2003 1.4 8 valve, running rough

Hi again, I need to just get my head around the air leak on the inlet manifold, I have had this before on other cars, but if it is a air leak surely in would be running lean?. not black and sooty.

am I correct in saying the MAF sensor is on the air intake before the manifold, if this is the case the MAF sensor is not reading a lean mixture and telling it to pump more fuel.

Paul

paullap wrote:am I correct in saying the MAF sensor is on the air intake before the manifold

Yes, you are correct.

paullap wrote:if this is the case the MAF sensor is not reading a lean mixture and telling it to pump more fuel.

The MAF doesn't read the mixture. It monitors the airflow. Its the O2 sensor that monitors the mixture.

MAF readings go to the engine ECU map and this is compared with other points on the map to calculate the correct quantity of fuel to inject.

Thanks for clearing that up for me, so air leak on the inlet would leave the plugs light brown, I have changed to sensor before the cat, so could it be the one after the cat? no codes showing up art this moment, and still, idling rough.

Paul

paullap wrote:I have changed to sensor before the cat, so could it be the one after the cat?

The one after the cat detects how well the cat is doing its job and would bring up a fault code if it was faulty. You can test the O2 sensors for the correct switching with an oscilloscope. When they get bad, they get slow to switch or give a weak signal.

paullap wrote:no codes showing up art this moment, and still, idling rough.

A rough idle due to fuel/air problems should bring up some codes.....

paullap wrote:Thanks for clearing that up for me, so air leak on the inlet would leave the plugs light brown,

It would mess up the mixture and therefore the running because the ECU would be using incorrect information in its calculations on the quantity of fuel to inject.

ok, I have taken the plugs out again, deep black soot, I was trying to see how to post a picture of them , but I could not work out how to it, I just don't know where to look next to sort this problem, any ideas?.

paullap wrote: was trying to see how to post a picture of them , but I could not work out how to it,

When you reply, scroll down a bit until you see something that looks like this (on a laptop or PC)
Then browse to your image, enter a description and click 'Add the file' (a pop-up will appear with a progress bar). Wait for the file to upload then press 'Submit' to post the topic.

If you are on a mobile device, the procedure is almost identical but the layout is slightly different.

paullap wrote:I just don't know where to look next to sort this problem, any ideas?.

How far did you get with all the things suggested in the previous replies?

What, if any, fault codes do you have showing?

Maybe a list of all the checks and substitutions you have done would help focus attention on what has been missed?

Hello again, things that I have changed from a donor car that was running perfect.
MAf sensor
Purge canister
throttle body
pre cat sensor
I have attached the picture of one of the plugs, they are all the same. very bl;ack and sooty
just going back to the air leak possibility, I was thinking it cant be, the maf sensor is before the manifold, so if it cannot sense the air leak, but if it did have an air leak on the inlet side somewhere giving it a lean mixture and the oxygen sensor picket that up, and sends more fuel in, the exhaust gases then becomes rich and it would then surely decrease the amount of fuel being pumped in, so one thing seems to counter acts to the other, if someone could explain to me how if it is an air leak, how would all the plugs be black and sooty. also could anyone give me some things to check on Lexia3 and what the values should be, It is new to me and I would like to understand it a bit more, you can look at all these readings but if you don't know what they should be reading, you don't have a chance.


Thanks again for all the help, I hope the picture has attached,

Paul

This is the pre cat sensor

paullap wrote:
This is the pre cat sensor

This O2 sensor is not going to sense the O2 level correctly in that state.

It may not be the cause, but it could well be having an effect........

paullap wrote:you can look at all these readings but if you don't know what they should be reading, you don't have a chance

Well, you do. Codes that are read by lexia usually come with a description and often a procedure list to diagnose further.
I am surprised there is no O2 'P code' for that one in the picture.

If you have some live data you want to compare with a working car, there are some on the forum or you could ask someone with lexia to make the same live data readings as you to compare?

here is a snap shot of a live reading data