Really Weird Idle+loss of power

[Atreus]

Okay, so driving to work today, sitting at the light, my idle went from vumvumvuvmvuvmvumvum(you get the idea) to
vumvum........vumvum.......vumvum. but really loud, and you could feel the engine shaking, like a deep heartbeat. as the light turned green, i gave it some gas and it did not want to go, barely broke 2000rpm, and my CEL came on. now its only happened this once, and i dont know if i can pull a code since the CEL is off now, but has anyone experienced this before? What are some basic things i should look now, to see what the culprit may be.

Any help is appreciated.

[Atreus]

update, i unhooked my ICV and the car died, however i read that if unhooked, the car should rev higher. so does anyone have any leads.

[ethree]

Unhooking your ICV will cause a huge vacuum leak and kill your engine. I have no idea what your problem might be but I'd start with cleaning your ICV and AFM.

[Fidhle007]

That can be indicative of a bad AFM or a large vacuum leak. Generally vacuum leaks take more time to show up so I'd suspect your AFM. Read the code and see what's been stored, that's your best indicator.

[Atreus]

thanks for the responses, i really appreciate it. i suspected it was fuel related, so i went to the yard and pulled a FP off a nice 325iS, to no avail. what is the "AFM" is it connected right after the intake? that box looking thing? i'm gonna clean my icv tonight. and try and figure out what an afm is.

the new FP seemed better for a little bit, but after highway cruising at 80mph, i'd feel the car stutter, and 5miles later it'll die out.

i'll look into the afm matter.

[Fidhle007]

What's the code say? And how often have you consulted your Bentley manual?

[Atreus]

bentley=sold out everywhere. for the past month. so nogo for me. however i have a bunch of pdf manuals at home. (working right now). i was about to post a new thread, asking "how do you pull a CEL code?" the guy told me that my car is ODB1, not OBDII so i can't use their scanner...

[whiltebeitel]

It's not even an OBD 1 car.

Do the foot stomp test, or get this:

http://www.turnermotorsport.com/html/detail.asp?PRODUCT_ID=FCX

[wagonizzle]

Okay, do a search for "stomp test" and motronic fault codes, if your car is a 1989 or newer. My car did something similar two days after I bought it. I was so dejected. With the help of R3V and $20, my new coolant temp sensor had it running strong and a beautiful relationship was born. I can fix this car!

Do your research. These cars are pretty simple so there isn't that much for you to 'diagnose'. Good luck and check the TPS settings too. A Bentley will save you thousands depending on how long you own the car.

[SpecM]

Unhooking your ICV will cause a huge vacuum leak and kill your engine

not so sure where you got that idea

to the OP: the AFM sit above and to the right of the air filter housing

[Atreus]

perfect, i'll do a stomp test and go from there. thanks a lot for the advice/pointing me in the right direction everyone. stomp test here i go.

[Atreus]

1-2-1-5 here i come. maf/afm=same thing?

[SpecM]

1-2-1-5 here i come. maf/afm=same thing?

sort of... close enough for the purposes of this thread.

AFM codes can also be vaccum leaks in disguise, tho!

[Fidhle007]

Try unplugging your AFM and see what happens too, a lot can be learned by how a motor reacts when you disconnect a vital part of it's system. As a professional tech, this is often the first thing I do to a car with weird running problems that my scan tool can't decipher.

Think of a your engine's management system like the human body/brain. We use a combination of information from various sources to function every day (sight, hearing, smell, touch) and if one of those senses were to suddenly malfunction, we'd start walking into things. Now imagine you're a doctor and your patient is mute and can't tell you what doesn't work (your car without a scantool.) If you start depriving senses one at a time and watch the reactions, you'll get a pretty good idea of what's not working or malfunctioning. It's a similar situation with a car, but slightly more complex as there are many different things that can cause similar symptoms. But then again, that's why we charge $75 an hour...

A quick vacuum leak check (if you don't already know this) is to remove the oil cap while the motor is running. A sputter or possible stall is good, no change is indicative of a leak or AFM issue.

Good luck and keep us posted!

[Atreus]

okay. cleaning my icv+afm now. i am using carb/choke cleaner on both. pulled the gas cap and it did stutter on me, but kept going. gonna take a shot at the TB now..... see you in a hour!

wait. will carb/choke cleaner mess up my TB if i use it on that?