RPM wont go above 2000, can barely drive in first gear

[Dibz]

Hello!

I recently bought my first BMW, a 2003 e46 320CI with manual gear.

Today when i started it up the EML, DSC and (!) light came on, and then the Check Engine Light. At idle the RPM goes up to 1500 and then drops to 1000 over and over. When i try to give it gas it goes up to about 2000 RMP MAX but then drops again, nearly choking.

Anyone have any clue what the cause might be? I'm buying a OBD2 tool later today.

Thanks in advance!

[bmwdirtracer]

Welcome to the forum.

Forget the OBD2 device; they are useless for diagnosing BMW's. The only codes they can read are emissions codes, written by government bureaucrats, and gross mistranslations of the actual BMW trouble codes in your computers. Turner Motorsport currently has a 20% off sale on a Foxwell/Schwaben diagnostic scan tool which can converse with every computer in your car -- and there are quite a few computers in your car.

As for your issue: The EML (Electro Motor Load) would tend to indicate that you have a throttle body issue, or throttle pedal issue. Each device has two potentiometers, which cross-check each other, and if they don't provide the same information, the car goes into "limp mode". You need to have the BMW specific codes before proceeding, or you're liable to throw expensive parts which you don't need.

Certainly, a thorough cleaning of the throttle assembly is a good idea, but be aware that this probably won't fix your problem, and will almost certainly create large intake leaks, as you fight with the old rubber intake elbows.

[Dibz]

Thank you for the response. I had a friend come and read the codes and it showed 3 codes related to the MAF. The MAF seem easy to change, but I was wondering if you know whether it needs to be programmed or not? Also, I checked with a shop nearby and they charge 470 euros for just the MAF. I found one on Maf-shop for 75 euros, is it totally crap or would you recommend that one?

http://www.maf-shop.com/product_info...621432356.html

[bmwdirtracer]

Let's do a test first. It's not the best test - the best thing to do would be to hook up a good scan tool and read the live data for the MAF. However, a bad MAF doesn't usually cause an EML light, in my experience, so try this: With engine off, unplug the MAF. Then start the car. Does the car now run almost correctly? If so, then you either have a bad MAF or a major intake system leak.....but again, I've not known either one to cause an EML light, just a "Check Engine" or "Service Engine Soon" light.

If you were in the U.S., I'd tell you absolutely to not buy the cheap MAF. I've never heard of Lowe, and the only MAF I would buy for any BMW would be one made by Siemens VDO, the OEM manufacturer.
https://www.fcpeuro.com/products/bmw...ns-13621432356

However, you're not in the U.S., I am unfamiliar with Lowe, and your prices are vastly higher for the OEM part. Still, for 75 Euros, that piece is almost certainly Chinese crap, sorry.

Is there anyone you know who has a scan tool which can read actual BMW codes? (I'm assuming your friend was just reading P-codes?)

Try unplugging the MAF, and see how it runs.

[JimLev]

If you have a friend with the same car see if you can borrow his MAF just to verify your's is bad.
In the past I had intermittent codes for the pedal pot and throttle body, maybe every 6 months. Shut the engine off and restart it all was fine for many months. Then last year it was coding every few days.
Both the TB and pot were changed, it did not rectify the problem.
I replaced the wiring and connectors to the TB and MAF, so far all is fine.

[Dibz]

Let's do a test first. It's not the best test - the best thing to do would be to hook up a good scan tool and read the live data for the MAF. However, a bad MAF doesn't usually cause an EML light, in my experience, so try this: With engine off, unplug the MAF. Then start the car. Does the car now run almost correctly? If so, then you either have a bad MAF or a major intake system leak.....but again, I've not known either one to cause an EML light, just a "Check Engine" or "Service Engine Soon" light.

If you were in the U.S., I'd tell you absolutely to not buy the cheap MAF. I've never heard of Lowe, and the only MAF I would buy for any BMW would be one made by Siemens VDO, the OEM manufacturer.
https://www.fcpeuro.com/products/bmw...ns-13621432356

However, you're not in the U.S., I am unfamiliar with Lowe, and your prices are vastly higher for the OEM part. Still, for 75 Euros, that piece is almost certainly Chinese crap, sorry.

Is there anyone you know who has a scan tool which can read actual BMW codes? (I'm assuming your friend was just reading P-codes?)

Try unplugging the MAF, and see how it runs.

Yes, my friend was just reading P-codes. Unfortunately I dont know anyone with an actual BMW scan tool. Whats strange is later that same day this happened, all of the lights disappeared and my car has been running totally fine without having made any changes. I drove for about an hour and it all seemed fine.

I saw a youtube video that explained that if you unplug the maf connector while the car is running it should stop if the maf is working correctly (although i'm guessing this doesnt apply for every car out there). I tried this and i noticed the rpm dropped for half a second and then it ran like normal again without stopping. Havent done any actual driving with the maf unplugged but I could give it a go.

[bmwdirtracer]

I'd have to advise against buying a MAF; there's little, besides the MAF codes, which points to that . An EML light will almost always implicate the throttle assemblies, either at the throttle motor, or the pedal -- or the wiring, as JimLev has pointed out. And if the throttle data is faulty, it's quite possibly going to cause MAF data to be wrong. If you had a device which could read BMW codes, you'd know whether there were throttle potentiometer codes, but it's possible an OBD reader has missed these.

If you're good with computers, you can buy a simple cable, and download INPA for free, and get excellent diagnostic capabilities for very cheap. A quick trip to the diagnostic software forum (just under this one on the forum list) will lead the way for you, or Abel (328 Power 04) will likely be along in a short while to hook you up. (Sorry, I don't know, because I have various really expensive pro diag computers available to me at work, so I don't use INPA, but I know it is excellent).

[santarosaguy]

Curious what are some of the expensive pro equipment your shop use? I might invest in one if I can find a used one for a good price. Preferably one that does many cars and not just BMW. Don't want to end up buying expensive useless outdated junk.

[bmwdirtracer]

The best computer which does multiple makes is Autologic. It's VERY expensive; starts at $20,000+, and works upwards from there, depending on how many makes you want to service. I think ours was just over 30k, covers most Euro cars.

We also have a $3000 Launch, which is out quick, "go to" scan tool, converses with every make including Chinese stuff I've never heard of....but, of course, it's a Chinese tool. (Autologic is British) The launch can be recalcitrant; there's really no support except repair. We bought ours from Matco, the tool truck, and it has their label.

Then, we have ISTA, BMW's own diag system, and we have both ISTA D (diagnostic), and P (programming). You need to be aware that if you do programming, you need to know and follow all the rules, or you can brick a computer. This means a top quality battery maintainer which holds voltage between 13-15 volts, no matter how the load changes. This is quite different from a charger.

We also have Mercedes Star / Sentry, and RossTech VCDS for Volkswagen. We own the Volvo factory system, but it's so contentious, no one uses it; the Autologic does most everything. We have Porsche's system, but really, we don't get that many Porsches that need much more than a quick scan or reset with Autologic.....and my boss is a Porsche factory "Premier Master Tech"....so I've never even used the system.

Are you a pro? What makes do you work on?