Z4M Engine Sputters/Misfires

[dannyacs]

Ever since I got the car about 6-7 months ago, I 've noticed the followinfg thing: after driving on the highway at ~75mph in 6th and slowing down to ~50 (still in 6th, costant ~1800 rpm) the engine would stutter for a second.

Now it got worse, but only after I start pushing it a lot: so if I go all the way in 2nd, 3rd, redline it a few more times and as soon as I quiet/slow down, the engine cannot maintain constant speed, sputtering/misfiring for about a minute.

I've also noticed that whenever I don't drive it for a few days, it takes 3-4 seconds to crank, then it starts.... embarrasing... (yes, i do let the fuel pump start first). Once, it started but the rpms were jumping and down between 500 and 1000rpm, applying full throttle did not do anything, just made the rattle worse, more misfiring, etc

So, do you thing these symptoms might be related? MAF sensor, vacuum leak, engine management...? I don't trust the stealers, very rarely they know what's going on..

[STEALTHYZ4]

Have u scanned for stored codes? Sounds like a intake leak.Mis-firing should have set off codes.

[dannyacs]

Dealer scanned, no engine errors. They found errors on the DSC hydraulic unit and replaced it, but that didn't change anything... The morning after I took the car back from the dealership (65 mile drive), the yellow engine light came on and doesn't turn off since..
I heard this come from a loose gas cap...???

Anyhow, I still experience the same rough and jerky output when I drive in 6th, barely touching the throttle (it feels as if it's going to run out of gas).

[vicj]

The SES light is most likely unrelated to the Dealership visit...but I would still makethe 65 mile drive to check it out.
If it's the the Check engine light, it could be emissions related, but could also be a couple other things. I'd have it checked soon, as the light says. If you cannot trust the Dealership that's near you, I would try to find one you CAN build a relationship with...you're going to need them sooner or later.
You might start by NOT assuming they "rarely" know what they're doing, and by inquiring about, and asking to meet, whoever they have that specializes in the S54.

[pokeybritches]

If you have a hard SES light, it's throwing a code.

This may be completely unrelated, but when my battery bit it unexpectedly and I had the car jumped, the RPM bounced around like you described. After the alternator charged it up for a few minutes, I turned off and restarted the car. The engine smoothed out, but there were several other electronic gremlins present - mainly, the car lost its one-touch operation of the windows. By the time I got to the dealer everything was working properly again. They replaced the battery, and I've had no issues since. So, your battery might be on its way out, but I don't think that's your only problem. Our cars seem to act funny when brought back from the dead. Sounds like you have other issues though.

[dazed^]

As for that engine light; it's not going to be the gas cap being loose. Wishful thinking may be playing a role here. There's clearly a problem of sorts with the way the engine is running.

I think you had best set aside your reluctance to go to the d/stealer. I'm sure you have good reasons to think they might be relatively clueless, but with a fairly exotic car like ours there's not going to be a more capable specialist around who'd do a better job.

[tjank123]

Probably a obvious question but ... what petro are you using. My ZM manual recommends "Super premium gasoline/AKI 93" with minimum approved fuel of AKI 91. For non-Z's it recommends AKI 91 with minimum AKI is 87.

[STEALTHYZ4]

+1 ,A question i was afraid to ask,for fear of maybe insulting OP.

[2kredz3]

Have you changed the spark plugs yet? how about run sea foam? Injector cleaner?

all these things are very important to maintain. particularly on a car that doesnt see much driving or a lot of short trips. I bet the check engine light is a misfire code on cyl 3 or 4 (maybe both) very typical when you have a plug that is fouled.

now, that is all the easy stuff. . .next it could be a cam sensor, which you would know right away when you get the codes checked (you can buzz by an autozone and they can read the non-BMW codes) report back with what autozone says. While there get a can of sea foam and start the cleaning process. be prepared to have to replace spark plugs after running the sea foam ;-) sea foam breaks up all the carbon deposits in the engine and can foul a plug.

I hope that helps, I have seen several Z3's that do the same thing and one of the above usually fixes it.

[dannyacs]

dazed^ , Having had a 1996 840Ci before, believe me, every stealer was clueless (ok I know I'm very picky somtimes, but I like my cars to be top notch) mainly because they are trained on recent and common models. Stealers also rely on error codes and think that there is no problem if no fault is recorded (which is what happened last time).

tjank123, I always buy premium from Shell

2kredz3, agree should have at least put some injector cleaner, but managed to book an appointment today, see what the stealer says...

"suprisingly" the gas cap didn't fix it...

[99C2]

Ever since I got the car about 6-7 months ago, I 've noticed the followinfg thing: after driving on the highway at ~75mph in 6th and slowing down to ~50 (still in 6th, costant ~1800 rpm) the engine would stutter for a second.

Now it got worse, but only after I start pushing it a lot: so if I go all the way in 2nd, 3rd, redline it a few more times and as soon as I quiet/slow down, the engine cannot maintain constant speed, sputtering/misfiring for about a minute.

I've also noticed that whenever I don't drive it for a few days, it takes 3-4 seconds to crank, then it starts.... embarrasing... (yes, i do let the fuel pump start first). Once, it started but the rpms were jumping and down between 500 and 1000rpm, applying full throttle did not do anything, just made the rattle worse, more misfiring, etc

So, do you thing these symptoms might be related? MAF sensor, vacuum leak, engine management...? I don't trust the stealers, very rarely they know what's going on..

...I use the higest Octane and always keep RPM's around 3000.

99C2

[jragan]

Could it be the HPFP?
Could the stations you go to be sneaking more than 10% ethanol in your fuel (it's a common problem)?

[dannyacs]

Problem finally fixed.

Turns out a cable loom in the engine bay has been rubbing against something which caused some of the wires to get shorted; one blown fuse and a secondary air pump changed... couldn't get more out of the dealer as we were both in a hurry at the end of the day..

Tested it out on the highway and it seems no more cutting or jerking!

[dazed^]

Problem finally fixed.

Turns out a cable loom in the engine bay has been rubbing against something which caused some of the wires to get shorted; one blown fuse and a secondary air pump changed... couldn't get more out of the dealer as we were both in a hurry at the end of the day..

Tested it out on the highway and it seems no more cutting or jerking!

Good to hear it's fixed.

Strange that a short-circuit is not detected and/or displayed as a problem on the dash.

[dannyacs]

Well... actually appeared again.... going nuts now! I thinking fuel pump doesn't supply the necessary pressure (especially when you start pushing it)?
Injectors? I'll try putting some injector cleaner and seen if any improvement....
I'm running out of ideas now..

[geftman]

Check it for the same problem (the cable rubbing)... If there's still rubbing, it may be the cause once again.

[mike87]

wouldn't hurt to try a good injector cleaner, techron by chevron is good.

[jragan]

wouldn't hurt to try a good injector cleaner, techron by chevron is good.

BMW actually private-labels the same stuff and recommends it periodically.

[JMac87]

Does Chevron put Techron in their gas? I.e. if I go fill up there would it be pretty much the same thing as buying a bottle of Techron?

[dannyacs]

I decided to fill up half a tank with normal gas: ono jerkiness, only consumption increased ~15%... I ran it until almost empty and filled up V Power and STP injector cleaner and so far I've not been able to observe any of the issues... So it was either crappy V power I've been buying or the injectors....

[geftman]

I decided to fill up half a tank with normal gas: ono jerkiness, only consumption increased ~15%... I ran it until almost empty and filled up V Power and STP injector cleaner and so far I've not been able to observe any of the issues... So it was either crappy V power I've been buying or the injectors....

In that case try any of the following: seafoam, bg44 (i think that's the name), gumout fuel cleaners.

However, as a note, the injectors shouldn't really get clogged/go bad in newer cars no matter which gas you put in.

And the difference in mpg shouldn't even be there, especially not by 15%