Engine failsafe followed by stalling at idle

[haromaster87]

Hello everyone,

I have a 2001 740il with approx 135,000 miles. I experienced these symptoms once a little over a month ago and once yesterday. Both times, I went to increase throttle and the car lost power and displayed the "Engine Failsafe" message on the cluster. Both times, I was able to turn the car off and back on to get it running normally again.

The first time it happened, I unplugged the maf and drove the car around for an evening without issue. I had previously replaced it with a 3rd party MAF and figured it had finally went out, so I ordered a Bosch unit and installed it. The car ran without issue for over a month so I assumed that had sorted it.

Yesterday while merging on the freeway, I lost power and got the failsaife message again. I was able to go into neutral and restart and it drove fine for the rest of my highway trip. As I found when getting off the freeway though, it would now stall when I was coming to a stop. I could bump into neutral and keep it running easily enough with the throttle, but the rpm's would surge a bit as I held my foot still.

I had to stop to run an errand, so I unplugged the MAF again and the car sat for about 15 minutes. When I drove home from there with the MAF unplugged, it ran fine again, no stalling when stopped. I got home and the car sat for a couple hours, then I went and plugged the MAF back in and drove around for about 10 minutes. No stalling or any issues. This morning I headed to work and about 25 minutes into my drive, it started stalling again when stopping/stopped.

When it does this, the car runs fine otherwise. Power seems on par, accelerates normally, etc. That being said, I don't give it heavy throttle when this is happening. The last time it happened, a normal OBDII reader couldn't read the code, so I ordered myself one of those oversea special BMW scanners from Amazon and was able to the DME errors stored

the numbers it provided don't line up with any normal DME codes, but the error messages do. There was the MAF error from when I unplugged, then there was errors:

83: Function, throttle actuator jammed
84: Activation, throttle actuator

I'm not sure if unplugging the MAF actually helps or if the issue is just intermittent. I doubt the 2nd MAF would fail with the exact same symptoms, but who knows. Has anyone had these symptoms and codes before? Those codes point right at the throttle body, but I know it might not be just that simple. I did see an article about a spot that can leak coolant near the ECU and possibly get the connector wet and cause some of these symptoms. I'm going to double check my E-Box to rule that out, but beyond that, could this be something other than throttle body?

Thanks for any help

[racer2086]

Dude you must live right down the road from me! I'm in Riverview. In fact, if you were the gold/light brown 7 that I saw turning onto Lithia Pinecrest from Bloomingdale about a week or two ago, then we drove right past each other. I waved

From the beginning of your description, I immediately was thinking throttle. The 01 is fly by wire, so there's an electronic throttle control. When those start going out, they will revert the engine to failsafe and only drive like 20mph. You may need a new throttle actuator.

I have a full BMW diagnostic set up if you ever need codes read.

[haromaster87]

Hey! Funny enough I'm not the goldish one, but I'm willing to bet that's the same champagne colored e38 that lives in the neighborhood right next to mine. Funny, I've seen your post all over the forum and never noticed your location!

Now that I think about it, I'd swear I drove by you while you were waiting at a light on St. Cloud to turn onto SR 60. My car is Anthracite and has black trim and M-pars. I remember thinking the dark tint really did something to make your car look that much more bad@ss.

Alright good so it sounds like I'm on the right track then, and the codes support that as well. If everything checks out with the ECU wiring, I'll be looking into a replacement throttle body.

Thanks a bunch for the offer! I may just take you up on that one day.

[haromaster87]

So I sourced a replacement throttle body and swapped it out. That definitely needed to be done, but it did not resolve my stalling issue. I had the battery unplugged for a while so the old codes had cleared, but it has two that persist:

8C Activation, Map Cooling
73 Signal, hot-film air-mass flow sensor

That was with the MAF plugged in. I still had my old MAF, so I installed it back in the car and get the very same behavior and same errors as the newer Bosch MAF. Car drives fairly normal for the most part, if not a little sluggish. But when I'm coming to a stop, it'll reliably die when I get down to 15 mph or so, sometimes not till I fully stop. I could always see the RPM's drop and nearly die, then sometimes it would catch and rev back up, but mostly it would just stall.

I unplugged the MAF and the car drives great. Runs really strong, catches a great idle when I slow down, etc. But I do get the same codes with the MAF unplugged. The Mass Flow Sensor error is to be expected, but I see the other error being related to various things when I look into it.

I did confirm I don't have any coolant leaking around my harness or on any ECU connectors. The symptoms all seem to line up with a faulty MAF, but that would mean both of them failed in the same way. Is there some connection between the two systems at fault that would make the failure of one system trigger the error for the other?

[COSteve]

Are you getting any lean indications? Fuel trim way out? Unplugging the MAF puts the car on an internally stored fuel map vs. load. With a vacuum leak the MAF will read little airflow and return little fuel, even though more air is reaching the engine through the leak. This often doesn't show up much at higher loads but can be dramatic at idle.

[TheAngryBear]

You are definitely going to need to check your:
1) trims for possible vacuum leaks
2) rough/smooth running values for performance and indicators, and
3) connections as you could have physical issues.
Between those three you should be able to diagnose this.

Check out Timm’s info
https://www.meeknet.co.uk/e38/Diagnostics.htm
Read the entirety of the pages and watch the videos. Then get the values and you should be able to pinpoint the issue.



2001 750iL DD74441
Stock

RIP: 2003 540iA Sport GS56111
H&R front springs, Ultimate Cup Holder, Euro Dash & Armrest, Grom, BavSound Stage1

[COSteve]

I hadn't seen Timm's page before, that is a nice presentation. For a lot of people getting INPA up and running is a daunting task. I've had success with OBDFusion, a $5 phone app. It requires a $5 bluetooth OBD dongle.
OBDFusion can monitor PIDs including fuel trims, most all sensors, etc. It's also capable of data logging so you can set it up and go for a drive and it will save all requested data over time.
Over on E46fanatics a member efoj had posted guides to the process. Start here: https://forum.e46fanatics.com/attach...9&d=1489505619