e34 535i rough idle please advise

[madbomber]

I have a 1990 535iA (150k mi) with a constant rough idle and I've done everything i can think of to fix it.. first the problem : The car idles steady at 700-750 but at that rpm it feels like its missing a little .. runs smooth at 800-1000, like glass smooth..
now heres what i've checked or replaced:

replaced all vaccuum lines, checked intake tract for leaks / cracks
cap and rotor replaced
plugs replaced (old ones were really white)
spark plug wires @ 0 ohms
valve adjustment according to bentleys
checked MAF for resistance change with movement of flap - yes,
checked tps according to bentley
cleaned ICV and Throttle body with carb cleaner
ICV is buzzing and voltage was good..

Fuel Filter was replaced 20k miles ago
I havent done a fuel pressure test because the car always fires up immediately..




Oh ya and i ran injector cleaner in a couple tanks of gas beforehand..
Idle is just rough no matter what i do..

So is there any thing i have overlooked here?? Or is the next step for me to just dive into my perfectly running 535i (other than slight miss at idle) and pull the cylinder head off ??


Im lost :redspot

any help is appreciated..


P.s. Anybody in Sacramento have a MAF I can test on my car?

[323I Junkie]

Well, I would find someone to swap in a perfectly good idle control motor, even if youve cleaned it, it may not be funtioning properly. I sure would nt pull the head yet. You may check the mounting position of your crank angle sensor (or whatever the Bentley calls it). A poorly mounted sensor could casue timing to be ever so slightly advancing your timing, ...this is a stretch though, and giving you a rough idle

Rough idles also can be from rich , but generally lean. Do this:

Get a propane torch (I am not shitting you here, this is old weber-balancing technology), run a small rubber line into the intake manifold in fron of the afm (The air tube is a great place.

Let idle stabilize, then slowly inject the propane by turning the valve. If you have to run a substantial amount of propane, you are lean-idling. If idle deteriates with an HC introduction, then you are rich.

I could right a book on here, but let me just say do that and check back. It sounds to me like you have a weak injector or IAC. as the computer feeds more fuel, more current flows through the injectors, and it is easier for a weak injector to feed fuel

You sound techy--do you have a digital scope by any chance?

[323I Junkie]

Does it idle rough the first 60 seconds of operation in the AM?

[madbomber]

Ahh i forgot to mention i checked the gap on the crankshaft position sensor and its right on.

thats a cool trick I'll give that a try tomorrow when i get to work. Ya I have access to a digital scope, not much experiance in using one tho.. I will try that tomorrow morning too tho.

a weak injector makes sense.. that should show up on a digital scope right?
maybe its time for those new mustang injectors


"Does it idle rough the first 60 seconds of operation in the AM?"

Yes, stumbles more.. not a happy camper those first 60 seconds..
i guess that would tend to be a lean situation?? I dunno,

Thanks very much for your post, set me in the right path
appreciate it,

Deke

[323I Junkie]

Connect the scope to your O2 signal, and see how fast the O2 is reacting

Sounds like you work at a shop? Am I talking to another tech here? Are you on IATN? :D

[madbomber]

Not a full time tech no, I have 3 years experiance though and right now i do alot of light duty work for a wholesale remarketing company.

Well I got a chance to use another techs digital scope today. I didn't hook it up to the O2 sensor but I did check each of the plug wires on the graph and that was a major help.. Cylinder 1 was dropping more than the rest, and also the inductive lead on wire 6 had broken off ... unable to find a replacement inductive wire so I just bought a set of O.E.M wires which had the "inductive sensor" on it.. (its a reference sensor for injector timing, and according to ALLDATA, if the sensor was not reading the injectors would fire at a default timing mode running injector pulse at a constant rate)

The car is running about 80% better, No apparent miss . I think there is some room for improvement though, I guess I should look into some new injectors?
I've read some good reviews about the mustang injectors and 3.5 BAR FPR..




thanks for the help


:buttrock

[323I Junkie]

Aweseome, dude :buttrock:

I dont know what the inductive wire is for, some type of cam sensor? Expensive wires, huh? :D

Mr. Project has had good success with the mustang injectors.

www.bmwe34.net has a completely tunab;e MAF good to 650 HP, thats what Im going to, it will be good for FI, and lean it out when I install the higher flowing injectors

[Denis///M]

but what really helped was AFM adjustement based on O2 sensor feed. I had sensor disconnected from DME. I moved big black wheel by two notches, it gave me 0.8V on O2 feed @3000 rpm. One notch movement was giving 0.2V (lean), at original position reading was below 0.1V. At idle speeds adjust valtage to be within the range using the hidden adjustement bolt (M6 allen wrench is needed). Do not forget to leave heater wires on O2 sensor.

So now I got better fuel economy, I can run it on regular gas almoust without pinging, it pools better and it does not shakes the Earth when idling!!!

The next step could be injectors check. They should be 183cc/min but mine are +/- 30cc off. Not good, cleaning with tank additives does not help too much. So I will go shopping for "low mileage" Ford 19lb/hr injectors soon.

Car has 280k+ kms.

[323I Junkie]

We need to talk

[Mr Project]

Denis, FYI, I got the ford injectors from fiveomotorsport.com for $125 for the set of 6 Design III injectors. Very satisfied with the company and the injectors. The design III requires some modification, though, so if you want plug-and-play you might be better off with the design II.

[Mobius20]

The design III requires some modification, though, so if you want plug-and-play you might be better off with the design II.Could you elaborate a bit on that?

It's possible I may *ahem* have a set of design IIIs coming - and.. yeah.. :)

[Mr Project]

The plastic 'end cap' (I think it's called a 'pintle') on the business end of the design III injector has to be cut down a little to fit all the way into the manifold. A steady hand and a sharp blade worked ok for me, a perfectly-sized hole punch or tiny lathe would be better, but I used what I had. :)

Also, the body of the injector is just a little too short. I was concerned that it would move either up or down in the holders and blow one of the O-rings out. So I 'ovaled' the mounting holes for the injector rail to allow the rail to sit down a little lower and hold the injectors nice and tight to the manifold.

Then I noticed that the Ford O-rings are just a little bit smaller in OD than the BMW pieces. Fortunately I had a set of new BMW-sized O-rings handy and swapped those on. I've heard that guys have used the Ford ones successfully, but they are definitely not as tight of a seal.

Nothing too major, but it was not plug and play.

[Mobius20]

Okay - that's very good to know. :)

Once again, Mr. Project saves the day.

[SehrSchnell]

I know I am chiming in really late, and this may be irrelevant, but out of curiousity, what brand/model of plugs are you running? My E34 acts up tremendously with Bosch Platinums, I learned the Supers are what to go with. A few others around here too have heard the same. Just curious.

[Denis///M]

NGK spark plugs. Regular ones just fine.
M30 one is ZGR5A, and there is http://ngksparkplugs.com at your service. Do not go to ngk.com :)

[323I Junkie]

I know I am chiming in really late, and this may be irrelevant, but out of curiousity, what brand/model of plugs are you running? My E34 acts up tremendously with Bosch Platinums, I learned the Supers are what to go with. A few others around here too have heard the same. Just curious.

How does it behave?

[madbomber]

Dennis///M: "but what really helped was AFM adjustement based on O2 sensor feed. I had sensor disconnected from DME. I moved big black wheel by two notches, it gave me 0.8V on O2 feed @3000 rpm. One notch movement was giving 0.2V (lean), at original position reading was below 0.1V. At idle speeds adjust valtage to be within the range using the hidden adjustement bolt (M6 allen wrench is needed). Do not forget to leave heater wires on O2 sensor."

I just had a couple questions before I give this a try.. Do I need to have my car hooked up to an exhaust gas analyzer to do this? What big black wheel did you move by two notches??

"So now I got better fuel economy, I can run it on regular gas almoust without pinging, it pools better and it does not shakes the Earth when idling!!!"

That's awesome..Is your engine chipped??

"The next step could be injectors check. They should be 183cc/min but mine are +/- 30cc off. Not good, cleaning with tank additives does not help too much. So I will go shopping for "low mileage" Ford 19lb/hr injectors soon."

Where can I take my injectors to get flow checked?? I just missed an auction where 8 injectors with under 6,000 miles sold for 60$ oh well.. I guess I will be buying fresh ones..

MrProject: what kinda mileage do you get? Have you done a 3.5 Bar fuel pressure regulator mod??


Ya I put Bosch Platinum 2's in my car.. :( it was the only Bosch plug the guy could pull up for my car.. So what symptoms are those Platinum plugs causing??

[Kdog2112]

If I were you I would replace the ICV since it is the brain of the engine...sounds like that is the issue even though it checked out okay. Also check to make sure you have enough coolant in the reservoir. My e36 325i idles rough occassionally when its a little low (95 w/162k on it...it gets fickle when it wants to be...and it can be...its an older girl)

[Mr Project]

With an EAT Chip, the Design III injectors, and a fresh HG (cleaned tons of carbon up, light port-matching on intake manifold), I'm getting 17-20 in town (depending on temp and distance averages) and 23-27 on the highway (depending mostly on speed, with 70ish being the 'sweet spot').

My daily commute is really short, which kills the mileage. If I mix in some highway driving, I get 20-21 average, otherwise its more like 18ish.

I haven't ever adjusted the AFM...been tempted to, but it runs well and seems to get decent mileage right now, so I haven't messed with it for fear I'd make it worse. :)

[Mr Project]

Oh, and no, I haven't done the 3.5 bar FPR.

[Denis///M]

use google.

this will give you the pictures:
http://members.roadfly.org/louielouie/AFM_adjustment.html

Clean the AFM potenziometer path with alcohol or contact cleaner.

Adjust black rotating wheel to make O2 reading to be 0.4 to 0.7 at 3000rpm (O2 feed should be disconnected from DME, but heater wires should be on!)
Hold your throttle mechanically at 3000prm or little bit less. (My highway cruising rpm is 2500 on 5th =~114 km/h)

Once you done at 3000 proceed with idle adjustments - use idle adjusting screw, make O2 readings at around 0.4 if you can.

You do not need a gas analyzer, but you may want to do emissions test when you finished. If everything is in working order (O2 sensor, catalytic conv, injectors, etc.) you will be within the spec.
BTW it is a good idea to replace spark plugs first (go to Carquest, they are everywhere in NA, $3/ NGK plug), and make sure that valves clearance is up to spec.

My DME chip is a factory one, but I have got 535 e28 flywheel/clutch/pressure plate installed. It is coulpe pounds less then regular dual-mass flywheel setup, and this lightening does not improves idle at all. I realized that my car is idling bad when I started it first time after flywheel replacement!!!!!

To check injectors flow I bought measuring cylinder at science shop for $10.
Then you remove fuel rail with all injectors, start the fuel pump and open injectors one by one directing gas sprayer in into measuring cylinder. Ratio is 183cm3/minute. Use google again to serch for info. This job takes like 3 hours on M30, it is not that easy to remove the fuel rail.

At http://www.autolib.diakom.ru:8001/CARS2/ (or better go to http://www.autolib.diakom.ru:8001/CAR/BMW/1989/535i/WIRING%20DIAGRAMS/ ) you can get wiring diagram for engine compartment to find out what O2 wires are.


Dennis///M: "but what really helped was AFM adjustement based on O2 sensor feed. I had sensor disconnected from DME. I moved big black wheel by two notches, it gave me 0.8V on O2 feed @3000 rpm. One notch movement was giving 0.2V (lean), at original position reading was below 0.1V. At idle speeds adjust valtage to be within the range using the hidden adjustement bolt (M6 allen wrench is needed). Do not forget to leave heater wires on O2 sensor."

I just had a couple questions before I give this a try.. Do I need to have my car hooked up to an exhaust gas analyzer to do this? What big black wheel did you move by two notches??

"So now I got better fuel economy, I can run it on regular gas almoust without pinging, it pools better and it does not shakes the Earth when idling!!!"

That's awesome..Is your engine chipped??

"The next step could be injectors check. They should be 183cc/min but mine are +/- 30cc off. Not good, cleaning with tank additives does not help too much. So I will go shopping for "low mileage" Ford 19lb/hr injectors soon."

Where can I take my injectors to get flow checked?? I just missed an auction where 8 injectors with under 6,000 miles sold for 60$ oh well.. I guess I will be buying fresh ones..

MrProject: what kinda mileage do you get? Have you done a 3.5 Bar fuel pressure regulator mod??


Ya I put Bosch Platinum 2's in my car.. :( it was the only Bosch plug the guy could pull up for my car.. So what symptoms are those Platinum plugs causing??

[tjn182]

I know mine is very rough at idle. At about 700rpm it's like "studder studder shake shake" -- if it idles at 900 or so rpms it's smooth.
I figure I'm just working around a turbo.. I've adjusted everything I can and it's still that way... so I'm not too worried about it.