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Discussion Starter #1 (Edited)
Hi all. I've been getting a few MCSF's popping up during a cold start and disappearing within a moment or two. Was using Torque on android phone reading an elm327 bluetooth obd2 scanner and getting 0303 misfire on cylinder 3 code.
Changed all sparks & no.3 coil but it still comes up maybe once or twice a week.

Today I downloaded Alfa obd and after a few hiccups getting it to work I found I also had a 4020 catalyst code which torque didn't detect.
After clearing that, aobd found a 1151 lambda code that made the engine idle irregularly which led me to look at the 02 sensor readings.

Both lambdas above cat (pre cat?) readings look almost identical. It's the lambda 1 below cat that looks bad, like an intermittent version of lambda 2.

The car drives fine although sometimes the exhaust sounds louder and engine seems a little sluggish. There's also some black soot buildup on the exhaust tip and the plugs had black dust on them when I changed them so I guess it's running rich. Mpg averages around 21 but mostly town driving (london traffic :mad: )

Can anyone shed some light on what the cause of the problem is? I'm Not too worried about it but I'd like to nip it in the bud if it's likely to get worse or affect the cat/engine in the long term.
 

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Do a search but I'm fairly sure the post cat lambdas don't effect engine running at all, they just check that the cats are working correctly. But they will still trigger a code. BTW I assume you mean a P0420 catalyst code.

For the missfire, have you tried a bottle of injector cleaner?
 

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Discussion Starter #3
Oops P0420 looks right sorry & thanks for the reply..

Yes I've run some BG44k through and gave it a good thrash. Also cleaned maf and temporarily patched up some splits in the intake hose with electrical tape.
Hoping injectors are ok as the car hasn't quite done 50k yet
 

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Discussion Starter #5
I removed the intake hose completely and made sure I sealed up the splits airtight. A new one is on the shopping list though. I'll give the lambda connectors a clean later and see if that helps.
No codes currently coming up this morning so fingers crossed..
 

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OP, I've been experiencing the same issue recently, again only in the cold. The strange thing is though, its only happened if I've stopped to close the gate to my drive.

So, I start in the cold, wait 30 seconds, drive out the gate and stop on the drive (which is on a slight incline). By the time I've gotten out and closed the gate, I have a flashing light and a beep. Code reader says 0300, and any of the 030 1 to 4.

If I don't stop to close the gate, the problem does not occur. I can only assume its being stopped on the incline for several seconds that it causing it. So, maybe something to do with the oil level...??

GT works fine for the rest of the day BTW, no loss of power or anything.

Confusing..eh..?
 

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Discussion Starter #7
Could be..or maybe the injectors aren't firing at their best in the cold and on an incline? The its is a quirky one at best eh :)
 

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P1151

Probable Cause
Fuel pressure high or low
MAF sensor dirty/defective
Vacuum leak on engine
Leaking fuel injector or fuel pressure regulator

Basically, codes say that your Oxygen Sensor reading is maxed out. which is the "upstream" sensor, usually in or very near the exhaust manifold.

P1131 Lack Of HO2S Switch - Sensor Indicates Lean
 

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Discussion Starter #10
Thanks Scott I'm guessing the maf's fine as the output signal matches throttle activity. Air Intake pipe splits have been sealed up so should be ok - anywhere else there could be a vaccuum leak?

Not sure how I could check fuel pressure or injectors but the car pulls well through all gears just has a slightly lumpy idle with no error code and irregular idle (up & down) when 1151 code registers.
 

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Vacuum leaks can be anywhere from the MAF to where the inlet manifold joins the head. An old trick - with engine at cold idle spray brake cleaner or similar around any areas that might leak and if it is it'll suck in the ether and engine will rev a bit.

Also, try another bottle of injector cleaner, maybe a different brand. I use Wurth and at fairly high concentration - less than 20l in the tank.
 

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I still think one of the injectors is failing or out of its range for working at certain throttle openings.
 

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Thanks Scott I'm guessing the maf's fine as the output signal matches throttle activity. Air Intake pipe splits have been sealed up so should be ok - anywhere else there could be a vaccuum leak?

Not sure how I could check fuel pressure or injectors but the car pulls well through all gears just has a slightly lumpy idle with no error code and irregular idle (up & down) when 1151 code registers.
Sealed up with what..? I've found the only sure way to cure splits in the intake flexi pipe is to get a new one. :thumbs:
 

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Discussion Starter #15
I'm hoping not mate that's gonna hurt the wallet big time. Got codes 1175 & 1176 today which points to maf or air leak I believe (correct me if I'm wrong) and I tried what Sprint veloce said and can't find any leaks so I'll be ordering a new maf payday and hope that sorts it. The engine runs great before the codes register and no warning lights or mcsf come up when they do so I'm hoping it's not the injectors.
 

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Discussion Starter #16
Sealed up with what..? I've found the only sure way to cure splits in the intake flexi pipe is to get a new one. :thumbs:
Vulcanising solution and electrical tape. The splits were on the 2 flexible parts of the pipe so I went over them with plenty of electrical tape nice & tight and took off the pipe to check for any other splits but couldn't see any
 

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Check that the metal manifold to engine is tight and not worked loose somewhere. Basically any where after the maf leak wise will cause an issue.

But I still say either a sensor is borked. Injector is borked.

Have you tried any injector cleaner at all?
 

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Discussion Starter #19
I put in a can of BG44K around a month ago and gave it an "italian tune up" on a long run and all seemed good. Mpg went up by 2 but the idle was still a little uneven but I hear that's just a trait of the jts engine because of the lean burn system. It's only when the codes come up that it starts hunting for idle and hesitating at low revs, and I'm worried it may cause problems in the long run.

From what I can understand, the codes relate to the sensor readings between the pre cat lambdas and maf conflicting causing over compensation of fuel trim by the ecu. Can't find any leaks anywhere so I'm hoping one of the sensors is intermittently at fault and as both lambdas have similar readings I'm thinking the maf is where the problem lies.

Fingers crossed :(

Thanks for all your input and if anyone can think of anything else please let me know :thumbs:
 

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have you tried running without the MAF.
Also the JTS should be smooth on idle. No way should it be hesitant.
 
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