Author Topic: Another idle issue post (Read 2744 times)

Ramblin MAn · « **on:** September 01, 2009, 01:20:37 PM »

Ok first off this is about a car that has not ran in two years so keep that in mind. Also keep in mind I have no history I can provide other than what I have done since I got it.

issue:

When the car warms up and is at idle, it will start to climb in the rpms and then fall like the fuel is being cut off, settle at a decent idle then repeat. So mmmMMMMBAAaammmMMMBaaammmMMMBaaammmMMMBaaa. I know, pretty scientiffic.

I had this issue before on a different car and it was because I had an aftermarket trottle body on and there was too much air getting by at lower throttle openings so the TPS was telling the cumputer the throttle was only open x% but now x% was twice what it used to be and the O2 sensor said hey you are way to lean, and the compueter said lets shutter down. And it would just loop. I fixed it by going back to the stock TB.

This car is completely stock except for the throttle heater delete mod.

I have replaced both upper and lower intake manifold gaskets. I have the IAC between the intake bellows and the valve cover, and I have the other side of the valve cover feeding the large connection under the throttle body. I will check for vacuum leaks again but it all seemed tight.

My question really is, have any of you experienced this same type of reeeeevvv-fall reeeeeevvv-fall idle thing before and what did it end up being. I'm sure a new O2 sensor wouldn't hurt, but I'm trying to keep in budget.

Ramblin MAn · « **Reply #1 on:** September 03, 2009, 07:53:19 PM »

Ok I guess I'll update this thread myself until I figure it out and log the things I've tried.

Checked for vacuum leaks. all good.

Tried three 2 other MAFs, one I know is fine because I pulled it from my e21.

Tried using a different intake bellows (from my e21) that has the IAC/ICV port in a different location.

Tomorrow will be cleaning the IAC/ICV and if I have time checking the fuel pressure, fuel pressure guage, taking vacuum readings.

Saturday will be testing the coolant temperature sender (may be that because it happens right about the same temp every time.) and the TPS.

romeomike · « **Reply #2 on:** September 03, 2009, 10:35:37 PM »

You said the car hasn't been run in two years. It might take a tankful or two plus some fuel injector cleaner to get the stale gas out of the system.

You can run a stomp test and check out whatever codes might turn up.

Adios for now,

RM

AcSchnitzer318is · « **Reply #3 on:** September 04, 2009, 12:01:18 AM »

^what he said.

Mose likely culprit though... ICV, TPS, or temp sender.

Ramblin MAn · « **Reply #4 on:** September 04, 2009, 10:18:45 PM »

No one reads my other posts

I pulled the tank and cleaned it using electrolisys, blew out the fule lines, gave it a new fuel filter, pump and ten gallons of 93 Sunoco Ultra.

bearsbmw called it first. It was the ICV. 2 years of oxidation inside the ICV. Cleaned it and now she is rock solid. So I am REALLY happy.

AcSchnitzer318is · « **Reply #5 on:** September 04, 2009, 10:53:13 PM »

Good to hear it... my ICV just took a crapper on me, but I am running MS so I just pulled it off... and manually adjusted the idle.

Can't use the AC at a dead stop or it will die, but that's the only down side. Will replace and fix later.

roundel318 · « **Reply #6 on:** September 05, 2009, 06:36:33 AM »

I have a spare old one thats in average condition, I could send it?

AcSchnitzer318is · « **Reply #7 on:** September 05, 2009, 07:07:49 AM »

I have a spare off the m20 I am going to try... if it doesn't work I'll let you know. Thanks though.