Idle issues - any suggestions?

[Black 535i]

I have been having some idle speed issues amongst other problems lately. When I coast down to lower speeds (15-25 mph) in 3rd or 4th gear and then get back on the gas, the car stumbles and shakes back and forth a few times until it finds that sweet spot and all is normal. At stop in neutral at a light it sounds like it wants to stall but never does-it just seems like the rpm's drop a fraction. I changed out the injectors as one was spraying a stream instead of a mist. It helped a little bit but not completely. Does anyone know if changing the cap, rotor and wires would make a difference as well. Do they have a direct relation to idle issues? Thanks.

[31Hertz]

I have been having some idle speed issues amongst other problems lately. When I coast down to lower speeds (15-25 mph) in 3rd or 4th gear and then get back on the gas, the car stumbles and shakes back and forth a few times until it finds that sweet spot and all is normal. At stop in neutral at a light it sounds like it wants to stall but never does-it just seems like the rpm's drop a fraction. I changed out the injectors as one was spraying a stream instead of a mist. It helped a little bit but not completely. Does anyone know if changing the cap, rotor and wires would make a difference as well. Do they have a direct relation to idle issues? Thanks.

If you are trying to take off from 15-25 MPH in fourth or third, I don't think you will have much grunt. You will be lugging the engine until it reaches the happy zone above 2K. I assume this is a manual trans? I can somtimes cheat and get into third at 25MPH using easy acceleration (and this would be on a level surface). But yes, if you have a bad rotor / cap / or wires, it could affect your idle. I dunno when they started the direct coil ignition on the 535 though... ICV? Valve Cover Gasket? FPR?

[BillionPa]

clean the ICV and throttle body, replace the ignition coil if its old, cap, rotor (wires maybe if they havent been done in 60K) and some new iridium plugs. replace fuel filter and air filter and charcoal canister, and throw a little acetone in your gas (3oz/10gals) if the gas is ethanol free.

of course there is more you can do, depends on how much time and money you have, but thats the short list and seems to do the trick....... however changing to 2nd gear will probably make all the difference.

[Black 535i]

...and what a difference!. Car had the original cap and rotor in it and boy was it fouled up with deposits aftre 190,000 miles. Idle is much smoother now. No more hesitation in any gear at any speed. Will replace the plugs and do a compression test this weekend. Total cost $150.00 and 30 minutes work in the garage.

BTW, the forecast for Chicago weather here is low 60's and rain for the meet this weekend.

[cableface]

...and what a difference!. Car had the original cap and rotor in it and boy was it fouled up with deposits aftre 190,000 miles. Idle is much smoother now. No more hesitation in any gear at any speed. Will replace the plugs and do a compression test this weekend. Total cost $150.00 and 30 minutes work in the garage.

BTW, the forecast for Chicago weather here is low 60's and rain for the meet this weekend.
That gives me some hope, as you're situation describes mine almost exactly except I have an AT. I've changed the air filter to a K&N ( it made a power diff, but didnt fix the idle and the hesitation), the plugs, and the fuel filter. I'm going to go get a cap and rotor right now. Wish me luck.

[Black 535i]

...do a compression test and see what the results are. I am doing mine tomorrow.

[shuriken]

I have been having some idle speed issues amongst other problems lately. When I coast down to lower speeds (15-25 mph) in 3rd or 4th gear and then get back on the gas, the car stumbles and shakes back and forth a few times until it finds that sweet spot and all is normal. At stop in neutral at a light it sounds like it wants to stall but never does-it just seems like the rpm's drop a fraction. I changed out the injectors as one was spraying a stream instead of a mist. It helped a little bit but not completely. Does anyone know if changing the cap, rotor and wires would make a difference as well. Do they have a direct relation to idle issues? Thanks.
Only time I have this problem, and I have a 535 e34, is when I've had a small(almost pin prick) hole in the pipes arrowed, they become hard and brittle after about 2-3 years. This has affected my e24 628csi my e28 525i and my 535i in the past. Given the same symptoms as you. Pipes cost around UK £5. Once fitted problem gone, but don't know if you have similar pipes. Look at photo to see which I mean. I know you have V8. It's just athought.
John

[cableface]

Only time I have this problem, and I have a 535 e34, is when I've had a small(almost pin prick) hole in the pipes arrowed, they become hard and brittle after about 2-3 years. This has affected my e24 628csi my e28 525i and my 535i in the past. Given the same symptoms as you. Pipes cost around UK £5. Once fitted problem gone, but don't know if you have similar pipes. Look at photo to see which I mean. I know you have V8. It's just athought.
JohnJohn, do you know exactly what the pipes do?

[borderchris]

Same issue a while back, but I solved by checking any hose that carries air or vacuum, and sealing them. Check all of the fitting ends; if they're not completely air-tight (remember we're talking about a vacuum here), seal them up with a good high-temp silicone, and then re-fit them befor it dries. Check all of the skinny little hoses too- they used to be soft, flexible rubber, but are probably now a brittle, crunchy almost plastic, possibly with cracks. Seal those bad ends with silicone, 100 MPH tape or both as a quick fix, or buy the hose pretty cheaply at an auto shop.

Chris

[John 535is (Sydney)]

the one on the left connects to the idle point. Check that one first, it may solve the problem

John 535is

[shuriken]

John, do you know exactly what the pipes do?
As mentioned after my last post, they are the idler vacuum hoses, not sure how they work but i do know if a small air leak in them then it all goes to pot! I personally would not repair them just replace them, cheap as chips mate. and all will be improved....... well i hope.:D

[cableface]

As mentioned after my last post, they are the idler vacuum hoses, not sure how they work but i do know if a small air leak in them then it all goes to pot! I personally would not repair them just replace them, cheap as chips mate. and all will be improved....... well i hope.:D
I'm going to check everything thoroughly today, I have a 525i so it's different from your picture, but I'm going to see what I can come up with. Thanks

[John 535is (Sydney)]

I read a post some time ago about using an aero-start spray to locate the vacuum leak. If you cannot see the hole (and there are a few places in these things that are hard to get too) spray the stuff around. If the engine oitch changes, then the leak is the last place you sprayed.
Never tried it myself, but could help if you are really stuck.

John 535is

[MBXB]

Use propane instead of autostart (ether). It's not as volatile.

[cableface]

I'll give the spray a try. I briefly looked today, I only had a minute. I was wondering how the hell I was going to find a leak. There's quite a bit of hose in there and some of it is difficult to see. If all else fails, I'll take it to my mechanic, but I really hate to do that....

[shuriken]

I'll give the spray a try. I briefly looked today, I only had a minute. I was wondering how the hell I was going to find a leak. There's quite a bit of hose in there and some of it is difficult to see. If all else fails, I'll take it to my mechanic, but I really hate to do that....
I have never found a hole yet, just always replaced the parts. But the spray idea sounds good.

[cableface]

Well, I just got back from trying out the ether idea. I ended up spraying an entire can but I couldnt find anything consistent enough to say that I found the location. Hell, there may not even be a leak and it may be something else. I think that I'm giving the mechanic a call on Monday... :(

[BillionPa]

cableface, when was the last time you changed the charcoal canister?

[t_marat]

What the charcoal conister has to do with idle or vacum leaks?

[BillionPa]

it captures vaporized gas and feeds it into the intake manifold through a valve. it is also connected to the atmosphere, so if the valve is stuck open it is a vacuum leak.

the vapor it holds enrichens startup, so the engine has to crank less. it also helps prevent vapor lock by acting as an atmospheric vent for fuel pressure.

because of the way it works, an old one wont be able to hold vapor and can let liquid gasoline into the manifold as well. a bad canister can also let water into the gas tank, because its connected directly to the expansion tank without a non-return valve on that line.

[cableface]

cableface, when was the last time you changed the charcoal canister?
I've actually only owned the car for a couple weeks so I have never changed the charcoal canister. I really dont even know what it is, as I am new to this whole scene.(Where is it located?) I went ahead and admitted the car to the local BMW doctor so if it's the canister, I suppose they'll figure it out. Hopefully whatever it is, it wont be too much hassle (or $$ for that matter). I should know by tomorrow and I'll post the results. I'm keeping my fingers crossed.