Consistant surging (hesitation?) under acceleration

[Woulf]

Good news, everyone!



I've figured out what's wrong with my 325e! It seems that now that I have daylight, I found the connector for the oxygen sensor. And, upon disconnecting it, the car stopped pulsing while driving! I have since purchased a replacement Bosch unit which will be delivered to my local auto parts depot tomorrow morning.

Thanks for all the help! :D

[Woulf]

Went down to the parts store and picked up my shiny new Bosch (:D) o2 sensor. Drove home, parked the front wheels on the curb and dove under with my wrench. Out with the old, in with the new, start the car aaaaaaand...

The pulsing is still there.

BUT! It's changed now. It's no longer consistent across the throttle spectrum. This tells us two things: A) The damn sensor needed changing anyway, and B) The pulsing follows the switching of the o2 sensor.

So now what? :|

[hotballs]

You still have all those sensors in the t-stat housing which effect fuel management. Also that cold start valve that goes into the intake manifold is kind of funky.

Might as well throw the ICV and TPS in the mix.

[Woulf]

You still have all those sensors in the t-stat housing which effect fuel management. Also that cold start valve that goes into the intake manifold is kind of funky.

Might as well throw the ICV and TPS in the mix.

Yes, and lucky for me I happen to have located a factory service manual in pdf form, so I now have locations and factory electrical specs for all of these components.

I'm not sure if this is a good thing, or a bad thing... :D

[Woulf]

Went to check the cold start valve and noticed a bolt was missing on one side.

One M6 x 1.0 bolt and some silicone later, no more hesitation. Yay.

[riceh8r]

dude....you've done well. i am impressed. welcome to the e30 life !

[hotballs]

One M6 x 1.0 bolt and some silicone later, no more hesitation. Yay.

Nice always good to hear an actual solution.

[Woulf]

What struck me was that the leak was so small without a load, the carb cleaner didn't jack the idle like it usually does. I would have NEVER found it if I hadn't considered that the cold start injector or the thermo-time switch might be bad.

On the plus side I've replaced a worn part, and now have the ability to accurately test the rest. Bentley BMW E30 Service Manual FTW.

[ROLLingKING]

I feel your pain bruh!!
ive got an 87 325is and i notice it smells like fuel when i first start the car kinda..then when i drive the smell seeps right through the vents. I changed my fuel filter and the little bosch piece that comes after it. that actually helped with rough idle....but like you im new to e30's and am not sure what to accept as just "normal" operating conditions. smelling fuel though I know shouldnt be there.haha

I dont want to spend lots of money on parts that dont need to be replaced in a car this old so im thinking it could be my fuel injectors or maybe even charcoal canister

after reading this though I also feel my car could have several other problems like fuel pump(s) or having to replace all fuel lines
i need to download that bentley manual asap and troubleshoot like what was done here. good work
CONGRATS!

[F34R]

More of the wife? nom no lol

[Kruzen]

This is the same issue i'm having.. maybe this will fix it :)

[sloweste30]

I know that this thread isn't exactly still active. But I've been having the same exact problem in my car since I bought it 3 months ago. Actually the same exact car to a t as yours Woulf but 4 door.

Anyway just wanted to let you know that I'm really really hoping and thinking that this informative thread has just saved me a lot of time, money, and anger.

I will be checking these things on my car in the morning and post back to let you know what I conclude.

[Aviator]

Mine does this as well. Actually it runs good when cold. Then as it warms up it surges and as a dead cylinder. Damn eta's are a pain.

[dnguyen1963]

Spraying carburetor fluid will not find a small leak, only a smoke test at 2-4 psi will located those leaks. BTW, if your car is over 20yrs old, replace all fuel lines. Mine looked fine until I took the fuel lines off and found all kind of micro-fractures (good source for fuel-smelling air)...boys, I was running on borrowed time.