 tanks but no improvement. It has had the EML light on since the cat was stolen 2 years ago but always managed to get it through MOT. New O2 sensors, plugs x 8 were fitted by garage but no difference ! Luckily they had the same year/model (2006  1.4 DSI manual) waiting for "stolen cat replacement". Good as gold the garage swopped over everything including coil packs etc from it but no luck finding the fault, the only thing they suggested was an injector issue ? Has anyone had similar and how difficult to replace/test the injectors ? Any suggestions/info very welcome.

[embee]

What are the fault codes from the OBD ?

[GarringtonL]

Morning,
update on my issue
Faults code is for o2 sensors but both have now been changed so many times I've lost count, if anyone needs any call me, i've got more than Lucas !
As I said since the cat was nicked it's always had the EML light on despite everyone's best efforts with diagnostics it only stays off for a short while. The fault is cleared before MOT and light goes off for the test but back on for the journey home !!!! This misfire has recently started hence my garage saying it could be an injector as it's the only item we haven't changed

[embee]

Any more detailed fault codes? With appropriate diagnostics you can get specific fault type, circuit high/low/open etc.
Example codes here https://hondacodes.wordpress.com/honda-fault-codes/
I'm not sure whether these all relate to your Jazz model.
Presumably the connector and wiring to it have been closely examined and checked, continuity etc?

[E27006]

Here is an informative youtube video by Diagnose Dan.
Dan  explains how the wideband and narrowband sensors of the Catalytic Convertor system  operate in the car, and the part they play in the control of fuel injection rich/lean/stochiometric  conditions in a typical modern  engine:

A video by Diagnose Dan dealing with an OBD11 code of a Catalytic Convertor, the OBD11 codes pointed to a faulty  exhaust gas sensor,  the sensor permanently  reading a hard-lean oxygen-rich condition,  Dan proved a few details by spraying brake cleaner into the engine intake with the engine running,  Dan diagnoses an air leak in the cat shell (a long crack in the metal body) allowing air into the exhaust gas, the sensor(s) of the Cat were not faulty at all, simply being "fooled" by the air leak into the Cat

[E27006]

So prior to the theft of the Cat,  the car did not have issues with the Engine Light. Is that correct?
The Cat was replaced along with 3rd party sensors and since then problems with the Engine Light.

Points to something not right with the 3rd party Cat parts
I would replace the Cat with a B&M cat, from Ebay .. £75,  and the rear sensor too,  £37,  you have tried everything else, i think it is worth risking another £75 - £110 just for peace of mind.

[GarringtonL]

Hi guys
Thanks for the input/suggestions, the car had no issues before the cat theft. I have tried another cat (different make), all makes of sensors fitted, wiring has been checked and no issues found.

Yesterday I took it out and drove it like I stole it. EML light stayed on but misfire disappeared but started on return to normal driving. Suggestion was it could be an injector playing up but not sure that is correct.
Read the OBD again and fault codes are now;
P0134 sensor 1 - Air/Fuel ratio no activity detected
P0401 EGR insufficient flow
 I'm going the check EGR valve and the sensor will get another clean but I'm not sure these will resolve the issue.

[embee]

One simple thing I'd suggest would be to clear the fault code, disconnect the sensor altogether and try running the engine and see what fault code it shows. It might not be a help but depending on what it shows it might indicate what is going on, or what connections are or are not being made. It kind of makes me suspect there is a break between the sensor and the ECU somewhere.
You can put a multimeter onto the feedback wires from the sensor to see what the voltage is. If it is clamped high (rich) you'll see 1.5V or something similar, clamped low (lean) it'll be zero, if it is working and feedback is operating correctly it should cycle between 0V and 1 or 1.5V or so, at least it should vary. The voltage it gives will be down to the gas it sees, whether this voltage is getting as far as the ECU is another question.

[GarringtonL]

Thanks for the input guys, been away so just getting back to this issue.
Had an auto electrician read the faults today and I couldn't get it to misfire whilst he was here. He says the wiring to the engine harness is at fault as the ecu is not receiving any info. He was unable to spend anymore time on it but suggested swopping the wires around ?? It's taken me nearly 2 hours to get the sensor and harness plug/socket up to a place where I can work on them in the engine bay
My problem is I don't know the correct position of the wires from the engine harness into the socket and can't find a wiring diagram anywhere, very frustrating.
Wires from sensor are; Black-Grey-2 x white
Wires from harness are; White-Green/Yellow-Black/White-Black/Yellow
If anyone knows which connects to which I'm eager to know as I think this is the issue, pics attached.