rough idle

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bavagain

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I did several searches regarding rough idle and backfiring and am generally convinced i have an ignition problem and a fuel problem. I just got the bavaria and it has weber 32/36 carbs and petronix ignitor ignition. the plug wires were not spiral wound so i put on a set of spriral wound, the coil was not the correct coil, a flamethower .6 ohm and i changed to a 3.0 ohm, new ngk plugs, disconnected the external resistor and checked the timing and set to factory spec and double checked valve clearances. none of this helped the rough idle and backfire. The car starts up easily and idles fair with occasional "pop" out the tailpipe. all this leads me to think i have a carburetion problem which leads to my question, does anyone have jetting prescription for weber 32/36 carbs on a 3.0 engine in the Bavaria.
Thanks
bavagain
 
You might want to make sure the carbs are clean and that the accelerator pumps are spraying well on each carb. Have they been balanced/synchronized using an air flow tool. Make sure linkage is tight and equal for both carbs. Have you checked the carb base gaskets? Are the bolts tight? You might have a vacuum leak. There are ways to check that. What is idle set at? Should be 900 to 1000 rpm. Have you taken idle jets out and cleaned them? What part of VA do you live in? I am in Maryland
 
My thinking...

I've had issues with Petronix in the past (check the pick up on the shaft)
Vacuum leak - smoke test
Is the problem only at idle?
What does it do at a steady 2500rpm?
 
bavagain said:
I did several searches regarding rough idle and backfiring and am generally convinced i have an ignition problem and a fuel problem. I just got the bavaria and it has weber 32/36 carbs and petronix ignitor ignition. the plug wires were not spiral wound so i put on a set of spriral wound, the coil was not the correct coil, a flamethower .6 ohm and i changed to a 3.0 ohm, new ngk plugs, disconnected the external resistor and checked the timing and set to factory spec and double checked valve clearances. none of this helped the rough idle and backfire. The car starts up easily and idles fair with occasional "pop" out the tailpipe. all this leads me to think i have a carburetion problem which leads to my question, does anyone have jetting prescription for weber 32/36 carbs on a 3.0 engine in the Bavaria.
Click to expand...

Rough idle could be due to a myriad of issues, from the simple to the more complicated. As others have suggested, fuel mixture is probably a good place to start. You do not mention anything regarding mixture screw adjustment or idle jet size. Yes, other jets and emulsion tubes and accelerator pump condition are not unimportant, but idle jet size is a good starting point. As with any carburetor equipped engine, it can be of equal importance to initially exclude vacuum leaks as a potential problem with idle mixture.

There are many ignition component choices that are compatible and adequate for most engine operations, but for the most part, stock, original equipment Bosch has proven both adequate and dependable for daily driver needs. You mention spiral wound ignition wires and a "correct" coil. Most likely, your Bavaria’s engine was originally equipped with solid core ignition wires and non-resistor spark plugs, but it is unlikely that a change to different resistor wires or spark plugs or a higher output ignition coil would have a significant effect on engine idle operation - especially if your engine has decent compression and adequate fuel/mixture delivery. Ignition component problems tend to reveal themselves under load/acceleration or at speed. You fail to mention engine operation and related issues at mid-throttle or at cruise. Images of your spark plugs might also prove helpful in diagnosing your idle issue. Spark plug type and gap might also be helpful.


Weber DGV jetting has been discussed before. For starters, try:
https://e9coupe.com/forum/threads/weber-32-36-jetting.40794/
https://e9coupe.com/forum/threads/dual-weber-dgav-32-36-jetting.35128/
https://e9coupe.com/forum/threads/seeking-opinions-air-fuel-ratios-with-32-36-weber-dgv-carbs.35599/
https://e9coupe.com/forum/threads/weber-32-36-jet-questions.805/

PERtronix has also been discussed.
https://e9coupe.com/forum/threads/pertronix-solution.10738/
https://e9coupe.com/forum/threads/pertronix.17056/

iu
 
Thanks all I started with the flange mounting bolts and discovered they were all loose to some degree. I’ve removed carbs reduilt and ready to reinstall. Now it looks like I may need to change manifolds front to rear etc. previous owner must not have had a clue.
 
installed the rebuilt carbs and it started as soon as it got fuel. I used the baseline tuning info for a single 32 36 and it runs good sounds good but i can tell the rear carb is not quite in sync with the front. I'll get my son's carb sync tool and do a final tune up. the motor sounds really good, strong and rev's quickly. I do know it has an 84 head and piano top pistons, I often us a wood skewer to run into number one hole to determine tdc and recently when i did i could feel the raised portion of the pistons. It is a numbers matching car so it is a 3.0 liter (or was because i dont know if it's been bored but most likely it has been). On to more items that need attention, install a new ignition switch which came in yesterday, so far been using toggle switch and push button, not mine but from the garage where i bought it. PO took it local garage with broken ignition switch and told them to "get it running", they did but with toggle and push button. they could have saved a lot of time and money if they would have installed a new switch,
 
It sounds like you are on your way to resolving your issue. I just wanted to add that when I bought my 2800 CS it was barely running, "rough" isn't even a close description and would also backfire out the carbs. Replacing the points with a Pertronix unit got it to run, but setting the timing was impossible as the spark timing was so erratic I couldn't see the ball in the transmission window. The engine would start and run ok, but still would randomly backfire through the carbs.

The Pertronix made the spark reliable, but the distributor needed a repair/rebuild to allow it to deliver smooth, correct timing. I found a rebuilt distributor on ebay which should resolve the issue, but I'm not at that point in my restoration yet.
If your spark seems solid enough to allow easy timing, I'd guess you can count your distributor as being in good shape, but if it occasionally glitches and the advance sticks enough to knock the timing off momentarily, that might be the source of your backfires. Just my $0.02.
 
Thanks, the distributor in this car appears to be a rebuilt unit and does have petronix in it. I checked the timing by first rolling number one up to tdc, checked the bouncy ball in the window, cleaned it off and marked it with white paint. i got it close but that was when it was running rough so i need to recheck timing now that it runs as it should. The stock distributors on the cars to get tired and if i could afford one i might go with one of the electronic carbs or a distributorless system. At this time i'm satisfied with the pertronix system, but as with all electronic systems, carry a set of points and condenser just in case. I've had pertronix in other cars and narry a problem but pays to be prepared.
 
bavagain said:
Thanks, the distributor in this car appears to be a rebuilt unit and does have petronix in it. I checked the timing by first rolling number one up to tdc, checked the bouncy ball in the window, cleaned it off and marked it with white paint. i got it close but that was when it was running rough so i need to recheck timing now that it runs as it should. The stock distributors on the cars to get tired and if i could afford one i might go with one of the electronic carbs or a distributorless system. At this time i'm satisfied with the pertronix system, but as with all electronic systems, carry a set of points and condenser just in case. I've had pertronix in other cars and narry a problem but pays to be prepared.
Click to expand...

the bouncy ball should be in the window at 1700 rpms, not sure if you are doing this well
 
yeh bouncy ball in window at 1700 rpm with vac advance disconnected, but this was before i rebuilt the carbs. still need to redo the timing check now that carbs are on and car running good.
 
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