Low/Rough Idle Question

Paulaner

Paulaner

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Hi E3 Brothers - I have recently had my air filter housing off on my Bavaria to service the spark plugs, plug wires, and repaint the air filter housing. At the time of disassembly I noticed that the tube that runs from the intake/air filter housing to the valve cover was disconnected and venting to atmosphere. Car ran fine this way before the ignition service. However upon reassembly, I reconnected that tube to the valve cover and the car isn't idling well. I have checked all the new spark plug gaps (0.7mm) and wire connections to the spark plugs, distributor, and ignition coil.

Has anyone observed this previously, and would you recommend disconnecting the vent tube at the valve cover again? I have not replaced the Distro Cap or Rotor (Bremi 9049) yet so easier to pinpoint the issue possibly.
 
Make sure that you have not accidently knocked off a vacuum line Also check if you have electric idle jets, you may have shorted them out and blew the fuse that controls them Happened to me more than once Make sure that you have power going to them Hooking up the vent pipe really should not affect idle or anything Your problem is just coincidental

Thanks, Rick
 
stphers said:
Make sure that you have not accidently knocked off a vacuum line Also check if you have electric idle jets, you may have shorted them out and blew the fuse that controls them Happened to me more than once Make sure that you have power going to them Hooking up the vent pipe really should not affect idle or anything Your problem is just coincidental

Thanks, Rick
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Thanks for the recommendations Rick, will have a look at these items and report back the findings.
 
Update:
All vacuum lines look connected properly and no cracks/splits
- from dizzy vacuum regulator to front carb
- charcoal canister under battery tray to T connector , from T to fuel line, and from T to bottom larger nipple on air filter housing
- rear carb vacuum port looks intentionally capped off by original owner who installed the 32/36s

Car does have electric idle jets, and look to be connected properly.

Fuse 11 (bottom row, second from right) looked a little suspect. Wasn't blown, but looks tired (image attached). Swapped out for new 8a fuse.

Still have the hose connected that goes from air filter housing to valve cover.

Can't imagine a simple fuse change will solve this, but worth a shot. Will try a start up in the AM as to not wake the sleeping baby and toddler tonight.
 

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Paulaner said:
charcoal canister under battery tray to T connector , from T to fuel line, and from T to bottom larger nipple on air filter housing
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Not vacuum lines. Part of the fuel vapor recovery system. Are you sure it T's to a fuel line? Doesn't make sense to me.

Paulaner said:
Car does have electric idle jets, and look to be connected properly.
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I don't know of any 32/36 Weber carbs that have electric idle jets.

When you say "not idling well"...when hot, cold, too slow, too fast, uneven?
 
Dick Steinkamp said:
Not vacuum lines. Part of the fuel vapor recovery system. Are you sure it T's to a fuel line? Doesn't make sense to me.


I don't know of any 32/36 Weber carbs that have electric idle jets.

When you say "not idling well"...when hot, cold, too slow, too fast, uneven?
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Dick - I meant to say idle cutoff solenoids, not idle jets.

It is now idiling too low ~400 to 500 rmp. Was idling well only a few days ago, ~900 or so.

I'll drop in a picture of the T setup I am referring to. Likely wrong with my terminology and description, still learning my way around these older cars.
 
Here is a good thread on Weber idle shut off solenoids...

CookeD

Thread 'Idle shut-off solenoid and Webers'

Hey all,

I'm troubleshooting my rough-running Webers, and a couple of things are suspect. Specifically, I don't have power going to the idle shut-off solenoids, and have a few questions about this:

1. First and foremost, if there is not power going to the solenoids, will I have symptoms that include poor running/will not idle? I've read on-line about snipping the pins off the solenoids that go into the jets, but this doesn't sound like the best thing to do....
2. I have power going into the relay (that's mounted on the rear of the vacuum booster), but there is not power coming...
 
Paulaner said:
Dick - I meant to say idle cutoff solenoids, not idle jets.

It is now idiling too low ~400 to 500 rmp. Was idling well only a few days ago, ~900 or so.

I'll drop in a picture of the T setup I am referring to. Likely wrong with my terminology and description, still learning my way around these older cars.
Click to expand...
Yeah, you likely have a malfunctioning idle solenoid. They are designed to close when they don't have 12v to cut off fuel and keep the car from dieseling. If one of yours is not retracting when getting 12v, or alternatively not getting 12v, you can expect your idle speed to be cut in half.

As to the T, that line you describe as a fuel line is actually the line to the reservoir in the trunk above the right rear tire that collects gasoline fumes from a hose connected to the fuel tank filler neck. The system is designed to hold fumes when the car isn't running, and then to draw them into the engine through that small connection on the air filter housing.
 
Paulaner said:
Dick - I meant to say idle cutoff solenoids, not idle jets.

It is now idiling too low ~400 to 500 rmp. Was idling well only a few days ago, ~900 or so.

I'll drop in a picture of the T setup I am referring to. Likely wrong with my terminology and description, still learning my way around these older cars.
Click to expand...
Dick - picture attached of the T connector with the lines running from charcoal canister, air filter housing, and a control valve?

Don't think any of this is related to my issue, but closing the loop with you on this item from yesterday.
 

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Update #2: car seems to idle a touch better today after fuse 11 swap, still not perfect. Low and rough at ~500 to ~600 rpm

Tried disconnecting the valve cover hose to air box, no change in idle as expected. Reconnected for further troubleshooting.

Checked distributor cap for any signs of corrosion, cracks, carbon tracking. None prevalent. Minimal to moderate wear on the contact points

Checked rotor (Bremi 9049) resistance, all ok at ~5000 ohms.

Checked rotor centrifugal weight operation. Moves out toward contact, and returns perfect when released.

Checked spark plugs again for proper gap all between 0.6 and 0.7mm

Performed spark plug tests with multimeter all around 4.25 to 4.5ohms

Performed spark plug test in line, all sparking well with blue to white color spark.

Plugs have only been in the car for maybe 75 miles, and look a little wet :(
Picture attached of plug example. All look about the same.

Took for test drove, operated just fine no issues. Just crappy idle while parked or at standstill.

I have yet to replace rotor or distributor cap or mess with the timing, and check voltage to idle stop solenoids - car diesels most of the time when turned off.
Guessing these would be the worthwhile next steps???
 

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If it idled well before you removed the air cleaner, replaced plugs and plug wires but doesn't idle well after these changes, I would not replace any other parts. That would just complicate the diagnosis. The low idle is most likely caused by something you did. Either directly related to what you did or accidently.
 
Dick Steinkamp said:
If it idled well before you removed the air cleaner, replaced plugs and plug wires but doesn't idle well after these changes, I would not replace any other parts. That would just complicate the diagnosis. The low idle is most likely caused by something you did. Either directly related to what you did or accidently.
Click to expand...
Noted on that Dick. Out of curiosity, spark plugs, wires, and coil were you running on yours before you cashed in?

I may try swapping back in my old wires and coil to see if the situation improves. I tossed my old plugs already b/c they looked well loved.
 
Did you alter the timing? Did I see that you put new points in, if that is the case, you have to adjust the timing BUT this is one time that I don't think that it is ign related Sounds like a carb idle issue Did you try checking to see if you are getting 12V to the electric idle jets If so with the ign on, disconnect them one at a time and go back and forth with touching the power lead to the jet and listen to make sure that they click it is quite audible when listening for it The fact that you say it is dieseling tells me one of those valves isnt working combined with the low idle

Thanks, Rick
 
Hi Stphers - no alteration of ignition timing yet. Car runs electronic ignition (Allison Performance), so no points.

Next on my check will be 12V power to the idle stops tomorrow. Will report an update following the check. Listened for the audible click today, but didn't hear a peep.

Appreciate the help everyone!
 
Paulaner said:
Update:
All vacuum lines look connected properly and no cracks/splits
- from dizzy vacuum regulator to front carb
- charcoal canister under battery tray to T connector , from T to fuel line, and from T to bottom larger nipple on air filter housing
- rear carb vacuum port looks intentionally capped off by original owner who installed the 32/36s

Car does have electric idle jets, and look to be connected properly.

Fuse 11 (bottom row, second from right) looked a little suspect. Wasn't blown, but looks tired (image attached). Swapped out for new 8a fuse.

Still have the hose connected that goes from air filter housing to valve cover.

Can't imagine a simple fuse change will solve this, but worth a shot. Will try a start up in the AM as to not wake the sleeping baby and toddler tonight.
Click to expand...
This probably isn't connected to your idle issue, but look closely at the fuse on the right end of the lower row of fuses. It's got corrosion at both the top and bottom. In addition, all the fuse links look pretty oxidized and the copper contacts are dirty. All the fuses should be removed and their ends cleaned. A bit of very fine sandpaper or even a pencil eraser should do the job, and the copper contacts should be cleaned as well. This is why the later blade style fuses are superior.
 
mulberryworks said:
This probably isn't connected to your idle issue, but look closely at the fuse on the right end of the lower row of fuses. It's got corrosion at both the top and bottom. In addition, all the fuse links look pretty oxidized and the copper contacts are dirty. All the fuses should be removed and their ends cleaned. A bit of very fine sandpaper or even a pencil eraser should do the job, and the copper contacts should be cleaned as well. This is why the later blade style fuses are superior.
Click to expand...
Good call out, thanks for the recommendation. Should clean them all. I did notice tho corrosion on terminal 12. Replaced that fuse the other night when I did #11.
 
Paulaner said:
Hi Stphers - no alteration of ignition timing yet. Car runs electronic ignition (Allison Performance), so no points.

Next on my check will be 12V power to the idle stops tomorrow. Will report an update following the check. Listened for the audible click today, but didn't hear a peep.

Appreciate the help everyone!
Click to expand...
Hi Stphers - getting good 12v power to both idle stop solenoids, and actually can hear them both click on when disconnecting and reconnecting the leads.

Likely one or both are mechanically not operating properly, correct?
 
Paulaner said:
Update #2: car seems to idle a touch better today after fuse 11 swap, still not perfect. Low and rough at ~500 to ~600 rpm

Tried disconnecting the valve cover hose to air box, no change in idle as expected. Reconnected for further troubleshooting.

Checked distributor cap for any signs of corrosion, cracks, carbon tracking. None prevalent. Minimal to moderate wear on the contact points

Checked rotor (Bremi 9049) resistance, all ok at ~5000 ohms.

Checked rotor centrifugal weight operation. Moves out toward contact, and returns perfect when released.

Checked spark plugs again for proper gap all between 0.6 and 0.7mm

Performed spark plug tests with multimeter all around 4.25 to 4.5ohms

Performed spark plug test in line, all sparking well with blue to white color spark.

Plugs have only been in the car for maybe 75 miles, and look a little wet :(
Picture attached of plug example. All look about the same.

Took for test drove, operated just fine no issues. Just crappy idle while parked or at standstill.

I have yet to replace rotor or distributor cap or mess with the timing, and check voltage to idle stop solenoids - car diesels most of the time when turned off.
Guessing these would be the worthwhile next steps???
Click to expand...
A few observations that may or may not have any direct connection with your idle concern.

First, a tiny bit of debris can easily affect a Weber downdraft 32/36 idle circuit and its operation. A visual inspection and/or a squirt of carburetor cleaner generally corrects the problem. However, I can recall resorting to the use of a dental pick in the field to address the issue. This is not to say that this is your problem, but it is worth considering.

Next, reasonable minds may differ but you might consider changing to a more conventional spark plug for reasons discussed here: https://e9coupe.com/forum/threads/spark-plug-recommendation-pls.14155/ One suspects that your Allison optically triggered ignition should have no problem with fine wire plugs. Nevertheless, the chorus of conventional wisdom seems to think otherwise.

A third observation involves vacuum line plumbing with Weber rather than original Zenith carburetors. Unless something has recently changed, the downdraft Weber’s vacuum porting location and vacuum source (above or below throttle plates) is different from the Zenith - and this can result in a few minor hiccups that are generally surmountable. Here is some more reading on this subject: https://e9coupe.com/forum/threads/help-vacuum-connections.7015/
My small screen limits my ability to fully explore your image and whether the “control valve” you reference is for fuel return or possibly part of an EGR system. It may be the former, since I cannot discern the existence of EGR ductwork. Needless to say, if any part of an egr system is stuck open, it can negatively impact engine operation, including the ability to achieve a smooth idle.

One last observation involves all of your resistance measurements. Is it possible that you bumped or disturbed the distributor or its innards when making these measurements? This merely suggests the possibility that you inadvertently retarded the ignition timing - which might easily account to a reduced idle speed and fouled plugs.
 
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