Jump to content
Jack_K

First Tune-Up Questions

6 posts / 835 viewsLast Reply

Recommended Posts

Hey All,

I'm about to take my '76 2002 in for its first tune-up since I've owned it. I bought the car about seven weeks ago, but I wanted to drive it for awhile and get a feel for any issues it might have, which I'll detail shortly. My mechanic is not a 2002 specialist, but he's honest, talented, and has plenty of experience on carbureted VW's and BMW's so I'm moderately confident a routine tune-up and oil change will suffice. Still, I thought I'd check here first to see if there are any common issues or (hopefully) simple fixes the good people on this board could clue me into that I could communicate to my mechanic. Okay, here's the specs:

- 1976 2002 Automatic. It's passed smog twice in the past 14 months so the smog-related equipment is clean and operating properly. It also has the big pancake air cleaner and a Weber carburetor. Almost certain it's the 32/36.

The issues:

- The car was getting pretty bad mileage in the city, about 14 mpg, and had an occasional rough idle. My friend and I deduced this was due to a rich fuel mixture. We leaned it out according to the manual--turning the screw all the way in, then turning it out. This greatly improved mileage and the idling problem, but the car began to stall occasionally. Not often, just once every few days. Then after a couple weeks the rough idle returned and it seems like the car's mileage isn't quite as good as it used to be. I don't believe there is a leak in the fuel lines, but that's something that I will have checked.

- The rough idle usually occurs after a quick deceleration. If I put the car in neutral and step on the gas a bit, the rough idle goes away.

- The car also uses a lot of oil. Might be up to a quart every 250-300 miles. I'm using 20W-50 and haven't noticed much of a leak, so I believe it's burning oil. I know that's to be expected on these cars, but a quart every 250-300 miles seems excessive. I've only put about 600 miles on the car, so I can't be sure of the exact rate. I'm hoping to go for some longer drives after an oil change and get a more precise figure.

Like I said, there aren't any huge issues with the car. And I apologize if it seems like this is way too vague. Not necessarily looking for a diagnosis, just some insider info/tips/suggestions to pass along to my mechanic. And hoping to take care of small things before they turn into big problems.

Thanks. I'll hang up and listen.

Oh, and here's a link to my introductory post with photos: http://www.bmw2002faq.com/component/option,com_forum/Itemid,57/page,viewtopic/t,376062/highlight,/

Share this post


Link to post
Share on other sites

They say that most carburetor problems are the ignition ; ) Have you serviced the ignition system? That is:

- new cap and rotor?

- is it time for new points and condenser? When installing the new one make sure to set the gap properly and then re-time the car. You may need someone to help you with this the first time.

- how do the spark plugs look? time for new ones or at least a cleaning? If putting in new ones, make sure they're regular 1-electrode type deals, not the fancy "4 electrode platinum" stuff for newer cars. Make sure they're gapped correctly.

- spark plug wires look OK? time for new ones? Boots look good too?

Beyond that make sure the choke on the Weber 32/36 is working properly (and adjust it if needed). You shouldn't need to adjust the carb much but if you did, did the idle screw have to come out more than 2 turns or so to get the car to run right? If so it's probably time for a carb rebuild.

Share this post


Link to post
Share on other sites
They say that most carburetor problems are the ignition ; ) Have you serviced the ignition system? That is:

- new cap and rotor?

- is it time for new points and condenser? When installing the new one make sure to set the gap properly and then re-time the car. You may need someone to help you with this the first time.

- how do the spark plugs look? time for new ones or at least a cleaning? If putting in new ones, make sure they're regular 1-electrode type deals, not the fancy "4 electrode platinum" stuff for newer cars. Make sure they're gapped correctly.

- spark plug wires look OK? time for new ones? Boots look good too?

Beyond that make sure the choke on the Weber 32/36 is working properly (and adjust it if needed). You shouldn't need to adjust the carb much but if you did, did the idle screw have to come out more than 2 turns or so to get the car to run right? If so it's probably time for a carb rebuild.

+1 I agree

Share this post


Link to post
Share on other sites

1. rough idle after deceleration--check the dashpot--that thing that looks like a vacuum advance unit mounted on the intake manifold that slows down the carb linkage's return to idle when you let off the gas. You can probably back off the adjustable link so that it doesn't function until you have to do another emission inspection. That may help the idle. Also, check for vacuum leaks--vac advance unit in the dizzy, the aforementioned dashpot, carb base, intake manifold gaskets and any plugged up vacuum ports on the manifold. Doesn't take much of a leak to upset the idle.

2. Oil consumption--quick and dirty test to see where the oil is going:

Accelerate hard in first gear--any smoke? If so it's probably worn rings. Then suddenly let the throttle snap shut from 4k rpms....any smoke on deceleration? If so, it's valve guides/stem seals--a known weak point on M10 engines. If you replace them be sure and have the shop use the guides and seals from a later M10 (E21/E30)--much better and longer lived design.

Hope this helps--let us know whatcha find.

cheers

mike

Share this post


Link to post
Share on other sites

Not that this really adds anything to what Mike and Andrey said, but: (1) 14mpg in the city doesn't strike me as abnormally bad; and (2) if you're burning a qt. every 300 miles I would think that the smoke would be REALLY noticeable. (If you put your finger in the tailpipe it'll be greasy.)

Good luck!

Share this post


Link to post
Share on other sites

Thanks guys! This is very helpful. Looks like I scheduled the tune-up just in time as the car started making a screeching sound on the way home from work last night. Pretty sure it's just the fan belt, at least that's what I'm hoping. Will keep you posted. Thanks again.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.




×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.