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.
John

John, 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