Stumbling at cruise range ??

[Chowchilla Skunkwerks]

Need a few suggestions here. '89 535im. Recent major tune less than 5k ago.
At cruise ( 2800rpm/5th/70mph ) she's starting to stutter. Not consistant, just for a second or two. Seems to be only in that highway cruise area. Happens only after it has run for about 45 minutes. Any ideas where to start looking? Appreciate the input
Rob

[Bin_jammin]

It's probably your EGR. Or a vacuum leak.

Seriously though, what did your tune include? New wires? Resistance check on them? Check the plugs? Do you mean it starts to stutter while you're traveling down the road?

New fuel filter done with the tune? Post more info, please, it will help with diagnosis.

[Sam-Son]

It's probably your EGR. Or a vacuum leak.

Seriously though, what did your tune include? New wires? Resistance check on them? Check the plugs? Do you mean it starts to stutter while you're traveling down the road?

New fuel filter done with the tune? Post more info, please, it will help with diagnosis.
+1 need more info but a bad fuel filter will cause some slight hesitation

[Chowchilla Skunkwerks]

Tune included wires, plugs, fuel and K+N filters. Happens only on the highway, in that happy zone about 70/75mph. Will pull fine all the way thru the gears just at that cruise speed. Thanks for the imput.
Rob

[ILoveMPower]

Does it almost feel as if you quickly tapped on the throttle and then let off again? A bit of a surge?

[Chowchilla Skunkwerks]

NO..more like split second loss of power...

[Ross]

Fuel starvation will not feel as sharp as an ignition fault. I suspect you are somehow losing power to the coil.

[eelley]

Fuel starvation will not feel as sharp as an ignition fault. I suspect you are somehow losing power to the coil.

I have the same problem! I searched through your posts and found this one.

I thought that my stuttering was related to a recent fuel pump and filter replacement. But I was driving the car home this evening -- in the dark -- and I noticed that when my car stumbles, the headlights flicker (along with the rest of the lighting) as well. Occasionally the CEL comes on for no longer then a second.

Just as in previous posts, my car also does not stumble when driving around town at all, only at highway speeds of about 65-75 miles per hour, and only when the car has been running at those speeds for about ten minutes.

After a series of one second stumbles, the car drives normally the rest of the twenty miles or so to my home.

Any info about this strange problem would be great.

Eric
1995 530i

[Chowchilla Skunkwerks]

Eric, after a month or so of checking things I finally just went thru and unplugged all of the electrical connections in and around the engine. Found that there was some corrosion in some of the sockets. Brushed out the connectors, sprayed them with an electrical spray and now she is running as sweet as ever. Might be worth a try. Good luck.
Rob

[eelley]

Thanks, I will inspect the connectors. Eric

[bsell]

But I was driving the car home this evening -- in the dark -- and I noticed that when my car stumbles, the headlights flicker (along with the rest of the lighting) as well. Occasionally the CEL comes on for no longer then a second.

Have a look-see at your grounds in the engine bay while you're at it. Include your grounding straps from the engine to the body. I bet you have either a loose multi-point ground or a bad/corroded ground strap.

It might be a case of the stumble moving the engine around which wiggles the loose/bad connection and turns off your lights. That would suck because that means you have to find your stumble problem after you fix the grounding problem that turns off the lights.

Or you could be lucky and fix both issues when you find the bad electrical connection...

Brian