warm weather related hesitation...

[RIPN RAY]

im not sure if it's actually possible but it seems that whenever the weather is hot that the hesitation gets worse. for instance, it did it last summer, then during the winter it seemed to lessen, and now it's back.

i keep up on all the tune up stuff; filter, plugs, oil, etc. my A/c doesn't work so that's not doing it.

i'm thinking maybe coil packs?

any ideas?

[BillionPa]

last O2 sensor replacement?

last time you replaced the fuel filter?

last time you replaced the charcoal canister?

[RIPN RAY]

O2 and fuel filter within a year, and i never did the canister...will that do it

[BillionPa]

it may, a failing canister can cause a vacuum leak, mess up the A/F ratios, and allow water to get into the intake and gas tank. the canister lasts about 120K miles before it should be replaced, if it has never been done, do it now!

its not a battery problem, although wierd electrical things can happen when its hot, specifically to failing capacitors and MOSFETs

replace the DME and fuel pump relays for good measure.
the crankshaft position sensor may be dying too, especially if its never been changed, considering the mileage.

the coil packs may be frying at that age, check their resistance, if they are in spec, the plug boots may be toast.

HOWEVER... if you havent changed the coil packs, i would do it anyway.
bavarian autosport has some "enhanced" ones that provide more forward voltage and come with new boots, and i think they are on sale right now.

also check out the MAF connector, clean that and ANY electrical connections with contact cleaner, then put a little electrical grease on them.
that will help keep the contacts clean and provide a better electrical connection.




also check the resistance values of your idle control valve, personally, i would clean it and the throttle body out VERY WELL with valvoline throttle/carb cleaner, and replace the throttle and intake manifold gaskets at the same time.

my first bet is still your first bet, coil packs, but the other stuff is more of a narrowing of the problem, and to prevent multiple compounding problems from occuring, and also just plain good preventitive maintainence.

[Alexlind123]

it may, a failing canister can cause a vacuum leak, mess up the A/F ratios, and allow water to get into the intake and gas tank. the canister lasts about 120K miles before it should be replaced, if it has never been done, do it now!


Couldnt you also just delete the evap canister?

[BillionPa]

yes, although it does provide vapor into the throttle for startup enrichment, which means less cranking. my car has started the instant the key gets to the right, and i bet if the canister wasnt there, it would have had to crank for at least .5s.

its also better for the planet to leave it there!

and better for the car as long as you know how and when to replace it.

[genphreak]

yes, although it does provide vapor into the throttle for startup enrichment, which means less cranking. my car has started the instant the key gets to the right, and i bet if the canister wasnt there, it would have had to crank for at least .5s.

its also better for the planet to leave it there!

and better for the car as long as you know how and when to replace it.Hey BilllionPa.

How? Is it not just a bolt on and off thing?

;) Seriously is it likely that I should have to change this? My car idles solidly at 750, starts but often needs to crank a little (like 2 secs). I checked the valve and that is working well. Would any old cannister from BMA do?

[Tiger]

Starting the car or driving the car? If hard starting with warm or hot engine, then it is fuel checkvalve.

[BillionPa]

its not as easy as it seems, i spent about 3 hours doing it today!!

you need to remove the bumper to get to it, the hose clamps on the canister take AMAZING patience to get off, and pulling the hoses off takes way too much force.

then.... you need a new hose clamp for the drain cap, since bmw used a crush clamp, and getting the new canister on the new hoses really hurts the hands.

i cut about 3mm of the ends of the hoses because the ends were all grungy, that helped them go on easier.

also, i have about 15 cuts on my hands, and a large bruise where my hand was crushed against the brake booster and hood hinge while twisting a screwdriver very hard for about 10 mins. my hands feel like bad leather right now.

i was lucky and had a 2nd person to hold and twist the canister so i could remove the crush clamp from the feed hose to the canister, that took about 15 mins.

getting the new canister on by myself took around 1.5 hours, would have taken .5 with 2 people.

mind you this is on a V8, the clearances may be easier to work with on the I6s.

i do have before and after pics, will post later.

[genphreak]

mind you this is on a V8, the clearances may be easier to work with on the I6sHeh, for a while there I thought you had changed the AC dryer instead of the charcoal can. On an L6 its atop the engine bay dead easy to do. But maybe I should look at the V8, when I go turbo I have to move it and will need to find (perhaps) an equally ingenious and difficult location for it... :) Nick
http://www.bimmer.info/forum/attachment.php?attachmentid=3188&stc=1&d=1150884961

[RIPN RAY]

replaced the coils and it's working better. it's still a little sluggish. it seems like there are some week spots will accelerating. but once it gets to the higher rpms it seems fine (is that the vanos correcting it?)

i'm going to order the canister to. i was looking for info on the canister in the bentley and didn't seem to find any. i'm not doubting that it should be replaced, but, i've never heard of replacing it. and i just want to read it (or a second opinion)

and thanks for the help guys....
RAY

[RIPN RAY]

replaced the coils and it's working better. it's still a little sluggish. it seems like there are some week spots will accelerating. but once it gets to the higher rpms it seems fine (is that the vanos correcting it?)

i'm going to order the canister to. i was looking for info on the canister in the bentley and didn't seem to find any. i'm not doubting that it should be replaced, but, i've never heard of replacing it. and i just want to read it (or a second opinion)

and thanks for the help guys....
RAY

i replaced the canister, and the problem is still there. although i seem to be getting better gas milage so that's good. i reread through the post and am wondering what the point of changing the DME and fuel pump relays would be. any ideas on that?

all the intake gaskets have been replaced. ICV had been cleaned a year ago, but maybe i'll go back in and check it again.

TIA,
RAY

[BillionPa]

it could be something to do with the air intake temp sensor, could be sending back a "colder" reading regarding the temp, and throwing the ECU out of whack.

its attatched to the side of the intake manifold. try cleaning the electrical contacts first.

if all else fails, have a leakdown/compression test done to see if there is exhaust blowby. a TBN analysis on your used oil can also detect it, but wont narrow it down to a specific clyinder.

... in a related story, its been a month since i replaced my charcoal canister, and im getting 40mpg on the highway at speeds between 40 and 50mph....... no idea how the hell thats possibly accurate, but my fuel guage is STILL at mid point, even though it should be empty by now.

the DME an fuel pump relays provide voltage to the DME ECU and the pump during engine operation. over time the contacts inside and outside the relay become oxidized and dont transfer voltage as well. the EM device inside the relay can also become flaky and not hold the contacts inside the relay as hard, which can cause voltage fluctuations, especially during vibration. BMW recommends having a DME relay as a spare in case the old one fails.