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1984 928s LHD will not idle. New green wire, new plugs, good fuel pressure and spark. Idles high but starts and idles with MAF unplugged. Starts and immediately dies when MAF plugged in. Just received newly reconditioned MAF (so I doubt the MAF is bad), and I have continuity in the harness from the MAF to the brain. Driving me crazy - any help to point me in the right direction would be appreciative...
No its US Spec. I can't the car to start with the MAF plugged in, even with the O2 sensor unplugged, to get to the point of dialing the MAF in (the adjustment on the MAF is about half-way). As soon as I unplug the MAF, the car starts and idles, though you can tell it is in "safe-mode" and won't rev much.
Could the brain be bad? Is there a way to test the L-Jet ECU? The car ran pretty well before a I replaced the vacuum and fuel lines. FYI - it's getting fuel and spark (as it runs ok with the MAF unplugged).
OK then you dont have a MAF,
you have a BARN DOOR and it wont run without the barn door plugged in,
try opening the barn door with piece of rubber hose put a long wire on it so it doesnt get sucked in
BUT Im confused please post a few pictures of your MAF and engine bay
Sorry to be unclear. I have the Barn Door AFM (just rebuilt). With it unplugged, it runs, but badly. With the AFM plugged in, starts and dies. I tried your trick with the hose and the cars idles and runs - so I'm guessing something is not telling the barn door to open properly...
Also, I hear a loud whining coming from the front right of the engine when it's running (with the hose blocking the barn door open).
its hard to see but is there a fat rubber O ring in the groove where the barn door seats?
look at the Green wire where it connects to the harness,
if it has URO stamped on one side of it I would suggest to return it and get the Bosch part.
was the green wire hard to seat into the distributor?
It is URO - are they notoriously bad? Also (and maybe more importantly) the PO had stripped the old (falling apart) green wire and cut off the harness and tried to solder directly. I've (tried - maybe unsuccessfully) to replace it with a bosch female plug. I don;t remember if it was hard to seat - though I feel it was difficult because of trying to reach under the distributor...
It seems I should check (or replace) my replacement female harness end before (and/or when) I replace the green wire with the Bosch one. Any suggestions on the best way to do this?
The green wire installation certainly sounds suspect and if the plug was forced into the distributor there’s a good chance that the wire has been compromised I would suggest only use Bosch green wires also you need to figure out the connector on the car side of the harness and that Hass to be properly replaced if you switch the wires the car might run but it won’t run well
Note you can put the connectors on to the wires of the car side of the harness and before plugging them into the connector housing plug them into the green wire and see what the engine does
once you figure that out then
plug the wires into the connector housing
Harness side connector repaired (it was a mess). New Bosch/Porsche OEM distributor (Green) wire installed. Smoke test on the vacuum and intake (was a small leak at one of the spider legs - fixed now).
Car tries to start, but will only start and idle with a hose holding the barn door open.
did you swap the wires that plug into the green wire and test them both ways?
have you verified the timing if the distributor was lifted up to swap the green wire its possible the rotors is off
NOTE when the timing is set at TDC the rotor will point to the hash mark in the distributor body
Ok - finally back in the saddle after a crazy week of work...
I checked the distributor/rotor and it's aligned correctly to the hash mark with the engine 0-TDC and verified the wiring leads/firing order.
Everything looks good, except now the car will not turn over with the Barn door open/closed, or the AFM plugged in or not.. I'm going a bit crazy as things seem to be getting worse (not better). The spark plug wires don;t look to be in the best shape, so I'm going to replace those (just in case). Any other things to look for?
I'm at the point to take it to someone much smarter than me to sort out - anyone have any suggestions of a good 928 specialist in Denver?
We don't have any dedicated 928 shops in town, but Eurosport Auto in Arvada works on 928s and has a good reputation in the Porsche community. They often have a 928 or two in the lot, and I've talked to the owner. He is knowledgable and has owned 928s himself. Good people and reasonable.
There is also a small community of local 928 guys that help each other out, but it's been pretty dormant lately. You can join that group at: https://groups.io/g/rms and post your question there.
10-10-2021, 07:41 PM
928 will not idle
