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90' 740 - Engine Miss after Coasting (pulling vacuum), Oil in Air Hose 700

posted by  Steve T on  Sat Jan 4 17:30 CST 2003
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I've had an intermittent miss / poor idle / stalling problem with my 90' 740 wagon (Bendix Regina fuel injection, non turbo charged) for several years that I've had several mechanics look at without any success. I've also tried fixing it by replacing the usual suspects: fuel pump relay, fuel pressure regulator, air mass sensor, and the IAC valve, but it still misses intermittently and has intermittent idle problems.

Recently, the symptoms changed a little and now are more predictable. Now, whenever I'm at highway speed and I use engine breaking on a long descent (pull high-vacuum), when I get back on the power, it starts to miss for a period (10-15 secs), then usually runs ok. Also, on several cold mornings, it would miss for several minutes and be down on power until I coasted for a period (slowed for the fast-trak toll plaza), then it would run OK. Lastly, when I recently replaced the IAC, I discovered a large amount of oil in the air hose at the low spot between the airbox and the intake manifold. I assume this is coming back from the crankcase, as if the PCV valve was not working properly. Can the PCV valve fail? When it pulls a big vacuum, could oil be fouling the plugs until it burns off, or is something else going on here? Any help would be appreciated.

Steve T 90 740 wagon, 94 850 GTAS






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