Awesome info, this is a keeper! (archive)

adjustments were only a partial turn. You could check how many turns from bottom each of yours are set now, write it down so you can duplicate if necessary, then remove and clean all of em and set 1 turn out and see what happens. Can always put back the way they were. You will need to adjust mixture and base idle. For mixture, you just need a half-way decent voltmeter, I used a $30 sears analog. Hook it up to hole 5 in diagnostic connector and ground. Needle will fluctuate between 1 an 12V. Moving CO screw will change amount of fluctuation. If it sits at 12v, doesn't fluctuate, its too lean and viceversa. when mixture is proper, it fluctuates evenly like a pendulum. You will then need a jumper to ground out the TPS for base idle setting. I used 3 small alligator clips hooked together with wires, simply remove TPS connector and hook clips to all 3 pins on TPS. Then turn central manifold screw to get idle of about 850 (tighten slows idle). Then check mixture 1 more time. For the vacuum measurement, you just need a $20 vacuum guage from Sears or autoparts, and a "universal check valve" from autoparts=$2. May need some small guage rubber hose as well so you can rig up guage to valve to throttle ports. If you want to discuss more, give me a call at home (check your email) Definitely helped the jerkiness, and seems to have almost cured the cold driveability issues...

Todd, once you screwed them all in and backed out 1 turn, how much did you then adjust each screw?
Just wondering if I could reset everything to 1 turn out and see any improvement without checking the vaccuum. Could you provide a list of the equipment necessary to do the vaccuum adjustment and where you got it, would really appreciate it!
Sheldon

Did the check valve thing. Was getting 17.5 inHg as average on each throttlebody. There was varying amounts of gack on/in each of the screws. #2 cylinder screw was quite oily/wet (sparkplug fine however). Cleaned them all, and used q-tips w/ throttle body cleaner to clean out the ports. Before I did this, I checked how they were set by tightening each screw all the way in. They were set anywhere from 1/2 - 1 3/4 turns from bottom. Set them all 1 turn out as per instructions, then balanced. Variations are quite small, all were withing 1 inHg. Did my best to set them all at average. ADjusted CO- it was now too lean, turned screw in about 5 turns and it was fine. Then bridged the TPS, and checked base idle setting. was VERY high now, like 1600rpm. SO I turned the screw just about all they way in to get to 900 or so. rechecked CO, had to lean it out a little. Final result is that car idles MUCH better. it idles higher now, like at 800, and fluctuated very little. Seems to be quite happy underway as well. It may have largely removed or at least reduced the jerky throttle response (Sheldon!). Have only driven it once so far, will see if my initial impressions hold. My theory at this point is it wasn't drawing enough air through the bypasses, so it couldn't idle high enough. Will see if it effects my cold driveability at all.

Todd

As you state readings are similar to mine. I also have 185+ PSI on compression test. I would welcome someone elses test results for clarity. Your fluxtuating vacuum may well be a small leak. Does it idle smooth or not? Poor ignition could also be the cause.

For the synchronisation test I was getting a much higher vacuum (more like 16in)on each throttle body but this was just from the wild deflection you get without a check valve. Again would welcome some more comments after you have done the trick with the check valve.

Best of luck

Ian

Well I may have anwered my own question... saw way below in first discussion of throttle balancing that Ian got something like 80kPa which is 9 in Hg. Also saw from throttle balancing instructions that in their example the average for each throttle was like 9 inHg (300 mBar). So as someone explained on the E28 board, this engine doesn't pull as much vacuum because of the cam overlap. Sound right??

Put a vacuum gauge on a "T" fitting between manifold and fuel press reg (so pressure reg still hooked up to vacuum line)/ Get a reading at warm idle of 6-10 inHg, which afaik is quite low??? expecting 15-22? needle fluctuates with idle speed +- 2-3 inHG. So maybe I have a vacuum leak somewhere? getting a check valve later so I can check each cylinder. Any comments appreciated! (note - compression good at 190 on all cylinders, valves just adjusted 2 days ago).

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