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I did confirm proper cold-start valve operation using an LED. The problem appears to be an undercharged battery. My trips in the E12 are all short and sporadic, with sometimes weeks between. My battery today was showing 12V on a voltmeter, but my smartcharger said 80%. After it was topped, I took a ...

Thanks Robert. So, yes on the warm start with the cold start valve unplugged. It behaves as it now does with the cold start valve plugged in, I.e., about 5-7 seconds of cranking. As luck would have it I replaced the in-tank pump a few months ago when I replaced the fuel tank. The thermo-time switch ...

I've replaced the engine temp sensor. Warm starts have improved (i.e., it starts) but still requires some cranking - maybe 5 seconds. Not terrible, but not perfect. I tried "key priming" (turning the engine switch to ON several times for a couple of seconds without cranking to get the fuel system ...

A low-cost thing to try is the coolant temp sensor (the two-wire one, not the sender to the gauge). Without the cold start valve, it's hard to know for sure, but if the temp sensor is failed-open, it will always think the engine is cold and that could explain the rough running and stalling. The no ...

O2 sensor checks OK, but you may be on the right track. Coolant temp sensor is out of spec, returning low resistances (which would lean out the mixture). I've ordered one and will report back.

Residual fuel pressure at the fuel rail held up well, and there's good vacuum at the FPR and a climb in ...

Had a very hard warm start situation. Replaced the ignition trigger coil in the dizzy. Runs a bit nicer especially at higher RPM, so I thought I was done.

Car starts fine cold. Runs fine. Still a hard start when warm. Verified cold start valve operation and replaced thermo-time switch. Still a hard ...

How are you pushing fuel into the intake? I was going to suggest running a diagnostic on the cold-start circuit. I would pull out the cold start valve and look for a nice spray of fuel when cranking. I suspect that might be the culprit because usually you can get a little stumbling just based on ...

I can almost hear the telltale sound, upon removing trim parts, of rust rain pattering on your well-intentioned piece of under-car cardboard. A good horsehair broom is your companion when exploring previously unseen regions of an E12. It totally stinks and I feel your pain. Did your US 530 have any ...

Robert, this is your usual perfectionism. Beautifully done. And it looks like I could eat of your garage floor, so there’s that.

I think it's the vacuum limiter for the EGR. From what I've read, this prevented the EGR valve from opening too aggressively an cause excessive exhaust recirculation disrupting the mixture and affecting performance, especially at idle. This is just based on research, my 81 528i does not have this ...

Thank you, sir. I ended up using a small amount of Curil T on the gasket, which is high temp and non-curing. I've never used it before, and I was basically trying to hedge my bets. Any reason this was a bad idea based on experience? If so, I can replace.

Neat and fastidious work as always, Robert. Have you mounted the compressor and all the lines yet?

PS. We see the Spal fan box in the background.

I'm reading this gasket goes on dry. The one I spent an hour and half a can of brake cleaner removing certainly didn't.

https://www.realoem.com/bmw/enUS/showpa ... Id=11_0468

What's the consensus? The blue manual doesn't mention any sealant or dressing.

If you're getting spark, and assuming the coil is OK and you're not getting a weak yellow spark, how's your fuel pressure? You might have previously stalled when the thermo-time switch shut off the cold start valve. You probably know this already, but with the engine off you can check fuel pump ...

My car had vac leaks at the dipstick and the oilpan gasket that caused roughness like you describe, among other symptoms. I found them after I had verified no leaks in any of the hoses. I used a large-diameter length of shrink tubing around the top of the dipstick. The oilpan gasket leak was solved ...