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Matt
Matt, Engineer
Category: BMW
Satisfied Customers: 20581
Experience:  Mechanical Engineer with 20 years experience in the auto industry, 8 yrs in formula 1 engine testing
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I have a 1994 BMW 318i convertible that I just purchased and

Customer Question

I have a 1994 BMW 318i convertible that I just purchased and on the way home it began to run rough and have a difficult time idling. I have all of the former service records. I have watch some youtube videos I need a BMW expert to assist me.
Submitted: 29 days ago.
Category: BMW
Customer: replied 29 days ago.
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call + Provide Diagrams, Manuals, or Instructions. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Customer: replied 29 days ago.
I have portions of the way 5 service invoices from repairs that are related to the same issue. They date back to several years however you would be able to see what has and has not been repaired or replaced and when it was performed including mileage
Expert:  Steve replied 29 days ago.
Hello and welcome,
My name is ***** ***** it will be my pleasure to assist you today.
What kind of info were you seeking?
Customer: replied 29 days ago.
Did you see my question?
Customer: replied 29 days ago.
I just sent the copies of the service records below
Customer: replied 29 days ago.
The vehicle was purchased by me just a couple days ago... it drove. Fine for a few miles then after maybe 6-7 miles seemed like it ran better if i kept rpms over 3000, once I exited highway and got on local roads would cut out if I did not race the engine. I drove it a total of 19.5 miles to my home and it has sat ever since. I see that there have been several services over the years and I copied anything that looked related. I would imagine some things come with time however I am not sure. The man that sold me the car was often deployed in the Air Force and the car would sit. That is all I really know. It seems to be well cared for a very clean. I hope I did not make a mistake. Cal you assist me? When I drove it in the basement of his building around 15-20 mph it was fine a few days before and he says he drove it daily to work 10 miles no problem.
Customer: replied 29 days ago.
When you start it it will not idle... unless you give it gas. Cuts out pretty fast
Customer: replied 29 days ago.
Are you there?
Customer: replied 29 days ago.
If you look at the records the CCV crank case vent was replaced with the hose 2 years ago and then driven only 4000 since.
Customer: replied 29 days ago.
I'm still waiting for you to answer my question
Customer: replied 28 days ago.
Is there are problem? Can you just let me know you are working on it? I took off all day waiting for an answer. The car WILL NOT IDLE.... I just tried a few minutes ago
Expert:  Matt replied 28 days ago.

Hello

another expert here

This could be an airleak after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and can lean the engine out causing rough running.

As its a mechanical fault it tends not to turn on the fault light and you can sometimes hear a 'hissing' noise with the engine running.

Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.

The best way to locate a leak is to have the engine running and warm and then spray lighter gas /propane or brake cleaner around each joint in turn. If the engine rev's up you've found your leak.

Now you might think that spraying lighter gas around a hot engine isn’t wise, however the flash /ignition point of gas is about 400°C so you need a naked flame or spark to set it off and I’ve used this method for many years without incident.

Work your way through each possible joint one at a time and you should find it. I use a slightly flattened piece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.

It’s also worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a poorly pump will all result in insufficient fuel being delivered to the engine

Might also be worth cleaning out the idle speed control motor / valve as these get clogged up with carbon and some brake cleaner washed through helps free things off.

Might also be worth checking the wiring and connector to the airflow meter for any signs of corrosion or damage. you can do a quick fault find if you unplug the meter and run the engine without it.

if the engine condition is the same then chances are the meter or the connection to it is faulty

It’s also worth cleaning the MAF sensor wires, as they can get coated with dirt over time which then offsets the reading

Use some contact cleaner or brake cleaner to spray onto the wires to remove the dirt – on no account touch the wires with anything as they are very fragile

Customer: replied 28 days ago.
I purchased choke cleaner... should I use Brake cleaner instead? What would be the best way to keep the engine running while I do this? Is there a reference I can use to locate these items to check? And finally the throttle cable closer to the window seems loose is this normal?
Expert:  Matt replied 28 days ago.

Hello

choke or brake cleaner is fine to try detecting leaks and the engine should stay running / idling while you do this

and the throttle cable towards the rear of the engine bay is the primary one from the pedal so that should be adjusted so there's no slack at the pedal

also looking at the image of the engine bay it looks like the cover on the airflow meter has been removed at some point( the silver box item just after the air filter box )

this is a little concerning as they are meant to be sealed items so its possible someone has been in there 'adjusting' something

this would have a strong effect on how the engine runs

Customer: replied 26 days ago.
Thank you very much for all of your info... I plan to get some time Tuesday to try some of your ideas. If money would not have been an issue I would just buy a new airflow meter. By the way... I'm thinking about installing a cold air intake... any thoughts.
Expert:  Matt replied 26 days ago.

No problem , just get back to me on this post

and a cold air intake can help but there's a lot of junk on the market and to be honest the stock intake isn't that bad as it already picks its air up from the front of the car

If you were to add some trunking so it gets its air from in front of the radiator and replace the air filter element for a more free-flowing item like a K & N then you'll be about 90% of the way there

Customer: replied 25 days ago.
Sorry I'm still messing with this car... I had not really had a chance to try what you said however I went to start the car today and it FINALLY idled fine so I went to get it inspected for
Our VA state safety sticker and it drove fine for about 3/4 of a mile then I gave it same gas maybe 4-5000 rpms and it cut out again. OMG. DOES THAT HELP NARROW ANYTHING DOWN? I'm sorry I keep asking... I've spent what I have in this car and as I was going to the car they were about to tow it because not safety sticker. I will try the things you said but does this tell you it could be....... one thing? Please help
Customer: replied 25 days ago.
Ok... I just checked all he hoses for leaks with choke
Cleaner.... nothing all seems fine. I tried you idea about disconnecting the air flow meter. Now it's idling again! I connect it and it stalls out! I also took up the slack on the throttle cable. Well it seems that it is the meter? What do you think? Still disconnected and still running....
Not sure for
How long but I don't know where I can get a new one FAST without it costing a ton of money. I APPRECIATE YOUR THIUGHTS
Expert:  Matt replied 25 days ago.

Hello

OK

with these older air flow meters they can often be refurbished see this video

https://www.youtube.com/watch?v=Z-QlPtsjh7g

Expert:  Matt replied 22 days ago.

Hi

do you still need help?

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