Idle drop

[DonovanPorter]

hi Guys i have just recently noticed that , when i put my lights on the revs drop ever so little which is fine, but when i put the blower on the windows and the demister on the revs plumit to about 500rpm and jump up and down , and sometimes the car would die , unless i intercept and give it a rev or two , i had the battery checked yesterday , and its fine , and the alternater is charging it , at a rate of 13.38 volts the guy at Autozone that tested it said it is fine but should be atleast 13.80 volts, any thoughts on this ?

 

[plonkster]

Well, the "physics" of the matter makes sense. You extract some power from the system and the system shows it. Couple things wrong though, usually the engine management should pick this up and compensate. For example, most air conditioner systems are connected to the ECU and when they are turned on the let the ECU know to up the power a little (on carb systems there is usually a similar diaphram based system on the carb).

Also, a charging battery can go as high as 2.45V per cell, that is over 14 volts, a fully charged battery at rest should measure between 12.5 and 13.2.

Check your ground wire (from battery to body) to start with.

 

[DonovanPorter]

ill check that tonight , and the battery water , that might be a culprit ?

 

[plonkster]

ill check that tonight , and the battery water , that might be a culprit ?

I doubt it is the water, but by all means check it and top it up. I once managed to make a Willard battery last 6 years and 3 months, and all I did was to regularly measure it with a hydrometer and top it up.

 

[BimmerMan]

Do the E46 BMWs come with an Idle Control Valve? This could be the problem. I have exactly the same symptoms on my E34 and I am pretty sure that it is the Idle Valve that has worn out. If you dont have one, it will be controlled by the Electronic Throttle in which case there is another problem...

 

[DonovanPorter]

I doubt it is the water, but by all means check it and top it up. I once managed to make a Willard battery last 6 years and 3 months, and all I did was to regularly measure it with a hydrometer and top it up.

i have never had a battery last longer than 4-5 years.

Do the E46 BMWs come with an Idle Control Valve? This could be the problem. I have exactly the same symptoms on my E34 and I am pretty sure that it is the Idle Valve that has worn out. If you dont have one, it will be controlled by the Electronic Throttle in which case there is another problem...

ill check tonight when i get home , i have heard that they can give issues.

 

[plonkster]

http://forums.bimmerforums.com/forum/showthread.php?t=900798

 

[DonovanPorter]

great find thanks man