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View Full Version : Hesitation, Rough Idle, and Sparks Smelled of Gas...?


CDE
12-26-2008, 05:00 PM
He guys, First off, I hope everyone has had a great Holiday!

1993 535i with 42,000 miles (yes, low miles, not a typo!)

For Christmas this year I drove up to my parents place which is about 300 miles from my place. I took a highway which sees a fair amount of snow and it had snowed lightly all day, and there was a few inches of compact snow on most of the roads.

Anyways, as I was getting closer to my destination the car started to hesitate more and more. It went from a barely noticeable thing to a holy crap wtf kind of hesitation where I should be pulling over and parking it. I found that at constant speeds it would be the worst. If I were just on the gas a little to keep the speed up it would be pretty bad, but if I mash the pedal it would be fine. I ended up driving pretty fast because at speeds over 120kph it was not as bad and I could drive fairly normal.

The mileage needle was bouncing all over the place as the car would hesitated. I would have the speed constant, but the mileage gauge on the cluster was bobbing back and forth.

When I changed the sparks a few months ago, I noticed the old ones smelled of gas a little. I was a little suspicious but didn't have time to follow up because the car was running OK - had just a monor hesitation if I were holding the car as a constant speed down a hill...usually 40mph or 60 kph or a wee faster. Now I'm definitely thinking the two are related and the same issue (and my current major hesitation prob).

When I was very close to my destination and back into a town, I pulled over because the car was hesitating very bad at this point and it was getting unsafe (icy conditions) for me to keep mashing the gas. I popped the hood and because of the travel conditions and the highway speeds, there was caked on snow in the engine bay and around my air box. I pulled off the air box from the air flow meter and there was a big of moisture on the engine side of the filter (but not a ton). I let it sit for 30 minutes and enjoyed a nice hot coffee...went back and the car managed to idle now, but very rough (it did idle a wee rough I thought before the trip). I still had the air box off at this point, and it was making a pretty gnarly restricted sucking noise...I pulled the throttle cable and it would improve and sound like a normal intake sucking noise, but it I only pulled the cable a little, it would idle very rough, and felt like the cable was being pulled back in as it idled rough.

I managed to limp it to my parents place 45 minutes away but was hesitating badly still. I had to put it in neutral at lights so it wouldn't buck as I held the brakes.

I just bought a few things today to clean out the air flow meter and throttle body...I'm thinking the air flow sensor in the AFM got a bit mangled from the extra moisture and cold. I'm going to remove it and spray it out (carb cleaner or throttle body cleaner) and I will update this thread later tonight if that helps. I need to go back home to work on Monday so I really hope it just needs a clean and not a new part...

I'm open to other suggestions if there are any, or I hope this thread helps someone else in a similar situation once I figure out what's wrong (I searched and didn't find anything useful to me). I had a different car that had a messed up AFM and it caused a lot of problems similar to these like the hesitation and the smelly spark plugs. I was priginally thinking fuel pump, but I don't think it is because it was fine at higher speeds and was also able to sort of drive for nearly 2 hours without it completely dying. It also starts right back up, so I'm thinking it is the air flow sensor (AFM or MAF).

:confused:

cpnwrench
12-26-2008, 10:26 PM
:smokin:

Hey,,

did you check for codes yet? might be similar to a post I just answered, possible bad O2 sensor....sounds zany, but my friends vette had the exact symptoms you are describing and when e fixed the o2 wiring it went away.


In my case i replaced the o2 sensor and the car is running wonderful..


hope it helps man, I know what its like to be stuck!!!!


RH

:smokin:

CDE
12-27-2008, 01:48 AM
Thanks cpnwrench. I'm going to look into that tomorrow.

It's worth a shot...even if the O2 sensor isn't bad, it is still be a good thing to replace. It was next on my hit-list if the MAF was OK which I'm leaning towards. I took the MAF apart, as well as the Idle Air/Speed Control Valve and throttle body. I inspected everything and cleaned it fairly well. There was some gunk but it wasn't too bad.

Luckily this didn't take that long, but unfortunately it didn't help much. At least I know they are clean now...but the car still idles like poo. you mash the gas and she revs up nice without hesitation, but the idle and steady speeds it hesitates badly.

I'm praying that the local parts store is OPEN tomorrow, and also has what I need in stock. I believe that is a common sensor for many bimmers so I hope it's there.

Update to come soon I hope...Thanks for the thoughts :)

CDE
12-27-2008, 02:54 AM
One more thing: when I check the codes tomorrow, should I EXPECT to see an O2 fault code? What I'm really asking is if I don't see the code, should I not replace them?

Just one more thing - do all 535i's when you first start them up say "catalyst" then "owners handbook" and then the temp? Mine does and my owners handbook is all in Japanese so I don't know what that means.

CDE
12-27-2008, 12:53 PM
Also, just one more thought - would the car really hesitate so badly if it were just an O2 sensor? It is at the point where I cannot even drive it due to this issue.

bimmer dot info
12-28-2008, 08:34 AM
Check or replace the distributor cap and rotor. If you have not done the wires recently I'd do those too.
Have you checked more recently for wet plugs?

mednetlive
12-28-2008, 09:47 AM
Probably one of the o2 sensors, OR very possibly the idle control valve (ICV)

As many years as I have been driving and fixing my BMW's I'm still amazed at what a bad O2 sensor sensor can do to these cars. I thought I had a transmission problem when suddenly the car began to loose power to the transmission. the check engine light on and I pulled an O2 sensor failure but I was certain it was a error. I finally could move no further and had it towed to my home garage. I immediatley went to the A/T and changed my fluid.
OK for a week, then the light came on and the car began to loose power. I went to Axels and ordered an new sensor and put it in. Everything went back to normal. Even an old dog like me learned to trust the gauges even when they tell you something that makes no sense.

Make your diagnosis based on the code. Probably one of the o2 sensors, OR very possibly the idle control valve.


Good Luck

Wool

CDE
12-28-2008, 10:16 AM
Check or replace the distributor cap and rotor. If you have not done the wires recently I'd do those too.
Have you checked more recently for wet plugs?

It looked newer so I didn't take it off. I haven't checked for wet plugs lately, but I can still smell the car is running very rich. I'll examine it closer this morning.

Probably one of the o2 sensors, OR very possibly the idle control valve (ICV)

As many years as I have been driving and fixing my BMW's I'm still amazed at what a bad O2 sensor sensor can do to these cars. I thought I had a transmission problem when suddenly the car began to loose power to the transmission. the check engine light on and I pulled an O2 sensor failure but I was certain it was a error. I finally could move no further and had it towed to my home garage. I immediatley went to the A/T and changed my fluid.
OK for a week, then the light came on and the car began to loose power. I went to Axels and ordered an new sensor and put it in. Everything went back to normal. Even an old dog like me learned to trust the gauges even when they tell you something that makes no sense.

Make your diagnosis based on the code. Probably one of the o2 sensors, OR very possibly the idle control valve.


Good Luck

Wool

The funny thing is the check engine light is not on. However, I tried to get any codes by decompressing the gas pedal 5 times but nothing showed up (could be a burnt out bulb I suppose. The ICV is old. It doesn't look like it has been replaced before. I cleaned it, but the solenoid could be screwed still. After I cleaned everything the car idles much better, but will still start to bog after a while, then smooth out, then bog, smooth out, etc..

I wish the car was back home and not here at my parents. I have to head back today because I have a few important things for my new job on Monday. Apparently there is a BMW wizard somewhere here near my parents place and knowing my dad he will just take it there and pay whatever to get it fixed. Robs me of the satisfaction of fixing it myself. :P

RocknRoll
12-28-2008, 12:48 PM
I believe Bimmer dot info is probably right. A bad spark plug, Plug wire, distributor or distributor cap is your problem. Just one bad spark plug would cause the engine to run rough at lower speeds and seem fine at higher speeds. The smell of gas could be from a bad spark plug.

CDE
12-28-2008, 01:28 PM
Thanks for all the info guys. I'm heading back home right now and will be back on the 5th of Jan. to deal further with this issue.

RocknRoll - I replaced the plugs within a few months ago...and it didn't fix the rich issue. the cables looked OK, and the distributor the same. My dad is taking it to a BMW specialist while I'm gone and he will diagnose it further...if it is just a sensor or something like that I will purchase the part and come back to fix it. I'm still interested to see what it is. I will update this thread. If there was a pool, I'd be putting my money on an O2 or ICV.

Could also be a coolant temp sensor, or something of that nature...so many different things. Thats why I'm paying to get it checked out by someone with more experience and tools. Will save me time and money too.

cpnwrench
12-28-2008, 05:47 PM
:smokin:


Ok, hope it works out the best for you, I know its a hassle....


But to answer your question "YES" the rough running bogging and hesitation can DEFINITELY be caused by a Bad O2 sensor!!

I know this for an absolute fact!

BUt, Bimmer.dot is also correct.... when plugs are put in, ya gotta make sure they are tightened all the way down (not super-tight) but good and snug.. and that the boots for the wires are on real good!


sorry i didn't get back to ya sooner!

Safe travels sir!

RH

:smokin:

CDE
12-28-2008, 11:44 PM
No worries cpn.

With the Holidays and my needing to get back home right away there was no way I'd get to the car. I choose to spend more time with friends and family then to let the bimmer consume my time.

I won't rule out the sparks or the distributor cap/rotor, but I am sure each one was installed correctly and tightly as I'm pretty anal :) I even had a torque wrench because I've busted something before by over tightening and that was a nightmare to deal with.

Car will be looked at tomorrow. There are also some electrical gremlins (those bastards!) but I haven't had time to check the Light Control Module for the solder points which sometimes cause the light sensors to trip when there are actually no dead bulbs (also bought new lights to see if it is just bad bulbs too). Also if you roll down a front window, the rear ones will roll down too, and then go up and down until you either shut off the car, or manage to hold the button long enough that it just stays shut.

I have confidence in this BMW guy as he was highly recommended by my dads mechanic. Usually he can diagnose a car while it's driving up tot he shop...so I hope his reputation precedes him! *edit* he's off until after new years...doh!