Update on rough idle

[wjbell]

Well, I put on brand new OEM cap rotor and wires and still no change. The old cap and rotor were pretty badly worn and the pulse sensor wire on #6 wire was broken off on the old wire set. I'm surprised there was no change in the idle.

Actually it might be a *little* smoother but the intermittent miss is still there. Maybe I can record audio of it idling and post it here. I'm thinking maybe dirty or leaking injectors.

Any what exactly does the pulse wire do? You'd think if it was broke off before and now it's got a new one there would be some change...

[Adnan]

Hi,

The pulse sensor tells the ECU when the second bank (on which #6 is) is lined up for injection. Perhaps the system has a limp mode that batch fires all six when it can't detect the #6 sensor. If this is the case, then idle won't be significantly affected.

Sounds like you have tried all the usual suspects - boots, bellows, ICV hose, intake hose (the one buried under the manifold), booster check valve...

Have you checked the tee fittings on the hoses? If I recall, there is one somewhere. How about the oil filler cap? Dipstick? Crank position sensor?

Hope you solve this.

Regards,
Adnan

[Tiger]

Clean your AFM. Disconnect battery to reset ECU.

[wjbell]

Thanks for the further tips guys.

So far I've done or had done:

-Valves adjusted
-New OEM plugs gapped at .032
-New OEM O2 sensor
-Cleaned ICV
-Had car checked for vacuum leaks when valves where adjusted
-Sprayed WD40 around all obvious (visible) vacuum lines including the master cylinder elbow/valve
-Checked oil cap and did the dipstick check while engine running (pulling it out lowers the idle then back to normal, seating it raises idle then back)
-New cap, rotor, wires.

I'll remove and clean the AFM and do a ECU reset.

I read something in one of the idle FAQ's that said to do a ECU reset you should disconnect the battery, jumper the terminals together for 10 min, reconnect to battery, take out for a drive reaching 5K RPM, turn off car for 5 min, run again normally for 5 min, etc or something along those lines. Is all that needed or should I just disconnect for about 10 min the reconnect?

Any how to's on how to test the crank position sensor? (my wallets getting a little light just replacing parts that aren't the primary problem)

Thanks

[ryan roopnarine]

wd40 isn't going to make your idle jump the way carburetor cleaner will. try it with that instead.

[Adnan]

Hi,

To begin with, check that the crank sensor (CPS) is not all gunked up on the sensing face. There is a spec. for clearance between the CPS and trigger wheel, which I don't know off-hand (Bentley should have it).

I wouldn't automatically replace it without attempting this first. Also, see if something as basic as a loose mounting screw is the culprit.

Regards,
Adnan

[wjbell]

wd40 isn't going to make your idle jump the way carburetor cleaner will. try it with that instead.

I thought the reason for RPMs changing when spraying liquid around potential vacuum leaks was because the liquid itself temporarily seals the vacuum leak resulting in a more normal mixture or running condition. I don't understand why the liquid itself would make a difference, it's just the means of sealing the leak temporarily. I could be wrong (and probably am) but that's how I thought it worked.

[wjbell]

Hi,

To begin with, check that the crank sensor (CPS) is not all gunked up on the sensing face. There is a spec. for clearance between the CPS and trigger wheel, which I don't know off-hand (Bentley should have it).

I wouldn't automatically replace it without attempting this first. Also, see if something as basic as a loose mounting screw is the culprit.

Regards,
Adnan


Ok, thanks. I'll check this too..

[ryan roopnarine]

I thought the reason for RPMs changing when spraying liquid around potential vacuum leaks was because the liquid itself temporarily seals the vacuum leak resulting in a more normal mixture or running condition. I don't understand why the liquid itself would make a difference, it's just the means of sealing the leak temporarily. I could be wrong (and probably am) but that's how I thought it worked.

ideally, it gets sucked in and burned, causing the idle to bump up and bump down noticeably, so you pick the most detectable/notable "substance". propane doesn't even work for me, from past experience, so i doubt that you'd be able to detect anything with wd40. carb cleaner just happens to be cheaper than anything else too.

[wjbell]

ideally, it gets sucked in and burned, causing the idle to bump up and bump down noticeably, so you pick the most detectable/notable "substance". propane doesn't even work for me, from past experience, so i doubt that you'd be able to detect anything with wd40. carb cleaner just happens to be cheaper than anything else too.

ok, gotcha.

Also, can anyone point me to where the crankshaft position sensor is? I couldn't find it on the realoem parts site. I'm gonna take a wild guess and look somewhere around the crankshaft in the front, but it would be nice to see a schematic of it

[wjbell]

Ok, more updates...

I took out the AFM and cleaned it with carb cleaner although it was pretty clean. I didn't take off the cover on the underside where I'm guessing the electronics are. I didn't want to risk messing something up.

I disconnected the battery to reset the ECU.

I checked all vacuum lines under the manifold and everywhere else. Sprayed carb cleaner on every vacuum line connection with no change in idle or RPM.

Cleaned off the throttle butterfly door both sides and made sure it operated smoothly. It was a little gritty before.

Crank position sensor was gunked with crap, cleaned that thoroughly.

With engine running, sprayed carb cleaner around throttle body and each intake port where the intake meets the head, no change in idle.

And just to recap on what i've done:

Valves recently adjusted.

New stock plugs to .032

New cap , rotor and wires.

Cleaned ICV.

Oh and I checked the valve that comes from the charcoal canister to make sure it didn't have any blockage.

The only thing I can think of now is my injectors. Can anyone think of anything else to check?

Also, can anyone else with a 535 tell me how your idles? does it have an intermittent dip in the idle or is it completely steady?

One thing to mention is after I changed my cap, rotor and wires it seems like the throttle response is a little sluggish. I don't know if it's because I'm being more critical now or what. Would there be any reason the throttle response off idle would get slower with new cap/rotor/wires?

Thanks again

[632 Regal]

you could reboot the compter again. after anything you do or change it wouldnt hurt anything to reboot. Im also thinking that the lash could be off a bit and causing your intermittant loopy idle. lash it a couple thou wider and see if that changes anything. what if any error codes are you getting?

[Tiger]

How rough is your idle... give us some examples... it could be normal. Now as far as loss of throttle response. Have your car ever failed emission or spewing out blue smokes... any smokes for extended time? What is the mileage on your car now? Has the cat ever been changed?

[70383roadrunner]

I have the same idle problem with my 1989 535i. I was told by the tech at the dealer that depending how the valves are set determines how the car idles. Meaning that if you want performance you have some roughness. If you want a smooth idle you sacrifice performance. I bought my car with 60K and I now have 92K. The car idled rough before I had the valves adjusted and still idles rough.

[Jeff in MN]

I have the same idle problem with my 1989 535i. I was told by the tech at the dealer that depending how the valves are set determines how the car idles. Meaning that if you want performance you have some roughness. If you want a smooth idle you sacrifice performance. I bought my car with 60K and I now have 92K. The car idled rough before I had the valves adjusted and still idles rough.

are reading ZERO ohms at closed throttle thru the contacts. If anything above zero, the computer gets all out of sorts.

Let me know if this helps

Good luck.

[70383roadrunner]

are reading ZERO ohms at closed throttle thru the contacts. If anything above zero, the computer gets all out of sorts.

Let me know if this helps

Good luck.

I have no idea what you are asking me to check. Contacts. What contacts? How do you get the computer out of sorts?

[Jeff in MN]

I have no idea what you are asking me to check. Contacts. What contacts? How do you get the computer out of sorts?

check your pm.

[wjbell]

you could reboot the compter again. after anything you do or change it wouldnt hurt anything to reboot. Im also thinking that the lash could be off a bit and causing your intermittant loopy idle. lash it a couple thou wider and see if that changes anything. what if any error codes are you getting?

What is the lash, spark plug gap? No error codes at all. The last and only error code I had was the O2 sensor. After I replaced it no error codes at all.

[wjbell]

How rough is your idle... give us some examples... it could be normal. Now as far as loss of throttle response. Have your car ever failed emission or spewing out blue smokes... any smokes for extended time? What is the mileage on your car now? Has the cat ever been changed?

What I'll try to do tomorrow morning is take a video with my laptop and webcam then post it here. It's hard to explain, but picture a rock steady idle and then add a slight dip randomly. Almost like if you had a momentary switch rigged up to kill spark to the engine and randomly tapped it really quickly so it only missed the spark for one cylinder.

Car has never smokes or failed emissions. It just turned 150K and when the head was replaced the mechanics said the car was well taken care of. They said there was little carbon build up, the valve train showed hardly any wear and compression was within a couple of pounds across all cylinders. I'm the third owner and have a lot of the service records since new. The car was well taken care of.

I'll have to check the records but as far as I know the cat has never been changed.

[Tiger]

Mmm... possibility of crank sensor going bad?

[70383roadrunner]

check your pm.


Jeff,
I got the PM but was not able to respond. It is not working. Too slow!
I have the Bentley and VOM and will check what you said.

John