Help with peculiar problem.

[Rouvld]

So as of late I've been having this peculiar problem with my car, my car is an 89 325i auto. So, the problem seems to happen at idle. Let's say I'm sitting in traffic or at a long light the revs will start to moderately rise and once the get at around 1k the car will jump forward and the check engine light would come one. All of this happens while my foot is on the brake. Then once I drive a few feet the CEL will go out and the car will drive perfectly and the problem usually doesn't happen again. I literally don't know what it could be, I was thinking idle control valve but I don't think that's it, my best guess would be the problem lies somewhere in the fuel system, but this is just my guess and could be completely wrong. Any help on this situation would be appreciated.

[spdracrm3]

i would guess its an Idle control motor issue, only thing that could cause the idle to rise in that way and the ECU is probably trying to correct it and reaches its control limit and sets a code (check engine light flashes on) and at that speed torque converter starts to engage which would cause car to move forward.

have you done the stomp test to pull code?

if you get an Idle motor code it could be the motor itself ,a wiring issue or the ECU starting to fail internally, i would start by replacing Idle motor with a good used or new unit and see if problem persists

[Rouvld]

i would guess its an Idle control motor issue, only thing that could cause the idle to rise in that way and the ECU is probably trying to correct it and reaches its control limit and sets a code (check engine light flashes on) and at that speed torque converter starts to engage which would cause car to move forward.

have you done the stomp test to pull code?

if you get an Idle motor code it could be the motor itself ,a wiring issue or the ECU starting to fail internally, i would start by replacing Idle motor with a good used or new unit and see if problem persists

Thanks for the quick response. I haven't done a stomp test yet, I'll be doing one when I get home. By idle control motor do you mean the idle control valve that's under the hood close to the throttle body? This is what I think you're talking about, Part number 13411286065? Just want to be sure this is what you talking about before i run off and get the wrong thing lol.

[YosemiteSam]

Thanks for the quick response. I haven't done a stomp test yet, I'll be doing one when I get home. By idle control motor do you mean the idle control valve that's under the hood close to the throttle body? This is what I think you're talking about, Part number 13411286065? Just want to be sure this is what you talking about before i run off and get the wrong thing lol.

I believe that is what he is talking about, but before you go buying a new one pull the old one off and make sure it's moving freely. Based on your problem I'd guess the door is moving fine, but those tend to get clogged up and cause rough idle issues. If it is clogged, try cleaning it with some carb cleaner or throttle body cleaner before you go and get a new one.

[b*saint]

Sounds like a bad ground somewhere

[Sputnik]

Does it happen in neutral or in any other gears?

[Rouvld]

I believe that is what he is talking about, but before you go buying a new one pull the old one off and make sure it's moving freely. Based on your problem I'd guess the door is moving fine, but those tend to get clogged up and cause rough idle issues. If it is clogged, try cleaning it with some carb cleaner or throttle body cleaner before you go and get a new one.

Thanks, I have some carb cleaners so I'll clean it an put it back in and test it out for a few days.

Does it happen in neutral or in any other gears?

It's an auto :(

[Seawolf]

Thanks, I have some carb cleaners so I'll clean it an put it back in and test it out for a few days.

Plus a squirt of teflon dry lubricant once it's clean and the carb cleaner has dried ~ don't use WD40 or wet lubricants, they'll just trap grit and jam it up again.