afr problem
15 January 2005, 06:26 PM
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afr problem
just fitted afr gauge-turn ignition on, furthest green light on the scale on.start the car same thing.go for short drive same.can anyone help? car is my99help appreciated its doing my head in
Lee
Lee
16 January 2005, 09:54 AM
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Hello again! 
From what you've told me so far I would say your MAF is shot. If it was reading lean its more likely to be the 02 sensor. When they fail they tend to read lean and thus the ECU bungs in more fuel, ence you get a rich mixture. Failed MAF's (from the ones ive had) tend to stick over the rich area and give random lights on occasion.
If your car is of 20-40k miles and never had a new o2 or MAF, its likely that they have failed anyway. They dont last long! MAF lives in the air filter intake pipe and governs the fuelling on boost - responsible for many an engine blow up if left unchecked!
One last check would be to move your earth from the strut direct to the battery. Remember the gauge is reading 0-1 volt which is pretty small. The slightest bad earth and your AFR readings will be out.
I personally always go to the ECU for signal live and earth, then you are seeing what the ECU is seeing - but many go to the stereo / battery and seems to work ok.
MB
From what you've told me so far I would say your MAF is shot. If it was reading lean its more likely to be the 02 sensor. When they fail they tend to read lean and thus the ECU bungs in more fuel, ence you get a rich mixture. Failed MAF's (from the ones ive had) tend to stick over the rich area and give random lights on occasion.
If your car is of 20-40k miles and never had a new o2 or MAF, its likely that they have failed anyway. They dont last long! MAF lives in the air filter intake pipe and governs the fuelling on boost - responsible for many an engine blow up if left unchecked!
One last check would be to move your earth from the strut direct to the battery. Remember the gauge is reading 0-1 volt which is pretty small. The slightest bad earth and your AFR readings will be out.
I personally always go to the ECU for signal live and earth, then you are seeing what the ECU is seeing - but many go to the stereo / battery and seems to work ok.
MB
16 January 2005, 10:40 AM
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Maf failure normally runs the car lean, hence the problem with engine failure if you dont get it sorted. Agreed about the earth though, 99% of AFR gauge probs are down to incorrect/poor earthing.
Rob
Rob
16 January 2005, 11:30 AM
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Rob, agreed they undoubtedly do fail lean (hence failure) but in my experience of looking at a few failed MAF's, it turns the AFR meter into random mode - rather than "display" lean as you would expect. Mine when completely shot, gave 3 lights in different places over the meter 
Never did find out how the MAF influences the lambda on closed loop
Also used to start high then fade to nothing.
MB
Never did find out how the MAF influences the lambda on closed loop
Also used to start high then fade to nothing.
MB
Last edited by Dark Blue Mark; 16 January 2005 at 11:52 AM.
16 January 2005, 02:44 PM
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thanks for the replies fellas,
took the car to work with me this morning and started again from scratch.i could see what i was doing this time. it looks as if it was a bad earth connection,as soon as i redone the connection it was fine
being abit kack handed doesn't help much. also this morning managed to fit my oil pressure sender so all my gauges are working fine now.
it is reasurring to know that if you have a problem that there are many on this board who will take the time to respond to threads and help if they can.
thanks again
Lee
took the car to work with me this morning and started again from scratch.i could see what i was doing this time. it looks as if it was a bad earth connection,as soon as i redone the connection it was fine
being abit kack handed doesn't help much. also this morning managed to fit my oil pressure sender so all my gauges are working fine now.it is reasurring to know that if you have a problem that there are many on this board who will take the time to respond to threads and help if they can.
thanks again
Lee
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