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Okay so i compiled a list. Wrote everything down. And crossed off the known variables and it leaves me with. Cam and crank position sensors, there is no test i can do on them. The spark plugs may be fouled. And the idle air control valve is known to be a bit sticky at almost closed positions. Can a sticky iacv cause it to be rough all the way through the rev range? I know it can cause my shitty idle but i dont think it would make it feel rough like its missing. Theres no cel, no codes stored. To me it feels like my ignition timing is too advanced or too retarded. And my wideband is showing extremely rich in open loop. Once it hits closed loop thats when the idle gets lopey and i lose power. In closed loop my afrs are within 11-14 range at various throttle positions. It cruises rich and leans out under load till wide open then it goes rich again.
Apprentice w/#yrs. exp.
Remove and inspect plugs, if worn-fouled , replace.
Most likely an intake leak-check rubber boots/hoses for cracks/tears.
A smoke test will find hard to detect leaks.
Clean IAC Valve with spray cleaner.
Member
Its been smoke tested. No leaks 100% positive
Member
I'm in the same boat as you and i've done pretty much everything. I fixed my surging idle today by replacing a bad ground that went from the injector harness to the front of the valve cover. Now however I am left with bad misfires and barely any power. I'm thinking my cats may be clogged. If you figure it out lmk because I may have the same problem you're having.
Member
Did you check that resistor on that ground. You need that to make the coils work properly. And after driving my idle settles out. But its rich like 12:1. After idling a minute it gets down to 10:1 and starts hunting. After driving it on the highway it idles back at 12:1 and the cycle repeats
Last edited by snow663; 01-02-2017 at 12:27 AM. Reason: Forgot information
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No I have not. How would I go about checking that?
Member
The ground wire that goes from the front of the valve cover goes into the harness on the fuel rail. The resistance is stamped on it. Just use a multimeter to see if its accurate. Its a little black rectangular box on that wire
Member
There's no black box in there... The ground wire just goes straight back and comes together with a bunch of other wires. I have an OBD1 car maybe that's why I don't have one?
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Maybe it's buried under some wires ill run out to my car and check real quick.
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Yep no resistor the ground wire goes straight back and down between the engine and firewall.
Apprentice w/#yrs. exp.
Similar to this:https://imgur.com/hyKvpjS
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Only it's burnt.
Member
Yeah I don't appear to have one and the wire is perfectly fine. No cracks or kinks and it doesn't appear that anyone has messed with it.
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Sorry for jacking your thread I'm going to start one myself.
Member
From my experience a poor idle and poor acceleration.....with no CEL...is almost always caused by vacuum leaks or similar issues. You had it smoke tested but cracks in the rubber hoses can easily show up only when the engine is under load. It's best to start with the basics.Originally Posted by snow663
Pull the plugs, check coils for hairline cracks, inspect the plugwells for oil, remove the intake boot and inspect it for cracks and splits. Remove and clean the ICV. I wouldn't worry about your wideband readings unless you've got a turbo or supercharger. If you're not at WOT the AFRs can vary a lot. A tiny pressure on the gas pedal can have a dramatic affect on them. A slight upgrade or downhill will have a dramatic affect on them. The only AFR numbers you should be concerned with are open loop idle, closed loop idle and WOT. Open loop idle is 10-12. Closed loop idle is 13.4. WOT is max of 12.
This is is my experience with intake elbows
http://www.bimmerforums.com/forum/sh...-know-you-have
Bleed your cooling system http://forums.bimmerforums.com/forum....php?t=1709482The ULTIMATE OEM Alarm/Keyless thread http://forums.bimmerforums.com/forum....php?t=1792200
Member
My closed loop idle is 12 and works its way down to 10 if i let it idle longer periods thats when the idle gets rough. Open loop is perfect. And wide open is 11-12.2 another thing i noticed is if you have the pedal steady and you either release it a tiny bit like. 1/8" or press it, the engine either suddenly cuts fuel and decelerates excessively or jerks and accelerates excessively. Again dude there are no vacuum leaks. I know because i just fixed em and now i have more problems than i had before i fixed thd leaks. Could an exhaust leak have an effect on the idle air ratio but not after a highway drive? Or even a sticky IACV. Those are my questions. Because those are known variables that dont have any proof of it working right. I have proof that everything else is working correctly. Including fuel pressure and that the intake holds air pressure for a length of time i found quite impressive. The odd thing is. Its still randomly low on power itll pull then it wont. Then itll pull then it wont. But the afr is consistent so its gotta be an ignition related issue if my fuel system is all up to par... correct?
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Obd1 cars are what have them my guess is someone salvaged it. You need to put a resistor in there. Or excessive voltage from the coils may damage your electronics. Its there kinda like a shock for electronics it absorbs the voltage spike from the coil. I belive its 240ohm but thats off the top of my head i may be wrong. It also depends on the year. 91-92 didnt have it as far asi know.
Last edited by snow663; 01-02-2017 at 02:46 PM.
Member
Okay i have in my hand an iacv that moves freely and it ohms out to 10, 20, 10. Ive read that people have seen this before but they still work. So im gonna put it tomorrow. But get this. My cel came on code 1221. O2 sensor. Since the cide came up the idle issue went away and afrs are more stable. Should i replace my o2 sensor as well?
Instructor
What was the issue in the end ?
Thanks.
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