At cold start Engine Surges after idling for 3 - 5 min

[pietern740il]

I have E39 530, currently I have no CELs. But when i start up in the mornings everything sounds normal and looks normal for the first three minutes. If I do not touch the gas pedal, I notice the engine starts to surge, idle speed drops to 400 RPM, then back to 600, then repeats 10 - 15 seconds later.

Not sure if it's related, but during three weeks ago something is draining my car battery. Called AAA and they said my Battery is okay, but noticed something is pulling 1.67V when the car is turned off.

Any ideas where I should start looking?

[BJerolimic]

some sort of vacuum leak? check CCV hoses, air intake boot and attachment points, etc. ?

[pietern740il]

I had the vac hoses swap around behind the intake manifold. Last month I swapped them and the CEL went away, but this cold start idle problem remains. Last while driving home, my battery light and a host of other lights came up on the dashboard. I figured it could be the battery or alternator, towed the car home.

[BJerolimic]

I had the vac hoses swap around behind the intake manifold. Last month I swapped them and the CEL went away, but this cold start idle problem remains. Last while driving home, my battery light and a host of other lights came up on the dashboard. I figured it could be the battery or alternator, towed the car home.

so the cold start idle issue was there before the vacuum hoses job? diy that job?


doh no fun! I've seen that for various things from loose connections, bad alt, bad voltage regulator but the battery may not be the cause (but alt issues can make a battery go bad). Have you been reading Rob Siegel's Roundel Weekly online the past few months? He's had some good posts specifically on all these electrical things we're talking about (well that and the Vixen of course), check it out: https://www.bmwcca.org/roundel

[Razzy23]

could be your idle sensor

[pietern740il]

Thank you for the link, as I was reading your post. I do recall last month replacing the oil filter housing gasket. Before I reinstalled the alternator, I had swapped out the voltage regulator because it looked dirty. All my problems started after that reinstall. So I'm looking for a replacement alternator 120AMP.


I know about the idle sensor, before this week's breakdown it normally idle well once i get pass the initial startup period.


WTB - 120 amp alternator

[pietern740il]

I was able to install a new alternator on Sunday, which corrected the battery light problem. But surging in idle when I start up in the morning still exist. I tried swapping the vacuum hoses behind the intake manifold, but no changes were felt or noticed.

[pietern740il]

One week after installing replacement alternator update:

This morning when to start my car and battery was dead. The last two days I've noticed when I start the car, the battery light would linger a few nano second longer then go out. I saw this Thursday, and Friday, to narrow down the options Saturday night I started disconnecting the radio cause it was the last electrical item installed. Drove 30 minutes on Sunday, and this morning battery was dead. So, I disconnected the DSP amp this morning and charged battery for five minutes.

Any suggestion?

I also disconnected the alarm trigger on driver side air box.

[BJerolimic]

what's the voltage of the battery when the car is not running?

since the old alternator was apparently bad that could've caused the battery to drain itself too much and end it's useful life. And a new alternator can't bring it back to life, maybe a battery charger could but you may just wind up needing a new battery now

[pietern740il]

It's a AAA battery, before last weekend. I had call them asking to have the battery replaced, but they refuse because they saw 1.6V battery drain. I want to believe my DSP amp was the cause of this drain. Disconnected the amp yesterday, but need to check Youtube for instruction to test for battery drain. Once there is no drain AAA will replace the battery.

[pietern740il]

UPdate

Tuesday I drove into work fine, but at 6pm battery was reading 10.2Volts. Car could not start. When I got home that night I connect the battery charger, Wednesday morning everything worked fine, Wednesday evening car started without any problems. Before I left the parking lot Wednesday evening, I did a drain test. I got 0.12 mA, I'm not sure if this is good or bad.

I must say for the from Thursday night to Saturday night, I did not start the car, and it starts without any problem.

The last item I disconnected was DSP amp, I want to believe this is the cause of all my problems.

To be sure, I'm going to reconnect the DSP amp & radio, on Sunday morning redo the drain test. (I will check battery volt before reconnection, after connection, and before drain test in the morning.)

*** Is there a way to replace the DSP Amp with standard AMP?

[RAYADAM]

.12mA is virtually zero in terms of current draw in vehicle , do you mean .12Amps or 12mA (.012Amps). your car should be no more than .030-.050Amps (30-50mA). Make sure you are testing after 30-45 minutes of your car locked and sleeping.

[pietern740il]

Hey Ray,

The meter I have read .12mA.

I was wondering about the sleep times, if I"m disconnecting the battery to complete the drain test, do I still have to wait 30 - 45 minutes?

Regards

[pietern740il]

Update:

I was able to get much testing completed on Sunday.
Before I reconnected the DSP amp and radio, battery was reading 12.24Volts, battery drain was still 0.12/0.11 mA

Connected the DSP for four hours
Battery volts dropped to 12.04

Then, I reconnected the Dynavin N6 Head unit for another 3 hours
Battery volts dropped again to 11.88

I was not able to get accurate drain test, because I have to disconnect the battery in order to complete test. So yesterday and today I've driven the car with DSP amp disconnected, but head unit is plugged in.

What I've noticed so far, that was a problem before. Now when I start the car, Dynavin head unit boots up normal, before when the DSP amp was connect, when I start the car, the head unit will open to Nav screen. So it was not shutting down for some strange reason.

I will monitor this setup for the next three days.

[pietern740il]

UPDATE

After three days of driving and with over night temps in mid 20s to low 30s. I have had no battery problems. This means my DSP amp needs to be replaced.

Surge in idle still exist, not sure where to turn on this issue.

At startup, I do smell oil/exhaust fumes, not sure if this means anything. How could one tell if exhaust manifold gasket needs replacing? This surge problem started after replacing Intake manifold gasket, and valve cover gasket.

Thanks