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: Broken speedometer

The speedometer on these vehicles may have a bad electrical solder joint that may be loose on the back of the cluster. The radio codes would be needed to reset the radio, after removing the cluster, to inspect and repair...

Q: Engine misfiring, black smoke out of tailpipe

Hello. The conditions you described could result of a fuel injector o-ring leakage, a fuel injector control module intermittent failure, or a glow plug failure. I would also recommend checking the electrodes on the spark plugs. Get some help from...

Q: Anti-Skid Brake Service Required

This message comes up when the computer detects a problem that will keep it from properly controlling this system. Most of the time, it is caused by a failure in the steering angle sensor or a wheel speed sensor. I...

Related articles

P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.