|
While not a cure all, please see to check the OBD for fault codes as described in the mighty, if wise, Volvo 700-900-90 series FAQ, hosted righter here on your fave brickboard.com:
https://www.brickboard.com/FAQ/700-900/EngineOBDCodes.htm
As Uncle Udo II asks, Bosch LH-2.4 (fuel)/ EZK (ignition - round coil) or the Regina (fuel) / Rex (ignition - square coil)? Each have their unique (and hopefully endearing to you) quirks!
The OBD check is a vague guide. Use your trusty multimeter with volt, OHM (resistance), and continuity function to check senors, wire harness connections, and connection to ground. A 20 year old 1995 Volvo 940 may have multiple causes exhibiting the symptoms you encounter. Onkel can guide you through a progressive diagnostic check on your model better than I through posts. (I tend to go on at length.)
As Chris Mullet asks here, are you using the proper spark plugs of the correct temperature. Check your 1995 Volvo 940 owner manual and check cross reference online if Bosch (listed in the owner manual) or NGK or ?
A few more entries to look at from the FAQ (You may have read these. So, apologies for plying the redundant)
Engine Tune and Performance: Symptoms
https://www.brickboard.com/FAQ/700-900/EnginePerformanceSymptoms.htm
Specifically: No or Poor Cold Start: Problem Diagnosis and Repair (not definitive)
https://www.brickboard.com/FAQ/700-900/EnginePerformanceSymptoms.htm#NoColdStartDiagnosis
For a listing of Engine Control Sensors and Devices see:
Electrical: Engine Sensors
https://www.brickboard.com/FAQ/700-900/EngineSensors.htm
The Fuel pressure Regulator is not treated here. The FPR can fail so that fuel leaks through the vacuum controlled diagram, through the vacuum line, and into the engine intake. You may have a brief whiff of gasoline. Search for posts. Low vacuum, like when you floor it, enriches the fuel to air ratio. High vacuum, meaning your foot is light or off the fuel pedal while driving, means a leaner full to air ratio.
Engine: FI and Ignition Computers
https://www.brickboard.com/FAQ/700-900/EngineFIComputer.htm
Engine: Fuel Injection
https://www.brickboard.com/FAQ/700-900/EngineFuelinjection.htm
And read through the FAQ:
https://www.brickboard.com/FAQ/700-900/
I read in your posting history you've had leaks possibly somewheres in the header pipe or at the exhaust connection union where the exhaust header pipe output meets the catalytic converter. Have you replaced the exhaust system?
You've had hard starting in cold weather problems since 2008 or so with rich running problems correspondingly on this normally-aspired (non turbo) 1995 Volvo 940?
As with an air intake leak, an exhaust leak at any point in front of the oxygen sensor will change the fuel to air ratio. I'm not sure, yet your 02 sensor, like Spook replies in your post history, is located in the header pipe in front of the exhaust header pipe output meets the catalytic converter. May want to check as the 02 sensor could be in the catalytic converter.
The union here on reblock RWD Volvo with the four-cylinder overhead cam engines is weak. A bracket secures and supports at the end of the exhaust header pipe output in front of the head pipe output with the catalytic converter input. The bracket secures to the transmission and is composed of an upper and lower L-shaped bracket. The L-shaped bracket secures directly to the header pipe. Sometimes the bottom L-shaped plate rusts. An unsupported exhaust at this union distresses it, and it may leak over time.
Else, the timing belt was replaced in the last 50k with the tension reset like during every every oil change or so? A few times in the first 500 miles helps as even the Continental brand timing belts give a stretch in the first 500 of running.
Air filter is clean?
A failing engine coolant sensor or faulty wiring / corrosion at the wire harness connectors at any point, including to ground, raises resistance. So, the higher the resistance (corrosion at wire harness connectors, connection to ground), the more fuel that the LH-Jetronic or Regina injects into the engine, lowering your fuel economy greatly, dirtying the emissions output, and possibly causing damage to the catalytic converter.
At 20 years and more, we could all replace the ECT sensors, probably. Though an easy check with a multimeter.
The warm air flap valve in the air filter box works okay? Like with 240, the design fails to hot air all the time as the springy thermostat fails. Inspect the air filter and air filter box. Some may remove the preheater hose from the air filter box. Those more mindful of emissions or must remain compliant to emission inspection maintain the warm air preheater function in the air filter box. If left unrepaired, hot air through the air filter box and into the AMM (or MAF) in the hot summertime shall ruin the AMM in a single or several hot summers.
Verify no leaks on the air intake side, including all vacuum lines. Though air intake (vacuum leaks) after the air filter usually cause the engine to run leaner.
So, check the OBD. Tell us whether you have Bosch LH-Jet / EZK or Regina / Rex?
Questions?
Hope that helps.
Buttermilk-less Sunday Boy.
--
Jonathan Harshman Winters III: The Mightiest, Greatest, & Most Powerful North American Comedian & Comedic Actor in Perpetuity
|
