Skip the auto shop - Our mechanics make house calls

Q: Issue with firing - 1991 Volvo 240

asked by on

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?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

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

Q: Car misfiring.

Having your code is a great asset in helping us narrow down the information on the issue your Isuzu Trooper is experiencing! When you notice random misfires in your vehicle, this means that the engine is detecting misfires in two...

Q: Heard a loud bang when I turned on my car yesterday. 2007 Volvo XC90

Hi there - this is highly unusual behavior, and should be checked out immediately. Check for problem codes, even if the Check Engine light is not yet on. This is a misfire condition due to an over-rich condition, possibly due...

Q: My third break light comes on when I apply the brake pedal, but my two main brake lights dont

Hello. Thank you for writing in. The working brake light is known as the center high mount stop lamp. It is wired differently from the normal brake lights in order to prevent them from all going out at once. The...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...