I experienced something similar when I found out that my choke (although, it was manual) on the carb came disconnected from the linkage and was stuck partway on. If your engine's from '76, though, I think it has an automatic choke.

Good point regarding the choke. Were you wearing clothing when you thought of this? How are your rear shocks?

Automatic chokes are fastened with small e-clips and occasionally stick, bind, or stop functioning. It is possible that an automatic choke can stick in an on or partially on position.

Although unlikely, it is also possible that during the winter, something crawled into the manifold and partially obstructs airflow to the cylinders. Alternatively, is the exhaust extra quiet?

Some claim poorly installed rear shocks result in an obstruction like this.

1.) IGNITION TIMING

OR


2.) THROTTLE LINKAGE
_________________
1976 BMW 2002 #2743711(sorry I sold it 12/25/06)
1986 BMW R65 650cc twin 19k miles
1964 BMW R27 250cc single 15K miles
2002 BMW 325xiTouring 29k miles
1984 MERCEDES-BENZ W123 300D Turbodiesel-188k miles fein-DIESEL

I checked the timing already with the ball bearing and a timing light.
It is still dead on from when I installed the motor awhile ago....that's what pointed me to the vacuum advance....as when I gradually accelerate it seems fine until I get up to 4000.
Regular rotor.

When I floor it...it BOGS (like it's starving for fuel/ thus the filters and new pump)....then when I let up on the pedal a lil it picks up again, but not to the higher rpms it used to have.
_________________

'72 02 Weber
'75 Opel Ascona Weber S
'82 e21Weber S
'84 535iS
'86 535i Uber Beater
'89 325iS
'89 325iC
15+ parts cars
http://myworld.ebay.com/fosters.3

Did you check the fuel "filter" screen on the bottom of the gas gauge sender?

ChuckP left me a message regarding your problem. As I told Chuck, this one may be very easy. Don’t keep your shirt on! Leave your pants on the chair!

If the carb is bogging down at full throttle but not part throttle, there may be something funky with one or both auxiliary venturi tubes.

There is a nice picture of them here:
http://www.bmw2002faq.com/component/option,com_forum/Itemid,57/page,viewtopic/t,291862/highlight,weber+bog/

If you notice in the picture, you can barely see the brass tube that sits into the middle of the auxiliary venturi. The tubes are interference fit and have a tendency to rotate so that the slot in the brass tube is not facing down. If one or both of yours has rotated and does/do not point downward, it will result in the symptom you are describing.

Here is an earlier writeup on the same subject: What you have described has happened to me on a couple of occasions involving that same carburettor. It is rather simple really, and involves a loose or rotated tube that sits in an auxiliary venturi. If you are familiar with what I am trying to describe, check to see that your's are fixed in the proper direction and stop reading now. If my description/explanation leaves you confused, keep reading and maybe it will make sense.

Looking at your carburettor from the top, with the choke open, you will notice that each carb barrel has an object/obstruction in the direct center of each barrel. I believe this part is labeled by Weber as an "auxiliary venturi." Going from memory, if you look at the dead center of that venturi, you will note a small brass tube sitting horizontally between the middle circle/ring. If your carb is new, the tube should appear to be shiny brass. If the carb has been exposed to the elements, including crankcase fumes, it will appear dark gray and may not be so obvious. These tubes contain a rectangular or slotted orifice that should be pointing downward. If you see either tube with an opening pointing towards the heavens or anywhere other than toward the ground, your engine will exhibit symptoms as you describe. Unfortunately, the Weber is not a Rolex and the tubes within the venturis are not always installed correctly or they have a tendency to rotate on their own. The fix is easy.

As I am sitting here now, I'm not sure if you need to remove the top cover of the carb to access the venturi tubes. The answer to that question probably turns on the size of your digits or instruments. In any event - IF you see one of the tubes is upside down, it is probably a good idea to remove the top of the carb (6 screws plus removal of 1 e/c clip from the choke assembly. The venturi's pull right up (they are secured by gravity). Rotate the tube to the appropriate position with your fingers or with a gentle application of some needlenose pliers. There is no obvious means of crimping the tube so that it remains in place for it is, I believe, a friction fit. But for our purposes, you might consider using a tooth pick and some fuel resistant adhesive on the edge between where the tube meets the body of the venturi. I think I have used Aviation Permatex but for all I know, one drop of crazy glue might do the trick.

http://www.bmw2002faq.com/component/option,com_forum/Itemid,50/page,viewtopic/t,290322/view,next/sid,1f0502809586d21f972d39f189df11c9/


Good luck.

Try it with the air filter housing lid removed. Measure the fuel pressure at the carb.
_________________
Curt Ingraham
1972 2002tii, 1976 2002
Improved 2002 Radiators

Berry wrote:

ChuckP left me a message regarding your problem. As I told Chuck, this one may be very easy. Don’t keep your shirt on! Leave your pants on the chair! If the carb is bogging down at full throttle but not part throttle, there may be something funky with one or both auxiliary venturi tubes.

Tanks...I'm am very familiar with carbs. I've rebuilt to many to count. I learned about venturi theory and atmospheric pressure back in the early '70's when I was 10 and never forgot it. I know exactly what you're talking about and will proceed as you explained.
I'm also gonna check the screen in the tank.
I had the tank out this past Winter (I'm sure you've seen THAT photo), but never touched the sender/pickup assy.

I will have to get to it this week after work some time and I will report back with my findings.

Would you like photos? I can oblige as it's very warm out so I will venture out to the 02 garage in my wife's thong if you'd like?
_________________

'72 02 Weber
'75 Opel Ascona Weber S
'82 e21Weber S
'84 535iS
'86 535i Uber Beater
'89 325iS
'89 325iC
15+ parts cars
http://myworld.ebay.com/fosters.3

Did not mean to be condescending. Know you are an expert. Also know that sometimes on these older cars, its easier to assume quality control is almost as good as it has become with the newer cars.

Berry has had several out-of-the box Webers that were not the best examples of superb quality. I hope he's right, although I wonder if maybe something else real obvious has occurred. Maybe the secondary is not opening. I used to have a quadrajet that was like that. Also wonder if something else isn't gumming up some of the carb's internal plumbing.

Again, good luck.

P.S. If you are wearing your Mrs' thong, what's she wearing?

Biscus made me do it?

ChuckP wrote:

Did not mean to be condescending. Know you are an expert. Also know that sometimes on these older cars, its easier to assume quality control is almost as good as it has become with the newer cars. Berry has had several out-of-the box Webers that were not the best examples of superb quality. I hope he's right, although I wonder if maybe something else real obvious has occurred. Maybe the secondary is not opening. I used to have a quadrajet that was like that. Also wonder if something else isn't gumming up some of the carb's internal plumbing. Again, good luck. P.S. If you are wearing your Mrs' thong, what's she wearing? Biscus made me do it?

Not condescending...great detail to explain that lil' brass thingy(not aware of this "rolling" problem). I'm no "expert"...if I was this thread would be non-existent.
I've bought 2 new Webers in the past 20 years and they always idled "right out of the box". Then adjust as needed.

Secondary IS squirting and flowing...I already thought of that or something gumming up too.
I'll sort it out, eventually, even if I have to pop the carb. top and inspect/clean. Also, I have spare Webers on perfect running M10's(backup motors/ not for sale),
I could toss on (last resort).

Mrs. jonny would be wearing MY boxer brief's , of course.
_________________

'72 02 Weber
'75 Opel Ascona Weber S
'82 e21Weber S
'84 535iS
'86 535i Uber Beater
'89 325iS
'89 325iC
15+ parts cars
http://myworld.ebay.com/fosters.3

Reporting back wiff my findings:

Spray carb. cleaner = a 'lil' better

Disassemble carb, thoroughly cleaned, float and everything checked, reassembled= even better!!!

Check plugs= 3 were a 'lil loose, but not sure if enough to cause intitial problem.

Also, 1 plug wire insulator at spark plug broken and exposing tip of plug, but no symtom of arching whilst under power nor idling= Replaced wire.
Plugs were perfect..rechecked gap.
Too late to test drive.

Tonight. test drive, then fuel tank pick up screen.

P.S. The brass tubes in the venturis were positioned correctly. Took everything apart and EVERY ORAFICE is clear.

Note: After intial spraying of carb. cleaning.. 6K-7K rpm's reached while parked ...under load = not so good.
_________________

'72 02 Weber
'75 Opel Ascona Weber S
'82 e21Weber S
'84 535iS
'86 535i Uber Beater
'89 325iS
'89 325iC
15+ parts cars
http://myworld.ebay.com/fosters.3

sheesh you've done just about everything and it still bogs under load?

The only thing left I can think of is that your fuel lines themselves might have a kink or a blockage somehow ???

100% better!
It seemed to run much better after the carb. cleaning.
Then I pulled the fuel sender and checked the screen. Looked fine, I blew it out anyway.
Then I blew through the fuel line from the tank up to the 1st filter, but had the end in a lil' can. I think, a couple of lil' black pieces came out?
Could've been a slight blockage. Inside of the 35 y/o fuel line ends degrading?
Re-timed it. Enriched the carb. screw mixture a 1/4 turn.
Then I took the car out and thrashed it for 1/2 hour.(some nice sideways on a 180 degree entrance ramp!!!)
It's much smoother now. There may be a slight dead spot in the carb. but overall is satisfactory.

I think I have not driven the car enough, nor hard enough in the last few years? I try not to over rev. ,nor thrash my cars as I have 10 and there is always a running work list on 'em, so I don't have time to blow one up!! <8-(
Whassup with that SEAFOAM stuff?
There could be carbon buildup and what not.
Your thoughts on SEAFOAM?? I have never used it.
I must investigate online re: SEAFOAM.
Tanks for all your support.
jonny
8-)
_________________

'72 02 Weber
'75 Opel Ascona Weber S
'82 e21Weber S
'84 535iS
'86 535i Uber Beater
'89 325iS
'89 325iC
15+ parts cars
http://myworld.ebay.com/fosters.3