With engine control in fine fettle so you know all emission sensors and controls operate well, the engine should burn cleanly. LH-Jetronic 2.2 you have is sort of a sipper.

I hope you have gotten into the air filter box and checked on the preheater flap valve disposition on the upstream side of the air filter. The thermostat (Wahler PN 70411) that controls the flap valve fails to all hot all the time and will fry an AMM. The silver accordion hose between the exhaust manifold heat shield and the bottom air filter box hot air inlet is an easy delete so long as your state or nation emissions do not mandate visual emission control inspection as they do in silly CA-state.

As I'm well below the Mason-Dixon line in confederate flag Saint Louis, MOe, no emissions test so I removed the air filter box preheater flap valve assembly, delete the silver accordion hose. If you were in Edmonton CA and like enduring cold climes, I'd preserve the preheater function and use the OEM or Volvo thermostat. Replace Wahler (PN 70411) every year or two so I read yet do not know directly.

So, not knowing the thermal performance of the engine, maybe once a week or so and some ten-twenty miles of sustained highway speed. As part of your usual errands so you do not waste fuel if you can. You need not floor it or maintain the engine as needlessly high RPM. Drive as normal yet no need to floor it. A light and easy touch on the gas pedal reduces emissions and maintains fuel economy. So, no need for floor it from the green light. Wen you floor it you ask engine control to dump more fuel than the engine can eat beyond fuel trim control (O2 sensor, Vehicle Speed Sensor) while fuel pressure rises to max with very low vacuum at the FPR yet longer spark dwell and injector open duration. Easy does it from stop lights.

Though Uncle Old Duke complains about the FL-state motoring public giving a single finger salute as he does not floor it from the stop sign or green light. It's a normally aspirated Volvo 240. Going nowhere fast, yet meeting the speed limit easily in North America. And 240 is not the most aerodynamic, so minding the posted speed limits also means ok fuel economy. Yet I'd prefer 70 MPH than the earlier 1980s max of 55 MPH.

The engine coolant temp gauge shows the engine coolant temp. There is latency in engine oil heating up well after coolant heats up. Yet as the engine coolant gauge is at the 9 AM position on the TEMP gauge, the oil does produce oil sump vapor the engine eats through the PCV. At sustained normal RPMs at the posted highway or freeway speed limit, collected moisture and heavier engine combustion products also boil out of the engine oil.

Engine control is very efficient. With normal oil changes there should nto be any sludge. Sort of a myth unless large, high mass V8 engines in Detroit iron cars. Those engines would take a much longer time to heat up for the type motoring they would be used for. Also, they were not the most clean burning of autos before and after the early ERA emissions control years.

The Italian tune-up was also concerned with carbon formation on the valve seats and bottom of the stem. There is some fact a sustained run as you would normally on the highway for some distance can help remove these deposits. You can hasten deposit removal using Chevron Techroline or Techron. Can also maybe remove stuff at the injector tip.

Good your PCV was clear? Yet you had to replace the engine oil seal at the front? What of the rear of the cylinder head round seal. I have to replace this seal on two or three also.

Blah, blah, blah all jacked up on earl grey tea now so better stop.

Where is Uncle Old Duke?

Questions? Sorry to ramble on and on and on.

Wants more Buttermilk and SourDough bread.
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