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Engine misfire on 1986 volvo turbo

I am at my wits end with my car. I know very little about car repair and maintenance and that alone makes me enraged.

So my car is very old and has not been taken care of before I owned it. It did misfire at idle speed before but very rarely, now it seems that ever since I put more oil in the misfires happen way more frequently. I put in a synthetic 10w 30 oil and the engine is way more quiet now and the gas mileage is slightly better…but ever since I put it in the misfires are frequent. I do not know if it is a vacuum leak or a spark plug problem, or if it has something to do with the oil

Those old Volvo’s need new plugs every 30K miles, and the distributor cap, rotor, and plug wires are replaced frequently too. If you don’t replace these parts you will get misfires. Since you state the car was not well taken care of, perhaps you need all these parts replaced and then see how it runs.

I was worried about a vacuum leak but I heard no hissing and fuel pump pressure is fine. I am just wondering what kind of plugs it takes? It didn’t come with an owners manual. And If I can take the plugs out one at a time instead of in the firing order.

This is not going to cause a misfire, but the whole story about adding oil & the engine getting quieter and all of that sounds like a problem. When was the oil changed last? How often do you check it?

A vacuum leak is more likely to show itself as a surging idle. The effects would also tend to go away as you accelerated/drove.

You don’t have to worry about what plugs it takes. Go to an auto parts store and give them the car’s info. Tell them you want OEM equivalent plugs. While you’re there - if you will be messing with the car yourself - drop $20 on a repair manual.

The biggest reason to go one plug at a time is so that all of the plug wires end up back where they belong. You cannot mess up the order of the plugs. I normally just label my wires.

You have an old volvo that was not cared for and you know nothing about cars. The most important thing you should be thinking about is how to get rid of the Volvo.

Well to be honest I am surprised the car has not blown up yet. I am getting an oil change as soon as I get a new filter, and I check the oil once a week. I am going to put new plugs in anyway because they last got replaced in 1995. The misfire happens when it gears down to 1st it putters then hits or misses.

I am going to change the plugs and just see if it helps. I have no money for a new or used car so I am just going to have to learn about cars, which is not a problem for me.

The problem I have is that in the service manual it says it takes a gap of 0.026 but lordco only has 0.028…

The plugs haven’t been changed since '95??? New plugs are a must, replace one at a time to make sure you don’t mess up the plug wires. Then a new distributor cap and rotor are next on the replacement list, followed very closely by new plug wires. You are lucky it runs at all!!!

the difference in plug gap from 0.026 or 0.028 is so minor - who cares!!