M20 ETA, no power, super rich, very rough idle

[bradnic]

my 86 325 was running beautifully, but now it is giving me trouble.. looking for suggestions. I haven't started diagnosis yet, but here's the situation

starts, but sputtering hard, like it's missing
when it's like this the engine does not respond to throttle at all
exhaust is super rich and smokey, so AFRs aren't right
problem gets worse after it's rained

car is basically undrivable right now, even up and down the driveway. Gonna pull the plug wires and AFM. maybe the TPS? coil?

all suggestions welcome - would like to get this bad boy running smoothly again today.

[bradnic]

ETAs are so weird.. pulled the plug on a valve on top of the valve cover and idle smoothed out quite a bit. still rough and running rich though.

Plug wires are brand new Bremi. pulling each plug worsened the idle. probably nothing wrong on the ignition side.

Also inspected the CPS wire and it's got a hacked up solder job with electrical tape on it right near the thermostat housing. will post pics and vids in a bit.

[jeffnhiscars]

Have you tried disconnecting the cold start valve

[bradnic]

yes...that's the valve I referred to in my 2nd post. idled faster and smoother, then turned rough again

[bradnic]

so there's no CPS on an ETA like a 325i. There's a TDC sensor mounted near the timing mark, but I'm not sure it works the same way. All I know:

-- spark plug wires look new
-- when I disconnect the valve on top of the motor (cold start valve?) the idle smooths out a bit, increases to 1500 or so
-- AFM looks fine mechanically, flap moves ok, air filter is clean
-- the engine produces little power, barely revs and backfires like its timing is off

car is obviously undrivable at the moment. I can wait to do a 325i conversion, but I'd really like to get this fixed now.

[e30davie]

Does it have a vacuum advance distributor?

[jeffnhiscars]

so there's no CPS on an ETA like a 325i. There's a TDC sensor mounted near the timing mark, but I'm not sure it works the same way. All I know:

-- spark plug wires look new
-- when I disconnect the valve on top of the motor (cold start valve?) the idle smooths out a bit, increases to 1500 or so
-- AFM looks fine mechanically, flap moves ok, air filter is clean
-- the engine produces little power, barely revs and backfires like its timing is off

car is obviously undrivable at the moment. I can wait to do a 325i conversion, but I'd really like to get this fixed now.

There are 2 references sensors I the bell housing that are identical and one does the job of a CPS. They are known to be problematic especially where they connect on the side of the block next to the starter. The plastic connectors there tend to disintegrate.

[LJ851]

Check for moisture or corrosion inside the distributor cap.

[bradnic]

Thanks for the suggestions. Gonna try again this weekend, starting with the cold start valve. @jeffnhiscars was kind enough to send out some spares. @LJ851 / Lorin I have a replacement distributor cap and rotor. Will head down that path once I’ve ruled out cold start valve problems

[Jshbrwr]

Hey I once accidentally swapped the cold start (“7th injector”) with one of the other plugs near the thermostat housing when I was putting it back together after replacing the head gasket. It ran but was super rich, then died on me. Hope that’s not your problem...