my buddy and I have the same problem with our e30's. what happens is no matter what temp the engine is at, when we just tap the throttle with our foot, the idle will bog for a second, and then catch back up with its self quickly.
I just wonder if there is a cure for this? itd just be really nice to get instant throttle response! thanks!!
You have a idle mixture control screw on your VAF to adjust CO mixture.
With the motor off, turn in completely untill it bottoms out & count the turns, call this X
Turn back out X turns & then start your warm engine
Now turn this screw back in slowly (again noting the turns) till the idle becomes rough, then back out again till she smoothes out :thumbup:
You should now know (and note) how many turns out your mixture screw is. Best lean idle :bigpimp:
Tap the throttle & check response & bog. If the bog persists turn out screw 1/8 turn & check response again.
Contuinue doing this, no more than 1/4 turn at a time, till the bog is gone.
If that does not cure your woes, then the carbon-track on your VAF is worn. Sadly this is normal as that is where your sweep is going to be at most of the time during the cars life :drive:
Hope this helps :dunno:
It bypasses air that shoud be metered by the Vane in your Air Flow meter.
It is either in front just behind the Airbox or behind the vane on the exhaust side.
I think on the M20 motor it is a allen bolt, accesible from the top, on the intake side of the VAF.
Remember to make notes and be gentle
Miller Maf conversion? I have the 3.5 and it does kinda the same thing. I've been through all the steps a couple of times and replaced with a few items. Instead of throwing more money at it I'm just gonna do the conversion get it tuned and call it a day.
I would make sure there are no vacuum leaks and the idle control valve, throttle positon sensor etc are working properly before adjusting the idle mixture screw.
I have found this same situation on the e30's I've owned and this is how I resolved this. Time consuming but hey makes the car run beautiful and resolves other potential issues. Remove the throttle body, while doing so it's a good idea to replace the cork gasket where the coolant hoses attach. I use gaskacynch gasket sealer on the gaskets for that and the throttle body.
Check the operation of the throttle switch contacts attached to the throttle plate. The adjustment is detailed in the Bentley manual. If its full of oil either replace it or cut it open with a dremel tool, clean it and glue it back together. Best to replace. Using a plumbers basin wrench, detach the round electrical connector near the oil pan and clean all of the contacts. Seal any openings/ripped boots, etc. with dialectric grease.
Replace the breather hose from the valve cover to the throttle body. If any of the vacuum spigots are loose, pull them off, clean and reinstall with the special loctite recommended for sealing the output flange/yoke of the manual transmission.
Once reinstalled and you've bled the coolant lines with the heater in the full hot position, test drive and make sure the heater blows hot, if not you've got an air pocket. Once all done tune the Vane Air Flow misture screw using propane induction. The settings are too sensitive to do by ear. You can buy a propane induction set up for about 80 bucks from tool topia dot com. With the engine at operating temp induce some propane. If the idle speed increases, turn mixture hex clockwise 1/8 and retry. Oh, if not already removed, best to remove the plug with 1/8" drill bit. Use vacuum hose to expose about 3/16" of the bit. Then use a sheet metal screw and a slide hammer to yank it out. Back to the propane. The mixture if too rich when inducing the propane with cause the engine to drop speed immediately. The ideal setting is when inducing the propane, the idle speed hesitates slightly and then looses speed. Propane is good stuff, great for finding vacuum leaks and testing O2 sensors. Good luck!
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