Hi eye5,

Sort of doubted the knock sensor is the cause of all poor tune problems on your 1985 240.

I was at the storage locker Sat-Your-Day this past and I have an unused knock sensor just like what you bought at Voluparts. I guess it is.

I also forgot yours uses the Chrysler MPG ignition as our Uncle Art reminds us. I skipped the 1980s-era 240s, specifically the rotting wire harness years as is your 1985 240. From 1979 240 to 1990 240.

Art and Phil Machine Man can far better help you than I can.

I hope the symptoms you describe do not affect whether you pass CA-state emissions.

With key out of ignition, have you tried starting the engine with the AMM / MAF connected and disconnected?

You will have a silver accordion hose between the exhaust manifold heat shield and the bottom of the air filter box. Inside the air filter box, in front and upstream of the air filter, is a thermostat that moves a flap valve back and forth maintaining a temperature of air inducted into the engine for emissions control. The thermostat failed in all of them, eventually, to hot only all the time. During a hot summer or two, the all hot all the time air will ruin an AMM / MAF. You AMM may be weak or failing. In CA-state, the emissions control like that are visually inspected. As you reside in a moderate SoCally environment, you do not need the preheat feature. Some will replace the thermostat. Other will force ambient air all the time and plug the preheat inlet, yet the silver accordion hose remains in place. The thermostat is Wahler 70411. There is a Volvo OEM version that may last more than a year or two.



I'll suggest the FAQ for information on tune:

https://www.brickboard.com/FAQ/700-900/EnginePerformanceSymptoms.htm

Though so far as I know, 700 and 900 series did not use the Chrysler MPG ignition.

If you perform emissions inspection, and you have high HC, there exist some article here to disconnect the vacuum line to the Chrysler MPG ignition control unit hanging on the washer fluid reservoir basket. Plug the vacuum port on the ignition control module and the vacuum line.

Do you know whether the engine control wire harness has been replaced?

Hope that halps yoo-hoop-hoo.

Questions?

Happy Mundane.

MacDuffed.
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