E36 M3 running rich?

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   Hello, Hoping some of you technical guys and gals out there maybe able to help.

BMW E36 M3 EVO 98 plate. Only mods are Decat pipe and rear exhaust section, (all Scorpion I think) and induction kit with the heat shield.

Just recently I have been getting very poor MPG in urban driving (16mpg) is this poor I guess is the first question as I was getting low 20s before.

Also noticed that it smells quite abit of petrol these days at rear which wasnt the case before.

When started it appears to run on 4 or 5 cylinders at low revs. I have brought new plugs to fit later see if that helps.

Someone told me it could be the coolant temp sensor, but the gauge is showing normal temp. Could it be this?

Another thing is when I took the CAT box out, the decat pipe has threaded lugs in for the lamba sensor, but there wasnt a lamba sensor in the original I took out. Is there another Lamba sensor up near the manifold? Could this cause my issues?

All help and advice appreciated.
Many thanks
Dan

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Dangerousdan Members Profile Send Private Message Find Members Posts Visit Members Homepage Add to Buddy List Newbie Joined: 21-October-2009 Location: Essex Status: Offline Points: 2	Post Options Post Reply Quote Dangerousdan Report Post Thanks(0) Quote Reply Topic: E36 M3 running rich? Posted: 22-October-2012 at 10:10
	Hello, Hoping some of you technical guys and gals out there maybe able to help. BMW E36 M3 EVO 98 plate. Only mods are Decat pipe and rear exhaust section, (all Scorpion I think) and induction kit with the heat shield. Just recently I have been getting very poor MPG in urban driving (16mpg) is this poor I guess is the first question as I was getting low 20s before. Also noticed that it smells quite abit of petrol these days at rear which wasnt the case before. When started it appears to run on 4 or 5 cylinders at low revs. I have brought new plugs to fit later see if that helps. Someone told me it could be the coolant temp sensor, but the gauge is showing normal temp. Could it be this? Another thing is when I took the CAT box out, the decat pipe has threaded lugs in for the lamba sensor, but there wasnt a lamba sensor in the original I took out. Is there another Lamba sensor up near the manifold? Could this cause my issues? All help and advice appreciated. Many thanks Dan

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Sporty1 Members Profile Send Private Message Find Members Posts Add to Buddy List Really Senior Member II Joined: 18-October-2006 Location: Hertfordshire, United Kingdom Status: Offline Points: 2297	Post Options Post Reply Quote Sporty1 Report Post Thanks(0) Quote Reply Posted: 23-October-2012 at 09:53
	There are lambda probes in the exhaust manifold. There are 2 temperature sensors on the car, 1 sends signal to the temp gauge on your instrument cluster the other feeds the cars ecu with info as to when cold start enrichment is required. There's also a air intake temp sensor if that is not working correctly it will also produce running issues. You could also have the beginnings of the coils breaking down. You can test the coils when you change the plugs, remove the fly lead from the coil and with a multimeter set to measure resistance (ohms) put yor probes on the outer 2 terminals ( there are 3) you should get a reading of between 0.4-0.8 ohms. Also check the condition of the coils casing for hairline cracks and condition of the insultor boot on the fly lead. Any brown marks/staining on the coils packs could be an indiction of arching. Could also be leaky injectors causing the issue Edited by Sporty1 - 23-October-2012 at 09:56
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UweM3 Members Profile Send Private Message Find Members Posts Add to Buddy List Moderator Group Joined: 11-February-2003 Location: United Kingdom Status: Offline Points: 5445	Post Options Post Reply Quote UweM3 Report Post Thanks(0) Quote Reply Posted: 26-October-2012 at 15:37
	The 3.2 has TWO Lambda probes in the exhaust manifold. Don't swap the plugs round.
	E61 520d, slow and buzzy but my wallet likes the mpg.....