Diagnosis from the dealer

Here was my previous post

http://forum.e46fanatics.com/showthr...218&highlight=

The long and short of it is when warm the idle bounced up and down and often stall. So the dealer says that the problem is the alternator is overcharging which is causing everything to shut down. Doesn't sound very likely to me. I'll throw an alternator in and see what happens. They want $1200 for the alternator for parts/labor/tax. Does it sound like the alternator would do this? I figure I could pay them $1200 and the problem would still exist. Then they would say well we had to rule out the alternator and then they would charge me for a vacuum leak, etc. Could this cause a warm erratic idle?

In my entire life I have only seen 1 alternator that the regulator was shorted, the car would start, run about 4-5 seconds, then turn off.

Removing the fan belt was the quick way to isolate that problem.

Anyway, forget the alternator for now until you see the link below in my signature about the Hidden OBC Menu, you can bring up the battery/charging Voltage right on the dashboard. If you are not seeing more than 14.5 Volts, charging/alternator is not your problem.

Suggest you also read the first 2 links below in my signature as well.

I will check out for other post and comment back here if I can add anything.

Dealers = Glorified parts replacement monkeys!

Just read your other post.

Do you get the Check Engine Light to come on?

Any codes?

If the oil leak was bad, OFHG, it may have saturated the alternator and caused problems??

Would also consider intake camshaft position sensor, of if you want no headaches and since you did the Vanos seals, replace both camshaft position sensors, they soft fail and cause stupid things to happen.

I didn't read your other post, but have you read the 'idle surging' thread? (NicB is the author)

Other than sensors for which you'd get a code, the ICV and TB both seem like they might be involved. You could clean both and plan on replacing the lower intake boot while you're there anyway...and the truth is, I bet this is just another torn lower intake boot issue, but while you're there look around...replace rubber parts and hoses.

Originally Posted by jfoj

Just read your other post.

Do you get the Check Engine Light to come on?

Any codes?

If the oil leak was bad, OFHG, it may have saturated the alternator and caused problems??

Would also consider intake camshaft position sensor, of if you want no headaches and since you did the Vanos seals, replace both camshaft position sensors, they soft fail and cause stupid things to happen.

No lights, no codes. The oil leak was bad so maybe that fubar'd the alt. Seems weird that it would only exhibit the problem when warm. I am getting the car with no new alternator tomorrow and will check the volts.

I might just do the cam sensors to rule them out. Some say they always throw a code, others say they don't

Originally Posted by dmax

I didn't read your other post, but have you read the 'idle surging' thread? (NicB is the author)

Other than sensors for which you'd get a code, the ICV and TB both seem like they might be involved. You could clean both and plan on replacing the lower intake boot while you're there anyway...and the truth is, I bet this is just another torn lower intake boot issue, but while you're there look around...replace rubber parts and hoses.

TB and ISV were cleaned and the ISV moves back and forth with voltage applied to it. The TB is open about 1mm with no power to it. I haven't checked with power to it but i'd assume it would throw a code since the angle is read. It is 100% not the lower boot. I checked it thoroughly and even pressure tested it.

Originally Posted by AlpinaB7

No lights, no codes. The oil leak was bad so maybe that fubar'd the alt. Seems weird that it would only exhibit the problem when warm. I am getting the car with no new alternator tomorrow and will check the volts.

I might just do the cam sensors to rule them out. Some say they always throw a code, others say they don't

Cam sensors throw a code...so do many things. So, you're looking for things that don't throw a code.

The alt would maybe have had a stored code from a bad oil leak dripping on it...vaguely recall something about reading that...but it could be cleaned...it's water proof (ish).

Not seeming the alt at all based on your symptoms, and you haven't mentioned an issue with battery, but, you know, the dealer did have your car and give you a diagnosis.

I don't know if you'll find a 'fixed alternator by cleaning it' thread, but maybe.

Don't rush out and do this, though, as it might be a really stupid random guess.

What things wouldn't throw codes and affect idle at the same time?

Hmmm...fuel filter/air filter/dirty maf? Maybe try reviewing where you're at with the basics.

Check as many places as you can for airleaks like oil dip stick...oil fill caps go bad...vcg/ccv...search diy smoke test (using cigar).

Cam sensors only throw codes when they hard fail or there is a wiring problem. The cam sensors are Hall Effect units so they have active electronics in them that can get weak and sloppy. The M cars get them proactively replaced all the time. The issue is the non M cars are tuned very differently and you will not notice a sloppy cam sensor as much as you would on an M car.

The alternator itself will not store any codes, however, there may be over Voltage codes stored? I have seen a lot of under Voltage codes in these cars.

Also check the engine to body ground on the passenger side near the motor mount. The body connection goes bad most often.

Originally Posted by jfoj

Cam sensors only throw codes when they hard fail or there is a wiring problem. The cam sensors are Hall Effect units so they have active electronics in them that can get weak and sloppy. The M cars get them proactively replaced all the time. The issue is the non M cars are tuned very differently and you will not notice a sloppy cam sensor as much as you would on an M car.

The alternator itself will not store any codes, however, there may be over Voltage codes stored? I have seen a lot of under Voltage codes in these cars.

Also check the engine to body ground on the passenger side near the motor mount. The body connection goes bad most often.

There are no codes stored. I cleaned the MAF but I know that only goes so far. I could replace the MAF and cam sensors but I would prefer to not throw parts at it. There is absolutely no issues under throttle. It pulls hard and drives great except at idle. Everything keeps leading back to a vacuum leak. But I have checked everywhere and don't see anything. I even smoke tested it.

Originally Posted by dmax

Cam sensors throw a code...so do many things. So, you're looking for things that don't throw a code.

The alt would maybe have had a stored code from a bad oil leak dripping on it...vaguely recall something about reading that...but it could be cleaned...it's water proof (ish).

Not seeming the alt at all based on your symptoms, and you haven't mentioned an issue with battery, but, you know, the dealer did have your car and give you a diagnosis.

I don't know if you'll find a 'fixed alternator by cleaning it' thread, but maybe.

Don't rush out and do this, though, as it might be a really stupid random guess.

What things wouldn't throw codes and affect idle at the same time?

Hmmm...fuel filter/air filter/dirty maf? Maybe try reviewing where you're at with the basics.

Check as many places as you can for airleaks like oil dip stick...oil fill caps go bad...vcg/ccv...search diy smoke test (using cigar).

I just did the oil tube "O"ring, oil cap gasket, air filter, cleaned the MAF. I don't know the age of the fuel filter. Just got the car. But would fuel filter problems show themselves at idle? It runs great at WOT. I have not checked the fuel pressure regulator hose under the car. I just did a smoke test and saw nothing

Put a fuel filter in the car. There is a vacuum line at the filter that breaks often, it does not show up under most smoke tests. Replace the DISA O-ring. May have a soft failing fuel pump as well?

Originally Posted by jfoj

Put a fuel filter in the car. There is a vacuum line at the filter that breaks often, it does not show up under most smoke tests. Replace the DISA O-ring. May have a soft failing fuel pump as well?

I'll try the filter. The disa unit is recent and I did some high temp RTV around it just to make sure. I'd imagine both the filter and pump would make themselves known more under throttle than at idle but since I don't know the age on the filter I will replace it.

If you read the 2nd link below in my signature, I believe there are members that indicated that replacing their fuel pump stabilized their idle and make the throttle more responsive.

So I just picked the car up from the dealer after they said the problem was the alternator. I went into the OBC codes and drove for 30 minutes while checking the volts. When the car was running normally it was 14.0v +/- .3v. When the idle was bouncing up and down it went as high as 16v. But I think the idle bounce is causing the volt spike and the alternator is not causing the idle bounce. The idle drops to about 450 rpms and then bounces up to about 1200. This takes place about once per second. On the upswing the voltage spikes--just as it is swinging up from 450. My theory is that as the car is about to stall it's demand for electricity drops significantly causing the voltage to go up. As the car tries to save itself from stalling the rpms climb and the car consumes more electricity so the voltage drops back to normal levels. I think the alternator is a $300 red herring. Back to the drawing board.

Also, when I got to work I parked at a slight incline in the shade and the car idled fine for 10 minutes with the voltage staying normal. When in traffic and it's hot it bounces. 90 degree days in traffic and it stalls out all the time.

16 Volts is likely close to the point that the DME may try to protect its self?

Also even a good Voltage regulator should be able to stabilize the output and clamp it at 14.5 Volts, so I suspect you should address your charging issues.

As I recall the Voltage regulator and brushes are a single unit that can possibly be changed with the alternator still on the car?? I think the module is less than $50 as I recall?

However, you may want to pull the alt and degrease it with brake cleaner or gunk and replace the regulator assembly while you are at it.

Do not think the Voltage spikes are "normal" as they are not.

The car I dealt with was a flood car and the regulator was shorted. You would start the car, it would idle/run for maybe 5 seconds then totally shut down. Car would restart as expected and then shut down over and over. The car was not a BMW but as I recall the charging Voltage would go up to 16.5 Volts and the engine computer was protecting itself and the other on board electronics by shutting the engine down.

Originally Posted by jfoj

16 Volts is likely close to the point that the DME may try to protect its self?

Also even a good Voltage regulator should be able to stabilize the output and clamp it at 14.5 Volts, so I suspect you should address your charging issues.

As I recall the Voltage regulator and brushes are a single unit that can possibly be changed with the alternator still on the car?? I think the module is less than $50 as I recall?

However, you may want to pull the alt and degrease it with brake cleaner or gunk and replace the regulator assembly while you are at it.

Do not think the Voltage spikes are "normal" as they are not.

The car I dealt with was a flood car and the regulator was shorted. You would start the car, it would idle/run for maybe 5 seconds then totally shut down. Car would restart as expected and then shut down over and over. The car was not a BMW but as I recall the charging Voltage would go up to 16.5 Volts and the engine computer was protecting itself and the other on board electronics by shutting the engine down.

I ordered a VR. Should be here soon ($39.xx). I'm still not convinced but I figure that the dealer has been trained by the people who made the car and they have the most advanced diagnostic tools so they should be better than anyone at determining the problem. That being said, it seems unlikely to me that the problem of a bouncing idle when it is hot outside would be caused by this and that no other problems would exist. HOWEVER!......i've been outwitted before. I'll post my results when the part comes.

Just the other day I had a 3.0l E53 X5 alternator that would spike to 17v (only when hot) and cause the trans to go into limp ****...food for thought.

I guess you can't say h o m o !?

Alpina,

Regardless if the VR solves your idle bouncing issue, I believe you need it anyway as a VR should be fast enough to keep the max Voltage clamped at close to 14.5 Volts, you should only see a 0.2-0.4 Volt variation at the max toward the upper end and the VR should clamp at 14.5-14.6 Volts without much effort.

Will be interested to see what you find and hopefully it is an easy swap and solves your issue.