Running lean?

[A4-Newboy]

audi a4 b5 1.8t running lean with lambda readings going up to 1.100 on mot emission sheet. Have replaced fuel filter, spark plugs, air filter, crankcase breather pipe, pcv valve and t-piece all under intake manifold. I will be doing the water pump soon as that is broken. It ran so hot that the oil light came on so had to shut it down. Been sat for 6 months having work done on it. Been for two mot's now and the first was running less lean then after the second but i had a vacuum leak under intake manifold fix? Strange or what. Will be scanning for ecu codes when my cable arrives and will be changing the maf, lambda and intake temp sensor if they come up with errors. But until then what else could i check for? So confussing becomes it runs really well and fast!!!! Any thoughts. Cheers

 

[Blue_Thunder]

Check your MAF.

 

[A4-Newboy]

I will be doing that tomorrow. Going to unplug it while its running to see if it makes a difference. If the MAF is bad will the motor stall or just run as normal?

 

[Blue_Thunder]

MAFs tend to die a slow death. They will under-read and this will gradually get worse. So your engine is taking in a lot more air than the MAF is telling it, therefore it's underfuelling - hence lean running and higher than normal EGT's.

Just re-read your original post and see that your water pump is broken. Why are you driving your car at all??? If your coolant isn't being circulated you could end up with a knackered head gasket and maybe even a cracked head.

 

[A4-Newboy]

Ok thanks for your advice. I didn’t even know the water pump was broken until after the second mot. Got home and the expansion tank looked like it wanted to explode and leaking a little bit. Luckily I don’t drive the car it only went down the road for the mot and back again! I have a daily driver until this one gets fixed. Cheers