318i Problem

[smiffi]

Hello everybody, this being my first post I think it is only right to get the drinks in, so this round is on me.

Ok now my problem.

I have just purchased a 1996 318i touring with a intermitant fault.

The car will drive fine at all engine speeds then all of a sudden it sort of dies for a few seconds. It seemed to do it more when the engine was put under greater load,eg going up a hill, but it'll also do it when setting off from a stand still. It just feels like you have taken your foot of the gas pedel. There is no pattern to when it will do it, it doesn't happen at every hill or at every set of lights but it will happen 2-3 times in a 20-30 mile journey. Even if you dip the clutch and try to rev the engine it makes no difference to the engine speed.
The rubber boot that connects the air flow meter to the throttle housing was split, so I purchased a new one, which seamed to help but didn't cure the problem.
The engine management light isn't on, but then again, I dont think it works because it doesnt light up with just the ignition on and the engine not running. I dont know how to check for fault codes either with this being my very first BMW, but I'm sure I can find a post about them somewhere.

Also I dont know if this is related to the same problem, but when I come to a stop at traffic lights the engine continues to rev to about 1200rpm then after about 5 seconds it will drop down to a steady 950rpm.

Hope someone can help.

Thanks
Smiffi

 

[selavia]

Sounds like a vacuum leak.

Could it also be the MAF Sensor?

I would first check all hoses and make sure MAF boot is on properly.

 

[mclarensmps]

get all of your oil seals checked, when my engine blew i was told i had a broken oil seal which leaked all the oil (which i did not see btw), causing the engine to sieze up and things going not so happy inside. The oil light DID NOT turn on to give me any sort of warning. I did suffer similar symptoms of losing power randomly while gassing it. Until you get it sorted, dont rev hard. Thats the only advice i would have from my own experience.

 

[smiffi]

Thanks but what is a MAF sensor, where is it located and what does it look like,
Can they be fixed or do they have to be replaced?

 

[viking_11]

The MAF or AFM is located in the sealed unit above the air filter. Unclip the Air filter top and disconnect the hose. Now looking inside from the air filter end you should see a probe. Clean this with carb cleaner or something to get the crap off. Be gentle as a new AFM is at least £200, but think you can also just buy a new probe for about 40 quid. I'd also change the fuel filter?

 

[smiffi]

So what does the probe actually do?

I'm gona try and clean it anyway and I have also bought a new fuel filter, I was surprised at how big the fuel filter is.

 

[viking_11]

Its a device that measures the volume of air flow on injection engines by using a heated probe to sense the flow into the inlet manifold, it then sends the info to E.C.U. It's job is to ensure an appropriate mix of air and fuel for combustion.

 

[smiffi]

Now this might sound a bit daft, but if the air flow sensor was at fault wouldn't the problem occur all the time?
Also I noticed today that when the car started having a "funny do" the mpg guage went right down to about 10mpg and the car wouldn't rev past 2800rpm.
Just thought I'd add that incase it helps with the diagnosis.

 

[viking_11]

did you say u changed the fuel filter??

 

[smiffi]

No not yet. I have gone and bought one this morning and hope to have it fitted by the weekend. Probably wont be the cause of my problem,but for £9 there is no harm in changing it.

 

[smiffi]

Ok just a update of what has happened today.

I went to pick up a couple of parts and the car started playing up BADLY, it wouldn't rev past 2500rpm and wouldn't drive over 30mph, unfortunatly I was on the motorway when this happened some 25miles from home.

Anyway I limpted it back home and I took it to a local garage for him to hook it up in to the computer. There were no fault codes stored and according to the ECU everything was working as it is supposed to do. We did indivdual checks of the oxygen sensor,MAF sensor and a few others that I cannot remember, and everything according to the ECU is fine!!

The mechanic recommended that I change the coolent temp sensor, as this may be telling the ECU that the car is cold when infact it is at optimum running temp,hence severly over fueling it and making it run like a bag of sh*t. He gave a example of the older cars which have a manual choke system,where if you pulled the choke out when the car was hot it would run very badly.

Anyway I'm going to give this a try, the temp sensor was only £11 but it looks a right pain in the arse to fit. The Inlet manifold has to come off as well as some other gubbins. The mechanics book said it'll take 2hrs to do the job,hence the reason I'm going to try and do it myself as I could really do without the expense of the mechanics bill.