Q: Issue with firing - 1991 Volvo 240

asked by on September 19, 2016

Hello! My car doesn't seem to be able to fire properly, i've just changed the rotor and distributor cap, and the sparkplugs, it seemed to run a lot better after i did so, the light which shows that it burns unclean also disapeared, but the problems returned (within a day) and it doesn't run on idle mostly, but sometimes it runs just fine (although still the light which indicates it burns unclean still is there) and sometimes it idles badly, but it doesn't die, sometimes it just dies instantly after driven then coming to a stop, other times it just vibrates and seem to be fighting to keep runninh, but while driving i feel no problems, what could the problem be and/or how should i approach troubleshooting?
My car has a manual transmission.

Misfires can occur from fuel supply, spark, and camshaft timing problems. You have replaced most of the ignition components that supply spark to your cylinders, but you could still need spark plug wires. They may look good and not be. Also, disturbing them by replacing the cap and spark plugs can make them work for a short time then fail as they did before.

What need to happen to figure out why your car is running bad is some diagnosis. This will require checking fuel pressure and doing a cylinder balance test. The cylinder balance test can be done in a myriad of ways. In your case, I would use a test light to short out one cylinder at a time. The car should run significantly worse when a cylinder is short out. If the idle of the motor changes very little when a particular cylinder is shorted, this cylinder would be suspect to having problems.

As stated in the first paragraph, it could be a bad injector (fuel supply), poor connection of the injector connector, bad spark plug wire or even a compression issue. The main thing that needs to happen here is some definitive diagnosis before any more parts are replaced. If you should need some help with this, a certified mechanic from YourMechanic can come to your location to perform a misfiring diagnostic.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Misfire in 2 cylinders

Hi, thanks for writing in. Was there oil down in the spark plug wells also? If so, the rubber plug boots may still have enough oil on them to short to the cylinder head. It is also possible, with your...

What happens if i replace the catalytic with a thrush muffler and put a DC sports exhaust about 2 feet away from the thrush.

Removal of the catalytic converter on a car that will be operated on the street is very illegal, and can get you a huge fine from the EPA. Also, since most modern vehicles are designed to run with some system...

Check Engine light comes on and goes off

If the speedometer is not working but the rest of the instrument cluster is, the issue is probably the vehicle speed sensor. This sensor is the main input to the control module for speedometer control. The problem could also be...

Related articles

A Buyer’s Guide to the 2012 Volvo XC90
While While the trend seems to be the bigger the vehicle the better, the 2012 Volvo XC90 proves that you can combine seven-passenger seating with a smaller size – without overly sacrificing comfort. For those who want a smaller footprint...
The Best Used Cars to Buy If You Need to Haul a Motocross Bike
Of Of course you would love to be able to ride your motocross bike everywhere, but the reality is, at some point you're going to need to transport it. A cargo van of almost any make or model would be...
Symptoms of a Bad or Failing Timing Chain
Common signs of a faulty timing chain include engine misfires, metal shavings found in the oil, and rattling sounds from the engine while idling.