I recently just got a ‘97 850 base with 235,000mi and I’m trying to diagnose some engine codes it’s giving me. I got it for free so I didn’t expect it to be perfect but It’s a little stubborn to start occasionally on cold days and the service light is on for the first probably 5 minutes running, then turns off.
I’m getting a P0300 multiple cylinder misfire, two of the same codes: P0300 cylinder 1 misfire, and P0455 large evap leak.
My first thought is to check the plugs, wires, and distributor but I’m wondering if anyone has seen any of those codes together and what it may be that’s causing it.
I’d really appreciate any help,
Thanks!

 

For the cylinder misfires I would check plugs, wires, rotor and cap. For the evap leaks I would check all of the vacuum lines and also the coolant temp sensor. Just for a start since this was a free car and probably has no service history.

 

There should be a vacuum line diagram under the hood. The first thing I would check is the vacuum tree near the throttle body. I've had one break in a way that you could not detect the crack without removing the tree and stressing it. Also had the nipples that cover the open spots on the tree fail. If you have access to a vacuum tester I would start there.

This is the tester I have and it gets the job done:

Here is some good info on vac lines in a non-turbo:
https://www.matthewsvolvosite.com/fo...ic.php?t=65002

The service light is just a reminder that you are at a service interval. It will go off every 5000 miles to remind you to change your oil. (It has nothing to do with the problems you are having.) Here is how to reset it.

Volvo 850-70 Service Light Reset

RESETTING 5000 MILE SERVICE LAMP ON 1994 + 1995 850

NOTE: This function is for the service reminder lamp, be sure you have performed the proper service such as changing the oil before resetting. If the check engine lamp is illuminated when the car is running, you'll need to have the car looked at by the Volvo dealer for proper diagnosis.

1. Turn on the ignition to the KPII position so the warning lamps on the dash are illuminated. Do not start the car.

2. Open the bonnet of the car and locate Diagnostic test port (A) behind the driver side headlamp.

3. Remove the cover and pull the jumper wire out of the holder in the cover.

4. Insert the jumper into terminal #7, then press button 4 times, wait approximately 5 seconds and the red lamp should glow continuously. You are now in the data reset mode.

5. Press the button 1 time and wait approximately 5 seconds for the lamp to glow again then press the button 5 times. After about 5 seconds the lamp will illuminate again, press the button 1 time and you will see the lamp flash repeatedly for a couple of seconds indicating that the service lamp has been properly reset.

6. If a mistake is made, simply switch the ignition off and back on to reset and start over.
1996 Model (Some of them)
On these models the diagnostic socket is in front of the gear stick. Switch the ignition on. As you look at the speedometer on the dash, beneath it opposite the trip reset button is a rubber plug. Remove the plug and with a thin pointer such as a ball point pen, depress the pin. This will reset the service light.
1999 Model Service Lamp Reset Procedure

1. Press and hold trip odometer reset button

2. Turn ignition key to run position KPII (not the start position)

3. Wait 30 seconds or until service light begins blinking

4. Release Trip Odometer button

5. Turn ignition to off position