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#1
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Engine not revving properly - Mass Air FLow issue?
Any thoughts on what might be the cause? What else I could check or whether it's worth spending £30 on cheap MAF sensor and see if that cures it? |
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#2
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Not a good idea to purchase a cheap MAF. Go with OE or OEM. MAF is a critical part of adjusting air/fuel ratio.
I suggest that you purchase MAF cleaner and liberally spray the sensor which are the wires that are not as obvious. Most of the time cleaning the MAF will solve the problem if that is the problem. It is an easy one to eliminate yourself. As far as other causes, there are many possibilities. In the major of cases reading codes and troubleshooting will get you to the core cause faster and less expensive than throwing parts at it. An example of some other possible causes----vacuum leak, fuel pump, gas filter--the list goes on.
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![]() Dallas |
#3
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Hi Brian.
You got PM. ![]() Stick with Bcredliner sound adivice, and only buy an OE or OEM MAF. Buy the BOSCH item ref:0928 400 527,but try cleaning yours first! If you disconnected the MAF and although car was better,the fact it still wouldnt rev past 3500 rpm,means its also another problem not picked up by your mechanic. No harm in cleaning the MAF as Becreliner suggested. First you remove the black engine cover behind the air ducts,then remove the MAF (need special torx key to remove the 2 screws), by undoing these scews and pulling it out!You then buy some brake cleaner and spray it on the metal elements and inside the MAF ,then immediately from some 30 cms (IMPORTANT) dry it with compressed air. Your symptons ,could be EGR ,vacuum pipe leak or turbo itself with the exhaust vanes getting stuck. Try disconnecting the egr Vac pipe that connects to EGR valve ,first and test! No change!Then check vacuum system for leaks!First thing you do is remove in and out hoses on vacuum reservoir (this usually cracks) and join them together with a plastic union.Test and if no change,get your mechanic to use vacuum gun on turbo pressure converter IN and OUT hoses and on hose going to wastegate valve. Let me know how you get on and we go from there. ![]()
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![]() 2003 BMW X5 E53 3.0D-Auto, Sportpack,full extras. Oxford green/Leder Dakota interior. 56, 875miles @24th October 2024 Heavily OE modded,including full facelift grill install.4.6is body kit,wheels,exhaust tips and ext.fender flares Non OE mods.Depo "custom" Angel eye headlights. |
#4
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Quote:
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#5
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Quote:
![]() Brake, Clutch & Parts Cleaner - 150ml Aerosol | eBay
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![]() 2003 BMW X5 E53 3.0D-Auto, Sportpack,full extras. Oxford green/Leder Dakota interior. 56, 875miles @24th October 2024 Heavily OE modded,including full facelift grill install.4.6is body kit,wheels,exhaust tips and ext.fender flares Non OE mods.Depo "custom" Angel eye headlights. |
#6
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Update - I now have some MAF cleaner but I'm struggling to get the MAF sensor off - I have the torx set to get it off but just cant get to the bottom torx bolt to get it off. I'll try again this weekend.
Also I was going to do the EGR check but not sure which part that is and which hose to disconnect - any help welcome... |
#7
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Update 2 ----
I ran the car yesterday , I did 11 short trips between 2 and 15 miles each and the car ran differently all the time, sometimes not going past 2ooo rpm, then zooming off to 4000 rpm no problem, then slowing down to 2500 rpm. It was erratic with no logical reason. Also twice from the 11 runs it would not start, just the starter spinning but nothing firing (normally it starts first turn of the key). Both times I found pulling of the vacuum pipe from the right hand side of the vacuum reservoir and releasing pressure it started fine. This is leading me to think the problem lies with the vacuum pipe or reservoir - any opinions? |
#8
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Update 2 ----
I ran the car yesterday , I did 11 short trips between 2 and 15 miles each and the car ran differently all the time, sometimes not going past 2ooo rpm, then zooming off to 4000 rpm no problem, then slowing down to 2500 rpm. It was erratic with no logical reason. Also twice from the 11 runs it would not start, just the starter spinning but nothing firing (normally it starts first turn of the key). Both times I found pulling of the vacuum pipe from the right hand side of the vacuum reservoir and releasing pressure it started fine. This is leading me to think the problem lies with the vacuum pipe or reservoir - any opinions? |
#9
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If you cleaned the MAF and its worst ,then you need a new MAF!Does the car run fine with MAF disconnected?
See my post #3 above for how to check vac reservoir and system! To answer your previous question on what EGR vac pipe to disconnect!Remove the inside black engine cover (the one that goes over the power steering reservoir) and on the right side (looking from the front of the car ) you will an EGR valve connected directly to inlet manifold and you will have small 6mm a vach hose pipe attached to it!Remove and blank the hose pipe with a 6mm M10 screw.Test car with this and see if any different! With error symptons,like you described ,you most definitely have error codes stored in ECU! Read it and it will point you in the right direction ![]() You could have a loose or leaking pressure pipe or vaccum!"
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![]() 2003 BMW X5 E53 3.0D-Auto, Sportpack,full extras. Oxford green/Leder Dakota interior. 56, 875miles @24th October 2024 Heavily OE modded,including full facelift grill install.4.6is body kit,wheels,exhaust tips and ext.fender flares Non OE mods.Depo "custom" Angel eye headlights. |
#10
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I cleaned the MAF thoroughly yesterday and this made no difference. If I disconnect the MAF there is no noticeable difference either. I have looked at the lengths of vacuum pipe and the cotton braided covering is damaged in many places but can't see any defects in the rubber underneath but I have ordered some lengths to replace anyway.
I tried to bypass the vacuum reservoir by connecting both pipe ends together with a piece of 3mm plastic pipe but the car would not start when i tried that so not sure whats happening there - I'm guessing it should at least start unless the seal was very poor maybe? I'll check the EGR valve when I get some time. Thanks for the help with this....... |
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