weird surging lately

[bmw325csi]

My car started acting up again today, fucking money pit.

Anyway, the car is a 88 325ic, almost stock with the exception of an maf kit. As Im driving it surges, not a lot but its noticeable. At idle the idle plays a bit from 700 to 1000 and sometimes feels like its gonna turn off but doesn't. When i accelerate, it randomly surges like my foot slipped of the pedal or something.

Im going to check for air leaks tonight but is there anything else that can cause this.

In the past my ICV was faulty so I changed it. Also the fuel injectors have been changed. Would spark plugs or wires cause this?

Any help or ideas would be appreciated as I have been searching all morning.
Thanks in advance.

[bmw325csi]

bump, please help

[gearheadE30]

Do you have some kind of tuning done to the car?

Surging is almost always caused by running too much advance/the mixture being too lean. I'd look at vacuum leaks as the primary suspect (it would also explain the idle), and maybe check the plugs and make sure that they don't look like they've been running too hot and make sure that they are in good shape. Note that changing the air fuel ratio will actually vary the idle quite a bit as well, all else held constant. I don't think it would be an o2 sensor, as the DME would typically cause the engine to run rich rather than lean. Considering the non-stock MAF, I'd look first at anything that changed in association with that that could leak air or is tuned differently.

EDIT: I know the money pit thing. Don't let it get to you too much. I put megasquirt in my car a little under a year ago, and I'm still tuning out the occasional surging, trying to fiddle with the advance and fueling. It's a tedious process, and I can go out and tune for hours, think I fixed it all, and then drive it the next day only to find another area that's too rich or too lean. Just imagine how good it will be to drive when you do get it sorted out, hah.

[jlevie]

An unsteady idle on this car will be intake leaks, a sticky or bad ICV, a flaky TPS, or a combination of those. Rarely it will be due to a problem with the throttle body or accelerator cable.

[bmw325csi]

Thanks guys.

I checked the stuff mentioned and all I could find wrong was the Idle Control Valve I believe. With the ignition on and the valve plugged in, it clicks like its stuck. I took it off and looked inside and the little trap door looks like it stuck closed and its trying to close even farther.

I was thinking that it opens randomly while im driving and causes my surges. Does that make sense at all?


PS. While I have an open thread, I gotta ask: My fuel empty light doesn't come on. I put in both senders new under the seat. Changed the bulb in the cluster still nothing. Is there anything else to be checked, or is my bulb just faulty?

[jlevie]

The ICV is a player in an unstable idle, but not likely to be a player at engine speeds above 2000rpm. Surging while driving is more likely to be a problem with the AFM or fuel delivery. In this case, since the engine has an "maf kit", that would be my first suspect. Though I would also run the fuel system tests and monitor rail pressure while the surging is present.

If you've replaced the right side fuel level sensor and don't see the low fuel light when you drain the tank, either there is a burned out bulb in the cluster or a wiring fault.

[bmw325csi]

Thanks again Jim. Your awesome.

[expressfish]

My car started acting up again today, fucking money pit.

.

ahhhhh the joys, I feel for ya. and for the fix....what everyone else said. good luck man.

[bmw325csi]

thanks :(

Im going to throw in another icv im getting from levant and then change my injectors as this was my problem last time. I really hope it gets fixed because this shits getting old already.

[jlevie]

Throwing parts at the problem while hoping for a favorable outcome seldom results in an improvement and just lightens your wallet. Have a smoke test run and fix the intake leaks it reveals. Then run the suite of fuel system tests. If the problem is still present after that, more diagnostic work is indicated.