[T3] Mysteries and FI Parts

[Jeremy Menzies]

Hey Everybody,
I've been chasing a mystery engine problem for a few months now on my '71 Squareback (MT, FI, rebuilt stock 1600 w/a '69 case) and I'd like to start collecting some FI parts for testing and just to have some spares on hand.  I'll try to keep the problem explanation brief but it's a strange one, so I apologize in advance for the length.  I also want to let people know what I've done so far and that it's not something trivial like, "whoops, forgot to reconnect the battery terminal".
In short, I've gone through everything that I and the guy I've started working with can think of: set all the basic settings (timing, points, valves, etc); replaced all the vacuum (even the charcoal canister) and 99% of fuel hoses (not the ring main yet, it's not too old); good rebuilt fuel pump and filter; removed, cleaned and replaced gaskets on the intake manifolds and intake air distributor; replaced head temp sensor (it was iffy); checked ohm and volt values on air temp, TVS, MPS, Injectors, Trigger points (all within spec from what I can tell and what the Bentley says).  I tested then pulled the trigger points and cleaned and bench tested them (ohms are 0 on one side and maybe .5-.6 on the other, openign and closing properly in car); pulled the plug to the brain and checked continuity to all end points (either 0 or at most .2); pulled all sensor plugs and cleaned and tightened up all internal contacts; made separate grounds from batt to case ground and both FI and fuel pump relays; cleaned up the trans ground and chassis ground at batt.; checked continuity from neg. batt. to engine, tranny, and chassis from various points on car; pulled a vacuum on MPS (holds at +15"hg); compression good (140 on 1&2, 145 on 3&4); fuel pressure set and holds at 28.5psi when engine is running; hooked a smoke machine up to the intake (small leak around TVS but none others spotted); pulled, cleaned, lubed and checked Aux. air regulator (closes around 150F out of car but seems to stay open in car after 1-2 miles of city driving); new spark plugs; new plug wires; tried both good coil and condenser (from well running cars); checked charging voltage at generator (haven't yet from regulator), 12.6-13.6 at idle, 14-15 at 2200; isolated generator from coil, no change in problem.  Trans mount looks original but no cracks, tears, not loose, feels solid; pulled, cleaned and lubed rubbing block in the TVS then adjusted as per Bentley 'click' test (haven't rechecked with ohm meter). Checked ignition oddities by pulling plug wires at idle to note changes, no one cyl. acts vastly different from the next; tried a different set of plugs, no change.  Pulled injectors to test spray, cleaned and bench tested, checked ohms (spray looks pretty fine and conical, sparkling clean, tips snap in and out on bench, ran some alcohol through to get any grime out, ohms are within Bentley specs).  Probably more but I don't have my list with me.
So, the mystery is: Pt. 1- Runs OK at idle set to 850 (way too high with aux. air reg. left open, like 1600 so I plug it) but something sounds amiss.  It's kinda like a misfire but it's very subtle and doesn't isolate to one cylinder through ignition wire pulling.  Pt. 2- When driving, no matter the speed of the car, the gear, or RPMs, the whole car lurches and bucks, especially at lower RPMs (like in the bottom of gears or under load).  It's as if you had a switch on it and were flicking it off and on, comes in and out of power, off and on with smooth RPMs.  It doesn't seem to do it in a pattern either, kind of when ever, randomly coming off and on while going.  It's hard to describe.  Pt 3- This happened once the other day and I haven't duplicated it yet.  I took it out for a test spin, trying to get it more warmed up to see if the AAR closed and see what generally happens when it's warmer.  I got maybe 1.5-2 miles from home (in rush hour city traffic, so it warms up quickly) and all of the sudden the idle just dropped out and it would putter at idle, kinda stumbling and low but not stalling (sounded like those low revving race engines, sputtering and grumbling).  Shortly thereafter, I pulled in to get gas (only had about 1/2 gal) and the gas pedal would not respond at all for 10-20 seconds, not with pumping or holding or gentle persuasion, nada.  And then boom, on all of a sudden, high revs and going.  Got gas, checked AAR (still wasn't closed) and exhaust was very sooty black, bumped up idle screw with no difference.  The gas pedal remained unresponsive every time I let off and came into a stop then tried to go again, so I wound up laying it on thicker and made it home.  Like I said, I haven't duplicated the non-existent gas pedal symptom, but I haven't driven it much at all  aside from around the block on test runs.  Pt. 4- It smells like it's way too rich (gas smell but no leaks), the plugs get coal black instantly, and the exhaust looks black but according to an emissions tester, it shows up lean.
Conclusions thus far: I'm pretty stumped!  Everything tests within specs and technically is functioning properly and or good but it still won't drive right (it used to!).  Next step: Start trying to swap out other components and see what happens, if anything.  The guy I'm working with has been doing AC Porsches and VWs for like 40 years and he said 'it's definitely a stumper' (he's done a lot with 914s w/D-jet and used to work on T3s for a living back in the 70s).  He's suggested we try to get ahold of some good FI sensors and an ECU and see what happens when we swap them out to troubleshoot (even though it's more like crapshooting because things don't always work the same on all cars).   So I'd like to see what parts, if any, people out there have to spare.  Plus, I'd like to get my own 'inventory' to have in case something happens on the road it'll give me more options.  Or, if anyone on here is in the SF Bay Area with some parts (or an FI car) we could play "switch 'em" with, maybe trying my parts on your car and vise versa (that is if they're compatible system to system) just to troubleshoot, I'm open for any suggestions or help.  And certainly beer and food would be involved.
These would be things I'd like to try first:1. ECU- 311 906 021D (I have black sticker, not sure if it matters)  side note: I saw a rebuilt unit with 021DX as the end in the part #, anyone know if this would work? (I imagine the X indicates remanufactured) anyone have luck with remans?2. Aux. Air Regulator- not sure on the # but it's not the electric version (mine seems to not close properly when it's in the car, so...)3. Wiring Harness or master plug to ECU & end plugs for Mar. '71 production (I want to rebuild mine but don't want to pull it all apart to do so. I'd rather get one with as many of the connectors as possible and redo the wiring and boots then install it)4. Manifold Pressure Sensor- 311 906 051C5. Throttle Valve Switch- 311 906 111C
I can get the Bosch #s when I get home later, if anyone wants those instead of VW.
I'm willing to pay fair prices or if you have a whole lot you want to get rid of, I don't have to go one by one.  I'm also going to look around on the samba classifieds but thought I'd put an APB out here first.
Any and all help or additional ideas are welcome, sorry for the length!
-Jeremy
 		 	   		  
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